A revision of the stratigraphy and geology of the south-western part of the Crotone Basin (South...

ABSTRACT

The Crotone Basin, located on a stack of nappes piled up duringthe late Paleogene-Neogene, formed in the late Neogene to Quaternaryas a forearc basin of the Ionian arc-trench system. The process of slabrollback caused rapid trench migration, resulting in an extensional-transtensional regime persisting most of the time in the forearc area.The late Neogene tectonic evolution was strongly influenced by aNW-directed fault system, interpreted as basement wrench faultsleading to partitioning of the basin into separate sub-basins subjectto differential subsidence and mutual displacements. Majorsequences identified in the area are regarded as tectono-strati-graphic sequences (TSS). The first of them was laid down in the lateSerravallian (?) – Tortonian – early Messinian, during the basinopening stage and is bounded at the top by an erosional unconfor-mity, which may be correlated with the well-known intra-Messinianevent of the Mediterranean Salinity Crisis. The second TSS, of mid-dle to late Messinian age, is characterized by strongly syntectonicdeposits mostly derived from cannibalization of the lower Messiniansuccession, first infilling extensional troughs, then involved in anepisode of sinistral transpression along the NW-trending fault sys-tem, which generated local overthrusts, sealed by a late Messinianerosional unconformity. The Messinian tectonics probably reflectsthe interplay between the processes linked to the kinematics of theCalabria block and those triggered by the Salinity Crisis. The ero-sional unconformity is overlain by widespread coarse fluvial con-glomerates, which are the first onlapping term of the third TSS, rep-resented by uppermost Messinian to lower Zanclean deposits, laiddown in an extensional-transtensional regime. This TSS was closedby an important late Zanclean episode of dextral transpression alongthe NW-trending fault system, leading to inversion of the formerbasins, and limited SW-verging thrusts on fault-restraining bends.The unconformity sealing the structures has a clear expression in thenorthern, marginal part of the Crotone Basin and correlates down-basin with a conformable surface. The fourth TSS is characterizedby a long-lasting phase dominated by extension-transtension, lead-ing to high subsidence rate during the latest Zanclean to Early Plei -stocene, and accommodating a thick succession of slope mudstonesincluding clusters of diatomaceous bands mostly in the D. tamalisand D. brouweri Zones. In the northern part of the Crotone Basintwo phases of drowning separated by an uplift pulse at ca. 2.55 Macan be recognized, the second of which was a dramatic collapse,between 2.3 and 2.1 Ma. The fifth TSS is bounded at the base by anunconformity at the transition between «large» and «small» Gephy-rocapsa Zones, i.e. at around 1.1-1.2 Ma, correlating basinwardswith a conformable surface. The unconformity is erosional andlocally angular in the marginal part of the basin, where it seals struc-tures generated by a contractional event documented also elsewherein the Calabria block. This event, which is accompanied by a strike-slip component, is inferred to be coeval to the Lower Pleistoceneimportant transpressional episode along the Pollino shear system,which led to release of the Calabria block from the southern Apen-

nines. The fifth TSS is characterized by resumed dextral transten-sion in the Middle Pleistocene along right-stepping NW-trendingfaults. This episode generated minor pull-apart sub-basins, showingspectacular growth structures in their infilling successions, whichdeveloped with shoaling trend up to inferred Marine Isotope Stages9-8. The onset of shoaling trend was diachronous, being remarkablyyounger in the southern sub-basin. In the late Middle Pleistocene toRecent times extensional tectonics was dominating, accompanied bylocal gravity gliding towards the Ionian Sea, arguably triggered byincrease in topographic gradient following hinterland uplift, andimplying the activation of a linked, thin-skinned extensional andcontractional NE- to NNE-directed fault system, with detachmentsurface possibly soling into Messinian evaporitic-mudstone deposits.It is concluded that the geologic evolution of the investigated forearcarea was characterized by an alternation of long-lived stages ofextension-transtension expressed by prolonged subsidence precededby uplift pulses, and short-lived episodes of contraction-transpres-sion. Major drowning episodes in the forearc area are thought to becoeval to the main phases of spreading in the Tyrrhenian basin.

KEY WORDS: Crotone Basin, late Neogene, Quaternary,stratigraphy, synsedimentary tectonics, structural evo-lution.

RIASSUNTO

Revisione della stratigrafia e geologia della parte sud-occi-dentale del Bacino di Crotone (Italia meridionale).

Il Bacino di Crotone, localizzato alla sommità di una successio-ne di falde impilate durante il Paleogene superiore-Neogene, si for-ma nel Neogene superiore-Quaternario come bacino di avanarco delsistema ionico arco-fossa calabro. Il processo di arretramento delloslab causa una rapida migrazione dell’arco, che si traduce in un pre-valente regime estensionale-trastensionale, persistente per la maggiorparte dell’evoluzione tettonica nel bacino di avanarco. Quest’ultima èstata fortemente influenzata da una tettonica trascorrente, per lo piùattiva lungo un sistema di faglie NO-SE coinvolgenti il basamento, cheha portato all’individuazione e dislocazione differenziale di diversisettori. Le sequenze maggiori identificate nell’area sono da conside-rare come sequenze tettono-stratigrafiche (STS). La prima di esse sidepone dal Serravalliano superiore(?)-Tortoniano al Messiniano in-ferore, contemporaneamente all’apertura del bacino di Crotone ed èdelimitata al tetto da una discontinuità erosiva correlabile con il bennoto evento intra-Messiniano della Crisi di Salinità. La seconda STS,è costituita da depositi sintettonici, in gran parte derivati da canni-balizzazione della successione del Messiniano inferiore, dapprimapresenti come riempimento di depressioni strutturali in regime di-stensivo, poi coinvolti in un episodio di traspressione sinistra lungofaglie NO-SE che genera localmente thrusts, suturati da una secondadiscontinuità erosiva del tardo Messiniano. La tettonica Messinianaprobabilmente riflette l’interferenza tra la cinematica dell’arco Cala-bro e i processi legati alla Crisi di Salinità. La discontinuità al tetto èricoperta in onlap da conglomerati fluviali di larga estensione, cherappresentano il primo termine della terza STS, costituita da sedi-menti del Messiniano terminale e dello Zancleano p.p. deposti in re-gime tettonico distensivo-trastensivo. Questa STS è chiusa da un epi-sodio importante di traspressione destra lungo il sistema di faglieNO-SE durante lo Zancleano, che determina l’inversione dei bacini

(*) Dipartimento di Geoscienze, Università di Padova, ViaGiotto, 1 - 35137 Padova, Italy. [email protected].

(**) Dipartimento di Scienze Geologiche, Università della Ba-silicata, Campus Macchia Romana - 85100 Potenza.

(***) University of Tromsø, Department of Geology, Drams -veien 201, N-9037 Tromsø, Norway.

A revision of the stratigraphy and geology of the south-western part of the Crotone Basin (South Italy)

FRANCESCO MASSARI (*), GIACOMO PROSSER (**), LUCA CAPRARO (*), ELIANA FORNACIARI (*) & CHIARA CONSOLARO (***), (*)

280-BROGI & GIORGETTI

Ital.J.Geosci. (Boll.Soc.Geol.It.), Vol. 129, No. 3 (2010), pp. 353-384, 17 figs., 1 pl. f.t. (DOI: 10.3301/IJG.2010.20)

precedenti. La discontinuità che sutura le strutture ha chiara espres-sione nella parte marginale (settentrionale) del bacino, mentre passaad una superficie conforme nella parte meridionale. La quarta STS ècaratterizzata da una lunga fase di distensione/trastensione tra loZancleano superiore e il Pleistocene inferiore, durante la quale haluogo la deposizione di una potente successione di peliti di scarpata,comprendente clusters di bande diatomitiche principalmente nelleZone a D. tamalis e D. brouweri. Nella parte settentrionale del Baci-no di Crotone l’«annegamento» appare articolato in due fasi succes-sive separate da un evento di sollevamento a circa 2.55 Ma, la secon-da delle quali è un vero e proprio collasso, avvenuto tra 2.3 e 2,1 Ma.La quinta STS è delimitata alla base da una discontinuità alla transi-zione tra Zona a «large» e Zona a «small» Gephyrocapsa, a circa 1,2-1,1 Ma, correlabile con una superficie conforme nell’area bacinale.Questa discontinuità presenta un carattere erosivo e localmente di-scordante a basso angolo nella parte marginale del bacino, dove su-tura strutture generate da un evento compressivo segnalato regional-mente in Calabria. Questo evento deformativo, accompagnato dauna componente strike-slip, è ritenuto contemporaneo alle note tra-spressioni sinistre lungo il sistema di faglie del Pollino, tradottesi inuno svincolamento del blocco calabro dall’Appennino meridionale.La quinta STS è caratterizzata da trastensione destra lungo faglieNO-SE con disposizione right-stepping, che genera nel Pleistocenemedio sotto-bacini pull-apart le cui successioni regressive di riempi-mento, sviluppatesi probabilmente fino ad una data intorno agli sta-di isotopici 9-8, mostrano spattacolari strutture di crescita. L’iniziodella regressione è diacrona, essendo sensibilmente più recente nelsotto-bacino meridionale. Infine, dalla parte superiore del Pleistoce-ne medio in poi, il regime prevalente è distensivo, accompagnato dauna tettonica gravitativa con trasporto verso il bacino ionico, inne-scata dall’aumento di gradiente topografico legato al recente solleva-mento dell’entroterra. Questa si realizza tramite un sistema coniuga-to di faglie normali NE-SO o NNE-SSO, e motivi frontali compres-sivi, e utilizza probabilmente come orizzonte di scollamento peliti-evaporiti messiniane. In conclusione, l’evoluzione geologica del Ba-cino di Crotone è caratterizzata da un’alternanza di prevalenti episo-di di distensione/trastensione, espressi da prolungata subsidenzapreceduta da brevi pulsazioni di sollevamento, e brevi episodi dicontrazione-traspressione. Gli episodi maggiori di collasso e subsi-denza nell’area di avanarco sono probabilmente coevi alle fasi diapertura di bacini di retro-arco nel Tirreno.

TERMINI CHIAVE: Bacino di Crotone, tardo Neogene, Qua-ternario, stratigrafia, tettonica sinsedimentaria, evolu-zione strutturale.

INTRODUCTION

The Crotone Basin is located on the Ionian side ofCalabria, and represents the upper Neogene-Quaternaryforearc basin of the Ionian arc-trench system, which wasgenerated by eastward rollback of a west-dipping subduc-tion zone associated with extension in the Tyrrhenianback arc basin (MALINVERNO & RYAN, 1986; KASTENS etalii, 1988; PATACCA & SCANDONE, 1989; PATACCA et alii,1990; MAZZOLI & HELMAN, 1994; SARTORI, 1989, 1990;FACCENNA et alii, 2001) (fig. 1). The literature concerningvarious aspects of the stratigraphy and geology of theCrotone Basin, and, more generally, the Calabria blockand adjacent marine areas is very extensive. The firstimportant stratigraphic and geologic syntheses are thoseof OGNIBEN (1955, 1973), SELLI (1962), and RODA (1964).Specifically, the Crotone basin stratigraphy established byRODA (1964), is still valid in its main lines.

A milestone paper concerning the geodynamic set-ting of the Calabrian Arc is that of MALINVERNO & RYAN

(1986), who recognized the nature of the Calabrian arcuateorogenic belt as resulting from processes associated withsubduction of a west-dipping lithospheric slab, simultane-ous with back-arc extension in the Tyrrhenian Sea. Geody-namic interactions linking subduction processes, back-arcextension and dynamics of mantle flow, particularly the

mantle circulation induced by slab breakoff, were treatedby ANDERSON & JACKSON (1987), GIUNCHI et alii (1996),GUEGUEN et alii (1998), VAN DER MEULEN et alii (1998),GVIRTZMAN & NUR (1999), FACCENNA et alii (2001, 2004),WORTEL & SPAKMAN (2004), SPAKMAN & WORTEL (2004),GUARNIERI (2006) and CHIARABBA et alii (2008) amongothers.

The role of strike-slip tectonics during the LateMiocene to present kinematic evolution of the Late Ceno-zoic basins in Calabria was stressed among others byMOUSSAT et alii (1986), MEULENKAMP & HILGEN (1986),MEULENKAMP et alii (1987), KNOTT & TURCO (1991), VAN

DIJK (1991, 1992, 1994), VAN DIJK & OKKES (1991), DEL

BEN et alii (2008), BARONE et alii (2008), FERRANTI et alii(2009), and MILIA et alii (2009). A wealth of paleomagneticdata, particularly concerning the rotations in southernItaly, and related geodynamic implications, were pre-sented by SAGNOTTI (1992), SCHEEPERS et alii (1994),SCHEEPERS & LANGEREIS (1994), VAN DIJK & SCHEEPERS

(1995), SPERANZA et alii (2000), MATTEI et alii (2004),MATTEI et alii (2007) and SPERANZA et alii (in press). Newbiostratigraphical data, mainly concerning the Pleistocenesuccession of the Crotone Basin, were provided by RIO etalii (1996), MASSARI et alii (2002), CAPRARO et alii (2005)and CAPRARO et alii (2006). Significant contributions onthe recent evolution of the Ionian side of Calabria, includ-ing the uplift history, age of the marine terraces and pre-sent-day deformations, are those of WESTAWAY (1993),MAUZ & HASSLER (2000), GALLI & BOSI (2003), ZECCHIN

et alii (2004b), MOLIN et alii (2004), NALIN et alii (2007),WESTAWAY & BRIDGLAND (2007), FERRANTI et alii (2009).

Other significant contributions for the geology ofsouthern Italy and particularly the onshore and offshoreCalabrian arc are those of PHILIP & TORTORICI (1980),ROSSI & SARTORI (1981), TORTORICI (1981), GHISETTI &VEZZANI (1981), BARONE et alii (1982), MORLOTTI et alii(1982), AUROUX et alii (1985), BOUSQUET & PHILIP (1986),GLIOZZI (1987), ROVERI et alii (1992), MORETTI (1993),HIPPOLYTE et alii (1994), TORTORICI et alii (1995),MONACO et alii (1996), MORETTI & GUERRA (1997),CAVAZZA et alii (1997), VAN DIJK et alii (1998), LUCENTE etalii (1999), VAN DIJK et alii (2000), MENARDI-NOGUERA &REA (2000), MONACO & TORTORICI (2000), PATACCA &SCANDONE (2001), SARTORI (2003), ZECCHIN et alii (2003,2004a), ROSENBAUM & LISTER (2004), PATACCA & SCAN-DONE (2004), GOES et alii (2004) and PRAEG et alii (2009).

Recently completed reviews of the Pliocene and Plei -stocene chronologic and magneto-stratigraphic frame of the sedimentary succession of the Crotone Basin(CAPRARO et alii, in press, and SPERANZA et alii, in press),provide a wealth of new data. Based on them, the paperaims at shedding new light on the depositional and geo-logic evolution of the basin. Of particular interest, in ouropinion, is the identification of a major change spanningfrom 1.1-1.2 Ma to ca. MIS 8-9. This was characterized bythe splitting of the basin into a number of fault-boundedpull-apart sub-basins, related to right transtension alongthe main NW-trending fault system, possibly during a laterollback phase of the Ionian slab.

