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Quaternary International 225 (2010) 44–57

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Quaternary International

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Pollen and macrofossil analyses of Pliocene lacustrine sediments(Salto river valley, Central Italy)

Laura Sadori a,*, Marco Giardini a, Edi Chiarini b, Massimo Mattei c, Felicia Papasodaro b,Massimiliano Porreca c

a Dipartimento di Biologia Vegetale, Universita di Roma ‘‘La Sapienza’’, Roma, Italyb Dipartimento Difesa del Suolo - Geological Survey of Italy, ISPRA, Roma, Italyc Dipartimento di Scienze Geologiche, Roma TRE University, Roma, Italy

a r t i c l e i n f o

Article history:Available online 23 June 2009

* Corresponding author. Tel.: þ39 06 49912402; faE-mail address: laura.sadori@uniroma1.it (L. Sador

1040-6182/$ – see front matter � 2009 Elsevier Ltd adoi:10.1016/j.quaint.2009.05.008

a b s t r a c t

The study of two sedimentary records sampled in the fluvio-lacustrine succession of high Salto rivervalley (Rieti, central Italy) was originated in the frame of the Geomorphologic Map of Italy (APAT, 2008)field survey and improved with a multidisciplinary approach addressed to a better knowledge of the Plio-Pleistocene continental environments of central Apennines. The two successions are associated todifferent sedimentary facies, with lateral heteropic relations: the deposits cropping out at Marano de’Marsi are thought to represent deposition in the distal portion of a lacustrine delta, while those ofBorgorose took place in a frankly lacustrine environment.

The sediment succession from Marano de’ Marsi (11 m) was sampled from an outcrop, the one fromBorgorose (24.5 m) from a drillhole. Palaeomagnetic investigations carried out on both sediment recordsindicate a normal magnetic polarity and very low magnetic susceptibility values.

In the record from Marano de’ Marsi section, gymnosperm pollen is prevailing. Four main and shortangiosperm arboreal pollen oscillations can however be observed, the oldest of which more marked. Thegymnosperms are mainly represented by Pinus haploxylon type, Pinus sylvestris type, Cedrus, Picea, Abies,Cathaya, Tsuga, Taxodium type. Among angiosperms the dominant taxa, some of which at present extinctin Italy, are Quercus, Zelkova, Ulmus, Carya and Pterocarya. The presence of pollen of subtropical taxa asNyssa, cfr. Rhoiptelea, Liquidambar, Engelhardia is worth to be mentioned. The investigation was inte-grated also by a preliminary study of macrofossils. Fossil impressions with some organic matter ofangiosperm and gymnosperm leaves and seeds/fruits were ascribed to Acer cfr. monspessulanum, Car-pinus cfr. orientalis, Engelhardia, Fagus, Hedera, Liquidambar, Quercus, Rosa, Abies and Pinus.

The 24.5 m long sediment core from Borgorose resulted very poor in pollen, with the same list ofarboreal taxa, at present extinct in Italy, found at Marano de’ Marsi, and a diagram was drawn only for thestretch of the core between 3 and 8.2 m. Gymnosperms (P. haploxylon type is dominant, and accompa-nied by P. sylvestris type, Picea, Taxodium type, Cedrus, and Tsuga) are always prevailing.

The results obtained by this interdisciplinary investigation indicate that Marano de’ Marsi and Bor-gorose successions can be possibly attributed to the Upper Pliocene (normal polarity Olduvai subchron)even if an older age, considering the present state of the art on Pliocene continental records, and thepeculiarity of the site and of the region, cannot be excluded.

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1. Introduction

In central Apennines ancient continental deposits extensivelycrop out; their sedimentation is closely connected to the formationof numerous fault-bounded extensional intermontane basins,

x: þ39 0649912279.i).

