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A new Serpukhovian (Mississippian) fossil flora from western Argentina:Paleoclimatic, paleobiogeographic and stratigraphic implications

Diego Balseiro a,⁎,1, Juan J. Rustán a,1, Miguel Ezpeleta b, Norberto E. Vaccari a

a Centro de Investigaciones Paleobiológicas, CICTERRA (CONICET- Universidad Nacional de Córdoba), Av. Vélez Sársfield 299, X5000JJC, Córdoba, Argentinab Laboratorio de Análisis de Cuencas, CICTERRA (CONICET-Universidad Nacional de Córdoba), Av. Vélez Sársfield, 1611, 2° piso, of. 7, X5016GCA, Córdoba, Argentina

a b s t r a c ta r t i c l e i n f o

Article history:Received 15 January 2009Received in revised form 7 July 2009Accepted 9 July 2009Available online 17 July 2009

Keywords:SerpukhovianGondwanaArgentinaFlorasPaleoclimatePaleogeographyBiostratigraphy

An uppermost Mississippian (Serpukhovian) fossil flora from western Argentina is described for the firsttime. Its particular composition includes both, warm climate plants typical from the Pennsylvanian ofGondwana, namely pteridosperms, sphenophytes as well as arboreous lycopsids; and small lycopsidscharacteristic of cooler climates of pre-Serpukhovian times. A warm–temperate climate is inferred for thisassociation, which fills a time gap between those Pennsylvanian and Mississippian classic floras previouslyknown. The presence of Tomiodendron, Nothorhacopteris kellaybelenensis and Paracalamites allow therecognition of the Paraca Floral Realm in Argentina, supporting the existence of a nonglacial paleoclimateperiod, developed just before of the Bashkirian–Moscovian Gondwanan glaciation and after a latest Viseanglaciation. It likewise would indicate the paleogeographic position of south west Gondwana, which wouldhave acceded to a warm temperature latitudinal belt during Serpukhovian times. The recognition of thisfloral assemblage has relevant biostratigraphic and lithostratigraphic implications for the western margin ofGondwana. It defines a new zone for western Argentina, herein named Frenguellia eximia–Nothorhacopteriskellaybelenensis–Cordaicarpus cesarii (FNC) zone, which is recorded in the oldest known lithostratigraphicunit from the Paganzo Basin, the Loma de los Piojos Formation nom. nov.

© 2009 Elsevier B.V. All rights reserved.

1. Introduction

The Late Paleozoic witnessed a major climatic event, known as theLate Paleozoic Ice Age (López-Gamundí, 1997; Fielding et al., 2008),which is classically depicted as a single protracted glaciation. However,novel contributions have challenged this idea, showing that the globalclimate dynamics were much more complex than previously envisaged(e.g. Fielding et al., 2008; Birgenheier et al., 2009). This view suggests acomplex hierarchical arrangement of glacial and nonglacial periods,named “nested cyclicity” by Birgenheier et al. (2009). This is particularlytrue for western Gondwana, where the recognition of more (Pazos,2007; Pérez Loinaze et al., 2008) and shorter glacial events (Isbell et al.,2008) as well as new dates for some events (Pazos, 2007; Astini andEzpeleta, 2008; Ezpeleta and Astini, 2009) is nowadays underdiscussion.

The Late Paleozoic Ice Age hadmajor effects on the biota (e.g. Ziegler,1990; Kelley and Raymond,1991; Anderson et al., 1999; Pfefferkorn andIannuzzi, 2005; Powell, 2007). Hence, the understandingof the complexclimatic framework helps to elucidate the equally complex fossil record,and viceversa. In the case ofwesternGondwana twodifferentfloras havebeen classically recognized in the fossil record. The Mississippian florawas dominated by small endemic lycopsids, while the Pennsylvanianflora was characterized by Nothorhacopteris and Botrychiopsis (NBGzone). Between these floras existed a floral lacuna that was difficult toclarify (Anderson et al., 1999). Only recently, Iannuzzi and Pfefferkorn(2002) filled that blank based on the review of someGondwanan floras,and defined a new floral realm: the “Paraca Floral Realm” (Iannuzzi andPfefferkorn, 2002; Pfefferkorn and Iannuzzi, 2005). This realm wascharacterized by a combination of elements known from other climaticbelts, and defined a new warm–temperate climatic belt for the LateVisean–earliest Serpukhovian.

Specifically, the Carboniferous floras of western Argentina have beenknown for more than a century (Geinitz, 1876), and received muchattention ever since (e.g. Kurtz, 1921; Frenguelli, 1949; Arrondo andPetriella,1978;Césari,1987;Archangelskyet al.,1987,1996;Gutiérrez et al.,1992; Gutiérrez, 1995; Vega, 1995; Carrizo and Azcuy, 1998; Césari andPérez Loinaze, 2006; Césari et al., 2007). These contributions dealt withsystematic, biogeographic and climatic aspects of both Mississippian and

Palaeogeography, Palaeoclimatology, Palaeoecology 280 (2009) 517–531

⁎ Corresponding author. Tel.: +54 351 4332098x251; fax: +54 351 4332097.E-mail addresses: balsedie@gmail.com (D. Balseiro), juanjorustan@gmail.com

(J.J. Rustán), mezpeleta@efn.uncor.edu (M. Ezpeleta), evaccari@efn.uncor.edu(N.E. Vaccari).

1 The order of the first two authors does not indicate seniority, and are listed inalphabetic order.

0031-0182/$ – see front matter © 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.palaeo.2009.07.005

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Pennsylvanian floras. However, the particular characteristics of Serpu-khovian floras remained unknown due to their absence from thewesternArgentinian fossil record (Archangelsky et al., 1996).

Herewepresent the studyof a unique fossilflora found at Lomade LosPiojos, southwest Jáchal, San Juan Province, western Argentina. Thecomposition of this flora is intermediate between typical Mississippianfloras and Pennsylvanian floras of western Gondwana, and has importantbiostratigraphic implications. Given its Serpukhovian age, this assemblagemay shed light on the Late Mississippian–Early Pennsylvanian biogeo-graphic, climatic, and paleogeographic history of Gondwana.

2. Geological setting and paleobotanic background

The Late Paleozoic deposits from western Argentina are usuallydivided into three main sedimentary basins: Calingasta–Uspallata and

Río Blanco to the west, and the Paganzo Basin to the east (Fig. 1B). ThePaganzo basin is characterized by two well differentiated zones, awestern region with marine influence, and an eastern regiondominated by continental sedimentation. The stratigraphy of westernPaganzo has been subdivided in Guandacol, Tupe and Patquíasupersequences (Fernández Seveso et al., 1993). In agreement withthis division, the history of this basin was summarized by Limarinoet al. (2006) in three main events: 1) a Bashkirian glacial eventrecorded at the base of Guandacol Formation, 2) a Pennsylvanianpostglacial fluvial succession with NBG megaflora zone in upperGuandacol and Tupe formations, and 3) Permian red beds with Glos-sopteris flora in the Patquía Formation and equivalents (Archangelskyet al., 1987).

Late Paleozoic outcrops at Loma de Los Piojos, 7 km southwest ofSan José de Jáchal, San Juan Province, correspond to western Paganzo

Fig. 1. A) Geographic location of study area in central western Argentina. B) Paleogeographic reconstruction of Upper Paleozoic basins in central western Argentina, showing mainlocalities. C) Detailed map of the type locality of Loma de Los Piojos Formation, and stratigraphic sections studied (A and B).

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(Fig. 1B). In this locality, García (1945) was the first one to recognizestrata having a possible Early Carboniferous flora. However, thisauthor did not clearly specify the stratigraphic position of theserecords, nor did he differentiate them from the Guandacol Formation.Later, this interval was mapped as Middle Devonian and included intothe underlying Punta Negra Formation (Furque, 1979). Most recently,a detailed map was made by Lehnert (1990) who assigned all theseoutcrops to the Carboniferous. Thematerial collected by García (1945)was revised and illustrated by Arrondo and Petriella (1978), andGutiérrez and Arrondo (1994) who agreed with its Mississippian agebased on the recognition of Frenguellia eximia. These Carboniferousoutcrops from Loma de los Piojos were correlated with those from LaUsina and Pasleam by Rolleri and Baldis (1967), Baldis and Cané(1968), Furque (1979) and Rodríguez (1985).

A detailed study of the outcrops at Loma de los Piojos allowed therecognition of a sandy-mudstone interval unconformably overlain bybasal diamictite of the Guandacol Formation, and overlying inunconformity the Talacasto Formation (Lower Devonian). Based on itsstratigraphic relations and its singular paleofloristic record, notrecognized previously in western Argentina, we separate this intervalas a different lithostratigraphic unit, the Loma de los Piojos Formationnom. nov., in allusion to the name of Loma de los Piojos, its type locality.

3. Stratigraphy of Loma de Los Piojos Formation

Overall, the Loma de Los Piojos Formation consists of a coarsening-upward basal section (between 35 and 130 m, Fig. 2) formed by blackshales, green mudstones, fine grained thin-bedded tabular sandstoneand coarse to medium graded sandstone beds, and an upper section(55 and 135 m, Fig. 2) of relatively monotonous green mudstonesalternating with bedded massive sandstone. The differences inthicknesses of these two intervals between close outcrops indicate amarked paleorelief at the time of deposition as well as an intenseglacial erosion prior of deposition of diamictites of the overlyingGuandacol Formation (Fig. 2).

The basal section of the Loma de Los Piojos Formation begins withthin conglomeradic bed followed by bioturbated black mudstones(~30 m) in thin intervals (b2.5 m), interbedded with tabularsandstones with carbonate matrix and showing no evidence of waveinfluence. The sandstone/mudstone ratio is very low (~1:10). Thesemassive or graded sandstone beds (5 and 20 cm) with frequent solemarks are separated by thin (b2 cm) bioturbated mudstone beds.Locally, small hummocky cross stratification is present (Fig. 2A).

A heterolithic succession (~40 m) overlies this muddy succession.This interval is formed by a rhythmic alternation of medium to finetabular sandstone interbedded with gray-greenish bioturbated silt-stones and silty-sandstones. The sandstones (10–30 cm), possess flat orirregular basal contacts, and commonly has carbonate cement thatoccupiesmore than 20%of thepore space. Locally, they develop load andflow structures in their base, and mud intraclasts are common.Internally, they are normally graded beds at the base, with parallellamination and cross laminationwith sinuous crests (outof phase and inphase) at the top. The lengths of waves are always shorter than 30 mm,these tabular and coarsening-upward sandstone beds are generallyaccompanied by subtle lateral granulometric changes. Sandstone/mudstone ratio is relatively high (2:1 and more) and fine depositsseldom surpass 10 cm in thickness. Basal contacts of sandstones aresharp and flat, and their tops usually have ripples cross lamination.