BRIEF OUTLINE OF GEODYNAMIC SETTING

As a preliminary note, it should be reminded that, fol-lowing the current use, the term Calabrian arc in the

354 F. MASSARI ET ALII

investigated area refers to the orogenic edifice, includingthe onshore and offshore forearc and the accretionarywedge, and is not related to the volcanic arc of the Aeo-lian Islands. The core of the Calabrian arc consists of aHercynian basement, Alpine polymetamorphic rock suc-cessions related to the deformation of the SouthernTethyan margin, and Mesozoic sedimentary units. Earlyphases of the orogenic construction (Eocene) were fol-lowed by an Oligocene extension-related collapse andexhumation phase (ROSSETTI et alii, 2004), and thenthrust stack migration toward the Adriatic foreland, withdevelopment and deformation of Oligocene and earlyMiocene basins. Since the middle to late Miocene the Ca -labro-Peloritani domain was rifted away from Corsica-Sardinia block as a continental fragment, and migratedrapidly at a rate of up to 6-8 cm/yr, to be finally assem-bled to its present position between Sicily and Apulia,while the Tyrrhenian basin opened in the back-arc(ALVAREZ et alii, 1974; MALINVERNO & RYAN, 1986;BONARDI et alii, 2001). Lithospheric retreat was muchfaster in the southern Tyrrhenian basin, south of the 41° N Lineament, corresponding to a major lithosphericdiscontinuity (PATACCA et alii, 1990). During the openingstage of the Crotone Basin the former thrust stack of theCalabria block was unconformably overlain along theIonian side by upper Tertiary to Quaternary forearc basinsedimentary sequences at the rear of an accretionarywedge located offshore in the Ionian Sea.

The Ionian arc-trench system and its back-arc basins(fig. 1) display several distinctive characteristics which arefar from typical when compared to other arc-trench sys-tems. Peculiar features include i) the narrow width (lessthan 300 km) of the subducting slab (MALINVERNO &RYAN, 1986), probably one of the smallest in the world(LUCENTE et alii, 1999); ii) the extreme rapidity of riftingand oceanization in the southern Tyrrhenian back-arcbasin when compared to the known rates of similarprocesses in other back-arc basins (NICOLOSI et alii, 2006)and the related high velocity of migration of the arc-trenchsystem (PATACCA et alii, 1990); iii) the lack of a typical andcontinuous trench zone and its relative shallowness. More-over, a stack of crystalline and ocean-derived nappes piledup during the late Paleogene-Neogene is present betweenthe accretionary wedge and the volcanic arc, preventingthe latter to act as a sediment source for the forearcbasins. Among the causes of the above anomalies, thecharacteristics of the old and cold subducting Ionianlithosphere and the steep angle of subduction, togetherwith the particular mantle circulation induced by repeatedslab breakoff, are thought to have played a critical role(DAVIES & VON BLANCKENBURG, 1995; CARMINATI et alii,1998; WORTEL & SPAKMAN, 2000; FACCENNA et alii, 2001;FACCENNA et alii, 2004; SPAKMAN & WORTEL, 2004).

The slab rollback does not correlate with the regionalconvergence between Africa and Eurasia, which is 5-6times slower (GVIRTZMAN & NUR, 2001), i.e., 1-2 cm/yraccording to FACCENNA et alii (2004). This implies thatdriving forces independent of Africa-Europe convergenceare important. The process of rollback of the slab, mostlydriven by its negative buoyancy, caused rapid trenchmigration and weak coupling between the upper andlower plates, leading to predominant extension in theupper plate (MALINVERNO & RYAN, 1986).

The back-arc extension in the Tyrrhenian Sea isknown to have been discontinuous, and the migration of

the locus of extension changed in time, as it was directedtoward the East during the Tortonian to Early Pliocene,when the Sardinia margin and the Vavilov basin formed,and toward the ESE or SE during the Late Pliocene-EarlyPleistocene, during the opening of the Marsili basin (PA -TACCA et alii, 1990; SARTORI, 2003). Back-arc extensionwas matched by the radial growth of the Apennine-Maghrebid fold and thrust belt. Episodicity in Tyrrhenianback-arc extension has been attributed to the interferenceof the retreating oceanic slab with intervening buoyantcontinental – Apulian and Sicilian (African) – forelandlithosphere leading to temporary stops or strong slowing

A REVISION OF THE STRATIGRAPHY AND GEOLOGY OF THE SOUTH-WESTERN PART OF THE CROTONE BASIN 355

Fig. 1 - a) Outline of the main geological units and structural elmentsof southern Italy and surrounding basins. Inset: Crotone Basin; b) Tectonic sketch-map of the onshore Crotone Basin. Box shows thelocation of the investigated area.– a) Schema delle principali unità geologiche ed elementi strutturalidell’Italia meridionale e dei bacini circostanti. Riquadro grigio: Bacinodi Crotone; b) Schema dell’assetto tettonico del Bacino di Crotone. Il riquadro mostra l’ubicazione dell’area di studio.

down of subduction (ARGNANI & SAVELLI, 1999; SARTORI,2003). Slab tearing episodes accompanied by lateral flowof the mantle are commonly invoked for subsequentresumption of the rollback (FACCENNA et alii, 2004;CHIARABBA et alii, 2008).

A major tectonic reorganization in the whole centralMediterranean area is thought to have occurred around0.8-0.5 Ma by ANDERSON & JACKSON (1987), PATACCA etalii (1990), WESTAWAY (1993), HIPPOLYTE et alii (1994),LUCENTE et alii (1999), PATACCA & SCANDONE (2004), andGOES et alii (2004), and interpreted as marking the dock-ing of Calabria between Apulia and Sicily, resulting installing or significant slowing down of the Calabrian Arcsubduction and accompanying Tyrrhenian back-arcextension.

Recent uplift in Calabria may be the result of morethan one process. Some authors (WESTAWAY, 1993; VAN

DIJK & SCHEEPERS, 1995; WORTEL & SPAKMAN, 2000)attribute the uplift and extensional regime to the isostaticrebound that occurred when the detached remnants of theruptured slab started to sink, whereas the non-detachedportion elastically bounced upwards due to increasedbuoyancy. Alternatively, the uplift is believed to have beeninduced by upward mantle flow (GVITZMAN & NUR, 2001;D’AGOSTINO & SELVAGGI, 2004), e.g., around a slab edgeformed by a propagating tear (GOES et alii, 2004).

GEOLOGIC SETTING OF THE CROTONE BASIN

The Crotone Basin is located on the Ionian side ofCalabria, and is the upper Neogene to Quaternary forearcbasin of the Ionian arc-trench system (fig. 1). Similarly toother Calabrian and Sicilian contemporaneous basins, itis located in a wedge-top position, developing on thehanging-wall buttress of the arc after the late Paleogene-Neogene emplacement of crystalline and sedimentarynappes, as proven by the basal unconformity of the upperSerravallian(?)-Tortonian transgressive sequence (con-glomerates, sandstones and clays) on the thrust sheets(AMODIO MORELLI et alii, 1976; FABBRI et alii, 1980;GHISETTI & VEZZANI, 1981). Due to extensive Quaternaryuplift, the basin houses one of the best-exposed UpperMiocene to Pleistocene sedimentary successions of south-ern Italy. The basin fill consists of more than 3000 mthick terrigenous clastics delivered from sources locatedwithin the adjacent crystalline nappes, without contribu-tion from the active magmatic arc.

As a result of the dominantly extensional regime sincethe late Serravallian(?)-Tortonian opening stage, and theoffshore migration of the hinge of the subducting slab,the infill of the forearc basin was not incorporated into acomplex collisional orogen, so that most peculiar featureswere preserved and not obscured by folding, thrustingand erosion.

The Late Miocene to present kinematic evolution ofthe Late Cenozoic basins in Calabria was strongly influ-enced by strike-slip tectonics, mainly active along a NW-directed system, interpreted as basement wrench faultsystem leading to partitioning of the basin into separatesub-basins subject to differential subsidence and mutualdisplacements, with extensional or compressive compo-nent changing repeatedly in time (MOUSSAT et alii, 1986;MEULENKAMP et alii, 1987; VAN DIJK, 1992; BARONE etalii, 2008; DEL BEN et alii, 2008).

VAN DIJK and co-workers (VAN DIJK, 1991, 1992,1994; VAN DIJK & OKKES, 1991; VAN DIJK & SCHEEPERS,1995; VAN DIJK et alii, 1998) reinterpreted the strati -graphy of the Crotone basin in connection with the dyna -mics of arc migration and back-arc extension. According to their model, repeated oceanization episodes in theTyrrhenian Sea, concomitant with long episodes of roll-back of the hinge zone of the subducting Ionian plate, ledto major phases of basin opening in the forearc area inlate Tortonian, Early Pliocene and Late Pliocene-EarlyPleistocene, achieved through transtensional movementsalong shear zones and extensional movements alonglistric faults. According to these authors, the long-lasting,overall extensional-transtensional regime was punctuatedby short-lived pulses of compression, backthrustingand/or transpression along major NW-trending shearzones in the middle Messinian, late Early Pliocene andEarly Pleistocene, leading to inversion of former exten-sional faults (see also PHILIP & TORTORICI, 1980; TOR-TORICI, 1981; GHISETTI & VEZZANI, 1981; AUROUX et alii,1985; MOUSSAT et alii, 1985; BOUSQUET & PHILIP, 1986).According to VAN DIJK (1992) these pulses record NE-directed oblique convergence of the African Plate relativeto the European Plate (a hypothesis already formulatedby MOUSSAT et alii, 1985, 1987), repeatedly operating dur-ing interruptions of the rollback process and cessation ofextension in the back-arc area.

RODA (1964) subdivided the Crotone Basin successioninto three tectono-stratigraphic sequences bounded bymajor unconformities related to tectonic-driven phases ofbasin reorganization. The first developed in late Serraval-lian to Messinian, the second in late Messinian to EarlyPliocene, and the third in Late Pliocene to Pleistocene.

METHODS

The south-western sector of the Crotone basin wasmapped to a scale of 1:10,000 in order to document therelationships between the sedimentary bodies and thestructural setting of the area. The revised stratigraphicscheme takes into account the wide and documenteddata set concerning the Pleistocene bio-, magneto-, andlitho-stratigraphy of the investigated area gathered byCAPRARO et alii (in press). We refer to RIO et alii (1990)(emend. by RAFFI et alii, 2006) for the nannofossil bio -stratigraphy, and to LOURENS et alii (2004) for therelated chronology (fig. 2). The revision of the physicalstratigraphy is completed by new data obtained bymeans of facies analysis.

Where possible, shear sense at tectonic contacts wasdeduced from kinematic indicators. Generally this infor-mation refers to the last tectonic stages, since most of theolder tectonic history has been mainly inferred from sedi-mentological and thickness variations in syntectonic unitsacross the main tectonic contacts. The ages of theinvolved units and major unconformities have been usedin order to frame the tectonic history of the area.

THE STRATIGRAPHIC SUCCESSION OF THE SOUTH-WESTERN CROTONE BASIN

A stratigraphic scheme of the succession of the south-western part of the onshore Crotone Basin, with indica-



Fig. 2 - Adopted time framework. Chronology after LOURENS et alii (1996). Calcareous nannofossil biostratigraphy after RIO et alii (1990)(emend.) and RAFFI et alii (2006). Planktonic foraminifera events after CITA (1975) (emend.). Standard Oxygen Isotope Stratigraphy after LISIECKI & RAYMO (2005). Mediterranean sapropel layers after LOURENS et alii (1996) and LOURENS et alii (2004). – Schema cronologico adottato. Dati cronologici secondo LOURENS et alii (1996). Biostratigrafia a nannofossili calcarei secondo RIO et alii(1990) (emend.) e RAFFI et alii (2006). Bioeventi a foraminiferi planctonici secondo CITA (1975) (emend.). Scala isotopica standard secondo LISIECKI & RAYMO (2005). Livelli di sapropel nel Mediterraneo secondo LOURENS et alii (1996) e LOURENS et alii (2004).

tion of the formational names used by previous authors,is shown in fig. 3. Note that, for sake of consistency withformer stratigraphy, we follow the use of placing the baseof the Quaternary at the boundary between Gelasian andCalabrian. In the following, the stratigraphic units crop-ping out in the Crotone Basin are briefly described start-ing from the base of the succession. Whenever possible,the formational names already occurring in the literaturewere used, with particular reference to those of RODA’s

(1964) stratigraphy. For minor units we refer either toVAN DIJK (1992) stratigraphical nomenclature (althoughit is crowded with local names), or, in the case of missingreferences in literature, we propose informal units, indi-cating the lithological term with lower-case initial letter.

The sequence stratigraphy of the onshore CrotoneBasin has been outlined since the sixties by RODA (1964)in a forerunning paper appeared in a time when thesequence stratigraphy was not yet born. We follow his


Fig. 3 - Stratigraphic scheme of the succession of the south-western part of the onshore Crotone Basin, with indication of formational namesadopted by previous authors. – Schema stratigrafico della successione affiorante nella porzione sud-occidentale del Bacino di Crotone, con indicazione dei nomi formazionaliadottati dagli autori precedenti.

approach of subdividing the basin fill into a number ofhigher-rank, tectono-stratigraphic sequences, whereaslower-rank sequences, arguably driven mostly by eustaticchanges, are not taken into account, except in the case ofmajor sea-level oscillations such as those linked to theMessinian Salinity Crisis.

THE PRE-PLIOCENE STRATIGRAPHY

Formazione di San Nicola (OGNIBEN, 1955) (upperSerravallian? - Tortonian)

A nonconformity marks the contact of the For-mazione di San Nicola on variable basement rocks(mostly granodiorite and tonalite of Sila Piccola). Theunit consists of generally clast-supported, brownish toreddish, pebble to boulder conglomerates and arkosicsandstones, occurring as alluvial fan and fluvial deposits,and locally as incised-valley fill (along the Cropa creek,near Petilia Policastro). Thickness ranges from 0 to amaximum of about 90 m in the incised valley fill.

The formation buries a rough, irregular basementtopography. Layers, commonly barely distinguishable,are from 30 cm to more than 1 m thick. Elements, gener-ally well rounded, include: granodiorite and tonalite, low-grade metamorphic rocks, gneiss, migmatite, aplite,black, yellow and reddish chert, quartz, micritic lime-stone, siltite and rare brown sandstone. Sorting is frommoderate in better organized facies to very poor indebrites. Conglomerate layers are massive or locallygraded, and the associated, commonly coarse, locallygranule-bearing sandstones may display thick planar la -mination. In places isolated pebbles/cobbles float in thesandstones. In the basal contact the formation displaysonlap relationships with respect to the substrate and agradual wedging out in the western marginal belt of thebasin, where generally increased angles of eastward dipare inferred to partly reflect a primary feature. A synsedi-mentary extensional tectonics can be documented partic-ularly in the northern part of the onshore Crotone Basin,outside the investigated area.

The deposits are interpreted as the product of alluvialfan to proximal braided stream sedimentation markingan important phase of uplift and denudation of nearbyareas west of the Crotone basin during the basin openingstage.

Molasse a Clipeastri (SELLI, 1962) (upper Serraval-lian?-Tortonian)

This unit, up to ca. 60 m thick, consists of shallow-water shoreface sandstone and conglomerate, occurringatop the Formazione di San Nicola, and locally lyingdirectly on the basement. It is commonly fossiliferous inthe lower part. Together with the Formazione di SanNicola, this unit shows onlap relationships with respectto the basement and a general pinching out toward thewestern margin of the basin. The formation of Molasse aClipeastri is partly the distal correlative of the youngerpart of the Formazione di San Nicola and the proximalcorrelative of the older part of the offshore mudstones ofthe «Argilla Marnosa del Ponda» (see below). In the caseof the formation directly lying on the basement, the basalcontact shows evidence of a certain roughness of theflooded topography, with hummocks of basement rocksonlapped by the sandstone (e.g., N of Petilia Policastro).The conglomerates contain clasts of basement rocks, gen-

erally well rounded, except for the coarsest boulders andblocks derived from nearby substrate (e.g., NE of Belca -stro), which are sub-angular to angular.

Above a basal ravinement surface, locally marked by atransgressive coarse lag, the lowermost part of the unit ismoderately fossiliferous (Clypeaster, Scutella, thick, heav-ily bored oyster shells, both whole and fragmented, pec-tinids, bryozoans, rare fish vertebrae), with fossil contentrapidly decreasing upwards. South-west of Cropani thebasal deposits are locally represented by clast-supportedpebble conglomerates showing regular plane-parallelstratification, well developed imbrication, and high clastrounding and sorting, all features providing evidence ofactive wave working in a shoreface environment.