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expression of post-orogenic tectonic. Central Apennines have beeninterested since the Late Miocene by normal faulting, affecting thewesternmost sectors at first, and progressively involving the east-ernmost ones (Cavinato and De Celles, 1999; D’Agostino et al., 2001;Galadini and Messina, 2004). Moreover other works assume somePliocene continental basins to be originated in a compressionalregime (Boccaletti et al., 1995; Coltorti and Pieruccini, 1997;Centamore and Nisio, 2002a,b). A mainly fluvio-lacustrinesedimentation characterized the intermontane basins; the oldest

L. Sadori et al. / Quaternary International 225 (2010) 44–57 45

deposits are generally referred to Pliocene or Early Pleistocene (Bosiet al., 2003; Mancini et al., 2004; APAT, 2006a,b,c, in press). Thereview of large literature available on this matter highlightswidespread difficulties in defining precise chronologicalconstraints. In lucky cases, the age settlement of ancient continentaldeposits was achieved by means of vertebrate faunas findings,referable to Villafranchian mammal ages in the biochronologicalscale. A complex discussion is however still going on Villafranchianstratigraphy (Carraro, 1996).

It is only in some fortunate cases (e.g. Bertini et al., 2010), in fact,that it is possible to attribute certain ages to sites of Pliocene andEarly Pleistocene age. Marine sequences, mostly concentrated inthe Mediterranean basin, are often better dated than continentalones, but they show taphonomical factors causing difficulties ina precise reconstruction of past vegetation history (Hooghiemstraet al., 2006). A sound scheme to correlate marine and continentalevents of the last 3.3 Ma in the Italian area was recently proposed(Bertini et al., 2010), but it still represents an exception in Quater-nary research.

In the absence of a robust independent dating system, thechronology of continental successions has often relied on thecomparison with local and regional palynostratigraphy, giving greatemphasys to the disappearance of pollen taxa, which turned out tobe time transgressive in Italy (Bertini, 2003).

Italy (e.g. Bertini, 2000, 2003; Martinetto 2001a; Sabato et al.,2005; Fusco, 2010) shows most of the southern European (seeLeroy, 2007) Late Pliocene and Early Pleistocene successionsrecording past vegetation history, which have also been used toreconstruct past climate (Fauquette et al., 1998a,b; Fauquette andBertini, 2003; Klotz et al., 2006).

Only a few of these vegetation records are located in central Italy(Umbria and Tuscany). Both macrofossils (Biondi and Brugiapaglia,1991, 2000; Martinetto, 2001b,c; Vassio et al., 2008) and pollendata (Ambrosetti et al., 1995; Bertini and Roiron, 1997; Pontini andBertini, 2000; Mazza et al., 2004; Bertini et al., 2010) are available.They indicate that central Italy played a fundamental role inpreserving many taxa, acting as a centre of refuge for thermophi-lous plants in the late Cenozoic (Martinetto, 2001c).

In the framework of the national geological mapping program(CARG Project), the Geological Survey of Italy (ISPRA-DDS) promotedthe study of the ancient continental deposits of high Salto rivervalley (central Italy), including terrain investigations, geoelectricalprospecting and researches capable to provide chronological refer-ences, to define the palaeoclimatic context of the sedimentaryevents and to improve the knowledge of the geologic evolution ofthe central Apennines during the Late Pliocene/Lower Pleistocene.

The abundance of plant macrofossils and the prevalence ofpelitic facies suggested to address the research to palaebotanicaland palaeomagnetic studies. The integrated analyses of pollenassemblages and magnetostratigraphy, which allowed to recon-struct the magnetic polarity of two continental successions,providing strong constraints on the age of their deposition.

2. Geological setting

The high Salto river valley lies in central Italy (Fig. 1) across theborder between the Abruzzi and Latium regions; it is bounded to theSW by the Carseolani Mts. chain and to the NE by the Velino Mt. chain.The valley forms part of the depression connecting Rieti and Fucinointermontane basins and follows regional tectonic lineaments,generated by a polyphased NW–SE trending Apenninic fault system(Nijman, 1970; Bosi et al., 1994; Bigi and Costa Pisani, 2003). Thesefaults, showing a main normal activity, have guided the location andevolution of continental basins both in the middle valley duringPliocene and Pleistocene (Galadini et al., 2000, 2003), namely in the

area where the Salto lake is presently located, and in the high valley(Chiarini et al., in press). The extension, shape and activity period ofthese ancient basins cannot be reconstructed in detail, because bothtectonic and morphogenetic events gave rise to their extinction andto the subsequent dissection and erosion of infilling deposits.