Overlying this interval, a coarse sandstones succession is observed(~55 m). It consists of amalgamated medium to coarse laminatedsandstone with erosive bases and tabular or lenticular expandedgeometries (b1,5 m thickness and ~100 m of lateral extension).Internally, planar bedded dominate and locally large-scale troughcross bedding is observed. Soft-sediment deformation and mudintraclasts are common at the base of these beds. At the top, sandstonesshow frequent symmetric ripples. Usually, thin (b1 cm), gray and

bioturbated silty levels are interbedded. Sandstone/silt ratio is N10:1.Locally, lenticular and fine conglomerates of reduced thickness areinterbedded.

The upper section of the Lomade Los Piojos Formation, records a thinsand transition (b10 m) to a continuous and monotonous mudstonesuccession (Fig. 2). This interval is similar to the facies associationdescribed at the base of the unit.

The dominant black shales at the base of the Loma de Los PiojosFormation suggest suspension and settling of sediments below stormwave base in anoxic conditions. Beds of relatively clean and tabularsandstones, with normal gradation and solemarks at their base, suggestdeposits resulting from gravitational to granular flows. Hummockycross-stratification in interbedded sandstones implya storm-dominatedsuccession, which eventually decayed into lower-energy wave oscilla-tion. The small size of these structures suggests a proximal prodeltabecause of a decrease of storm wave size (Yang et al., 2006). In theheterolithic middle section of the basal succession, the high proportionof sandstones beds, their geometry, contacts and internal structuresreflecting conditions of waning flow, suggest the periodic occurrence offlood-generated hyperpycnal flows (Mutti et al., 2003). Processes ofsuspension and settling in this interval would have increased thepotential of preservation of the paleoflora described in this contribution.The coarse grained upper interval of the basal succession is interpretedas product of relatively expanded canalized flows forming distributary-mouth bars that coalesced into complex bar assemblages. Interbeddedlenticularfine-graineddeposits are interpreted as settling in smallwaterbodies confined between the channels.

The coarsening-upward pattern of basal section of the Loma de LosPiojos Formation, leads to an interpretation of the basal sequence aspart of a prodelta gradually replaced by shallower facies of a deltafront and delta plain as a result of prograding deltaic lobes. The Lowerfacies association is interpreted as prodelta deposits (Fig. 2).Mudstones deposited from suspension accumulated at rates whichare an order of magnitude slower than accumulation rates ofhyperpycnal muds and consequently show much higher degrees ofbioturbation (Allison et al., 2000). The Middle facies association isconsidered to be delta front deposits with a relatively low gradient,under the action of stormwaves. The internal arrangement reflects theconstruction of lobes by relative fluctuations in the base level or inclastic influx (Fig. 2). The presence of distributary channels at the topof the basal section suggests a delta plain paleoenvironment(Bhattacharya, 2006, Fig. 2). This facies association includes a widevariety of brackish, paralic to wetland sub-environments includingswamps, marshes, and interdistributary bays. Soft-sediment deforma-tion features result from high sedimentation rates and are common inriver-dominated deltas (Bhattacharya, 2006). The fine grained uppersection of the Loma de Los Piojos Formation is similar to the faciesassociation described at the base of the unit, and is interpreted as aprodelta facies association.

Sudden overlap of anothermudstone succession in the upper sectionof the unit, indicates a transgressive event and a change in the dischargerate (Fig. 2). The marked paleorelief prior to the deposition of the Lomade Los Piojos Formation, suggests that this delta system was confinedinside an estuary. In estuarine environments the absence of marinefauna, high supply of fragmentary flora and intense bioturbation arecommon, due to the brackish conditions of deposition.

In general, the shales of the basas Loma de los Piojos Fm. lackmacroflora, while through the upper part, fossiliferous levels are morefrequent and dominated by fragmentary stems. The fossils studied comemainly from three levels (LM1, LM2 and LP9, Fig. 2). The LM1 bears seeds,small and fragmentary fronds and sphenophytes remains preserved asadpressions. The LP9 is characterized by the abundance of sphenophytes,together with lycopsids and scarce pinnules ofNothorhacopteris; here thefossils appear as moulds or reddish impressions–compressions. Anotherlevel (LM2) presents some remains of Diplothmema, Cordaicarpus andNothorhacopteris as the only identifiable fossils.

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4. Systematic paleontology

Materials are housed in the collection of the CIPAL (Centro deInvestigaciones Paleobiológicas) (CEGH-UNC), Facultad de CienciasExactas Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba,Argentina. Materials from the Museo de Paleontología (CORD-PB),UniversidadNacional de Córdoba, have also been revisedwhennecessary.

The terminology used in the description of the Lycophyta followsMeyen (1976), while the phyllotaxis angle was measured as indicatedby Gutiérrez and Arrondo (1994). The nomenclature defined byArchangelsky (2000) is used for the description of the seeds.

Frenguellia Arrondo, Césari and Gutiérrez, 1991Type species: Protolepidodendron eximium Frenguelli, 1954, MalimánFormation, Mississippian, San Juan Province, Argentina.Frenguellia eximia (Frenguelli) Arrondo, Césari and Gutiérrez, 1991

Fig. 3I–J, N–OMaterials assigned and stratigraphic position: LP9: CEGH-UNC

23552–23554, 23556–23559; LM3: CEGH-UNC 23555Description

The assignable material corresponds to several remains of stems,preserved as impressions and moulds in siltstones and sandstones.The best preserved (CEGH-UNC 23552) is a stemmould, conserved inmedium-grained sandstone. For the observation of morphologicaldetails we took into account the latex mould of this specimen andused the originals of the other specimens.

This specimen lacks bifurcations and is 51 mm in length and 13 mminwidth. The decurrent bases of the leaf cushions are not clearly defined,and exhibit false leaf scars in its apical part. The leaf cushions aredistributed in a 20° lepidodendroid phyllotaxy with orthostichies andhorizontal lines clearly visible. The false leaf scars are approximately0.6 mm in the maximum width, and they are within a horizontaldistance of 1.5 mm and a vertical distance of 5.2 mm of each other.

Strong striations run longitudinally through the stem in adiscontinuous way, connecting the leaf cushions. The interference ofthe decurrent base of the leaf cushion with these longitudinal linesgives the specimen a distinctive rhomboidal ornamentation pattern. Afalse leaf scar is located in each vertex of the rhomboidal areas formed.

The disposition of the leaf cushions and the false leaf scars issomewhat irregular (especially in the upper and the right sections).There are also some variations in the orientation of the horizontal linesand in the definition of the longitudinal striation, which may be due totaphonomic processes. Taking this into consideration, all the measure-ments were obtained from the lower right section which, to ourunderstanding, hasmaintained theoriginal disposition of the structures.

On the upper leftmargin of the fragment there is a falcate leaf whichis partially covered by sediment. It is 4 mm in length and 0.4 mm inwidth. This leaf is separated from the stem by an angle of 38°, and itpresents an inflection in its distal half and an acuminated end, where afine line indicates a partition.Discussion

Thematerial is assigned to F. eximia based on its size (interpreted hereas evidence for a herbaceous growth habit) and its false leaf scars arrayedin a lepidodendroid phyllotaxy, and its adaxially recurved distallysegmented falcate leaves. All of these are diagnostic characters for F.eximia (Arrondo et al., 1991). The false leaf scars and the longitudinalstriation are characters that are present in several specimens undoubtedlyassigned to this taxon (e.g.:Morel et al.,1993Plate IfigureA;Gutiérrez andArrondo, 1994).

Although none of the studied materials show dichotomousbranching, the specimen LP-PB469 does (illustrated by Arrondo and

Petriella, 1978 Plate I figures B and C). This specimenwas collected byDr. E. García as part of his PhD thesis (1945) from the same levels andlocality of the materials studied here; and Gutiérrez and Arrondo(1994) assigned it to F. eximia in their revision of the genus Frenguellia.Likewise, the five segments of the leaf are not clearly observed in ourmaterials. However, many specimens lack this diagnostic character(e.g.: Morel et al., 1993 Plate I figure A), so this does not impede thespecific assignment.

It is worthmentioning that thematerial here studied bears a strongsimilarity to those from Mina la Negra (Sierra de Maz, La RiojaProvince), which come from the strata assigned to the GuandacolFormation. These materials were illustrated by Arrondo and Petriella(1978, Plate I figures A and D), who referred them as Lepidodrendopsissekondiensis Mensah and Chaloner 1971. We think that they shouldalso be referred to Frenguellia eximia.

Malanzania Archangelsky et al., 1981Type species: Malanzania nana Archangelsky et al., 1981, MalanzánFormation, Pennsylvanian, La Rioja Province, Argentina.Malanzania sp.

Fig. 3K–LMaterials assigned and stratigraphic position: LP9: CEGH-UNC

23560–23561, 23563–23565; LM1: CEGH-UNC 23562; LM2: CEGH-UNC 23566Description

The best preserved material (CEGH-UNC 23563) is an adpressionof a fragmented stem. It is 23.4 mm long and 13 mm wide and it hasexcrescences distributed in a 40° lepidodendroid phyllotaxy. There is a70° angle between whorls and the orthostichies are not evident.

The excrescences are approximately 0.74 mm in size measurednormally to the stem and 0.5 mm longitudinally. They exhibit a flatsurface in its apical part, awell defined outline and no evidence of a leaftrace. Their shapes vary from rounded to sub-rhombic in cross section.The excrescences on the margins of the stem are short and truncatedending abruptly in a plane. The distance between them can be variable,possibly due to deformation (12–18 mm) but it is never less than thelength of their maximum diameter.

The extensive interareas between the false leaf scars are smooth,with some irregular and discontinuous lines which may be explainedby taphonomic effects. Since the stem fragment we have is deformed,measurements were taken from the upper left part, where thedeformation is lesser.Discussion

The placement in the genus Malanzania is based on the followingdiagnostic characters: the excrescences are irregular and sub-circularoutline, they have lepidodendroid arrangement, and are separated bysmooth and ample interareas.

The holotype description ofM. nana Archangelsky et al., 1981 fromthe Pennsylvanian of Malanzán includes some of the charactersobserved in our material, such as sub-rhombic section of the false leafscar's sub-rhombic section, and its arrangement in a lepidodendroidphyllotaxy without apparent orthostichies. Nonetheless, in this newmaterial the false leaf scars show well delimited and clear borders.There are neither spiniform excrescences nor longitudinal lines in theinterareas as there are in the specimens from Malanzán.