The unit commonly shows upward-fining trend fromconglomerates to arkosic sandstones, the latter showingplanar to low-angle lamination and bioturbation (Scoli-cia). The characteristics of the unit, particularly wherethe overall thickness is lower, indicate in most cases ahigh-energy lower shoreface environment, with local peb-ble imbrication suggesting a NE-SW-trending shoreline.North of Petilia Policastro unfossiliferous sandstones,occurring directly on a rough basement topography, dis-play large-scale cross bedding of upward-decreasingscale, suggesting an origin by sand-wave migration, possi-bly related to high-energy tidal flows accelerating along a narrow seaway confined between basement highs.Thicker successions (Belcastro and Cropani areas) showlower fossil content and local roundness bimodality(angular clasts occurring together with well roundedones, possibly due to mixing of locally sourced clasts witha longshore-drifted fraction), and, in places, pocket andpillar structures (Belcastro area) suggesting seismically-induced liquefaction. Gilbert-type deltas occur in theMesoraca area and are reported also outside the investi-gated area (e.g., near Cotronei). The deposits are inter-preted to represent a range of settings, from wave- andlocally tidal-influenced shoreface to delta-front.

Argilla marnosa del Ponda (OGNIBEN, 1955) (Torto -nian) (fig. 4a)

The unit consists of outer-shelf clayey and silty mud-stones with Neogloboquadrina acostaensis, whereas aprodelta setting may be envisaged for the basinwardequivalent of the local delta-front facies of the upperMolasse a Clipeastri. The unit crops out poorly in theinvestigated area, and shows variable but limited thick-ness (0-20 m).

Formazione del Tripoli (OGNIBEN, 1955) (lowerMessinian)

Interval up to a few metres thick of sapropel-like,white diatomaceous laminites at the transition betweenthe Argilla Marnosa del Ponda and the Calcare di base(fig. 4a). Like elsewhere in the Mediterranean, thedeposits are linked to anoxic bottom conditions due tostratification of the water column as prelude of theMessinian Salinity Crisis. In the enclosed geological mapthe Argilla Marnosa del Ponda and Formazione delTripoli are lumped together, due to the usual thinness ofboth units and scarcity of outcrops.

Calcare di base (lower Messinian) (fig. 4a)This unit, 7-25 m thick, only occurs in the western

marginal part of the study area, and, according to RODA


(1964), represents, in the most complete succession ofCrotone Basin penetrated by boreholes, the lower unit ofhis «Formazione evaporitica inferiore», consisting of pri-mary evaporites in the upper part. The Calcare di base isa limestone, in places dolomitic, sometimes containing asiliciclastic fraction, occurring in beds some dm-thick,and lying, with local low-angle unconformity, on differentsubstrates, ranging from the Argilla Marnosa del Ponda,Molasse a Clipeastri and Formazione di San Nicola. Inthe latter case the top of the Formazione di San Nicolalocally appears heavily pedogenized, and the lower part ofthe Calcare di base contains rounded clasts of basementrocks, probably recycled from the substrate, decreasing inabundance upwards. The limestone is commonly vacuo-lar, in places stromatolitic, and may contain a moderateamount of silty to sandy siliciclastic debris (e.g., WNW ofPalazzo Martelletto).

GUIDO et alii (2007) established that the Calcare dibase is mainly a product of microbial-induced carbonateprecipitation under aerobic conditions in a marine envi-ronment stressed by episodic fresh-water input. Low-angle basal discordances suggest eastward tilting of thewestern basin margin.

Petilia Policastro formation (named with reference tothe village of Petilia Policastro, where the unit is bestexposed) (upper Messinian)

This formation (PPF for brevity) includes the RODA’s(1964) unconformably-based complex of «Formazione de -tritico-salina» and «Formazione evaporitica superiore» andprobably corresponds to the unit designated as post-eva -poritic 1 (p-ev1) by ROVERI et alii (2005, 2008a). It showshighly variable thickness and composition even over shortdistances, pointing to active synsedimentary tectonics.


Fig. 4 - a) Transition Argilla Marnosa del Ponda – Formazione del Tripoli – Calcare di base (road Petilia Policastro-Rocca Bernarda); b) rese-dimented sandstones interbedded with coarse debrites with large blocks. Lower unit of Petilia Policastro formation, near the village of PetiliaPolicastro. The debrite is about 85 cm thick; c) verticalized subaerial conglomerate and sandstone of the lower unit of Petilia Policastroformation, near the Petilia-Martelletto Fault zone, NE of the village of Mesoraca; d) Gypsarenite layer, with planar-horizontal laminationpassing upwards into ripple drift cross lamination. NE of Contrada dei Gigli. Pencil 14.5 cm long for scale.– a) Transizione Argilla Marnosa del Ponda – Formazione del Tripoli – Calcare di base (strada Petilia Policastro-Rocca Bernarda); b) arenarie risedi-mentate intercalate a depositi grossolani di debris flows con grandi blocchi (unità inferiore della formazione di Petilia Policastro, presso il villaggiodi Petilia Policastro). Il deposito grossolano è spesso circa 85 cm; c) conglomerati e arenarie continentali dell’unità inferiore della formazione di Petilia Policastro, verticalizzati presso la zona di faglia Petilia-Martelletto, a NE del villaggio di Mesoraca; d) Strato gessarenitico con laminazioneplanare-orizzontale passante verso l’alto a laminazione obliqua da ripples. Località a NE di Contrada dei Gigli. La matita è lunga 14.5 cm.

The PPF is bounded at the base by a major erosionalunconformity, in places cutting deeply into the substrate,corresponding to the unconformity recognized by RODA

(1964) between his «Formazione evaporitica inferiore»and «Formazione detritico salina», and to that identifiedby VAN DIJK (1990, 1994) at the base of his Mes-3 se -quence. In the study area the youngest term underlyingthe unconformity is the Calcare di base, locally draped bya very thin cover of mudstones. The upper boundary ofthe PPF is another major unconformity, already recog-nized by VAN DIJK (1990, 1994), marking the base of thecoarse-grained fluvial deposits of the Upper MessinianConglomerato delle Carvane. This contact is locally char-acterized by low-angle erosional truncation of the PPF.The two unconformity surfaces, and locally also the baseof the Pliocene mudstones, tend to converge in a singleunconformity on the western basin margin at the foot ofthe Sila Piccola massif.

The most complete succession, with a thickness of upto 230 m, is well exposed in the Petilia Policastro area. Inthe hills east of the Fosso Umbro valley the formation isvery thick, but only its upper part is cropping out.

The lower unit of the PPF (Teodoro Formation of VAN

DIJK, 1990, 1994) displays the coarsest grain size, andconsists of a complex of conglomerates, local heteromet-ric megabreccias and sandstones (figs. 4b and c). It showsmost pronounced thickness variations, and overlies asubstrate of variable age. Locally, the erosion is so deepthat the unit lies directly on basement rocks. The con-glomerates range from clast- to sand-matrix-supported,and typically contain clasts of Calcare di base, locallyoccurring as large boulders or blocks, associated withclasts of basement rocks, probably recycled in part fromthe Formazione di San Nicola.

In the Mesoraca area sandstones and conglomerates(fig. 4c) of the lower unit are particularly thick (at least120 m) and show evidence of deposition in a subaerial, allu-vial fan environment. A subdivision is observed here intothree stacked facies sequences characterized by upward-fining trend from conglomerates to sandstones, the lattercommonly displaying planar lamination and medium-scale trough cross bedding with paleoflow towards south-ern sectors. This area show significant differences inthickness and facies associations with respect to thenearby area located WSW of Petilia Policastro, N of Soleoriver, where the lower unit of the formation is remarkablythinner, and consists of alternating coarse to fine sand-stone beds with normal grading, lenticular layers ofrudites with local scoured and loaded base, coarse debritelayers and mudstone interbeds. These features suggestdeposition in a subaqueous setting, by means of turbidityflows, hyperconcentrated flows and debris flows (fig. 4b).

The lower unit is overlain by a thick complex domi-nated by silty and clayey mudstone barren of fossils (orcontaining resedimented, older foraminifer assemblages),locally containing whitish resedimented gypsarenite lay-ers or secondary gypsum, and interbedded in some inter-vals with generally thin and fine-grained sandstone layerslocally showing groove- and locally load-casts at the base,normal grading, planar-lamination, and wave or climbingripples at the top with paleoflow towards N 105°-110°.

Within this fine-grained background lithology, a num-ber of sandstone/conglomerate bodies from 2.5 to 8 mthick and gypsarenite bed packages up to 12 m thick areencased. The former are stratified in medium to thick lay-

ers with thin mud interbeds. Predominantly they showchannelized geometry, with erosional base and upward-thinning and -fining trends from clast-supported con-glomerates or pebbly sandstones to sandstones. Secon-darily they appear as upward-thickening and coarseningfacies sequences. Clasts of conglomerates are sourcedfrom basement rocks and Calcare di base and may show abimodality of roundness, with angular clasts mixed withrounded clasts (probably recycled from older conglomer-ates). Channelized bodies show eastward paleoflow andvariable organization, with evidence of both subaqueousand subaerial depositional environments. Evidence of theformer is given by flute casts, normal grading, clay chips,water escape structures and locally pervasive planar lami-nation with pelitic drapes separating groups of laminae.Evidence of subaerial setting is provided by lateral accre-tion deposits reflecting point-bar migration (e.g., Tim-pone Tenese area), with inclined layers separated by discontinuous mud drapes and displaying either planarlamination or trough cross-bedding with scoured bases.Encasing mudstones locally contain lenticular layers 15-20 cm thick probably representing crevasse splays.Upward-thickening, non-channelized sandstone units,thought to represent mouth-bar units, generally consist ofstructureless beds, and in places show cross-bedded setsat the top, indicating paleoflow towards N105°-110°.

The gypsarenite bed packages consist of thin- tomedium-bedded white to light-grey gypsarenites (fig. 4d),commonly associated with a fine terrigenous fraction(hybrid gypsarenites). They are inferred to derive fromcannibalization at the expense of previous evaporiticdeposits. Layers commonly show planar lamination andclimbing ripple cross-lamination, locally developed abovea graded, massive division. In the Petilia Policastro areagypsarenite bed packages are particularly well representedand are part of cyclical facies sequences a few tens ofmetres thick, including from the base a conglomerate/sandstone unit, a gypsarenite unit and a mudstone unit: acyclicity possibly induced by climatic fluctuations.

The encasing mudstones should have been laid downin a low-energy non-marine basin, with depth sufficientto host subaqueous channelized or non-channelized bod-ies and resedimented gypsarenites, but shallow enough toexperience periodic phases of subaerial exposure, withdevelopment of a network of low-sinuosity channels.

Carvane Group (VAN DIJK, 1990) (Upper Messinian) An erosional and locally (Timpone Tenese, Petilia

Policastro) low-angle angular unconformity bounds at thebase the Carvane Group, which comprises the youngestMessinian units: the Conglomerato delle Carvane and theprobably coeval Cropani conglomerate, the Gigli Forma-tion and Arvano Formation. The group is characterizedby a transgressive trend and is probably correlative of theunit p-ev2 of ROVERI et alii (2008a). It is bounded at thetop by the abrupt contact with the Lower Pliocenehemipelagites.

Conglomerato delle Carvane (RODA, 1964)This unit consists of fluvial conglomerate and sand-

stone, and is mostly developed and best exposed south ofMarcedusa, particularly along the road Botricello-Marce-dusa, whereas it is missing on the western margin of thebasin, except in the Petilia Policastro area. It consists ofclast-supported brownish conglomerates, pebbly sand-


stones and coarse to fine sandstones, with local, thin,lenticular mudstone interbeds and variable degree ofcementation. The stratification is usually distinct, exceptin the case of coarsest and thickest, variably amalga-mated and massive sandstone and pebbly sandstone layers, in places normally graded, possibly laid down bydebris flows. Better organized layers show well developedclast imbrication, and sandstones commonly displaytrough cross-bedding and planar-horizontal or low-anglelamination, locally accompanied by parting lineation.More or less marked scouring is common at the base ofbeds and is expressed by broadly concave-up basal con-tacts. Paleoflow ranges from SSE- to SSW-wards. Clastsrange in size from pebbles to boulders (up to 40 cm indiameter) and are generally well rounded to sub-rounded.Lithologies represented include: granodiorite, tonalite,kinzigites, various types of arenites, among which cal-carenite and quartzarenite, green, white, black and purplechert, yellowish limestone, marble, gneiss and phyllite.The overall trend is usually fining upwards. The upper-most layers transitional to the Gigli Formation locallyshow wave ripple marks.

The Conglomerato delle Carvane is interpreted as therecord of a coarse-bedload and very extensive fluvial sys-tem, probably of braided type.

Cropani conglomerate (named with reference to itsposition S and SSE of the village of Cropani)

Fine-grained almost monogenic alluvial-fan conglom-erates cropping out in a limited area S and SSE of the vil-lage of Cropani unconformably overlie the Calcare di baseand are onlapped by Lower Pliocene mudstones. Theyoccur on the western margin of the Crotone Basin, andare thought to preserve, at least partly, the primary dip.They consist of well-bedded granule and pebble conglom-erate, mostly composed of angular to sub-rounded clastsof phyllitic rocks. It is worth noting that source rocks ofthis type are now missing updip of the deposit.

Gigli Formation (VAN DIJK, 1990)The unit mostly consists of deep-grey to blackish

argillaceous and silty mudstone, sometimes with greenishshading. In some intervals mudstones alternate with thin-bedded (some cm to 10-15 cm), in places medium-bedded(up to 30 cm), fine-grained sandstones, locally involved inslump folds together with associated mudstones, andshowing in places liquefaction pillows. Maximum thick-ness (~65 m) occurs in the Case Faragò area. Local gyp-sum crystals are probably the product of alteration oforiginal sulfides. The mudstones are barren, except forsparse smooth-shelled hypohaline ostracods (Cyprideis)reported by RODA (1964), and reworked foraminifersfrom older formations.

The unit was arguably laid down within «Lago-Mare»fresh-water to brackish, low-energy pools, with episodicdeposition of sands crevassing from nearby fluvial systems.

Arvano Formation (VAN DIJK, 1990)The unit is a sandstone body with thickness ranging

from a few metres to 9-10 metres (maximum thickness inthe Case Faragò area). Due to high lateral persistence, itis a key stratigraphic unit, useful for intrabasinal correla-tions. Two types of internal organization have beenfound, locally passing laterally into one another: anupward coarsening and thickening trend with distinctive

clinoforms, and a channelized geometry. In the formercase, which is the most common, the trend is from silt-stones and fine-grained sandstones to coarse sandstonesand microrudites with granules, sparse pebbles and claychips. In addition of a clinoform-bedded master bedding,the layers show trough cross-bedding with paleoflowtoward ESE, and planar-horizontal lamination. The chan-nelized bodies display sharp and erosional bases, andsimilarly consist of trough cross-bedded and planar-lami-nated sandstone, locally with sparse pebbles. In bothtypes of units thin mud interbeds may occur between thesandstone layers. The transition to the overlying LowerPliocene mudstones is remarkably sharp, with the top-most 10 cm of the bodies usually showing a tight cemen-tation, an ocraceous staining, and sparse small crystals ofsecondary gypsum.

This unit is interpreted as the record of relatively thinGilbert-type deltaic bodies and associated feeding systemof distributary channels. The limited thickness of the cli-noform-bedded deltaic bodies is an indirect proof of theshallow depth of the receiving Gigli «Lago Mare» basin.The sharpness of the contact with the Lower Pliocenemudstones and abrupt facies change fits well the knowncharacteristics of the Pliocene transgression in theMediterranean.