In the high Salto river valley, large remnants of continentaldeposits, formed within or along the margins of a lacustrine basintestify the first stages of the Plio-Pleistocene geological evolution ofthe area. The sedimentation of this first continental unit, namedMarano de’ Marsi unit (Chiarini et al., in press; Fig. 2), has beenfollowed by the formation of a wide and flat palaeolandscape andthen, in the Early Pleistocene (Bosi and Federici, 1993), by thedevelopment of the small Corvaro intermontane basin (Chiariniet al., 2007; Fig. 2) that induced a radical palaeogeographic change.

The Marano de’ Marsi succession discontinuously crops outalong the left hydrographic flank of the valley, from 710 m to 980 ma.s.l. close to the homonymous village; it also crops out betweenTorano and Borgorose villages, from 670 m to 951 m a.s.l. NearBorgorose the unit is partially overlain by alluvial deposits ofyounger sedimentary events. Chiarini et al. (in press), after detailedfield surveys and reconstruction of facies distribution, ascribed theMarano de’ Marsi unit to a single sedimentary cycle.

The succession rests unconformably on the carbonaticsubstratum with a maximum outcropping thickness of ca. a hundredmetres. It consists of lacustrine claystones, siltstones and marls. Onthe eastern border of the basin the fine deposits are interfingeredwith deltaic conglomerates and sandstones. Coarse-grained sedi-ments cropping out in the southern sector and well exposed nearMarano de’ Marsi have been related to a Gilbert-type delta, for theoccurrence of the typical tripartite facies associations (bottomsets,foresets and topsets). In detail, facies referable to deltaic front, deltaicplain and to alluvial environments have been distinguished. In thenorthern area (Borgorose), ruditic facies are instead referable both tomass transport and to tractive flow in a fan-delta environment.Coarse sediments generally have a disorganized fabric withsubangular clasts, whereas well-expressed foreset facies are lacking.In the Torano area, deposits of the Gilbert-type delta and those of thefan-deltas are interbedded (Chiarini et al., in press).

The collected data show that the main delta has prograded fromsouth-east to north-east (along the main faults direction), while thefan-deltas could come from the eastern margin of the basin.

The deposits lack helpful fossil fauna: only fresh water ostracodsand gasteropods fragments, which do not provide age constraints,were found; some characeans thalluses are also present.

The chronological reconstruction of these deposits is contro-versial, due to a general shortage of dating materials. Previousstudies suggest a Pliocene age (Servizio Geologico d’Italia, 2005) oreven older (Bosi and Federici, 1993) essentially on the basis ofanalogies with other lacustrine successions of central Apenninesand morphostratigraphic observations.

3. Material and methods

On the basis of the study of facies and of preliminary palae-obotanical analyses, two lacustrine successions were selected forcontinuous sediment samplings.

Samples were taken for different types of investigationspresented in this paper: measurements of palaeomagnetic prop-erties, pollen and plant macrofossil analyses.

3.1. The lacustrine successions

The succession cropping out at Marano de’ Marsi, raising for about11 m in a marginal position of the present-day Salto river valley, at anelevation of 720 m a.s.l., was sampled in March 2004. The exposure of

Fig. 1. Shaded relief of the Apenninic sector between the Fucino and Rieti intermontane basins and location of the study area.

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a terraced outcrop of lacustrine sediments edge was obtained usinga caterpillar. The 11 m long sediment record is subject of this paper.