M. ottonei Carrizo and Azcuy, 1998, from theMississippian (Visean)of Cerro Mudadero and Punilla Formation (Quebrada de la Jarilla), LaRioja Province, resembles our material in the following character-istics: the false leaf scar has a sub-circular and wide base, they showsimilar separation distance between leaf scars (1.5–3 times themaximum diameter), and a similar phyllotaxy angle (in the vertical

Fig. 2. Stratigraphic columns for the Loma de Los Piojos Formation. See map in Fig. 1 to location of columns A and B. Paleoenvironments are associated to the sea level curve. Note thecoarsening-upward basal section and sudden transgressive event in the upper section of the unit. A) Black shales interbedded with tabular fine sandstones in a prodelta setting. B)Details of hummocky and swalley cross stratification. C) Turbiditic deposits in sandstones beds generated by sudden decelerating unidirectional currents. D) Details of flutemarks. E)Coarse sandstone-filled channel eroding into laminated fine wave sandstone. F and G) Wave laminated fine sandstones. H) Green mudstone interbedded with tabular finesandstones. I) Erosive discordance between Loma de Los Piojos Fm and glacial diamictites of Guandacol Fm.

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and between whorls). The excrescences have, however, very differentmorphologies, being much longer in M. ottonei.

M.antiguaArchangelsky,1983, fromtheMiddleDevonianofMalvinasIslands and La Rioja Province, shares the following characteristics withthe Loma de Los Piojosmaterial: the shape of the excrescence, their cleardefinition, and their truncated apex. Because Archangeslky's (1983) andour description are based on latex molds, our Serpukhovian speciesshares many characteristics with Archangeslky's Middle Devonianspecies. The poor quality of the natural moulds of the rock matrix of M.nana andM. ottoneimay explain the absence of clear borders in the falseleaf scars of these species. The phyllotaxy with well defined vertical andhorizontal lines of M. antigua (Archangelsky, 1983, Figs. 3 and 4) werenot observed in the studied material.

Although the material studied shares characters with all threespecies of the genus, it also differs in many others. Consequently thesespecimens possibly correspond to a new taxon, however, as the qualityof the material is not sufficient to erect a new species the nomenclatureis left open.

Tomiodendron Radczenko, 1955, enmd. Meyen, 1972Type species: Lepidodendron ostrogianum Zalessky in Zalesskij andČirkova, 1935; Kuznetsk Basin, Serpukhovian, Angara, Russia.Tomiodendron sp.

Fig. 3 A–B, E, HMaterials assigned and stratigraphic position: LP9:CEGH-UNC23551

DescriptionThe only specimen assignable is an impression/compression of

bark, which presents part and counterpart. The most informative ofthese shows the stalk from the inside, thus our description will bebased on that fragment and its latex mould.

This specimen is 54 mm in length and 28 mm in width. The leafcushions show different degrees of preservation: some are clearlydefined, others are represented by their outline and the sedimentsfilling the ligule pit, and others are absent. The phyllotaxy is alepidodendroid of 37°, with scalariform parastichies and withoutothostichies or horizontal lines.

The leaf cushions are 5 mm in length and 2 mm in width, with aninverted flame appearance, conveyed by their fusiform shape and theirasymmetry. In the latexmould the right side of the leaf cushions is slightlyconcave in its lower part while the left side is smoothly convex. From theupper third and onwards the leaf cushions became progressivelyacuminate downwards, losing relief towards the interarea, and they donot show a heel. In at least two leaf cushions the upper margin, subtlypreserved, is acuminate; nevertheless in most cases it is sub-rounded inappearance due to compaction. The presence of some variability in theoutline of some leaf cushions can be explained by the rupture of thesedimentary matrix below the wings. The leaf cushions do not haveevident leaf scars or associated elements such as leaf traces and parichnos.The axilar line of a false leaf scar is hard to appreciate and the infrafoliarbladder cannot be seen, but this may be due to poor preservation.

The leaf cushions are flat and widely separated (3.7 mm), defininginterareas with a slight ornamentation consisting in longitudinalstriations that cover the interarea. There are some fine lines denselyarranged, and otherwider linesmore separated. The disposition of thesestriations is irregular; they are sinuous and discontinuous. There is noevidence for anastomosis or convergence towards the leaf cushions.Discussion

The generic placement is based on the presence of the followingitems: lepidodendroid phyllotaxy, fusiform and spaced leaf cushions,existence of a ligule pit, ample interareas, absence of leaf scars, and

inferred presence of wings. They are all characters mentioned in thegenus enmended diagnosis by Meyen (1972, 1976). The apparentabsence of an infrafoliar bladder may be attributed to taphonomicprocesses. Decomposition of the specimen under study prior to burialis inferred from the differential preservation of leaf cushions and otherstructures (such as the striation of the interarea surface).

The studied material bears a great resemblance with T. kemer-oviense (Chachlov) Radczenko, 1955 from the Mississippian (Serpu-khovian) of Angara (Russia) and with T. peruvianum (Gothan)Pfefferkorn and Alleman in Ianuzzi and Pfefferkorn, 2002, from theMississippian (Visean) of Paracas (Peru). The lepidodendroid phyllo-taxy, the leaf cushions asymmetrically narrowed and downwardsattenuated, and the ample and ornamented interareas are charactersshared with T. kemeroviense. Nonetheless, the leaf cushions with anarrower and flame inverted appearance, the absence of a conspic-uous infrafoliar bladder and the disposition of the ornamentation inthe interareas differentiates our material from the latter species.

Our material is even more similar to T. peruvianum. The main char-acteristics are the likeness in the outline, the leaf cushion's asymmetry,the greater extension of the interareas and the very conspicuous ligulepit. However, the leaf cushions of the material from Loma de Los Piojosare less rhomboidal, with their maximumwidth in the upper third. Thestriated ornamentation of the interareas is subparallel rather thananastomosingor convergent to the leaf cushions. It is interesting to pointout that T. peruvianum infrafoliar bladder is less noticeable than that of T.kemeroviense. This characteristic makes it more similar to our material,where that structure is not observed.

In spite of the remarkable similarity of the Loma de Los Piojosmaterial with T. peruvianum, a clear placement can not be made due tothe quality of the preservation of the only specimen available andtherefore the nomenclature is left open.

The genus Tomiodendron has been compared to the genus Bumbu-dendron Archangelsky et al., 1981. Cogeneric or even cospecific relationsbetween B. paganzianum Archangelsky et al., 1981 and T. kemeroviensehave been particularly discussed, based on the possibility that theabsence of the leaf scar in the latter is a result of the decortication of thematerial. Yet, the occurrence of the ligula pit in T. kemeroviense, which isdiagnostic for the genus, eliminates the possibility to relate this speciesto Bumbudendron, which does not posses a ligule pit in any of its species.

The material from Paracas (Peru) assigned to Tomiodendronperuvianum by Pfefferkorn and Alleman (in Ianuzzi and Pfefferkorn,2002) was first referred to as Lepidodendron rimosum Sternberg byBerry (1922), then as Lepidodendron peruvianum by Gothan (1928),and finally in 1954 as Lepidodendropsis peruvianum by Jongmans(1954). In Argentina, materials identified as “Lepidodendron/Lepido-dendropsis peruvianum” are known for the Carboniferous (Frenguelli,1949; Arrondo and Petriella, 1978; Furque, 1979) and many of themhave been revised (Archangelsky et al., 1981; Gutiérrez, 1996). Theseauthors showed that the previous material is hard to assign to a genusowing to the poor preservation of diagnostic characters and conse-quently this material will not be dealt with in this discussion.

This is the first record of a ligulated lycopsid and particularly of thisgenus in Argentina and has important paleoclimatic and paleobiogeo-graphic implications that will be discussed below.

Bumbudendron Archangelsky et al., 1981Type species: Bumbudendron paganzianum Archangelsky et al., 1981,Lagares Formation, Pennsylvanian, La Rioja Province, Argentina.Bumbudendron millani (Arrondo and Petriella, 1978) Arrondo andPetriella, 1985

Fig. 3. A, B, E and H) Tomiodendron sp. (CEGH-UNC 23552A) A) General view, scale bar=1 cm. B) Detail of ligule pit, scale bar=0.5 mm. E) Leaf cushion, scale bar=1 mm. H) Detailof the phyllotaxis, note the poor preserved leaf cushions just betweenwell preserved ones, scale bar=5 mm. C, D, F and G) Bumbudendron millani (CEGH-UNC 23567A) C) Detail ofleaf scar, scale bar=2mm. D) General view, scale bar=1 cm. F) Leaf cushion, scale bar=5mm. G) Detail of the phyllotaxis, scale bar=5mm. I and J) Frenguellia eximia (CEGH-UNC23554A) I) Detail of leaf, scale bar=1 mm. J) General view, scale bar=5 mm. K and L) Malanzania sp. (CEGH-UNC 23563) K) General view, scale bar=1 cm. L) Detail of theexcrescence in lateral view, scale bar=1 mm. M) Paracalamites sp. (CEGH-UNC 23570A) scale bar=5 mm. N) General view of Frenguellia eximia (CEGH-UNC 23553), scalebar=1 cm. O) General view of Frenguellia eximia (CEGH-UNC 23552), scale bar=1 cm.

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Fig. 3C–D, F–GMaterials assigned and stratigraphic position: LP9: CEGH-UNC

23567Description

The material is an impression of a stem fragment preserved insandstones, which length is about 54 mm in length and 22 mm wide.The specimen shows leaf cushions clearly defined in all along its surfacein a 25° lepidodendroid phyllotaxis without evident ortostichies norhorizontal lines, but shows scalariform parastichies. The lower leafcushions are fusiform and 9 mm long and 3 mmwide, while the upperones tend to be equidimensional and smaller, being 4.3 mm long and1.7mmwide. This variation in size and shape of the leaf cushions allowsthe recognition of a growth zone. In general the leaf cushions insinuate aleaf scar, show an infrafoliar bladder and a leaf trace. Although thesecharacteristics allow inferring a rather high decortication state as shownin the Fig. 7d–e and Fig. 8f–gof Archangelskyet al. (1981), the absence ofa ligule pit and wings can be taken for sure.

The leaf cushions are separated by a deep furrow of constant width(0.5 mm)with a thin striation, which clearly delimits the leaf-cushioncontour. The preservation does not allow recognition of detailedpatterns in the furrows striations.

DiscussionThe placement in the genus Bumbudendron is based on the presence

of fusiform leaf cushions in a lepidodendroid phyllotaxis, separated bydeep narrow furrows with thin striations and only one leaf trace in themiddle of the leaf scar. All these characters are mentioned in thediagnosis of the genus (Archangelsky et al., 1981). Due to thepreservation, it is not possible to see other diagnostic characters.