THE PLIO-PLEISTOCENE STRATIGRAPHY: GENERAL ASPECTS

AND FORMERLY IDENTIFIED UNITS

In the northern part of the Crotone Basin RODA

(1964) subdivided the Pliocene and lower Pleistocene succession into the Lower Pliocene Marna argillosa deiCavalieri, the shallow-marine Molassa di Zinga (also ofinferred Early Pliocene age), the transgressive Middle(?)Pliocene lagoonal to shoreface backstepping complexincluding the Argilla marnosa di Spartizzo and theMolassa di Scandale (Spartizzo-Scandale complex), andthe Upper Pliocene to Lower Pleistocene hemipelagicArgilla marnosa di Cutro (AMC for brevity). A major, erosional unconformity, locally accompanied by angulardiscordance, was recognized by RODA (1964) between theMolassa di Zinga and the Spartizzo-Scandale complex.The latter represents the lower part of RODA’s (1964) thirdtectono-stratigraphic cycle and developed in a regime ofextensional tectonics (MELLERE et alii, 2005). The lowertransgressive part of AMC was interpreted by RODA

(1964) to develop laterally offshore with respect to theSpartizzo/Scandale complex. In the northern sector of theCrotone basin the AMC includes in the lower part, abovea first hemipelagic unit, a prominent, shallow-water sand-stone body. These two units were formerly distinguishedby OGNIBEN (1955) as Argilla marnosa di Timpa Biso(AMTB for brevity) and respectively Arenaria di Strongoli(AS), and considered by him as parts of a Pliocene tran-gressive-regressive cycle. The overlying pelitic unit, calledby him Argilla di Gigliolo (AG) was considered the localrecord of the «Calabrian transgression» of GIGNOUX

(1913), RUGGERI & SELLI (1948) and SELLI (1949), asupra-regional event identified in several localities of theItalian peninsula, and regarded as marking the onset of amajor Pleistocene sedimentary cycle. A different subdivi-sion was adopted by RODA (1964) who considered theAMTB and AG of OGNIBEN (1955) as belonging to theAMC, and regarded the AS as only one of the many sand-stone bodies intercalated within the AMC. CAPRARO et alii


(2006) dated the AMTB to the D. Tamalis and partly D.pentaradiatus Zones, the AS to the D. pentaradiatus Zoneand the AG to the lower part of the D. brouweri Zone.

Shallow-water units like the Molassa di Zinga, theSpartizzo-Scandale complex and the Strongoli Sandstoneare typical of the northern marginal part of the CrotoneBasin (RODA, 1964). In the southern part of the basin theygrade into a deeper-water, lithologically more uniformsuccession, predominantly made up of slope mudstonescontaining a number of resedimented sandstone bodies.Here the pelite-dominated succession spans the wholetime interval from the Early Pliocene to the Early Plei -stocene, and locally includes also part of the Middle Plei -stocene. Despite the greater facies uniformity, a LowerPliocene unit (corresponding to the RODA’s 1964 MarnaArgillosa dei Cavalieri) can be separated in this areafrom the younger part of the succession, as will bedetailed below. The unconformity separating the Molassadi Zinga from the Spartizzo-Scandale complex in thenorthern part of the Crotone Basin pass SSE-wards, i.e.,basinwards, into a correlative conformity. The Middle-Upper Pliocene part of the succession was subdivided by EMILIANI et alii (1961) into a lower part rich in dia -tomaceous bands, named Formazione tripolacea, and anupper pelite-dominated portion, named Formazione diPapanice.

In the upper part of the AMC cropping out in the SanMauro Marchesato area RIO et alii (1996) could identifyan unconformity marked by a gap encompassing theuppermost part of the «large» Gephyrocapsa and thelower part of the «small» Gephyrocapsa Zones. Even thisunconformity grades SSE-wards, i.e., basinwards, into acorrelative conformity.

THE PLIO-PLEISTOCENE STRATIGRAPHY: A REVISION

Marna argillosa dei Cavalieri (RODA, 1964) (Zanclean,upper MPL1 to lower MPL3)

Lower Pliocene outer-shelf to slope pelitic deposits ofthis formation abruptly cover the Lago Mare deposits.The unit is particularly represented in the south-westerncorner of the investigated area, and consists of hemi -pelagic bluish-grey marl and mudstone, commonly mas-sive, very rich in foraminifers and calcareous nanno-plankton, and very poor in macrofossils. A banding islocally present, due to lighter more limy bands alternat-ing with darker more siliciclastic bands. Where this unitcrops out in stratigraphic contact above Messiniandeposits, as in the Cropani area, it shows onlap relation-ships at the base. Elsewhere, it accumulates within tec-tonically-controlled depocentres (see below), or forms a paleovalley infill, as in the western marginal area, at the foot of the Sila Piccola massif, south of the village of Belcastro.

Timpone Arciere sandstone (named with reference to apeak located in the south-eastern part of the study area)(Zanclean)

A lenticular body of resedimented, sparsely bioclasticsandstone, encased in a deep-water succession of alter-nating mudstones and thin-bedded sandstones of the G.margaritae Zone, crops out in the Timpone Arciere area.The body is sharp-based and consists of thick, normallygraded and commonly amalgamated beds of medium-fineto coarse, locally granule-bearing sandstones containing

variable amounts of clay chips and rounded skeletal frag-ments, especially of oysters and pectinids, and interbed-ded with sparse, thin muddy layers. In the uppermostpart it passes transitionally into the overlying mudstonesby means of an upward-thinning sand/mud alternation.The bioclastic content suggests resedimentation from anearby platform where the bioclasts could be rounded bywave-working in a littoral zone. Parting lineation indi-cates NW-SE paleoflow.

Timpone Giudei flysch (named with reference to apeak located SSE of Belcastro) (Zanclean, upper MPL2and lower MPL3)

This unit comprises flyschoid deposits partly hete ropicwith the Marna argillosa dei Cavalieri, consisting of analternation of bluish-grey and grey argillaceous mudstonesand fine- to medium-grained sandstone layers, usuallythin- to medium-bedded, with occasional thicker sand-stone beds (up to 1m). Sandstone layers are Bouma Tb-esequences, or Ta-e in thicker beds. Bioturbation is scantyand macrofossils are generally missing. Parting lineationand climbing ripples indicate paleoflow towards SSE.

Molassa di Zinga (OGNIBEN, 1955) (Lower Pliocene?)This unit crops out only in the north-eastern corner of

the mapped area. It is a thick and monotonous successionof massive to planar-laminated, or trough cross-bedded,shoreface to delta-front sandstones, with pebbles occur-ring sparsely or as rows, and common sedimentologicalfossil concentrations (generally pectinids, thick-shelledoysters and barnacles) occurring as discrete layers orpavements emplaced by storm-induced flows.

The Spartizzo-Scandale complex (Middle Pliocene?)This is an onlapping transgressive complex particu-

larly developed in the northern part of the Crotone Basinand consisting of a stack of lagoonal (locally fluviatile) toshoreface (Argilla marnosa di Spartizzo and Molassa diScandale) backstepping parasequences, lying on theMolassa di Zinga by means of a major erosional andlocally angular unconformity.

Argilla marnosa di Spartizzo (OGNIBEN, 1955)The unit mainly consists of greenish-grey mudstone,

locally rich in Cerastoderma glaucum, a typical dweller oflagoonal environments.

Molassa di Scandale (OGNIBEN, 1955)This unit mainly consists of shoreface sandstone, gen-

erally rich in shell pavements and layers (pectinids, thick-shelled oysters, turritellids, Glycymeris).

In the northernmost part of the mapped area, the con-tacts between the Molassa di Zinga and the Argillamarnosa di Spartizzo are tectonic. Along the western sideof the Tacina river the Argilla marnosa di Spartizzo andthe Molassa di Scandale, locally associated with thin fluvia -tile conglomerates, appear interbedded in a way similar tothat occurring in the northern part of the Crotone Basin.

Argilla marnosa di Cutro (RODA, 1964) (UppermostZanclean-middle Pleistocene: upper MPL3 – uppermostMNN19f or MNN20)

Dominant lithologies are pelitic, including hemipelagicbluish-grey and grey marls, marly clays, silty siliceous


mudstones and siltstones, with rich assemblages of cal-careous nannofossils and foraminifers. Some intervalsconsist of generally thin-bedded, sand/mud couplets. In theinvestigated area the succession displays an overall regres-sive trend from slope to mid-shelf deposits. The macro-fauna is very sparse in the Upper Pliocene mudstones andbecomes locally rich in the Lower Pleistocene mudstones.Slope to outer-shelf hemipelagites contain Nassarius gr.semistriatus, Funiculina quadrangularis, Isidella, Delec-topecten vitreus, Dentalium agile, Aporrhais huttingeriana,Phycis blennoides, Coryphaenoides rupestris. Mid-shelfmudstones contain Parvicardium minimum, Ditrupa arie -tina, Nassarius limatus, Neopycnodonte cochlear, Bathyarcapectunculoides, Xenophora crispa, Chlamys opercularis,Pseudamussium septemradiatum, Turritella communis,Abra nitida, and reteporiform bryozoans.

Minor lithologies occurring encased within peliticdeposits are: clusters of diatomaceous laminites inter -bedded with hemipelagic muds in the D. tamalis Zoneand D. brouweri-productus Zones; resedimented sand-stone-conglomerate bodies encased in uppermost Gela -sian to Lower Pleistocene hemipelagite; sapropel-likelaminites, commonly grouped into clusters (Lower Plei -stocene); olistoliths of biocalcarenite and biocalciruditewith a rich, shallow-water fauna and abundant rhodo -liths, embedded in MIS 24-22 hemipelagite (Marcuccioarea, NNE of Petrogallo section); ash layers and metano -genic carbonates. The latter are particularly associatedwith the Piacenzian to Gelasian siliceous and diatoma-ceous lithologies but also occur sporadically in theLower Pleistocene succession.

In the following the stratigraphic succession of theArgilla marnosa di Cutro (AMC for brevity) is describedfrom the base upwards.

The lower part of the AMC, rich in clusters of diatoma-ceous bands, corresponds to the «Formazione tripolacea»of EMILIANI et alii (1961). Two characteristic intervalscan be distinguished, a siliceous (A) and a diatomaceous(B) interval.

(A) A major change in the sedimentation regimeoccurs above the Marna argillosa dei Cavalieri and itspartly heteropic Timpone Giudei flysch. The change isparticularly striking where the blue-grey hemipelagites ofthe Marna argillosa dei Cavalieri, with a mean sedimenta-tion rate of about 110÷150 m/Myr (as inferred from theintegrated calcareous plankton biostratigraphy), are over-lain by silty and siliceous marls recording a significantincrease in the terrigenous fraction, remarkably highermean sedimentation rate (about 500÷600m/Myr), andappearance of a distinctive siliceous component (spongespicules and sometimes radiolaria and diatoms), suggest-ing relatively high productivity. Such change occurred inthe upper part of the MPL4a Zone, after the HighestOccurrence (HO) of Sphenolithus spp. (3.70 Ma) andbefore the D. pentaradiatus paracme end (3.61 Ma) (CON-SOLARO, 2004). The siliceous interval covers the time spanfrom ca. 3.6 Ma to ca. 3.35 Ma, and is characterized byfaintly and irregularly laminated silty marls and siliceousmarls, locally with sandstone interbeds. A striking featureis the appearance of a siliceous sedimentation in the Cro-tone Basin well before the time of the Mediterraneanrhythmic sedimentation pattern characterized by diatoma-ceous (or sapropelitic) laminated layers, which typicallybegins at 3.2-3.1 Ma.

(B) The following interval is characterized by develop-ment of thinly and regularly laminated diatomites occur-ring in distinctive packages. The first diatomaceous lam-ina-set (5-6 m thick) appears in the lower part of theMPL4b Zone, before the G. bononiensis LO (3.31 Ma),and is followed by several other, well laminated, com-monly clustered diatomaceous packages, locally severalmetres thick and in places affected by slumping, occur-ring in the D. tamalis Zone, less commonly in the D. pen-taradiatus and lower D. brouweri Zones, and particularlyin the upper part of D. brouweri Zone (fig. 5a) and in theD. productus Zone.

The background sedimentation of the diatomite-bear-ing interval is represented by a siliciclastic slope succes-sion consisting of alternating bed packages consisting


Fig. 5 - a) Diatomite (D. brouweri Zone, NW of Timpone Inferno); b) section of sub-cyclindrical body of inferred metanogenic carbonate withaxial pipe (D. brouweri Zone, NW of Timpone Inferno) (hoe 80 cm long for scale). – a) Diatomite (Zona a D. brouweri, località a NW di Timpone Inferno); b) sezione trasversale di una massa subcilindrica di carbonato metanogenico con condotto assiale (Zona a D. brouweri, località a NW di Timpone Inferno). La zappa è lunga 80 cm.

either of mudstones/marls or thin- to medium-beddedturbiditic sand-mud couplets, locally accompanied by afew small channelized bodies of massive sand. The inter-val includes a few coquinoid sand layers up to 1 m thick,useful as potential marker beds, containing vegetal debrisand a rich, platform-sourced resedimented fauna of mol-luscs, brachiopods and echinoids.

Metanogenic carbonates, locally accompanied by amonotonous bivalve fauna are particularly associatedwith both siliceous and diatomaceous units, and mayappear as sub-cyclindrical bodies (diameter from a fewdm to 1.7 m) locally showing an axial pipe a few cm indiameter (interpreted as the conduit of gas venting) (fig.5b), or as irregular, sometimes nodular masses severaldecimetres wide, or stratiform bodies with generally lim-ited lateral extent. Locally they preserve a regular lamina-tion reminiscent of that of the associated diatomaceouslayers or show a stromatolite-like lamination.

The upper part of the AMC corresponds to the «For-mazione di Papanice» of EMILIANI et alii (1961). A subdi-vision into two intervals is adopted in the description (notin the enclosed geological map), with a boundary at aboutthe transition from the «large» Gephyrocapsa Zone to«small» Gephyrocapsa Zone. The separation is justified bythe presence of an unconformity, recognized in the mar-ginal part of the basin (San Mauro area), implying a gapwhich encompasses the uppermost part of the «large»Gephyrocapsa Zone and the lower part of the «small»Gephyrocapsa Zone. The discontinuity marks in this areaa sharp bathymetric change from upper slope/outermost-shelf muds (Cutro 1 of RIO et alii, 1996) to a series of mid-to inner-shelf cyclothems of the «small» GephyrocapsaZone (Cutro 2 of RIO et alii, 1996), and locally appears asangular unconformity with respect to a gently deformedsubstrate. In the SSE-ward direction, i.e., basinwards, theunconformity passes into a correlative conformity. As willbe detailed later, this boundary is thought to mark an

important change in the structural setting of the CrotoneBasin, leading to the confinement of the younger part ofthe succession into four structurally-controlled depocen-tres, interpreted as pull-apart sub-basins, which are theForesta, San Mauro, Troiani and Marcedusa sub-basins(see fig. 11 for their location).

(A) The lower interval shows a clear differentiation ofthe Lower Pleistocene stratigraphy, particularly concerningthickness of the deposits and style of sedimentation, intothree sectors separated by inferred growth faults (fig. 6).Actually, it cannot be excluded that the differentiationalready initiated in Late Pliocene times, although avail-able data do not allow to attain a certain conclusion onthis point.

Sector 1, bounded to the east by the NNW-trendingMarcedusa-Steccato Fault and to the north by the NW-trending San Antonio Fault, shows a spectacularlyexpanded stratigraphical succession containing a numberof turbidite sandstone bodies and recurrent laminatedsapropel-like layers.

Sector 2, located in the Timpone Serrano area, andbounded to the south by the San Antonio Fault, and tothe east by the approximately N-trending Casella MonacaFault, shows a stratigraphy similar to that of sector 1, yetwith significantly lower overall thickness.

Sector 3, located in the Colle Erbebianche area, NE ofthe San Antonio Fault, is dominated by hemipelagic mud-stones, with the least overall thickness and remarkablylower number of sapropel-like laminites with respect tothe adjacent Sector 1. It is therefore characterized byremarkably condensed stratigraphy.