The succession is referable to the distal portion of the lacustrinedelta above mentioned; it consists of pale to dark grey marls,calcareous siltstones and silty claystones, with massive to thinlylaminated beds and horizons. Sandy oxidized laminae, a few milli-metres thick, and cross-laminated levels, also occur. From a litho-logical point of view the section is rather homogenous andseemingly lacking in significant disconformities except in the upperportion, where a weakly north dipping cut surface records theboundary with an intraformational slump of laminated siltstonesand marly claystones, including mesofolds and fractures. Sidewaysbelow the base of the section, whitish horizons of particularly lightclayey marls with fresh water diatom remnants have been observed.

The location of the core drilled at Borgorose was established on thebasis of an accurate survey of the outcropping facies, integrated withgeomorphological observation to exclude the presence of landslidedeposits, occurring in nearby areas; data available from geoelectricalprospections and previous cores obtained for water supplies have alsobeen examined. The 24.50 m long sediment core from Borgorose(725 m a.s.l.) was taken in July 2005 with an engine operating drillingmachine, obtaining core segments 2 m long and 8 cm in diameter.

The drilled succession, quite monotonous, consists of massive orthinly laminated marls and silty claystones; sediments havea greater clay content with respect of those cropping out in theMarano de’ Marsi section above described, according with a franklylacustrine origin.

3.2. Magnetic properties: sampling and methods

Palaeomagnetic samples from Marano de’ Marsi succession weretaken from the entire outcropping section in the undisturbed lacus-trine clay.154 samples were obtained at an average sampling interval

of 10 cm (Fig. 3). Palaeomagnetic samples from the Borgorose corewere taken from 200 to 2450 cm depth (above 200 cm depth, the corewas very weathered) at an average sampling interval of about 25 cm,producing a total of 84 samples for analysis (Fig. 4).

Cores have been drilled with an ASC-280 gasoline-powered drilland oriented in situ with a magnetic compass for Marano de’ Marsisection. The samples collected from Borgorose core were orientedwith respect to the top, whereas the azimuth was not defined, asthe core was not oriented with respect to the north. On this basis,only the palaeomagnetic inclination was considered to define themagnetic polarity in the case of Borgorose core.

Low-field magnetic susceptibility was measured at the palae-omagnetic laboratory of Roma Tre University with an AGICO KLY-3kappabridge. Successively, the natural magnetic remanence (NRM)was measured with a JR6 spinner magnetometer at Roma TreUniversity and 2 G-Enterprise SQUID cryogenic magnetometers atpalaeomagnetic laboratory of ETH in Zurich and ALP palae-omagnetic laboratory at Peveragno.

Thermal demagnetization technique was applied for most of thespecimens, whereas alternating field (AF) technique was applied forsome representative specimens of Marano de’ Marsi section. In thefirst kind of measurements the samples were thermally demagne-tised with temperature increments of 30 and 50 �C, up to440–500 �C, whereas in the second treatment the samples wereprogressively demagnetised in an alternating field (AF) up to 100 mT.Demagnetization diagrams are analysed by principal componentanalysis (Kirschvink, 1980), in order to determine the ChRM (char-acteristic remanent magnetization) directions for each sample.

3.3. Pollen analyses

A total of 41 sediment samples for pollen analysis fromBorgorose core and of 61 ones from Marano de’ Marsi outcrop were

Fig. 2. Geological sketch map of continental deposits of the study area (simplified afterChiarini et al., in press). 1) Quaternary deposits; 2) Marano de’ Marsi unit – lacustrine-deltaic facies (marls, marly claystones, siltstones and sandstones); 3) Marano de’ Marsiunit – alluvial-deltaic facies (sandstones, gravels and conglomerates); 4) location ofsampling sites: a) Marano de’ Marsi (Tore) succession; b) Borgorose (Fornace deiLaterizi) succession.

L. Sadori et al. / Quaternary International 225 (2010) 44–57 47

chemically processed at different intervals. Pollen samples wereprepared at 40 cm interval in the Borgorose core, at 20 cm (withsampling improving at 10 cm at key depths) in the second sedimentsuccession. For each sample, about 2 g of dry sediment waschemically processed with HCl (37%), HF (40%) and hot NaOH (10%).A tablet containing a known amount of Lycopodium spores wasadded to each sample in order to estimate the pollen concentrationvalues within the sediment.