As has been discussed above, the absence of a ligule pit and wingsin Bumbudendron, differentiates this genus from Tomiodendronwherethis structures are diagnostic (Meyen, 1972, 1976).

The studied material shows great similarity with the knownspecies of the genus, particularly with B. nitidum Archangelsky et al.,1981 and B. millani. The variation in shape and size of the leaf cushiondue to the presence of a growth zone in our material makes it difficultto place the specimens in either species. Nonetheless, the generalsmall size of the leaf cushions, their length/width ratio not higherthan 4:1, the thin furrows of constant width delimitating the leafcushions and the phyllotaxis angle, suggest that our material belongsto B. millani (Arrondo and Petriella) Arrondo and Petriella, 1985. It hasto be said that the holotype of B. millani shows growth zones just likethe ones in our material (Arrondo and Petriella, 1978, 1985).

Fig. 4. A) Pinnule of Nothorhacopteris kellaybelenensis (CEGH-UNC 23587), scale bar=5 mm. B) Paracalamites sp. (CEGH-UNC 23573), scale bar=2 mm. C) Diplothmemabodenbenderi (CEGH-UNC 23592A), scale bar=1 cm. D) Pinnule of Nothorhacopteris kellaybelenensis (CEGH-UNC 235878) scale bar=5 mm. E and G) Nothorhacopteriskellaybelenensis (CEGH-UNC 235) E) Fragment of pinnule, scale bar=5 mm. G) Detail of the distal margin, note the lobes delimitated by incisions, scale bar=1 mm. F) Pinnule ofNothorhacopteris kellaybelenensis (CEGH-UNC 23588) note the differentiated petiole, scale bar=5 mm. H) Cordaicarpus cesarii (CEGH-UNC 23574A), scale bar=1 mm.

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The finding of remains undoubtedly assigned to Bumbudendronmillani, extends the stratigraphic range of the genus in general, andthis species in particular, up to the Late Mississippian (Serpukhovian).

Paracalamites Zalessky, 1927Type species: Phyllotheca sibiricus Zalessky, 1927Paracalamites sp.

Fig. 3M and Fig. 4BMaterials assigned and stratigraphic position: LP9: CEGH-UNC

23568, 23571–23573; LM1: 23569–23570Description

The materials we assigned to this form genus comprise compres-sions and pith casts of articulate stems of up to 20 mm in length and7.5 mm in width. The internodes are notably longer than the stem'sdiameter. The ribs are usually opposite in nodes and on some casesthey are delicately striated. The ribs are 0.5 mm in width while thesenus are 0.75 mmwide. There are neither leaf nor branch scars in anyof the specimens we studied.Discussion

The form genus Paracalamites was defined by Zalessky (1927) inorder to include the remains of sphenophytes from Angara. Thesewere pith casts with a continuous ribbing. Later, Rigby (1966a)included in the genus not only the pith casts, but also the stemimpressions with the characteristic ribbing and recommended the useof this genus for materials from the Late Paleozoic of Gondwana.Finally, Naugolnykh (2002) distinguished Paracalamites from Paraca-lamitina Zalessky,1934 based on the presence of leaf scars in the latter.He suggested the usage of Paracalamites for pith casts.

The genus Archaeocalamites Stur, 1875 refers to a whole plant inwhich there are Paracalamites-like stems in organic connection to leaves(Mamay and Bateman, 1991). Yet, several pith casts, impressions orcompressions from theMississippian of Euramerica that had continuousribbing and lacked foliage were assigned to this genus (Mamay andBateman, 1991). Accordingly, Iannuzzi and Pfefferkorn (2002) referredtoArchaeocalamites all thematerial from theMississippianof Gondwanathat had been originally assigned to Paracalamites.

The material under study is assigned to Paracalamites based in thefollowing characters: its continuous ribbing, absence of leaf/branchscars, and the presence of fine striations. These characters arediagnostic of the form genus. Given the characteristics of the material,we prefer to assign it to a form genus instead of a whole plant genussuch as Archaeocalamites. In addition, at least some genera from thePennsylvanian of Paganzo Basin, such as Gondwanites Césari and PérezLoinaze, 2006, have Paracalamites-like stems.

Paracalamites australis Rigby, 1966a,b has been reported in theCarboniferous of Argentina (e.g.: Archangelsky and Archangelsky, 1987;Ottone and García, 1990; Gutiérrez, 1995); probably due to its broaddiagnosis. We preferred to leave the nomenclature open because thematerial from Loma de Los Piojos is morphologically very varied, whichsuggests the presence of more than one taxon at the species level.

This is the first report of sphenophytes in the Mississippian ofArgentina and as such, it has important paleobiogeographic andpaleoclimatologic implications that will be discussed later. Althoughsphenophyte fossils from Loma de Los Piojos Fm. are abundant andvary in size, unfortunately, we are unable to provide a more precisesystematic given the quality of our material. Further studies will beneeded considering the relevance of this flora.

Nothorhacopteris Archangelsky, 1983Type species: Otopteris argentinica Geinitz, 1876, Cuesta Colorada,Pennsylvanian, La Rioja Province, Argentina.Nothorhacopteris kellaybelenensis Azcuy and Suárez-Soruco, 1993

Fig. 4A, D–GMaterials assigned and stratigraphic position: LP9: CEGH-UNC

23589–23591; LM1: CEGH-UNC 23578–23584; LM2: CEGH-UNC23585–23588

DescriptionThe study material includes thirteen fragments of adpressions with

coaly remains of isolated rhacopterideanpinnules. Theyare preserved indark grey siltstones (LM1) and light gray-greenish sandstones (LP9).

The specimen that is most complete (CEGH-UNC 23578) shows animpression of a flabelliform pinnule, and is 20 mm long and 25 mmwide. It is attached to a fragment of rachis by means of a short, widepetiole.

The catadromic and anadromic margins of the lamina are clearlydifferentiated and they are slightly curved, defining an obtuse angle.The distal margin is curved and has regular lobes which show distalincisions.

In the lamina, large veins leave the petiole with a radial disposition.The vein pattern is clearly dichotomous. Each vein delimits a cuneiformsegment. There are 18 in total, each corresponding to a lobe in themargin of the pinnule. The veins end in the incision between eachsegment. There are fine interveinal striations parallel to the veins.Discussion

The placement in the genus Nothorhacopteris is based on the non-lacinated flabelliform rhacopteridean pinnules. Their margins havesome smooth lobes and inter-venal striations, as mentioned in thediagnosis by Archangelsky (1983).

We did not use the number of veins to determine the placement atthe species level, given that Archangelsky and Archangelsky (1987)showed the intraspecific variability of this character.

N. argentinica (Geinitz) Archangelsky, 1983 differs from our materialin the general morphology of its pinnules, which are sub-circular andslightly rhomboidal, according to the original description and examina-tion of the holotype (CORD PB 869) and the paratype (CORD PB 867). Italso differs in the following: absence of a defined petiole, its biggerlength–width relation, curved and sinuous veins that don't defineclearly cuneiform segments, absence of lobes and incisions in the distalmargin, and curved undefined catadromic and anadromic margins.

N. chubutiana (Archangelsky and Arrondo) Archangelsky, 1983, ischaracteristic of the Lower Permian of Nueva Lubecka Formation,Chubut province, Argentina. In contrast to the material from Loma deLos Piojos, the distal margin of the sessile pinnules do not show lobesor incisions and the catadromic and anadromic margins are curvedand not clearly distinguishable.

N. kellaybelensis from the Mississippian of the Ambo Group ofBolivia and Perú is similar to our material in that the distal margin ofthe lamina is regularly lobed and has incisions in between thesegments, the anadromic and catadromic margins are well definedand straight, the petiole is conspicuous, and the veins definecuneiform segments. In the Loma de Los Piojos material there is ashort and wide petiole, and a variable angle between the anadromicand catadromic margins (Fig. 4A, D). On the Peruvian species thepetiole is longer and thinner, and there is a normal angle between theanadromic and catadromic margins. The shape of the pinnules in N.kellaybelenensis has been described as typically cuneiform; however,the pinnules of the basal portion of the fronds have a flabelliformshape (as it can be seen in Plate 1, Fig. 2 from Azcuy and Suárez-Soruco,1993). Taking this into account, the pinnules from Loma de LosPiojos have the same range of morphology as the Peruvian material,and consequently they can be considered cospecific.

This is the first record of Nothorhacopteris for the Mississippian ofArgentina, and the first mention of N. kellaybelenensis, in this country.The biostratigraphic, paleobiogeographic and paleoclimatic implica-tions of this taxon will be discussed below.

Diplothmema Stur, 1877Type species: Diplothmema schuetzei Stur, 1877Diplothmema bodenbenderi (Kurtz, 1921) Césari, 1987

Fig. 4CMaterials assigned and stratigraphic position: LM2: CEGH-UNC

23592

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DescriptionCompression of a third order pinnule, preserved in medium

grained sandstone. It is 21.5 mm length and 11.6 mm wide.The rachis is 1.18 mm wide and carries a fourth order pinnule of

suborbicular shape. This pinnule is attached in a 90° angle, and itslamina is deeply lobated. Each lobe defines an apparently entiresegment which are long, cuneiform, and have rounded margins. Eachsegment is nearly 3.5 mm in length. The vein pattern is not clearlyobservable, but in certain regions only one vein can be seen runningalong the rachis. In the distal region fragments of another pinnule canbe seen, which seems to be attached at an acute angle.Discussion

The material is attributable to D. bodenbenderi because it presentsfourth order pinnules of suborbicular shape, with deeply lobated laminahaving subrounded margin that are attached at nearly 90° angles. Theseare all characteristics described in the enmendeddiagnoses (Césari,1987).

It differs from D. gothanica (Dolianiti) Iannuzzi in Iannuzzi andPfefferkorn, 2002, which has fourth order pinnules attached at acuteangles, which have cuneiform narrow shape, and are never sub-orbicular (Iannuzzi et al., 2006).

The material, due to its fragmentary nature, does not allow theobservation of fourth order pinnules in alternate disposition; never-theless, this does not prevent its specific assignment.