Sector 1 accommodates the thickest succession(around 450 m in the C. macintyrei, H. sellii, and «large»Gephyrocapsa Zones; 360 m from the base of the H. selliiZone), including a number of sandstone bodies, clustersof sapropel-like laminated layers, and a few resedi-mented, locally pebbly, coquinoid layers. With respect to


Fig. 6 - Spatial and structural relationshipsbetween three sectors differentiated in theEarly Pleistocene, and schematic respectivestratigraphy.– Relazioni spaziali e strutturali fra i tre settoridifferenziatisi nel Pleistocene Inferiore, con in -dicazione schematica delle rispettive stratigrafie.

adjacent areas this sector clearly behaved as a structurallow, subject to significantly higher subsidence and sedi-mentation rates.

Among the sandstone bodies occurring in this sector,the oldest, i.e., the Timpone Baronello body, is encased inmudstones ranging in age from the D. productus Zone (lat-est Gelasian) to the macintyrei Zone, whereas the youngerbodies are contained in mudstones of the H. sellii and«large» Gephyrocapsa Zones. The sandstone bodies showlimited lateral persistence, rapid facies changes normal tothe paleoflow direction, and paleocurrent data indicatingsouth-easterly flows, with directions ranging from N170° toN135°. Pinching out in direction normal to paleoflow is

accompanied by fraying of massive amalgamated sandsinto packages of turbidite couplets with progressivelydecreasing sand/mud ratio, and eventually into a fringe ofthin-bedded turbidites. The sandstone bodies are unchan-nelized in the lower part of the succession and apparentlychannelized in the upper part. This change in geometrymay reflect slope progradation, with turbidite lobes spread-ing out onto a low-gradient seafloor, passing upwards toslope channels. Given the overall slope setting, an emplace-ment of sandstone bodies in intra-slope basins created bythe synsedimentary tectonics cannot be excluded. The Tim-pone Baronello body, which is the oldest in the local suc-cession, was studied in higher detail (fig. 7). It consists of


Fig. 7 - Stratigraphic and sedimentologic log of Timpone Baronello section.– Colonna stratigrafico-sedimentologica della sezione di Timpone Baronello.

three cycles thickening and coarsening upwards fromthin- to medium-bedded turbidite sand-mud couplets tothicker, massive and amalgamated, commonly erosion-ally-based sand or conglomerate beds. The sand layerslocally contain plant debris and fragmented or wholeshells of inner-shelf to littoral molluscs (ostreids, pec-tinids), indicating resedimentation from shallow-waterareas. Each of the three observed CU cycles are underlainby packages consisting of a regular, rhythmic alternationof very thin silty and clayey laminae devoid of bioturba-tion, with a quasi-varved appearance, commonly showingslump-induced folds. In the lower two laminated pack-ages the foraminiferal assemblages indicate a poorly oxy-genated environment, sub-oxic in the lower package andstrongly disoxic in the upper one, which may be regardedas a sapropel-like horizon.

Sector 2 shows stratigraphic organization and faciesassociations comparable to those of the Sector 1, with asimilar number of sandstone bodies encased within slopemudstones (fig. 6). However, both the overall succession(about 200 m from the base of the H. sellii Zone to the topof the «large» Gephyrocapsa zone) and the individual sand-stone bodies are thinner. Similarly to Sector 1, the succes-sive bodies show an upward change from unchannelized(Timpone Serrano body) to channelized organization.

Sector 3 shows strikingly different stratigraphy, faciesand sedimentation pattern when compared to the adja-cent ones (fig. 6), as it consists exclusively of a highly con-densed succession of hemipelagic muds very poor insapropel-like laminites and devoid of resedimented sandbodies. The overall thickness of the deposits in the inter-val of C. macintyrei to «large» Gephyrocapsa Zone isaround 110 m (75 m from the base of the H. sellii Zone).These characteristics indicate that sector 3 acted as struc-tural high during the sedimentation, subject to muchlower subsidence rate than the adjacent sectors.

(B) The upper interval spans the uppermost LowerPleistocene and lower Middle Pleistocene part of theAMC. The chronology is well constrained in the Marce-dusa and San Mauro sub-basins, being based on d18O andmagneto-biostratigraphic data (RIO et alii, 1996; CAPRAROet alii, 2005; CAPRARO et alii, in press), whereas in theother two sub-basins (Foresta and Troiani sub-basins) itis essentially based on the sole nannoplankton biostrati -graphy (fig. 8).

The upper part of the AMC in the Marcedusa sub-basin has been analysed with particular detail in the largeand well exposed Petrogallo section, located SSE of thevillage of Marcedusa. The succession (fig. 8), particularlythick, shows a progressive trend shallowing upwardsfrom slope to shelf settings. A complete oxygen isotopestratigraphy for benthic and planktonic foraminifera(CAPRARO et alii, in press) reveals a distinct repetition ofisotopic fluctuations, which we interpret as glacial-inter-glacial cycles in gross agreement with the standard d18Oreference records. Environmental changes are also sug-gested by lithologic changes, with more silty, thickerintervals, corresponding to the glacial periods, alternatingwith thinner packages of bluish-grey marls correspondingto the interglacials. In this section the time span from lateMIS 26 to MIS 22 is documented in hemipelagic slopemudstones (fig. 8) by means of d18O and biomagne-

tostratigraphy. The uppermost part of this interval iscrossed by a reddish, bioclastic key layer, consisting ofrhodoliths, debris of shallow-water molluscs and smallquartz and granite pebbles (rhodolithic layer in fig. 8).This bed can be traced laterally into two large, stratifiedolistoliths (5.5 m and respectively 2.5 m thick) of thesame composition, locally showing slump folds. Deposi-tion of the bioclastic layer is interpreted as an event oflateral dispersal accompanying the emplacement of olis-toliths, which in turn may reflect the collapse of a shelfmargin. Emplacement during a lowstand episode correla-tive of MIS 22 is supported by «heavy» d18O values andmagnetostratigraphic data documented in the encasingmudstones (fig. 8).

Fine-grained slope sedimentation persisted up to anupward-shallowing silty package with sparse Arcticainterpreted to represent a shelf-edge lowstand unitemplaced during a glacial stage, as supported by «heavy»d18O values. This package contains in the upper part awhitish ash layer, 10-15 cm thick (MIRANDOLA MINUZZI,1996) (fig. 8), which can be correlated, on the basis ofgeochemical characteristics, with the Parmenide ash, akey layer first identified in the San Mauro sub-basin (seebelow), where it occurs within transgressive lagoonalmuds of the Lamone formation.

This segment is followed by an outer-shelf, muddyinterval indicating a very prominent interglacial stage(CAPRARO et alii, in press), for which two options are pos-sible, MIS 11 or MIS 15, based on the HO of Pseudoemi -liania lacunosa and extremely «light» d18Oplanktonic values,or respectively the occurrence of a short, albeit signifi-cant, spike of Gephyrocapsa sp. 3 (CAPRARO et alii, inpress). Illustration of the arguments concerning the com-parison of the two age models is out of the scope of thisarticle, as they are exhaustively treated in CAPRARO et alii(in press). These authors conclude that, in the light ofavailable information, the first age attribution is lessproblematic, being in better agreement with the underly-ing stratigraphic record and supported by larger points ofevidence. We will therefore follow this choice.

The uppermost part of the AMC in the Petrogallo sec-tion above this interval shows a definite shallowing trend,being recorded by a ca. 60 m thick package of south-east-erly dipping low-angle clinobeds mainly consisting ofmuds and coarse silts with common plant debris andplenty of Turritella and Arctica, suggesting a distal delta-front facies association linked to a south-easterly pro-grading delta system. The d18O record in this unit shows ashift towards extreme glacial conditions (CAPRARO et alii,in press), which are consistent with MIS 10.

It is worth noting that in the San Mauro, Foresta andTroiani sub-basins the upper part of the AMC, i.e., thatoccurring below the first shallow-water deposits, is signif-icantly older. A sharp facies change above the silty mud-stones of the «small» Gephyrocapsa Zone is marked by theappearance of a hybrid biocalcarenite/biocalcirudite unit(Timpone San Litano formation, see below) correlatedwith the glacial MIS 24-22 (RIO et alii, 1996). In the SanMauro sub-basin this formation wedges out basinwards,so that an overlying package of outer- to mid-shelf mud-stones, attributed to MIS 21 and 19, is formationallyincorporated in the AMC. This package straddles theBrunhes/Matuyama magnetic reversal, which almostcoincides here with an important key bed, the «PitagoraAsh» (RIO et alii, 1996; CAPRARO et alii, 2005).


Molassa di San Mauro group (Molassa di San Mauro,RODA, 1964) (uppermost Lower Pleistocene-Middle Plei -stocene).

RODA (1964) named «Molassa di San Mauro» a sand-prone formation representing the younger, regressive partof the Cotone Basin fill. Given its compound internalarchitecture, with subdivision into a number of sub-units,a rank of group has been attributed to this unit. We pro-pose two informal formations: the Timpone San Litano

formation and the Lamone formation, as components ofthe group.

Timpone San Litano formation (named with referenceto a peak in the south-western part of the San Mauro sub-basin) (MIS 24-22 in San Mauro sub-basin; MIS 24-22? inTroiani and Foresta sub-basins) (fig. 9a).

This formation is a prograding, clinoform-beddedshoreface wedge consisting of richly fossiliferous hybrid


Fig. 8 - Correlation between representative logs of the youngest stratigraphic successions of San Mauro, Foresta, Troiani and Marcedusa sub-basins.– Correlazione tra colonne stratigrafiche rappresentative delle successioni più recenti affioranti nei sotto-bacini di Marcedusa, San Mauro, Troianie Foresta.

biocalcarenite/biocalcirudite with Arctica islandica, andsubordinately Scolicia-bearing fine siliciclastic sands. Itlocally appears as slump scar infill. The carbonate andsandy lithologies may occur on different scales, either asalternating, interbedded layers, or as clinoform-beddedsedimentary bodies following one another, even repeat-edly, in the direction of progradation, and dominatednow by carbonate, now by siliciclastic deposits (SanMauro, Troiani and Foresta sub-basins, and area locatedSW of Rocca Bernarda).

The formation overlies, with very rapid transition, orsharp contact, shelf mudstones of the upper part of the«small» Gephyrocapsa Zone dated to MIS 25 in the SanMauro sub-basin (RIO et alii, 1996). It records the firstmassive incoming of cold-water mollusc Arctica islandica,and consists of an upward coarsening progradationalwedge up to 45 m thick, with well developed basinwarddipping clinoforms. The facies change can be correlatedwith the beginning of long-lasting, severe glaciation asso-ciated with the MIS 24-22 interval (RIO et alii, 1996), and,where abrupt, indicates forced regression. The uppermostpart of the clinoform-bedded wedges locally consists of siliciclastic pebble/cobble conglomerates with clastssourced from the nearby Sila Piccola massif (e.g., Tim-pone San Litano section in the San Mauro sub-basin).The bioclastic content consists of commonly abradedmolluscan shells, bryozoans, serpulids, echinoid frag-ments, branches of corallines and rhodoliths, in a matrixof comminuted bio-debris.

These prograding bodies of carbonate or mixed com-position, with clinoforms dipping consistently offshore,are thought to be generated in a wave- and storm-domi-nated setting characterized by high accumulation rate,due to active basinward transport of skeletal material bystorm-driven downwelling flows (MASSARI et alii, 1999).The purely siliciclastic bodies locally show the character-istic features of a delta-front setting, particularly in the

Troiani sub-basin, where a conspicuous sand body up to55 m thick, well exposed in a section located NE of Tim-pone Cocuzzito, along the Fiumara di Mesoraca, showsan upward-coarsening and thickening trend from a thin-bedded alternation of sands and blackish laminated mudsassociated with slump scars to increasingly thicker andeventually amalgamated sand layers containing Arcticaislandica. This vertical trend may be interpreted as therecord of a deltaic progradation with transition fromprodelta thin-bedded turbidites or hyperpycnites, to delta-front sands. Local clinoforms (along Fosso Canalette)indicate SE-ward progradation.

Spectacular growth strata can be documented in theSan Mauro and Troiani sub-basin fills. Growth faultingalong the Fuscaldo Fault, bounding to the west the SanMauro sub-basin is particularly documented in theForesta locality NW of village of S. Mauro Marchesato,where a significant thickening of the Timpone SanLitano formation near the fault is accompanied by thepresence of large blocks and slabs of the Molassa diZinga up to 90 cm long, included in the bioclastic facies,suggesting repeated failure of the fault scarp forming asea cliff.

Lamone formation (named with reference to a local-ity east of the village of San Mauro Marchesato) (MiddlePleistocene). This unit consists of transgressive-regres-sive cyclothems which make up the youngest part of thesub-basin fills (fig. 8). The dominant facies consists ofinner-shelf to shoreface sand/sandstone with pectinidsand Glycymeris violacescens; subordinate facies are flu-vial gravel, lagoonal mud with Cerastoderma glaucum,and inner- to middle-shelf mud with Neopycnodontecochlear, Turritella communis, Isocardia cor, Acanthocar-dia echinata, Nucula sulcata, Venus multilamella, Pseuda -mussium septemradiatum, Ditrupa arietina and cellepori-form bryozoans.


Fig 9 - a) Calcarenite-sandstone wedge of Timpone San Litano formation S of the village of San Mauro Marchesato. Section is oblique to de -positional dip of clinoforms; height of the wall is about 30 m; b) prominent coarse-grained and tightly cemented transgressive deposits (at the top) unconformably lying by means of a ravinement surface on regressive shoreface sands of an underlying cyclothem, showing planar- horizontal lamination, swaley cross stratification and local trough cross bedding. Northern periphery of the village of San Mauro Marchesato.– a) Cuneo calcarenitico-arenaceo della formazione di Timpone San Litano affiorante a sud del villaggio di San Mauro Marchesato. La sezione è obliqua rispetto all’immersione dei clinoformi; l’altezza della parete è di circa 30 m; b) depositi trasgressivi grossolani e tenacemente cementatidelimitati alla base da una superficie di ravinement ricoprono sabbie regressive di shoreface con laminazione planare-orizzontale, stratificazioneincrociata swaley e localmente concava. Periferia settentrionale del villaggio di San Mauro Marchesato.

Cyclothems in the lower part of the formation aredominated by more or less bioclastic, prograding, storm-dominated sandstones with common swaley cross stra -tification, overlying, with commonly sharp contact, agenerally thin, transgressive to maximum-flooding shelf-mudstone unit. In the upper part of the formationthe cyclothems tend to incorporate upward-increasingamounts of marginal-marine and continental deposits(RIO et alii, 1996; MASSARI et alii, 1999, 2002, 2007) (fig. 8). Here, they typically consist of the following verti-cal sequence of terms: i) unconformably- and erosion-ally-based unit of braided-stream gravel ii) lagoonalmud; iii) transgressive sheet-like unit of sandstone orbiocalcarenite/biocalcarenite bounded at the base by aravinement surface (fig. 9b); iv) locally occurring band ofshelf mud; v) prograding sand body, commonly sharp-based due to forced regression. Details of the internalorganization and inferred correlations for the Marcedusasub-basin are shown in fig. 10.

Two transgressive horizons are particularly prominentand characteristic in the Lamone formation and are sin-gled out as members: the Dardani mud and the Valle delRe calcarenite. The former, cropping out in the Marcedusaarea, is an inner-shelf mudstone unit, particularly rich inTurritella shells, whereas the latter, cropping out in the San

Mauro sub-basin, is an almost pure skeletal grainstone andfine-grained rudstone, very rich in bryozoan remains.

Firm chronological constraints are lacking, except forthe tie points at the base of the formation. They highlighta strong diachroneity of the oldest terms of the forma-tion. In fact, in the Marcedusa sub-basin (figs. 8 and 10)the substrate of the formation is represented by deltaicsiltstones (included in the AMC as its youngest term) ten-tatively attributed to MIS 10 in the Petrogallo section.Conversely, in the San Mauro sub-basin the substrate ofthe formation is represented by MIS 19 mudstones (RIO

et alii, 1996; CAPRARO et alii, 2005). The diachroneity iseven larger if reference is made to the first appearance ofshallow-water deposits, represented in the northern partof the investigated area by the San Litano formation,dated to MIS 24-22, and in the southern part by the oldestterms of the Lamone formation, lying, as above noted, oninferred MIS 10 siltstones.