Cordaicarpus Geinitz, 1862 enmd. Archangelsky, 2000Type species: Cordaicarpus cordai Geinitz, 1862 ex Seward, 1917Cordaicarpus cesarii Gutiérrez et al., 1992 enmd. Archangelsky, 2000

Fig. 4HMaterials assigned and stratigraphic position: LM1: CEGH-UNC

23574–23576; LM2: CEGH-UNC 23577, 23593Description

Compression/impression of flat seeds, bilaterally symmetric (platis-permic). It has an oval to circular shape, lacks wings, and its maximumlength is 5.8 mm and maximum width is 4.25 mm. The base is wide,rounded andwithout umbilicus or rafe. The apex presents two roundedprojectionswhich define an acute and triangular incision correspondingto the micropylar zone. The sclerotesta has thin longitudinal striationsand an acuminate apex that does not project outside the seed's body. Insome specimens, preserved in sandstone, a wide straight longitudinalcarena can be observed. Following the shape of the nucula, there is asmooth sarcotesta, which is thin at the base and thickens distally,reaching itsmaximumwidthnear thedistal end. Themaximumwidthofthe sarcotesta is 0.4 mm. The sarcotesta width/nucula width ratio isabout 1:12. Due to the nature of the preservation, it is impossible toobserve the endotesta or any other structure.Discussion

The material is assigned to Cordaicarpus because it shows bilateralsymmetry, a sclerotesta with an acuminated apex that does not projectoutside the body, and a narrow sarcotesta. All these characteristics havebeen mentioned by Archangelsky (2000) in the emended diagnoses ofthe genus. Oliveira and Da Silva Pontes (1976) proposed the sarcotestawidth/nucula width ratio as a criterion to differentiate Cordaicarpusfrom Samaropsis Goeppert, 1864. This ratio is smaller than 1:5 in Cor-daicarpus. The specimens from Loma de Los Piojos have a ratio of 1:12,which is clearly within the range of Cordaicarpus.

At a specific level, thematerial is assigned toC. cesarii because it has asubcircular shape, rounded base, and narrow sarcotesta (less than1 mm), which is wider in the apical region. All of these are diagnosticcharacters according toGutiérrez et al. (1992) andArchangelsky (2000).It is worth mentioning that the 1:12 value of the sarcotesta width/nucula width ratio coincides with the value given by Gutiérrez et al.(1992) for this species. The sizeof the studiedmaterials is alsowithin thesize range given by Archangelsky (2000) for this species.

This is the first Mississippian record of this genus in westernArgentina, consequently it can't be considered restricted to NBG zone,as previously postulated (Archangelsky, 1999).

5. Discussions

5.1. Biostratigraphy and age

The classic continental biostratigraphic scheme proposed for theCarboniferous of Argentina, based on plant macrofossils, has beensummarized in the Fig. 5 (Archangelskyet al.,1987;Azcuyet al., 2007a,b;Césari et al., 2007). A gap encompassing the Serpukhovian is presentbetween the Frenguellia–Paulophyton zone (Mississippian) and the NBGzone (Pennsylvanian), however its stratigraphic limits had never beenclearly defined.

The studied assemblage is unique due to the presence of Tomioden-dron andNothorhacopteris kellaybelenensis, in associationwith elementsfrom the NGB and Frenguellia–Paulophyton zones (i.e. Frenguellia, Bum-budendron and Cordaicarpus). Because of these compositional charac-teristics, this assemblage corresponds neither to the Frenguellia–Paulophyton zone, nor to the NBG zone, and defines a new intermediatezone, herein named the Frenguellia eximia–Nothorhacopteris kellaybele-nensis–Cordaicarpus cesarii zone (FNC zone).

Recently Rustán et al. (2008) assigned a Visean age to the florafrom the Loma de Los Piojos Formation, based on the presence ofFrenguellia eximia. However, new collections have allowed theadjustment of this age taking into account new evidence.

The age assigned to the FNC zone in this contribution is latestMississippian (Serpukhovian). This age is based on the presence ofTomiodendron, Frenguellia eximia and Nothorhacopteris kellaybelenen-sis, associated with Cordaicarpus cesarii.

The presence of Tomiodendron is fundamental because it occursalmost exclusively in the Serpukhovian, with scarce Late Viseanrecords (Meyen, 1976; Iannuzzi et al., 1998; Iannuzzi and Pfefferkorn,2002).

The genus Nothorhacopteris has been classically considered char-acteristic of thePennsylvanian. Nevertheless, assemblages characterized

Fig. 5. Biostratigraphic chart of Mississippian–Lower Pennsylvanian zones fromArgentina, showing the age of the NFC zone. Modified from Archangelsky et al.(1996) and Azcuy et al. (2007b). Note the uncertainty in the limits of the FNC zone.

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by Nothorhacopteris kellaybelenensis together with Tomiodendron andsphenophytes have been assigned to the Late Visean–Lower Serpukho-vian on basis on marine invertebrates, palynomorphs, and isotopic data(Roberts et al., 1995; Iannuzzi and Rösler, 2000; Iannuzzi andPfefferkorn, 2002; Azcuy and di Pasquo, 2005; Fasolo et al., 2006 andreferences therein). This is particularly significant in Bolivia, where theNothorhacopteris kellaybelenensis–Triphyllopteris boliviana zone waserected for Latest Visean–Early Serpukhovian (Iannuzzi et al., 2003).Due to the compositional similarity, it is possible to assign a similar ageto the FNC zone (Fig. 5), and correlate it, at least partially, with N.kellaybelenensis–T. boliviana zone from Bolivia.

Finally, the FNC zone is unique due to the presence of seedsassignable toCordaicarpus. This genus has been relatedmainly to groupsof gymnosperms (Cordaitales and Coniferales) whose earliest recordsare Serpukhovian (Gorelova, 1978; Wagner et al., 1979; Wagner, 1984;Rothwell, 1988; Trivett and Rothwell, 1991; Scott et al., 1997).

As previously explained, the fossiliferous strata studied lieimmediately under the glacial beds that characterize the base of theGuandacol Formation, dated as not older than earliest Pennsylvanian(Bashkirian) (Pérez Loinaze et al., 2008).

Provided that the association of Tomiodendron and N. kellaybelen-esis with Cordaicarpus would characterize an age not older than EarlySerpukhovian, and the studied strata underlie the Guandacol Forma-tion, we assign a Serpukhovian age to the FNC zone. Unfortunately,neither the precise moment of the Serpuhkovian nor the extent oftime represented by the FNC floral zone can be yet known.

The FNC zone, represents a particular moment in the LateMississippian (Serpukhovian) previously undocumented by meansof fossil plants in Argentina, and fills the stratigraphic gap between theFrenguellia–Paulophyton and NBG zones (Fig. 5).

Although other authors have proposed a Mississippian history forthe Paganzo Basin (Férnandez Seveso et al., 1993; Limarino et al.,2006), the only unit previously recognized underlying the GuandacolFormation was the Aguas Blanquitas Formation (Pazos, 1993). Thisunit crops out both at the Cerro Guandacol and Cerro Bola (Sierra deMaz, La Rioja Province) (Pazos, 1993; Caselli and Limarino, 2002).

However, recent interpretations related the Aguas Blanquitas Forma-tion to Glacial Event II (Pazos,1997, 2007 Fig. 3), making its correlationwith the Loma de los Piojos Formation impossible (Fig. 6).

Sediments at Pasleam, San Juan Province (Volkheimer, 1962) andthe south of Sierra deMaz, La Rioja Province (Frenguelli, 1949; Andreisand Arrondo, 1974; Arrondo and Petriella, 1978), may have FNC zonefossils and correlate with the Loma de los Piojos Formation (Fig. 6).However, these strata need more investigation.

In this scenario, the Loma de los Piojos Formation represents theonly certain pre-Bashkirian unit. This unit not only has precisestratigraphic relationships, but carries fossils that indicate a Serpu-khovian age. Stratigraphic relationships suggest that the deposits ofLoma de los Piojos Formation belong to the Paganzo Basin, rather thanto a possible earlier basin, known as the Protopaganzo Basin (Limarinoet al., 2006). Instead, we refer the Loma de los Piojos Formation to theinitial structuring and functioning of the Paganzo Basin. Future studiesof this new unit will allow a better understanding of the magnitude,development and early tectono-stratigraphic evolution of this Basin.

5.2. Paleobiogeography and paleoclimatology

The Mississippian floras from western Gondwana are characterizedby the presence of herbaceous lycopsids, and they have been consideredto belong to a cold climate. Conversely, the Pennsylvanian floras containNothorhacopteris and Botrychiopsis, which are indicative of a warmerclimate (Archangelsky et al., 1987; Anderson et al., 1999; Césari et al.,2007). Only recently, have associations of intermediate compositionbeen identified. Floras of Late Visean–Early Serpukhovian age, andintermediate compositionfill a void between Early toMiddle Visean andBashkirian floras (Iannuzzi and Pfefferkorn, 2002). These Late Visean–Early Serpukhovian floras are characterized by the presence ofpteridosperms (distinctively Nothorhacopteris kellaybelenensis),together with arboreous lycopsids (particularly Tomiodendron) andtropical elements such as Archaeocalamites (= Paracalamites); whileendemic lycopsids from Argentina such as Frenguellia and Malanzaniaare absent. These floras have been recognized in South America, Africa,

Fig. 6. Stratigraphic columns and correlation of principal South American Mississippian–Lower Pennsylvanian localities. Note the temporal and geographic distribution of the ParacaFloral Realm and the stratigraphic position of Loma de los Piojos Formation and possible coeval strata at Sierra de Maz. AG, Aguas Blanquitas Fm. Modified from Iannuzzi and Rösler(2000), López-Gamundí and Martínez (2000), Iannuzzi and Pfefferkorn (2002), Fasolo et al. (2006), Azcuy et al. (2007b) and Pazos (2007).

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India and Australia, pre dating the Glacial Episode II (Bashkirian), andthey have been referred to as the Paraca Floral Realm (Iannuzzi andPfefferkorn, 2002).

This realmwas put forward to describe floras that developed alonga Gondwanan belt of warm climate, located approximately between30° and 60° of paleolatitude. It comprises a preglacial period of hightemperatures which developed during the Late Visean–Early Serpu-khovian (Iannuzzi and Pfefferkorn, 2002). The high temperaturesproposed for these associations are based on the presence ofarborescent lycopsids, sphenophytes and paleosinecological charac-teristics of awarm temperate vegetational zone (Walter, 1985; Ziegler,1990; Pfefferkorn, 1997; Iannuzzi and Rösler, 2000; Iannuzzi andPfefferkorn, 2002).

The paleoclimatic and paleobiogeographic models of Iannuzzi andRösler (2000) and Iannuzzi and Pfefferkorn (2002) suggest it wouldbe reasonable to find Paracan floral elements in the Mississippian ofArgentina. Nonetheless, these records had not been found up to thepresent, and previous work suggested cold climates for LateMississippian from Argentina (López-Gamundí et al., 1992). Particu-larly, palynological data in relation to glacial diamictites from theCortaderas Formation, San Juan Province suggested a global coolingevent for the Late Visean (Limarino et al., 2006; Césari et al., 2007;Pérez Loinaze, 2007).

The flora from Loma de los Piojos acquires a significant importancein this discrepancy. The presence of the arboreous lycopsid Tomio-dendron associated with Nothorhacopteris kellaybelenensis and Para-calamites stems in the Loma de los Piojos Fm. allows the recognition ofthe Paraca Floral Realm in Argentina. Consequently, it confirms theexistence of warm–temperate climates for the Late Mississippian(Serpukhovian) of Argentina (Fig. 6). Nevertheless, the Paracan florafrom Loma de los Piojos is an impoverished assemblage, containingsmall lycopsids (Frenguellia and Malanzania) from colder environ-ments. Thus, the climate of the FNC zone could be interpreted asslightly colder than the Paraca sensu strictu, but surely warmer thanearlier Visean climates of western Argentina.

Hence, the flora from Loma de los Piojos Fm. may represent arestructured paleocommunity, mixing relict elements from the cold

climate floras from the Visean (Frenguellia and Malanzania) andelements of the warmer floras from the Paraca Floral Realm(Tomiodendron, N. kellaybelenesis and Paracalamites).

The unusual characteristics of this flora can be explained consideringthe superimposition of paleogeographic and paleoclimatic effects.

On the one hand, a clockwise rotation of Gondwana has beensuggested for the Carboniferous (Scotese et al., 1979; Scotese andMcKerrow, 1990). This implies a consequent migration of SouthAmerica to lower latitudes, during the Carboniferous. According tothis idea, the central region of Argentina would have entered a warmand humid climate belt during the Serpukhovian (Scotese, 2000),while during earlier times, the higher paleolatitudinal positionallowed the development of glaciations (Fig. 7A). This would havepermitted the flora from the Paraca Floral Realm to move towards thesouth of South America, as postulated by Iannuzzi and Rösler (2000),but not before Serpukhovian times (Figs. 6 and 7B). The fact that theAustralian record has evidence of warm climates during theMissisippian (Fielding et al., 2008: 134), while western Gondwanaregisters glaciations (Isaacson et al., 2008), is in agreement with thisclockwise rotation. Similar evidence is found in the fossil record. Asexplained by Iannuzzi and Pfefferkorn (2002 and references therein),in Australia the fossil record shows an increasingly colder climatethrough the Carboniferous up to the Permian. Meanwhile in westernArgentina the evidence shows cold climates for the Mississipian andmilder climates for the Pennsylvanian and Permian (López-Gamundíet al., 1992; Vega, 1995; Iannuzzi and Rösler, 2000; Iannuzzi andPfefferkorn, 2002).

On the other hand, the identification of a warm–temperateSerpukhovian climate implies the recognition of a nonglacial intervalfor this moment, and the differentiation of a Bashkirian glacial interval(López-Gamundí, 1997) from the glacial interval proposed for theUpper Visean of Argentina (Pérez Loinaze, 2007). The FNC isrecognized as a nonglacial flora developed during this interval. Theidentification of such glacial and nonglacial intervals is in agreementwith the dynamics of the glaciations put forward by Fielding et al.(2008). Particularly, these intervals are broadly correlationable withtheir C1 and C2 glaciations, and the nonglacial period in-between

Fig. 7. Paleogeographic reconstructions for the Mississippian–Lower Pennsylvanian. A) Position of America in Gondwanan context. The arrow points towards central westernArgentina. Note that this area enters the 60°–30° climatic belt during the Serpukhovian. B) Detail of South America and Argentina, showing the known relevant fossil floras andlocalities for each time interval. Modified from Iannuzzi and Rösler (2000) and Scotese (2000).

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(Fielding et al., 2008; Birgenheier et al., 2009). This correspondence isremarkable, as Fielding et al. (2008) model is based on the record ofeastern Australia, while our findings are fromwestern Argentina, twoopposite extremes of Gondwana. Furthermore, the finding of a warm–

temperate climate in the Serpukhovian of western Gondwanacoincides with the recent identification of a mid-Serpuhkovianwarm interval in Euramerican paleotropics (Gastaldo et al., 2009:362). This coincidence may reflect that this warming had importantconsequences throughout the globe, at least for plant assemblages.We must emphasise, however, that this simple correlation should bedone with caution, because it is not known the precise timing andduration of the FNC zone relative to this warm interval.

Overall, regarding its Serpukhovian age, the Loma de los Piojosflora agrees with the climatic and biostratigraphic models put forwardby Iannuzzi and Rösler (2000) and Iannuzzi and Pfefferkorn (2002),and the glaciations model proposed by Fielding et al. (2008). NewVisean–Serpukhovian data along with detailed biostratigraphicstudies at western Argentina will be needed to test these hypotheses.

6. Conclusions

1) Mississippian fossiliferous sedimentary rocks are recognized atLoma de Los Piojos, southwest Jáchal, San Juan Province, Argentina.Clear stratigraphic relationships show that they unconformablyunderlie the diamictites of the base of Guandacol Formation(Bashkirian), and unconformably overlie the Talacasto Formation(Lower Devonian). This sequence is named the Loma de los PiojosFormation.

2) The fossil flora is compositionally intermediate between typicalMississippian floras and Pennsylvanian floras of western Gond-wana, and is indicative of a Late Mississippian (Serpukhovian) age.

3) This new flora comes from a time interval previously unrecognizedin western Argentinean basins. It overlies the Frenguellia–Paulo-phyton zone and underlies the NBG zone and correlates, at leastpartially, with the Nothorhacopteris kellaybelenensis–Triphyllopterisboliviana zone (Iannuzzi et al., 2003). We here name this as theFrenguellia eximia–Nothorhacopteris kellaybelenensis–Cordaicarpuscesarii zone (FNC zone).

4) The association of the FNC zone, due to its unique composition,belongs to the Gondwanan “Paraca Floral Realm” (Iannuzzi andPfefferkorn, 2002). The paleoecological characteristics of thesefloras, suggest a warm temperate climate (Iannuzzi and Pfeffer-korn, 2002 and references therein).

5) This finding is in agreement with the existence of a nonglacialinterval developed between a Late Visean glaciation and anotherone of Bashkirian age (Glacial Episode II).

6) The Loma de los Piojos Formation records the initial functioningand structure of the Paganzo basin and establishes a minimumSerpukhovian age for this event. This will allow a better under-standing of the magnitude, development and earliest tectono-stratigraphic evolution of this basin.

Acknowledgments

The manuscript was greatly improved by the excellent reviews oftwo anonymous reviewers. The authors wish to thank Dr. E. Morel forreviewing the earlier versions of the manuscript and providing advice.Dr. A. Sterren has specially contributed with comments andbibliography. Dr. C. Rodríguez Amenábar and Lic. F. Degrange havekindly provided useful bibliography. Ms. J. Martinelli has collaboratedinvaluably for the English version. Financial support for this study wasprovided by ANPCyT (Agencia Nacional de Promoción Científica yTecnológica) PICT-2006-01272 grant to Dr. Claudia Rubinstein.

References

Anderson, J.M., Anderson, H.M., Archangelsky, S., Bamford, M., Chandra, S., Dettmann, M.,Hill, R., McLoughlin, S., Rösler, O., 1999. Patterns of Gondwana plant colonization anddiversification. Journal of African Earth Sciences 28, 145–167.

Allison, M.A., Kineke, G.C., Gordon, E.S., Goñi, M.A., 2000. Development and reworkingof a seasonal flood deposit on the inner continental shelf off the Atchafalaya River.Continental Shelf Research 20, 2267–2294.

Andreis, R.R., Arrondo, O.G., 1974. Acerca de la discordancia angular entre las FormacionesGuandacol y Tupe en la sierra deMaz (Provincia de La Rioja). Ameghiniana 9, 373–378.

Archangelsky, A., 1999. Semillas del Paleozoico Superior de Argentina: Su utilizacionbioestratigráfica. Ameghiniana 36, 465–476.

Archangelsky, A., 2000. Estudio sobre semillas neopaleozoicas de Argentina. Boletín dela Academia Nacional de Ciencias 64, 79–115.

Archangelsky, A., Archangelsky, S., 1987. Tafoflora de la Formación Tramojo, PaleozoicoTardío, en la región de Uspallata, provincia de Mendoza, República Argentina.Ameghiniana 24, 251–256.

Archangelsky, S., 1983. Nothorhacopteris, a new generic name for some Carboniferousmonopinnate fronds of Gondwanaland (Rhacopteris ovata auct. and Pseudorha-copteris Rigby 1973). Review of Palaeobotany and Palynology 38, 157–172.

Archangelsky, S., Azcuy, C.L., Wagner, R.H., 1981. Three dwarf lycophytes from theCarboniferous of Argentina. Scripta Geologica 64, 1–35.

Archangelsky, S., Amos, A.J., Andreis, R.R., Azcuy, C.L., González, C.R., López-Gamundí, O.,Sabattini, N., 1987. El Sistema Carbonífero en la República Argentina. AcademiaNacional de Ciencias, Córdoba, Argentina.

Archangeslky, S., Azcuy, C.l., Césari, S., González, C., Hünicken,M.,Mazzoni, A., Sabattini, N.,1996. Edad y Correlacion de las biozonas. In: Archangelsky, S. (Ed.), El Sistema Pérmicoen la República Argentina y en la República Oriental del Uruguay. Academia Nacionalde Ciencias, Córdoba. 203–226.

Arrondo, O.G., Petriella, B., 1978. El género Lepidodendropsis Lutz del Carbónico Inferior deArgentina. Ameghiniana 15, 440–444.

Arrondo, O.G., Petriella, B.,1985. Bumbudendronmillani (Arrondo et Petriella) n. comb., delCarbónico-Pérmico de Argentina y Brasil. Ameghiniana 21, 169–171.

Arrondo, O.G., Césari, S.N., Gutiérrez, P.R., 1991. Frenguellia a new genus of lycopods from theEarly Carboniferous of Argentina. Review of Palaeobotany and Palynology 70, 187–197.

Astini, R.A., Ezpeleta, M., 2008. Evidencias de la glaciación Devónica en el ámbitoandino, Sierra de lasMinitas, provinciade LaRioja, Argentina:XVIICongresoGeológicoArgentino Actas, vol. 3, p. 1061.

Azcuy, C.L., di Pasquo, M.M., 2005. Early Carboniferous palynomorphs from the AmboFormation, Pongo de Mainique, Peru. Review of Palaeobotany and Palynology 134,153–184.

Azcuy, C.L., Suárez-Soruco, R., 1993. Nothorhacopteris kellaybelenensis. Una nuevaespecie del Carbonífero Inferior de Bolivia. Revista Técnica de YacimientosPetrolíferos Fiscales Bolivianos 13–14, 173–179.