Based on the age of the substrate, and on the count ofcyclothems, the youngest terms of the Lamone formationare tentatively attributed to MIS 9-8 times.

Growth faulting and folding, including rollover alti-clines, affect the entire succession and point to continu-ous deformation in an extensional-transtensional regime(see below for details).


Fig. 10 - Stratigraphic relationships and sedimentologic features of representative sections of the most recent cyclothemic part of the Pleistocene succession within the Marcedusa sub-basin and the southernmost part of Troiani sub-basin.– Relazioni stratigrafiche e caratteristiche sedimentologiche di sezioni rappresentative dei ciclotemi presenti nella parte più recente della successione Pleistocenica nel sotto-bacino di Marcedusa e nella parte più meridionale del sotto-bacino di Troiani.

Fluvial terraces

Terraced fluvial sand and gravel, partly infilling incisedvalleys, grade upslope into progressively higher-gradientpediments developed at the foot of the Sila Piccola massif.

Interstratified pebble/cobble gravels and sands of flu-vial terraces in most cases display sheet-like geometry.Terrace altitude ranges from 230 m above sea level in theinternal areas, to 130 m in the coastal belt. The depositsare usually a few metres thick; in places, however (e.g.,Timpone dell’Inferno and Timpone Cerchione areas) theycut into the substrate, attaining a higher thickness (up to35-40 m) and appear as remnants of infills of broad pale-ovalleys, particularly linked to the axis of major fluvialcourses such as that of the Tacina system.

The deposits are well organized, moderately sorted,and may have been laid down by a high-gradient braidedriver system with coarse bedload. The composition isdominated by intrusive igneous rocks largely representedin the Sila Piccola massif. In the coastal belt the depositsare locally overlain by littoral (lagoonal and shoreface)deposits ascribed to MIS 5e. Therefore, the incised valley-fills are tentatively attributed to the late MIS 6 and theupper, sheet-like deposits to the transition from MIS 6 toMIS 5e. Deposits occurring upslope, at the foot of the SilaPiccola massif, might be locally older.

Marine terraces

Fossiliferous shoreface and foreshore yellow sands andgravels, locally underlain by grey-greenish lagoonal mudsby means of a ravinement surface, form the bulk of thesedimentary cover of marine terraces attributed to MIS 5e.

Madama Lucrezia breccia

This unit consists of chaotic breccias with a matrix ofyellowish, sometimes vacuolar, calcareous and gypsifer-ous siltstone. The breccia typically forms elongate, lentic-ular bodies along major NW-trending faults. Clasts arepresent in a very large range of sizes, from small frag-ments to blocks several metres across. The breccia con-tains mostly gypsum, as massive or crystalline facies or asgypsum breccia, and clasts of laminated gypsarenites andvacuolar limestones of the Calcare di base. Minor compo-nents consist of basement rocks, sandstones and con-glomerates with rounded basement clasts of the For-mazione di San Nicola, sandstones, conglomerates andmudstones of the Petilia Policastro formation. Slabs ofupper Messinian interstratified sandstones and mud-stones are affected in places by randomly oriented folds(Case Palazzo locality, S of Petrogallo), with folded sand-stone layers displaying joints or small faults, which indi-cate their competence during the deformation. Finer-grained breccias of gypsum and Calcare di base locallyoccur as infill of subvertical dykes several dm wide withinthe coarser-grained breccia.

These chaotic breccias are interpreted as tectonicbreccias resulting from diapiric extrusion, especially alongrestraining bends of the major NW-trending strike-slipfaults.

GEOLOGIC EVOLUTION

In the analysis of the successive steps of the geologicevolution, a reference is frequently made to the whole

Crotone Basin, in order to present a more complete pic-ture of the forearc history. This is justified by the fact thestudy area comprises the geologically most significantpart of the southern, more basinal part of the CrotoneBasin, whereas the geology of the northern, marginal partof the basin is known from the literature, particularly thepaper by RODA (1964), still valid in its main lines, and therecent papers by ZECCHIN et alii (2003, 2004a, 2004b) andMELLERE et alii (2005).

LATE SERRAVALLIAN (?)-TORTONIAN EVENTS

The opening of the Crotone basin is dated to the Tor-tonian, or, possibly late Serravallian, probably in con-comitance with the onset of extension in the southernTyrrhenian Sea and peri-Tyrrhenian basins, as suggestedby BONARDI et alii (2001) and MATTEI et alii (2002).

Similarly to other forearc basins, the Crotone Basin,at its initial opening, was shallow, with coarse-grainedbasal deposits (the alluvial fan and coarse fluvial depositsof the Formazione di San Nicola) recording the creationof a rugged relief and intense denudation in the sourcearea. In our opinion this event can be recognised in theapatite fission track data concerning the timing ofexhumation of the Calabria basement rocks obtained byTHOMSON (1994). These data in fact evidence two groupsof results, one centered at about 25-30 Ma, probablyrelated to the Oligocene extension-related collapse andexhumation of the Calabria basement (ROSSETTI et alii,2004), the other at about 15-12 Ma, which could corre-spond to uplift and exhumation, connected with theextension related to the onset of the Tyrrhenian basinopening. Extensional synsedimentary tectonics in north-ern Calabria (Crati and Crotone basins) at this time wasalso emphasized by TORTORICI (1981), who pointed outthe effects of synsedimentary differential subsidence withrapid and impressive thickness changes of the sedimen-tary successions and thick coarse-grained deposits liningfault scarps and rapidly passing laterally into basinalmudstones.

MESSINIAN EVENTS

The Messinian of the Crotone Basin is characterizedby the highest accumulation rates of the whole Late Neo-gene-Quaternary, interaction of severe sea-level changeswith high tectonic mobility, and alternating pulses of subsidence and uplift (VAN DIJK et alii, 1998).

The Calcare di base, up to some tens of metres thick,is only represented in the marginal part of the basin, andlocally lies with low-angle erosional unconformity on abasinward tilted substrate of variable age. Most prominentin the Messinian succession are two unconformities whichbound the Petilia Policastro formation (PPF) at the baseand top, referred to as respectively intra-Messinian andupper Messinian unconformities. The first of them, at thetop of the Calcare di base, also occur in the RossanoBasin, north of the Crotone Basin (BARONE et alii, 2008;CAVAZZA & BARONE, 2010). The unconformity is reportedby BARONE et alii (2008) to erosionally truncate the culmi-nations and limbs of asymmetric folds involving theunderlying Calcare di Base limestones. However, evidenceof folding has not been found by us in the Crotone Basin.

In the study area the Intra-Messinian unconformity isaccompanied by a severe phase of denudation cutting


deeply downwards, up to basement rocks, particularly atthe western margin of the basin. The overlying, thick,syntectonic, non-marine deposits of the Petilia Policastroformation were affected in a first stage by extensional-transtensional tectonics and later by contraction-trans-pression. The lower part of the PPF appears hostedwithin tectonic troughs bounded by extensional ortranstensional faults (fig. 11). Deposits directly coveringthe unconformity, are locally exceptionally coarse, repre-sented in places by fault-scarp breccias including largeblocks of the Calcare di base. Marked facies and thick-ness changes occur, particularly between the Mesoracaand Petilia Policastro areas, as shown above. In this stagedextral transtension was possibly active along the mainN- to N15°W-oriented fault system, producing in particu-lar the structural depression located east of the FossoUmbro Fault. The muddy infill of this depression shows aprogressive unconformity and anomalous thickeningnear the Fosso Umbro growth fault. The above men-tioned fault system is associated with oblique-slip sini -

stral faults oriented about N100° (e.g., WSW of PetiliaPolicastro, where a N107°-oriented fault is sealed by avery coarse conglomerate with large blocks of Calcare dibase), and NE- to ENE-oriented extensional growth faults(e.g., E of Arietta, SSE of Belcastro and near Mesoraca).Worth mentioning is an enigmatic, funnel-shaped, fault-bounded depression, trending about N60°, up to a fewtens of metres wide, visibile along the road Mesoraca-Marcedusa, near Mesoraca. The south-eastern flank ofthe depression is significantly less inclined than theopposite, suggesting that on this side a fault scarp wassubjected to some erosional dismantling during the in -filling stage. The infill consists of a chaotic breccia ofCalcare di base, possibly derived from fault-scarp failure,grading upwards into distinctly stratified finer-grainedbreccia and coarse, microruditic sandstone, both pre-sumably laid down by tractive flows.

During the deposition of the upper part of the PPFsinistral transpression along the NW-trending fault sys-tem inverted the former extensional features and gener-


Fig. 11 - Interpretative and simplified depiction of main steps of tectonic evolution of the investigated area. In the sketch of Middle Pleisto -cene situation, letters indicate the identified sub-basins: a) Foresta sub-basin; b) San Mauro sub-basin; c) Troiani sub-basin; d) Marcedusasub-basin). Grey areas indicate the main depocentres and grey lines indicate inactive faults. Thick arrows show the approximate extensionand contraction direction in the different stages. – Schema interpretativo delle fasi principali in cui si articola l’evoluzione tettonica dell’area di studio. Nel quadro della situazione Medio-Pleisto-cenica, le lettere indicano i sotto-bacini che sono stati individuati nel presente lavoro: a) sotto-bacino di Foresta; b) sotto-bacino di San Mauro;c) sotto-bacino di Troiani; d) sotto-bacino di Marcedusa. Le aree in grigio indicano i depocentri principali e le linee grigie indicano le faglie inat-tive nel relativo intervallo temporale. Le frecce in grassetto indicano le direzioni approssimative di estensione e di contrazione nelle diverse fasi.

ated local SW-verging overthrusts (Petilia-MartellettoFault zone) which are sealed by an erosional unconfor-mity, already recognized by VAN DIJK (1990, 1991). Thisis overlain by widespread upper Messinian coarse fluvialconglomerates (the Conglomerato delle Carvane) (fig. 11,fig. 12: profile A-A’ – trace in the enclosed geologicalmap – and fig. 13). A NNW-SSE trending, gentle, trun-cated anticlinal fold at Timpone Tenese (see the enclosedgeological map), may be attributed to the same event.Such late Messinian tectonics is also documented north ofthe Crotone Basin, in the Cirò-Cariati area, where theemplacement of a major thrust sheet, formerly describedas «Cariati nappe» by OGNIBEN (1955), RODA (1967) andTORTORICI (1981), and variably attributed by theseauthors to either Messinian or Pliocene tectonics, wasrecently re-interpreted by BARONE et alii (2008) as theproduct of a late Messinian transpressional episode. Thisled to the upthrust of Serravallian?-Tortonian sequencesand formation of the «Cirò structural high», which sepa-

rated, since then, the Rossano and Crotone basins. Asobserved by BARONE et alii (2008), the above time attribu-tion for the structure emplacement is supported by thefact that Messinian stratigraphies of the two basins arevery similar, whereas the upper Messinian Conglomeratodelle Carvane and subsequent Pliocene deposits are miss-ing in the Rossano basin. BARONE et alii (2008) noted thatthe composition of the Conglomerato delle Carvane is dif-ferent from that of the other terrigenous Messinian unitssourced from the Sila massif, and indicates a provenancefrom Mesozoic to Tertiary basinal sequences of south-Apennine type. They argued that the conglomerates weresourced from varicolored clay olistostromes of the SicilideComplex terranes. However, this hypothesis is at oddswith the paleocurrent pattern and presence of clasts oftonalite and granodiorite of probable Sila provenance inthe conglomerates (see also CAVAZZA & DECELLES, 1998).

Although firm chronological constraints are missing,we suggest that the first (intra-Messinian) unconformity


Fig. 12 - Geologic sections across the surveyed area (traces in the enclosed map). In the first section (A-A’) the vertical scale is doubled withrespect to the horizontal scale.– Sezioni geologiche attraverso l’area rilevata (tracce nella carta geologica allegata). Nella prima sezione (A-A’) la scala verticale è doppia rispettoalla scala orizzontale.

corresponds to the well known Messinian Erosional Sur-face (MES) documented along several Mediterraneanmargins (RYAN & CITA, 1978), and marking the majordrawdown event in the Mediterranean inferred to havebegun at 5.59 Ma (KRIJGSMAN et alii, 1999). The overly-ing, thick, syntectonic, non-marine deposits of the PPFare inferred to have been laid down at low sea level and tocorrespond to the p-ev1 deposits of ROVERI et alii (2005,2008b). The two unconformities bounding the PPFarguably correspond to the two strong reflectors in seis-mic profiles highlighted by BUTLER (2009) in offshoreCalabria and BERTONI & CARTWRIGHT (2007) in the Lev-ant Basin of eastern Mediterranean. The upper unconfor-mity (the so-called Horizon M) is regarded by the latterauthors as a widespread, erosional and discordant sur-face, locally covered by fluvial or brackish «Lago Mare»deposits. It probably corresponds to the unconformityplaced at 5.42 Ma by ROVERI et alii (2008a), between thefirst (p-ev1) and the second (p-ev2) units of the post-evap-oritic stage (ROVERI et alii, 2001; ROVERI & ME.LA.GROUP, 2005; ROVERI et alii, 2008a). The Conglomeratodelle Carvane which overlies this erosional and locallyangular unconformity documents a sudden increase involume and grain size of sediment input. This may beregarded as the regional expression of the event of abrupttextural coarsening recognized throughout the centraland eastern Mediterranean regions in the late Messinian(CAVAZZA & DECELLES, 1998 and references therein;ROVERI et alii, 2008a). ROVERI et alii (2008a) suggested amajor paleogeographic change possibly resulting from acomplex interplay between tectonic and climatic factors.

Interpretation of Messinian events in the CrotoneBasin is problematic. Rapid drawdown of the Mediter-ranean water level during the Salinity Crisis is believed tohave been accompanied by important isostatic/flexuralrebound processes (tectonic tilting and erosion) (NORMAN

& CHASE, 1986; DECELLES & CAVAZZA, 1995; KRIJGSMAN

et alii, 1999; HILGEN et alii, 2007; GOVERS et alii, 2009).According to the general model elaborated by GOVERS etalii (2008), evaporite loading is expected to cause rapidsubsidence of the basins and simultaneous flexural uplift,erosion and normal faulting of the margins, with the dif-ferential movement leading to significant basinwardslope-angle increase, most pronounced in marginal areas.Subsequent severe sea-level drop results on one hand inrebound and significant uplift of the deep basins, and onthe other hand subsidence and decrease in slope-anglesand in potential of erosion on the continental margins,where river-bed sedimentation takes place. In this stagereverse faulting is predicted at the margins.

Interpreting in this perspective the Messinianstratigraphy of the Crotone Basin, it may be suggestedthat the relative uplift of the marginal areas as aresponse to deposition of the Lower Evaporites in basi-nal areas during early Messinian times may account forthe fact that only relatively thin successions of Calcaredi base are deposited in this stage along the westernmargin of the basin. Also the normal faulting affectingthe Calcare di base and older rocks may be interpretedin this context (GOVERS et alii, 2009). Compressionaldeformations occurring during the deposition of theupper part of the PPF, particularly the thrusts identifiedin the Petilia Policastro and Cirò areas, are moreambiguous. In the Calabrian arc compressional effectsfollowing drawdown of the Ionian water mass are attri -buted by CAVAZZA & DECELLES (1995, 1998) to flexuralbacktilting which would have caused the accretionarywedge to become subcritically tapered. This would haveresulted in shifting of the locus of deformation towardthe rear of the wedge and consequent out-of-sequenceinternal shortening.