Azcuy, C.L., Beri, A., Bernardes-De-Oliveira, M.E.C., Carrizo, H.A., di Pasquo, M., DíazSaravia, P., González, C., Iannuzzi, R., Lemos, V.B., Melo, J.H.G., Pagani, A., Rohn, R.,Rodríguez Amenábar, C., Sabattini, N., Souza, P.A., Taboada, A., Vergel, M.M., 2007a.Cronoestratigrafía del Paleozoico Superior de América del Sur: Primera etapa detrabajo hacia una nueva propuesta. In: Díaz-Martínez, E., Rábano, I. (Eds.), 4thEuropean Meeting on the Palaeontology and Stratigraphy of Latin America:Cuadernos del Museo Geominero, vol. 8, pp. 27–32.

Azcuy, C.L., Beri, A., Bernardes-De-Oliveira, M.E.C., Carrizo, H.A., di Pasquo, M., DíazSaravia, P., González, C., Iannuzzi, R., Lemos, V.B., Melo, J.H.G., Pagani, A., Rohn, R.,Rodríguez Amenábar, C., Sabattini, N., Souza, P.A., Taboada, A., Vergel, M.M., 2007b.Bioestratigrafía del Paleozoico Superior de América del Sur: Primera etapa detrabajo hacia una nueva propuesta cronoestratigráfica. Asociación GeológicaArgentina Serie Publicación Especial 11, 9–64.

Baldis, B.A., Cané, T.C., 1968. El paleozoico en la región occidental y austral de Jáchal(Provincia de San Juan). Revista de la Asociación Geológica Argentina 23, 121–128.

Berry, E.W.,1922. Carboniferous plants from Perú. American Journal of Science 3,189–194.Bhattacharya, J.P., 2006. Deltas. In: Posamentier, H.W., Walker, R.G. (Eds.), Facies Models

Revisited. SEPM Special Publication, vol. 84, pp. 237–292.Birgenheier, L.P., Fielding, C.R., Rygel,M.C., Frank, T.D., Roberts, J., 2009.Evidence fordynamic

climate change on sub-106-year scales from the Late Paleozoic glacial record, TamworthBelt, New South Wales, Australia. Journal of Sedimentary Research 79, 56–82.

Carrizo, H.A., Azcuy, C.L., 1998. El perfil del cerro Mudadero y su flora fósil. Provincia deLa Rioja. Argentina. Acta Geológica Lilloana 18, 81–99.

Caselli, A., Limarino, C., 2002. Sedimentología y evolución paleoambiental de la FormaciónPatquía (Pérmico) en el extremo sur de la Sierra de Maz y cerro Bola, Provincia de LaRioja, Argentina. Revista de la Asociación Geológica Argentina 57, 415–436.

Césari, S., 1987. Diplothmema bodenbenderi Kurtz nov. comb. (Pteridospermales?) delCarbonífero de Argentina. Ameghiniana 24, 263–269.

Césari, S.N., Pérez Loinaze, V.S., 2006. A new Carboniferous equisetale from westernGondwana. Geobios 39, 785–790.

Césari, S., Gutiérrez, P.R., Sabattini, N., Archangelsky, A., Azcuy, C.L., Carrizo, H.A.,Cisterna, G., Crisafulli, A., Cúneo, R.N., Díaz Saravia, P., di Pasquo, M., González, C.R.,Lech, R., Pagani, M.A., Sterren, A., Taboada, A.C., Vergel, M.M., 2007. PaleozoicoSuperior de Argentina: un registro fosilífero integral para el Gondwana occidental.In: Archangelsky, S., Sánchez, T., Tonni, E.P. (Eds.), Ameghiniana 50° Aniversario:Asociación Paleontológica Argentina Publicación Especial, vol. 11, pp. 35–56.

Ezpeleta, M., Astini, R.A., 2009. The Late Devonian glaciation in western Argentina:Expanding the frontiers of Gondwanan Glacial Epoch. In: Wörner, G., Möller-NcNett, S.(Eds.), International Latinamerika–Kolloquium2009Abstracts andProgram, pp. 95–96.

Fasolo, Z., Vergel, M.M., Oller, J., Azcuy, C.L., 2006. Nuevos datos palinológicos de laFormación Kaka (Viseano–Serpukhoviano) en la Encañada de Beu, SubandinoNorte de Bolivia. Revista Brasileira de Paleontología 9, 53–62.

529D. Balseiro et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 280 (2009) 517–531

Author's personal copy

Fernández Seveso, F., Pérez, M., Brisson, I.E., Álvarez, L.,1993. Análisis estratigráfico secuencialde la Cuenca de Paganzo –Depósitosmarinos y continentales del Paleozoico Superior enel Oeste Argentino. Douzième congrès international de la stratigraphie et gèologie duCarbonifère et Permien. Buenos Aires, Argentina, pp. 223–260.

Fielding, C.R., Frank, T.D., Birgenheier, L.P., Rygel, M.C., Jones, A.T., Roberts, J., 2008.Stratigraphy imprint of the Late Paleozoic Ice Age in eastern Australia: a record ofalternating glacial and nonglacial climate regime. Journal of the Geological Society(London) 165, 129–140.

Frenguelli, J., 1949. El perfil de la cortadera en las faldas orientales de los Cerros de VillaUnión Provincia de La Rioja). Revista de la AsociaciónGeológica Argentina 4, 298–335.

Frenguelli, J., 1954. Plantas devónicas de la Quebrada de la Charnela, en la Precordillerade San Juan. Notas Museo de la Plata 18, 359–376.

Furque, G., 1979. Descripción geológica de la Hoja 18c, Jáchal, Provincia de San Juan:Servicio Geológico Nacional Boletín, vol. 164, pp. 1–79.

García, E., 1945. Estratigrafía y tectónica de la zona situada inmediatamente al SW deJáchal. Ph.D. thesis, Universidad Nacional de la Plata, La Plata, Argentina.

Gastaldo, R.A., Purkyňová, E., Šimůnek, Z., 2009. Meglafloral perturbation across the Ennamarine zone in the Upper Silesian Basin attest to Late Mississippian (Serpukhovian)deglaciation and climate change. Palaios 24, 351–366.

Geinitz, H.B., 1862. Dyas oder die Zechsteinformation und das Rotliegende. Heft 2. DiePflanzen der Dyas und Geologisches, pp. 131–242.

Geinitz, H.B.,1876. Über rhätischepflanzenund thierreste indenArgentinischenProvinzen LaRioja, San Juan und Mendoza. Palaeontographica Abteilung B 3, 1–14.

Goeppert, H.R., 1864. Die fossile Flora der Permischen Formation. PaleontographicaAbteilung B 121–224.

Gothan, W., 1928. Bemerkungen zur Alt-Carbonflora von Peru, besonders von Paracas.Neues Jahrbuch für Mineralogie, Geologie und Palaöntologie 59, 292–299.

Gutiérrez, P.R., 1995. Nuevos registros paleofloristicos para la Formacion Agua Colorada,Carbonífero Superior, en el sector sudoriental de la Sierra de Famatina, Provincia deLa Rioja, Argentina. Ameghiniana 32, 111–128.

Gutiérrez, P.R.,1996. Revisión de las licópsidas de laArgentina. 2.MalanzaniaArchangelsky,Azcuy et Wagner y Haplostigma Seward; con notas sobre Cyclostigma Haughton.Ameghiniana 33, 127–144.

Gutiérrez, P.R., Arrondo, O.G., 1994. Revisión de las licopsidas de la Argentina. 1. Archaeosigil-laria Kidston y Frenguellia Arrondo, Césari y Gutiérrez. Ameghiniana 31, 381–393.

Gutiérrez, P.R., Ganuza, D.G., Morel, E., Arrondo, O.G., 1992. Los generos CordaicarpusGeinitz, Cornucarpus Arbery Samaropsis Goeppert (Semillas platispérmicas) en elNeopaleozoico argentino. Ameghiniana 29, 49–68.

Gorelova, S.G., 1978. The flora and stratigraphy of the coal-bearing Carboniferous ofMiddle Siberia. Palaeontographica Abteilung B 165, 54–77.

Iannuzzi, R., Rösler, O., 2000. Floristic migration in South America during theCarboniferous: phytogeographic and biostratigraphic implications. Palaeogoegra-phy, Palaeoclimatology, Palaeoecology 161, 71–94.

Iannuzzi, R., Pfefferkorn, H.W., 2002. A pre-glacial, warm–temperate floral belt inGondwana (Late Visean, Early Carboniferous). Palaios 17, 571–590.

Iannuzzi, R., Pfefferkorn, H.W., Díaz-Martínez, E., Alleman, V., Suárez-Soruco, R., 1998.Eocarboniferous flora of Siripaca formation (Ambo group, Bolivia) and theircorrelation with the Paracas flora (Ambo group, Perú). Boletín de la SociedadGeológica del Perú 88, 39–51.

Iannuzzi, R., Pfefferkorn, H.W., Rösler, O., 2006. Reavaliação da flora da Formação Poti: Di-plothmema gothanica (Dolianiti) Iannuzzi. Revista Brasileira de Paleontologia 9, 9–20.

Iannuzzi, R., Azcuy, C.L., Suárez Soruco, R., 2003. Fitozona de Nothorhacopteriskellaybelenensis–Triphyllopteris boliviana, una nueva unidad bioestratigráfica para elCarbonífero de Bolivia. Revista Técnica de Yacimientos Petrolíferos Fiscales Bolivianos21, 125–131.

Isaacson, P.E.,Diaz-Martinez, E., Grader, G.W., Kalvoda, J., Babek,O., Devuyst, F.X., 2008. LateDevonian–earliest Mississippian glaciation in Gondwanaland and its biogeographicconsequences. Palaeogeography, Palaeoclimatology, Palaeoecology 268, 126–142.

Isbell, J.L., Fraiser, M.L., Henry, L.C., 2008. Examining the complexity of environmentalchange during the late Paleozoic and Early Mesozoic. Palaios 23, 267–269.

Jongmans, W.J., 1954. The Carboniferous flora of Perú. Bulletin of the British Museum,Natural History. Geology 2, 189–224.

Kelley, P.H., Raymond, A., 1991. Migration, origination and extinction of SouthernHemisphere brachiopods during the Middle Carboniferous. Palaeogeography,Palaeoclimatology, Palaeoecology 86, 23–39.

Kurtz, F., 1921. Atlas de plantas fósiles de la República Argentina. Actas de la AcademiaNacional de Ciencias 7, 129–153.