In a first hypothesis, the above outlined compres-sional structures could be regarded as the effects of therebound following the severe drawdown event. On theother hand, both Petilia-Martelletto Thrust and CiròUpthrust (BARONE et alii, 2008) are linked to high-anglestrike-slip faults suggested to be major transpressionalstructures involving the basement. They apparently can-not match with the typical structures indicated byCAVAZZA & DECELLES (1998) as resulting from an eusta-tic-driven isostatic rebound, which are suggested by theseauthors to be shallow thrusts resulting from subcriticaltaper of the accretionary wedge. It is tentatively con-cluded, therefore, that Messinian tectonics of the CrotoneBasin results from the combination of processes con-nected to the Messinian salinity crisis with those linked tothe kinematics of the Calabria block.

In the northern onshore part of the Crotone basin andin the Rossano basin mass-wasting episodes emplacedlarge chaotic olistostromes of «Argille Scagliose» (alterna-tively named «Argille Varicolori» or varicolored clays), ina number of episodes, particularly during the Messinian(OGNIBEN, 1962, 1973; RODA, 1967; CAVAZZA et alii, 1997;CAVAZZA & BARONE 2010). These episodes, also recog-nized in the Plio-Pleistocene of the offshore area (MOR-LOTTI et alii, 1982), attest to large-scale instability(LUCENTE et alii, 2005), with gravitational mobilizationand mass wasting toward the forearc basin probablyrelated to the activation of mud volcanism on the Cala -brian accretionary prism (MALINVERNO & RYAN, 1986;PRAEG et alii, 2009).


Fig. 13 - Drawing from a photomosaic, illustra-ting the Petilia Policastro thrust of the Petilia-Martelletto Fault zone (view from the hillslocated SW of the village of Petilia Policastro).The vertical scale is doubled with respect tothe horizontal scale.– Disegno da fotomosaico per illustrare il thrustdi Petilia Policastro appartenente alla zona difaglia Petilia-Martelletto (veduta dalle colline aSW del villaggio di Petilia Policastro). La scalaverticale è doppia rispetto alla scala orizzontale.

LATEST MESSINIAN - EARLY PLIOCENE

In the south-western part of the Crotone Basin theonlapping transgressive deposits of the Carvane Groupand the overlying Lower Zanclean succession are con-fined in some depocentres controlled by N- to NW trend-ing major faults, which are apparently organized accord-ing to an en-echelon left-stepping system, suggesting adextral displacement along the N- to NW- trending faultsystem, consistent with a dextral transtensional motion(fig. 11).

The effects of extensional-transtensional regime areparticularly spectacular in the Zanclean succession of thenorthern part of Crotone Basin, where they consist ofspectacular growth faulting along listric normal faultsaccompanied by progressive unconformities in the Marnaargillosa dei Cavalieri and Molassa di Zinga (VAN DIJK,1991; MORETTI, 1993; ZECCHIN et alii, 2003). Local domestructures are caused by halokinetic effects in the Messin-ian evaporites and are accompanied by local collapses ofthe cover (ZECCHIN et alii, 2003).

THE LATE ZANCLEAN EVENT

During the late Zanclean, most probably in thepuncticulata-margaritae concurrent-range Zone, a majorcontraction phase produced extensive transpressional

effects in the Crotone basin along the regional system of~N160 high-angle to subvertical faults affecting the base-ment (RODA, 1964, 1965; VAN DIJK, 1991, 1994; ZECCHIN

et alii, 2004a; CAPRARO et alii, 2006). This episode ismarked by a major unconformity in the northern, mar-ginal part of the Crotone Basin, where it is accompaniedby evidence of deep denudation of the substrate (RODA,1964). In the southern, more basinal area this unconfor-mity grades into a conformable surface coinciding withthe abrupt increase in sedimentation rate and onset of thesiliceous sedimentation.

Structural data collected along the N160°-trendingfault system indicate a dextral shear sense, locally associ-ated with SW- to SSW-verging thrusts in restraining bendsof the faults. This is particularly evident along the Tacina,Fosso Umbro and Marcedusa-Steccato faults, whose kine-matics is coherent with a NNE-trending shortening direc-tion (fig. 11; fig. 12, profiles C-C’, D-D’, E-E’; traces in theenclosed geological map; figs. 14a and 14b). Dextral shearsense along the Marcedusa-Steccato Fault is well docu-mented near Fosso Condolè by the presence of gypsum-mylonites with S-C structures and asymmetric porphyro-clasts (figs. 15a-b) and in the Steccato locality by thepresence of disrupted sandstone layers forming asymmet-ric boudins in a shear zone developed in clays and sand-stones of the Petilia Policastro formation (fig. 15c). Evi-dence of transpression is provided by the Timpone Arciere


Fig. 14 - Structural sketch-map of the investi-gated area; WULFF nets (lower hemisphere) re-port orientation of fault planes (great circles)and related striae (small arrows). Large arrowsindicate shortening and extension directionsobtained with the Faultkin software by R.W.ALLMENDINGER. Structural data have been col-lected: a) from the pure transcurrent Marcedu-sa-Steccato Fault; b) from the oblique-sliptranspressional Timpone Arciere thrust; c) andd) from extensional faults within Marcedusasub-basin (c) and San Mauro sub-basin (d). Indiagram b) (Timpone Arciere) letters C and Sindicate shear planes and sigmoidal foliationplanes, respectively.– Schema strutturale dell’area di studio; i dia-grammi di WULFF (emisfero inferiore) riportanol’orientazione dei piani di faglia (grandi cerchi) edelle strie associate (frecce piccole). Le freccegrandi indicano le direzioni di estensione e con-trazione ottenute con il software Faultkin diR.W. ALLMENDINGER. I dati strutturali proven-gono: a) dalla faglia trascorrente pura di Marce-dusa-Steccato; b) dal sovrascorrimento traspres-sivo oblique-slip di Timpone Arciere; c) e d) dallefaglie normali misurate nel sotto-bacino di Mar-cedusa (c) e di San Mauro (d). Nel diagramma b) le lettere C e S indicano rispettivamente i pianidi taglio e i piani di foliazione sigmoidale.

thrust, whose kinematics can be inferred from S-C and C’structures in a shear zone developed in Messinian sand-stones. More specifically, the relationships between S andC surfaces indicate a SSW-directed shear sense, coherentwith dextral transpression (fig. 14, diagram b). The N160-trending Marcedusa-Steccato Fault is accompanied bysinistral NE-trending faults which can be interpreted assynthetic Riedel shears (fig. 14, diagram a).

Chaotic breccias (Madama Lucrezia breccia), mostlyconsisting of variably sized clasts and also slabs of oldersediments in a matrix of Messinian gypsum-bearing mud-stone (fig. 16a), were emplaced along the fault bends,subjected to particularly intense contractional deforma-tion, probably as a result of a process of extrusion.

A compressional component oriented NE-SW wasattributed by VAN DIJK (1992) to a concomitant conver-

gence between the Calabria block and the Apulian mar-gin. The effects of this contractional phase, leading to animportant paleogeographic reorganization, can be recog-nized from the Tyrrhenian to the Ionian side of Calabria,as well as in the offshore area (SELLI & FABBRI, 1971;FABBRI et alii, 1980; GHISETTI, 1980; PHILIP & TORTORICI,1980; GHISETTI & VEZZANI, 1981; LANZAFAME & TOR-TORICI, 1981; ROSSI & SARTORI, 1981; BARONE et alii,1982; PATACCA et alii, 1990; ROVERI et alii, 1992;GUARNIERI & CARBONE, 2003; GUARNIERI, 2006; PRAEG etalii, 2009).

MIDDLE PLIOCENE - EARLY PLEISTOCENE

From the Middle Pliocene to Early Pleistocene theforearc area was persistently dominated by an extensional-


Fig. 15 - Kinematic indicators in shear zones developed in Messinian evaporites, sandstones and clays of the Petilia Policastro formation: a) S-C structure in a gypsum mylonite from the Marcedusa-Steccato Fault, near Fosso Condolè; b) asymmetric porphyroclast in a gypsummylonite from the same locality; c) asymmetric boudins derived from disrupted sandstone layers (lighter) within pelites (darker) of the Petilia Policastro formation observed along the Marcedusa-Steccato Fault in the Steccato locality (hoe 115 cm long for scale); d) shear planes (C) associated with synthetic C’ planes in a shear zone at Timpone Arciere (coin with diameter of 21 mm for scale). – Indicatori cinematici nelle zone di taglio sviluppate in gessareniti, arenarie e peliti Messiniane della formazione di Petilia Policastro: a) strutturaS-C in una milonite di gesso lungo la Faglia Marcedusa-Steccato, presso Fosso Condolè; b) porfiroclasto asimmetrico in una milonite di gesso,nella stessa località; c) boudins asimmetrici derivati da livelli smembrati di arenaria (più chiari) entro peliti (più scure) della formazione di Petilia Policastro osservati lungo la Faglia Marcedusa-Steccato nella località di Steccato (la zappa è lunga 115 cm); d) piani di taglio (C) associatia piani sintetici C’ in una zona di taglio a Timpone Arciere (la moneta ha un diametro di 21 mm).

transtensional regime. A substantial enlargement of theCrotone basin occurred at this time. In fact, the thresholdsbounding the basin during the Messinian and EarlyPliocene were overtaken during the Late Pliocene andearly Pleistocene, so that the basin became completelyopen northwards and southwards and the relative depositswere laid down uniformly from the Rossano area to theCatanzaro zone (RODA, 1965). Active transtension in theN-S Crati graben was reported by LANZAFAME & TOR-TORICI (1981) and TANSI et alii (2007) since late Pliocene.

Exceptionally thick, dominantly deep-water slopedeposits accumulated under high subsidence rates in theCrotone Basin. Structural depressions created in thisphase were probably linked to a regime of sinistraltranstension along the major system of NNW-trendingfaults. This is conceivably the case of the subsidingtrough which accommodated the thick succession of sec-tor 1, south of the San Antonio normal fault. In severalcases faults of the transpressional Zanclean tectonicswere inverted to create accommodation space for theArgilla marnosa di Cutro.

An extensional regime was regionally widespread dur-ing this time span, and led to a profound reorganizationof the paleogeography and generalized stratigraphiconlaps in the Calabria block and elsewhere in the centralMediterranean area (OGNIBEN, 1955; RODA, 1964; PHILIP

& TORTORICI, 1980; GHISETTI & VEZZANI, 1981; TOR-TORICI, 1981; MEULENKAMP & HILGEN, 1986; PATACCA etalii, 1990; VAN DIJK, 1992; SCHEEPERS & LANGEREIS,1994; VAN DIJK & SCHEEPERS, 1995). The stratigraphicarchitecture of Pliocene deposits in the northern part ofthe Crotone Basin suggests that drowning took place intwo distinct steps, separated by a pulse of uplift. In thefirst stage, a system of normal listric growth faults,mostly NE- to ENE-directed, created subsidence andaccommodation for the Spartizzo-Scandale complex(MELLERE et alii, 2005) and for outer-shelf mudstones of

the Argilla marnosa di Timpa Biso, the latter dated to thetamalis Zone p.p. and pentaradiatus Zone p.p by CONSO-LARO (2004) and CAPRARO et alii (2006). An abrupt regres-sion, recorded by the shallow-water Arenaria di Strongoli(AS), interrupted the drowning trend at ca. 2.55 Ma as aresult of a strong synsedimentary uplift (CONSOLARO,2004; CAPRARO et alii, 2006). A similar abrupt shallowingepisode is reported by CORBI et alii (2009) in the RossanoBasin, where an Upper Pliocene-Lower Pleistocene onlap-ping marine sequence beginning with littoral sands over-lies bathyal deposits of the Middle Pliocene. After thedeposition of the AS, a sudden subsidence led to a truecollapse event, spectacularly expressed by the very rapidtransition to hemipelagic slope mudstones of the Argilladi Gigliolo (AG), attributed to the Discoaster brouweriZone by CONSOLARO (2004) and CAPRARO et alii (2006).By means of planktonic foraminifera and correlation ofsapropel layers with Mediterranean cluster B, theseauthors could establish that the beginning of the AG sedi-mentation occurred between 2.3 and 2.1 Ma. The majordrowning episode probably corresponds with the so-called «Calabrian transgression» of old authors (GI -GNOUX, 1913; RUGGERI & SELLI, 1948; SELLI, 1949;OGNIBEN, 1955), identified in several localities of the Ita -lian peninsula. It is worth noting that this event mostprobably coincides in time with the onset of the openingof Marsili Basin in the back-arc area (CAPRARO et alii,2006), dated to 2.1 Ma by NICOLOSI et alii (2006). Thespreading of this basin lasted according to these authorsup to 1.6 Ma, and occurred with an extremely rapid rate(19 cm/yr), corresponding to a similar coeval drift velocityof the Calabrian arc (see also ROSSI & SARTORI, 1981;SARTORI, 1990; PATACCA et alii, 1993).

MATTEI et alii (2007) argued that the fast back-arcopening of the Marsili basin in the Tyrrhenian Sea mayhave been concomitant with the episode of clockwiserotation affecting the Calabria block, documented by sev-


Fig. 16 - a) Diamicton of inferred tectonic origin: chaotic breccia containing a wide range of clast sizes, in a fine-grained matrix (Madama Lucrezia breccia, Madama Lucrezia area, SE of the village of Belcastro) (hammer 35 cm long for scale); b) progressive unconformity affectingthe upper part of the Argilla marnosa di Cutro, the Timpone San Litano formation and the Lamone formation (Timpone S. Margherita,southern part of the San Mauro sub-basin).– a) Diamicton di probabile origine tettonica contenente clasti di dimensioni molto variabili in una matrice fine (breccia di Madama Lucrezia, località Madama Lucrezia, a SE del villaggio di Belcastro) (il martello è lungo 35 cm); b) discordanza progressiva osservata al Timpone S. Mar-gherita (parte meridionale del sotto-bacino di San Mauro), nella parte superiore dell’Argilla marnosa di Cutro e nelle successive formazioni diTimpone San Litano e di Lamone.

eral paleomagnetic studies (SAGNOTTI, 1992; SCHEEPERS

et alii, 1994; SPERANZA et alii, 2000; MATTEI et alii, 2004,2007, among others).

A MAJOR PALEOGEOGRAPHIC CHANGE IN THE LATE EARLY

PLEISTOCENE

In the San Mauro Marchesato area RIO et alii (1996)identified, at the transition between the «large» Gephyro-capsa and «small» Gephyrocapsa Zones (corresponding tothe transition from «Cutro 1» to «Cutro 2» in their strati-graphical nomenclature), an important erosional uncon-formity (fig. 8), accompanied by evidence of abrupt upliftdue to the superposition of middle to inner shelfcyclothems on slope to outer-shelf mudstones. Moreover,angular relationships with a gently deformed substrateprovides evidence of a tectonic episode affecting this mar-ginal area. In the south-western area of the Crotone Basinthe effects of this Early Pleistocene tectonic event aremore subtle, and may be represented by the formation ofgentle anticlines such as that occurring in the TimponeSerrano area, with an inferred NNW-trending axis, andthe inversion of the N-trending Casella Monaca Fault. Inthe deeper, more basinal settings, such as the Marcedusaarea, the unconformity generally passes into a con-formable surface without evidence of stratigraphic gap.SPERANZA et alii (in press) could document, by means ofpaleomagnetic data, post-1.2 Ma counterclockwise rota-tion in two ~10 km wide blocks (the Strongoli-Neto andBotricello domains) suggesting left-lateral shear alongtwo NW-SE fault zones (respectively corresponding to theRossano-San Nicola shear zone of VAN DIJK, 1990 andour Fosso Umbro Fault).

The Lower Pleistocene unconformity may be equiva-lent to that observed by PRAEG et alii (2009) in theSpartivento Basin (offshore Calabria), sealing contrac-tional deformations in a Piacenzian to Calabrian unit.Moreover, episodic compression and/or transpressionaffecting lower Pleistocene sediments were reported inthe onshore and offshore area of the Crotone Basin, aswell as in the Crati and Paola basins by SELLI (1962),PHILIP & TORTORICI (1980), LANZAFAME & TORTORICI(1981), ARGNANI & TRINCARDI (1990), and GUARNIERI

(2006). Early Pleistocene transpressional tectonics alongNW-trending left-lateral faults and associated folding arereported by MILIA et alii (2009) in the south-eastern Peri-Tyrrhenian basins.