Lehnert, Oliver, 1990s. Conodontenstratigraphie und Fazies der Formation San JuanProvince bei Niquivil (Unteres Ordoviz, Argentinien Präkordillere). Diplomarbeit,Institut für Geologie und Mineralogie der Universität Erlagen–Nürnberg, Germany.

Limarino, C.O., Tripaldi, A., Marenssi, S., Fauqué, L., 2006. Tectonic, sea-level, andclimatic controls on Late Paleozoic sedimentation in the western basins ofArgentina. Journal of South American Earth Sciences 22, 205–226.

López-Gamundí, O.R., 1997. Glacial–postglacial transition in the Late Paleozoic Basins ofsouthern South America. In: Martini, P.I. (Ed.), Late glacial and postglacialenvironmental changes—Quaternary, Carboniferous–Permian, and Proterozoic.Oxford University Press, New York, pp. 147–168.

López-Gamundí, O., Martínez, M., 2000. Evidence of glacial abrasion in the Calingasta-Uspallata and western Paganzo basins, mid-Carboniferous of western Argentina.Palaeogeography, Palaeoclimatology, Palaeoecology 159, 145–165.

López-Gamundí, O.R., Limarino, C., Césari, S., 1992. Late Paleozoic paleoclimatology ofcentral west Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology 91,305–329.

Mamay, S.H., Bateman, R.M., 1991. Archaeocalamites lazarii, sp. nov.: the range ofArchaeocalamitaceae extended from the lowermost Pennsylvanian to the mid-Lower Permian. American Journal of Botany 78, 489–496.

Mensah, M.K., Chaloner, W.G., 1971. Lower Carboniferous Lycopods from Ghana.Palaeontology 24, 357–369.

Meyen, S.V.,1972. Are there ligula and parichnos in Angara Carboniferous lepidophytes?Review of Palaeobotany and Palynology 14, 149–157.

Meyen, S.V., 1976. Carboniferous and Permian lepidophytes of Angaraland. Palaeonto-graphica Abteilung B 157, 112–157.

Morel, E., Cingolani, C., Varela, R., Zúñiga, A., 1993. Devonian and Lower Carboniferousplant remains from the northern Precordillera, La Rioja Province, Argentina.Douzième congrès international de la stratigraphie et gèologie du Carbonifère etPermien Buenos Aires, Argentina, pp. 127–140.

Mutti, E., Tinterri, R., Benevelli, G., di Biase, D., Cavanna,G., 2003.Deltaic,mixed and turbiditesedimentation of ancient foreland basins. Marine and PetroleumGeology 20, 733–755.

Naugolnykh, S.V., 2002. Paracalamitina striata — a newly reconstructed Equisetophytefrom the Permian of Angaraland. Journal of Paleontology 76, 377–385.

Oliveira, M.E.C., da Silva Pontes C.E., 1976. Algumas observações sobre Cordaitófitas daFormação Rio Bonito, Grupo Tubarão, Bacia do Paraná, Brasil. I. Congreso GológicoChileno 3, L22–L81.

Ottone, E.G., García, G.B., 1990. Algunos elementos megaflorísticos de la FormaciónSanta Máxima. Paleozoico Superior, Argentina. Ameghiniana 27, 311–316.

Pazos, P.J., 1993. Estratigrafía de la secuencia sedimentaria basal aflorante en el CerroGuandacol: su implicancia tectónica y paleoambiental, Sierra de Maz, Provincia deLa Rioja, Argentina. XII Congreso geológico Argentino y II Congreso de Exploraciónde Hidrocarburos, Mendoza, Argentina, Actas 1, pp. 148–156.

Pazos, P.J., 1997. Estratigrafía de los depósitos carboníferos aflorantes a lo largo dellineamiento Valle Fértil (Provincia de San Juan–La Rioja ). Cuenca Paganzo,Argentina. VIII Congreso Geológico Chileno Actas1, pp. 563–567.

Pazos, P.J., 2007. Cyclostratigraphy during the Carboniferous glaciations in central westernArgentina: glacial ageism and tectonic framework. In: Iannuzzi, R., Boardman, D.R.(Eds.), Problems in Western Gondwana Geology I. Gramado, Brasil, pp. 108–114.

Pérez Loinaze, V.S., 2007. A Mississippian Miospore Biozone for Southern Gondwana.Palynology 31, 101–117.

Pérez Loinaze, V.S., Limarino, C.O., Césari, S.N., 2008. Secuencias glacigénicas delCarbonífero del noroeste argentino. Ameghiniana 45 suplemento, pp. 14R–15R.

Pfefferkorn, H.W.,1997. Paleoclimates of Perú during the late Paleozoic— fossil plants andmoving continents: SociedadGeológicadel PerúVolumenEspecial, vol.1, pp. 671–673.

Pfefferkorn, H.W., Iannuzzi, R., 2005. A pre-glacial floral belt in Gondwana indicatingwarm climate during the Late Visean (Late Early Carboniferous). GSA AnnualMeeting, Salt Lake City, Utah, USA. paper no 218–6 http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96137.htm.

Powell, M.G., 2007. Latitudinal diversity gradients for brachiopod genera during latePalaeozoic time: Links between climate, biogeography and evolutionary rates.Global Ecology and Biogeography 16, 519–528.

Radczenko, G.P., 1955. Index-fossils of the Upper Paleozoic flora of the Sayan–Altairegion. Atlas rukovod. form iskop. fauny i flory Zap. Sibirica 2, 42–153 (in Russian).

Rigby, J.F.,1966a. SomeGondwanaarticulates fromNewSouthWales. SymposiumFloristicsand Stratigraphy of Gondwanaland. Birbal Sahni Institute, Lucknow, India, pp. 48–54.

Rigby, J.F., 1966b. The Lower Gondwana floras of the Perth and Collie Basins, WesternAustralia. Palaeontographica Abteilung B 118, 113–152.

Roberts, J., Claoue-Long, J., Jones, P.J., Foster, C.B., 1995. Shrimp zircon age control ofGondwanan sequences in Late Carboniferous and Early Permian Australia. SpecialPublications Geological Society of London 89, 145–174.

Rodríguez, E., 1985. Análisis paleoambiental de las sedimentitas de Loma de la Usina,Jáchal, Provincia de San Juan. Trabajo final de licenciatura. Universidad de BuenosAires, Buenos Aires, Argentina.

Rothwell, G.W., 1988. Cordaitales. In: Beck, C.B. (Ed.), Origin and evolution ofGymnosperms. Columbia University Press, New York, pp. 273–297.

Rolleri, E., Baldis, B., 1967. Paleogeography and distribution of Carboniferous deposits inthe Argentine Precordillera. I Simposio Internacional de Estratigrafía y Paleonto-logía del Gondwana, Mar del Plata, Argentina, pp. 1005–1024.

Rustán, J.J., Balseiro, D., and Vaccari, N.E., , 2008. El Carbonífero Inferior al sudoeste deJáchal (Provincia de San Juan, Argentina). Ameghiniana 45 suplemento, 15R.

Scotese, C.R., 2000. Paleo Map Project, Climate History, Early Late Carboniferous(Serpukhovian) Climate. web site: http://www.scotese.com/earth.htm.

Scotese, C.R.,Mckerrow,W.S.,1990.RevisedWorldmapsand introduction. In:McKerrow,W.S.,Scotese, C.R. (Eds.), Palaeozoic Palaeogeography and Biogeography. Memoir, vol. 12.Geological Society of London, pp. 1–21.

Scotese, C.R., Bambach, R., Barton, C., Van Der Voo, R., Ziegler, A., 1979. Palaeozoic basemaps. Journal of Geology 87, 217–277.

Scott, A.C., Galtier, J., Mapes, R.H., Mapes, G., 1997. Palaeoecological and evolutionarysignificance of anatomically preserved terrestrial plants. Journal of the GeologicalSociety 154, 61–68.

Seward, A.C., 1917. Fossils plants. In: Pteridospermae, Cycadofilices, Cordaitales,Cycadophyta, vol. 3. Cambridge University Press, Cambridge, pp. 1–656.

Stur, D., 1875. Die Culmflora des märsich-schlesischen Dachschiefers. AbhandlungenKaiserlich-Königlischen Geologische Reichstanstalt 8, 1–106.

Stur, D., 1877. Die Culm-Flora der Ostrauer undWaldenburger Schichten. Abhandlungender Kaiserlich-Königlichen Geologischen Reichsanstalt 8 (2), 1–366.

Trivett, M.L., Rothwell, G.W., 1991. Diversity among Paleozoic Cordaitales. NeuesJahrbuch für Paläontologie Abhandlungen 183, 289–305.

Vega, J.C., 1995. La flora fósil de la Formación Jejenes (Carbonífero). Implicanciaspaleoclimáticas y paleogeográficas. Ameghiniana 32, 31–40.

Volkheimer, W., 1962. Nuevos hallazgos de Paleozoico marino en la Precordillera de SanJuan. Revista de la Asociación Geológica Argentina 17, 97–104.

Wagner, R.H., 1984. Megafloral zones of the Carboniferous. IX Congrès International dela Stratigraphie et Géologie du Carbonifère. Southern Illinois University, Urbana,Illinois, pp. 109–134.

530 D. Balseiro et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 280 (2009) 517–531

Author's personal copy

Wagner, R.H., Higgins, A.C., Meyen, S.V., 1979. The Carboniferous of the USSR. YorkshireGeological Society, Moscow, Russia.

Walter, H., 1985. Vegetation of the Earth and Ecological Systems of the Geo-Biosphere.Springer-Verlag, New York.

Yang, B., Dalrymple, R.W., Chun, S., 2006. The significance of Hummocky Cross-Stratification (HCS) wavelengths: evidence from an open-coast tidal flat, SouthKorea. Journal of Sedimentary Research 76, 2–8.

Zalessky, M.D., 1927. Flore permienne des limites ouraliennes d'Angaride: Atlas.Memoirs, Commite Geologique St. Petersburg, vol. 176, pp. 5–52.

Zalessky, M.D., 1934. Observations sur les vegetaux permiens du bassin de la Petchora, I.Bulletin of Academy of Sciences, URSS. Mathematics and Natural Sciences 2–3, 241–290.

Zalesskij, M.D., Čirkova, H.F., 1935. Observation sur queles végétaux fossiles du terrainpermien du bassin de Kousnetzk. Bulletin of Academy of Sciences, URSS.Mathematics and Natural Sciences 8–9, 1091–1116.

Ziegler, A.M., 1990. Phytogeographic patterns and continental configurations during thePermian Period. In: McKerrow, W.S., Scotese, C.R. (Eds.), Palaeozoic Palaeogeographyand Biogeography. Memoir, vol. 12. Geological Society of London, pp. 363–379.

531D. Balseiro et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 280 (2009) 517–531