These Lower Pleistocene deformations are believed tobe connected with, and coeval to, a major event known tohave occurred along the boundary between the Calabriablock and Calabro-Lucanian Apennines. This is repre-sented by sinistral transpression along the NW-trendingPollino shear zone, thought to be an important sinistrallithospheric tear (KNOTT & TURCO, 1991) and the north-east boundary between the actively subducting Ionianoceanic slab and the Apulian continental margin. Thisevent is inferred to mark the onset of continental collisionfollowing the encroachment of buoyant continentallithosphere at the southern Apenninic front, as supportedby the stop of the thrust front migration, and a differen-tial motion of the Calabria block with respect to thesouthern Apennines (PHILIP & TORTORICI, 1980; LAN-ZAFAME & TORTORICI, 1981; AUROUX et alii, 1985; PA -TACCA et alii, 1990; KNOTT & TURCO, 1991; SCHEEPERS &LANGEREIS, 1994; VAN DIJK & SCHEEPERS, 1995; PA -

TACCA & SCANDONE, 2007; MONACO et alii, 1998). Theevent was accompanied by a change from thin- to thick-skinned contraction, with stepping of deformation todeeper structural levels (BERTOTTI et alii, 2001; FERRANTI& OLDOW, 2006). PATACCA et alii (1990) fixed the date ofthis event around the Emilian-Sicilian boundary, a speci-fication matched by MATTEI et alii (2007), who placed theend of compressional tectonics in the latest Early Plei -stocene (at about 1 Ma), as proved by sealing of the defor-mations by sediments of Sicilian age. Importantly, PA -TACCA et alii (1990) argued that the activity of theNW-trending Pollino shear zone, working as lithospherictear and sinistral transfer fault system, allowed differen-tial motion between Apennines and Calabria, involvingcontinuation of flexure retreat and orogenic transport inthe Calabrian Arc, following NW-SE slip vectors.

MIDDLE PLEISTOCENE

The above episode was followed in the Crotone Basinby dextral transtensional movements along right-step-ping, en echelon NW-trending faults, which generated anumber of rhomboidal, pull-apart sub-basins (the SanMauro, Troiani, Foresta and Marcedusa sub-basins)bounded by extensional sidewall fault systems trendingNE to ENE (fig. 11). Along these faults liquefaction struc-tures possibly triggered by seismic shocks were locallyobserved. An associated minor fault system is representedby N-S to N10°-oriented oblique-slip dextral transten-sional faults. Effects of this tectonic regime are recordedby the Middle Pleistocene development of growth struc-tures, such as rollover anticlines, growth faults, growthsynclines and progressive unconformities occurring inshelf to littoral sediments mostly of the P. lacunosa Zone,particularly in the San Mauro sub-basin (RIO et alii, 1996;MASSARI et alii, 2002) (fig. 16b) and in the Marcedusasub-basin (fig. 17, trace of the profile in the enclosed geo-logical map). These geometries indicate a deformationcontinuum during deposition.

A similar structural pattern is documented by MILIA

et alii (2009) in the south-eastern peri-Tyrrhenian basins.They describe a change in the slip direction along a sys-tem of NW-trending faults, from sinistral transpressionrelated to an Early Pleistocene tectonic phase, to dextraltranstension during the Middle Pleistocene, between 1.0and 0.7 Ma, leading to generation of minor pull-apartrhombic/sigmoid basins.

Most part of the sub-basin fills consist of a sand-prone succession. The arrival of massive amounts ofarkosic sand, clearly sourced from the Sila Piccola massif,suggests that this massif underwent active denudationduring this stage. The overall regressive trend was inter-rupted by an inferred deepening pulse, recorded by outer-shelf mudstones dated in the San Mauro basin fill toMIS 21 to 19 (RIO et alii, 1996; MASSARI et alii, 1999, 2002).

As above noted, a large-scale diachroneity in the firstappearance of shallow-water deposits is indicated by thestrongly different ages of the pelitic substrate, attributedto MIS 25 in the northern part of the study area and to aprobable MIS 10 in the southern (Marcedusa) sub-basin(Petrogallo area). This cannot be simply explained by ashift in facies tracts in a marginal-to-basinal direction.Such a facies shift, in fact, can account for only limiteddiachroneity occurring within individual sub-basins, as in


the case of the Marcedusa sub-basin, where the prodeltamudstones of the Petrogallo area grade proximally north-wards into delta front sands, so that in the former areathe first shallow-water deposits are slightly younger. It issuggested that the large-scale diachroneity, specificallythe longer persistence of pelitic sedimentation in theMarcedusa sub-basin, compared with the other sub-basins, reflects the combined action of a number of fac-tors, including inheritance from a former deeper-watersetting, compactional subsidence affecting the formerlyaccumulated muds, here much thicker than elsewhere,and probably also higher rates of tectonic subsidence.

THE RECENT TECTONICS AND UPLIFT

A series of NE- to NNE-striking, probably listric nor-mal faults, affected the growth folds of the sub-basin fills,particularly in the San Mauro and Marcedusa sub-basins,leading to tilt of the adjacent blocks in a domino-like pat-tern, particularly evident east of the Marcedusa-SteccatoFault (fig. 11, fig. 12: profile F-F’, and fig. 17 – trace of theprofiles in the enclosed geological map). Analysis of NE-to NNE-striking normal faults in both S Mauro andMarcedusa sub-basins indicates a NW-SE trending exten-sion direction, suggesting nearly pure extension associ-ated in some cases with a dextral oblique-slip componentin the case of NNE-trending faults (fig. 14, diagrams cand d). This structural configuration is thought to resultfrom fragmentation during limited south-eastward gravi-tational transport of the upper levels of the sedimentarysuccession, favoured by downslope instability due toincrease in topographic gradient, in response to differen-tial uplift. The inferred gravity-driven tectonic glidingshould imply rooting of the faults at shallow depths, withdownward soling into a regional-scale detachment surface, most probably located at the level of Messiniangypsum-clay deposits, acting as a tectonic lubricant.

The emplacement of the south-easterly verging Tim-pone Tenese thrust in the southern part of the investigatedarea (figs. 11 and 12, profile F-F’, trace in the enclosedgeological map) may be interpreted in the light of thisgravitational tectonics. This compressional structure islocated at the south-eastern edge of the block bounded by

the NW-trending Fosso Umbro and Marcedusa-Steccatofaults. A gravitational movement of the block basinwards,with internal fragmentation by extensional faults in therear, may have resulted in compression of the frontaledge. This may be an example of linked gravity-driventhin-skinned extensional and contractional fault system.

Development of shallow-rooted fault systems parallelto the present-day coast and accommodating seawardgravitational collapse of the uppermost crust is alsoreported by FERRANTI et alii (2009) in N Calabria. Gravita-tional tectonics is also documented in the eastern Mediter-ranean during the Plio-Pleistocene and Messinian (e.g.,BERTONI & CARTWRIGHT, 2007). In the investigated areathis tectonics is probably the continuation of a processalready initiated during the Pliocene and possibly also thelate Messinian. However, it seems most probable that thePleistocene regional uplift accentuated the instability andgave an important impulse to the process. The recent ageof the last movements is suggested by the strong morpho-logic evidence of the Timpone Tenese thrust, which formsan outstanding relief in the present-day coastal area.

The onset of recent uplift in outer area of the onshoreCrotone Basin is apparently constrained in age by the for-mation of the older marine terrace, the Cutro terrace,attributed to MIS 7 by GLIOZZI (1987). In this area thebeginning of recent uplift probably corresponds to thechange from a transtensional regime occurred during thedevelopment of the sub-basins to a predominantly exten-sional setting. The change may have occurred in the lateMiddle Pleistocene, after ~MIS 9-8, which is the possibleage of youngest cyclothems in the infill of San Mauro andMarcedusa sub-basins. GALLI & BOSI (2003) and GALLI &SCIONTI (2005) assume active extension, directed ~NNE,to be mainly accommodated in the northern Sila massifby the ~NW-SE-trending, seismically active, Cecita andLakes faults with normal-to-sinistral kinematics. More-over, normal faulting, mostly along a ENE- to NNE-strik-ing fault system, affected the marine terraces in the Cro-tone area, as documented by GLIOZZI (1987), COSENTINOet alii (1989) and ZECCHIN et alii (2004b). Regional analy-sis of the relief indicates that the Quaternary uplift has acomplicated interaction with the rates of local activefaulting (MOLIN et alii, 2004). Therefore, uplift rate of


Fig. 17 - Geologic section (trace in the enclosed geological map) across the Middle Pleistocene stratigraphic terms in the Marcedusa area(Lamone formation), showing the syndepositional pattern of growth folds and the post-depositional system of domino-like normal faults:1) slope and prodelta muds; 2) delta front wedge; 3) shoreface sands; 4) fluvial gravel; 5) lagoonal mud; 6) Neopycnodonte-bearing transgressivemud; 7) shoreface sand; 8) downward shift of facies tracts. The d18O record in the Petrogallo section suggests MIS 10 for unit 2.– Profilo geologico attraverso la successione Medio-Pleistocenica nell’area di Marcedusa (formazione di Lamone). Si può notare la presenza dipieghe di crescita e il sistema di faglie a domino successive alla deposizione (la traccia del profilo è nella carta geologica allegata): 1) peliti discarpata e di prodelta; 2) cuneo sedimentario di fronte deltizia; 3) sabbie di shoreface; 4) ghiaie fluviali; 5) peliti lagunari; 6) peliti trasgressivecon Neopycnodonte; 7) sabbie di shoreface; 8) superficie di erosione legata a regressione forzata. I dati isotopici (d18O) nella sezione di Petrogallo indicano come probabile l’attribuzione dell’unità 2 al MIS 10.

marine terraces is variable, and has been determined asranging from 0.6 to 1.0 mm/yr (LANZAFAME & TORTORICI,1981; CAROBENE & DAI PRA, 1990; TORTORICI et alii,1995; MAUZ & HASSLER, 2000; ZECCHIN et alii, 2004b;NALIN et alii, 2007).

In contrast with this scenario of predominantly exten-sional regime, other evidences indicate a recent to present-day transpressional strike-slip tectonics in the offshore Ionian area. FERRANTI et alii (2009) found widespread evi-dence of recent and still active transpression in the offshore area between the NE Calabrian coast and the Apulian margin, where Middle Pleistocene and youngersequences submerged beneath the shelf are involved infolding and local transpressional faulting, interpreted asreflecting a recent and still active transpressional fieldadjacent to the active extensional belt of the western Apen-nines. Similar evidence of recent and still active transpres-sion along major NW-, WNW- and E-directed strike-slipfaults, commonly implying inversion of former transten-sion, was documented by DEL BEN et alii (2008) by meansof the analysis of seismic profiles in the Ionian offshorearea, from the Sibari Gulf to the area off Cape Spartivento.

SEQUENCE STRATIGRAPHY

The successive steps in the geological evolution of theCrotone Basin are materialized by tectono-stratigraphicsequences bounded by important unconformities relatedto major phases of basin reorganization (fig. 11). Most ofthem were already identified by RODA (1964). In the typi-cal case these sequences comprises a lower onlappingpart, laid down in conditions of active subsidence pro-moted by extensional-transtensional tectonics, and anupper offlapping part bounded atop by an unconformitysealing contractional-transpressional structures.

The first sequence (Upper Serravallian (?) – LowerMessinian) is bounded at the base by the nonconformityat the contact with basement rocks and at the top by theintra-Messinian erosional unconformity. The secondsequence is bounded at the top by the erosional, UpperMessinian unconformity, locally suturing transpressionalstructures. The third sequence (Uppermost Messinian toupper Zanclean) crosses the sharp Messinian-Plioceneboundary, and is bounded at the top by the upper Zan-clean unconformity (and correlative basinal conformity)sealing deformations linked to the late Zanclean tecton-ics. The fourth sequence (uppermost Zanclean to LowerPleistocene) is bounded at the top by the unconformityand correlative conformity between the large Gephyro-capsa and small Gephyrocapsa Zones at about 1.2-1.1 Ma,sealing deformations linked to the lower Pleistoceneevent. The fifth sequence is represented by the shelf tocontinental infills of the Crotone sub-basins, and is subdi-vided into a number of glacio-eustastic Lower and MiddlePleistocene cyclothems (small-scale sequences), theyoungest of which are tentatively attributed to MIS 9-8times (around 0.3 Ma).

TECTONIC IMPLICATIONS AND CONCLUSIONS

The tectonic evolution of the Crotone Basin has beenstrongly influenced by the strike-slip activity of NW- toNNW-directed fault systems, interpreted as basement

wrench faults leading to partitioning of the basin intoseparate sub-basins subject to differential subsidence andmutual displacements, in agreement with the model pro-posed by VAN DIJK (1994).

The geologic evolution is recorded by tectono-strati-graphic sequences, most of which reflect an alternation oflong-lived stages of extension-transtension and short-livedepisodes of contraction-transpression, the latter duringlate Messinian, late Zanclean and Early Pleistocene. Theformer stages are thought to have been concomitant withactive rollback of the subduction hinge accompanyingmajor phases of back-arc spreading. Specifically,although highly resolved chronological data concerningthe age of Vavilov basin opening and spreading in theback-arc area are lacking, available data suggest that theprocess is most probably coeval to the extension-transten-sion occurring in the forearc area during the late Messin-ian to Zanclean times. Similarly, the major drowningepisode in the Crotone Basin, bracketed in time between2.3 and 2.1 Ma, is thought to be coeval to the onset of theopening of Marsili Basin in the back-arc area, dated to 2.1Ma by NICOLOSI et alii (2006).

On the other hand, short-lived episodes of contrac-tion-transpression may reflect episodes of temporarystops or strong slowing down of subduction, possibly dueto relatively buoyant continental crust entering the sub-duction zone. It is speculated that these episodes mayeventually trigger slab tear events, which in turn canprompt to resumption of active rollback. The above out-lined evolution is thought to be also recorded by theobserved alternation between long-lasting phases of sub-sidence and pulses of uplift (GVIRTZMAN & NUR, 1999).

Of particular interest, in our opinion, is the identifica-tion of a major paleogeographic change occurred since thelate small Gephyrocapsa Zone (aroung 1.2-1.1 Ma) in theCrotone Basin, marked by the splitting of the basin into a number of fault-bounded pull-apart sub-basins relatedto right transtension along the main NW-trending faultsystem. These sub-basins developed in late Early Pleis-tocene to Middle Pleistocene, up to inferred MIS 9-8 times.The transtensional episode is thought to reflect resumptionof regional NW-SE-directed extension as a response to alate, probably slow, phase of rollback of the Ionian slab.After the currently assumed stalling or significant slowingdown of the Calabrian Arc subduction, the recent and present-day setting seems to be characterized by the co- existence of a predominantly extensional regime associatedwith thin-skinned gravity-driven tectonics in the onshorearea, and a diffuse transpression in the offshore area.

ACKNOWLEDGMENTS

This work was financed by MIUR (PRIN 1997 to D. RIO, PRIN1999-2001 to F. MASSARI, 2004 to R. SPROVIERI) and Basilicata Uni-versity funds. We thank A. ASIOLI, R. SPROVIERI and E. DI STEFANOfor help in biostratigraphical analysis, D. RIO and D. ZAMPIERI forinformative discussions; L. RACCAGNI for digitalizing the map,N. MICHELON and S. CASTELLI for technical support; S. CRITELLIand an anonymous referee for helpful reviews, and particularly theeditor of the Italian Journal of Geosciences W. CAVAZZA, for construc-tive and insightful suggestions.

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Manuscript received 16 March 2010; accepted 27 July 2010; editorial responsability and handling by W. Cavazza.

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