The pollen percentage diagram was drawn using different pollenbasis sums, following the criterion suggested by Berglund andRalska-Jasiewiczowa (1986). The terrestrial spermatophytes aregrouped according to their main subdivision (gymnosperm trees,angiosperm trees, and herbs) and the basis sum on which theirpercentages were calculated included none but themselves. Forother pollen and spore groups (aquatic angiosperms, ferns, andAlgae) the basis sum included terrestrial spermatophytes and, inturn, each group of considered palynomorphs.

Pinus pollen grains have been subdivided into Pinus haploxylontype and Pinus sylvestris type sensu Rudolph (1936) as reported byKlaus (1977) and discussed by Zanni and Ravazzi (2007).

A curve of Pinus undiff. is presented as well, including pollengrains for which was not possible a better taxonomic identification.The bad state of exine preservation did not always allow also thediscrimination of Cathaya pollen grains from that of P. haploxylontype on the basis of the features listed by Caratini et al. (1972) andSivak (1975). For this reason a separate curve for this genus is notprovided, being its presence rarely surely assessed and probablyunderestimated in both records. Due to the scarce preservation ofpollen exine, not even the distinction of Pseudolarix from P. sylvestristype (as suggested by Zanni and Ravazzi, 2007) was attempted.

Cedrus pollen show different morphological features, likelymasking the presence of more than one species. Cedrus is nowadaysrepresented by three species, two of which living in the southernMediterranean basin, from Turkey to Morocco and one growing inthe Himalayan region.

No attempt was made to discriminate Abies and Keteleeriapollen. Abies alba is still widespread in northern and southern Italy,while in the peninsular central regions its drastic reduction datesback at ca. 70,000 years BP (e.g. Follieri et al., 1998; Magri, 1999;Magri and Sadori, 1999). Keteleeria fossil wood was found nearRome (Follieri, 1963) in volcanic materials ascribable to the MiddlePleistocene (younger than 700,000 years BP).

Sequoia pollen was never detected in both records, so Taxodiumtype pollen comprehends Taxodium/Glyptostrobus genera, bothpresent in Pliocene and Pleistocene macrofossil records (Follieri andMagrı, 1961; Vassio et al., 2008). P. haploxylon type may mask thepresence of a number of gymnosperms no more represented in theEuropean flora, as it appears from macrofossils finds (e.g. Martinettoet al., 2007). Picea pollen grains show quite different grains size. Thegenus is still present in Italy, with rare stands of Picea excelsa incentral Italy, and a wide distribution in northeastern Alps.

As far as Tsuga pollen, both the two types T. canadensis andT. diversifolia are present.

Taxaceae/Cupressaceae can include a very high number of taxanot distinguishable on the basis of the pollen morphology; many ofthese taxa are at present extinct, but their relevant presence in Italyduring Pliocene and Pleistocene is deduced by macrofossils (Follieriand Magrı, 1961; Follieri, 1963; Bertoldi and Martinetto, 2001a,b;Martinetto, 2001b,c).

Three oaks pollen taxa have been distinguished, Quercus roburtype (comprehending all deciduos oaks minus Quercus cerris),Q. cerris/Quercus suber (at present represented in Italy by only thetwo species), and Quercus ilex type (including all the evergreen oaksexcepting Q. suber) on the basis of the present-day featuresreported by Smit (1973). As concerns hornbeams, two pollen typeshave been distinguished: Ostrya carpinifolia/Carpinus orientalis andCarpinus betulus.

Ulmaceae are broken down into Ulmus, Zelkova, and Celtis. Zelkovapollen grains show sometimes a bigger size than those preserved inthe upper Pleistocene sediments of central Italy, where the genusbecame extinct around 30,000 years BP (Follieri et al., 1986).

Juglandaceae pollen grains have been assigned to Carya, Engel-hardia, Juglans, and Pterocarya. The morphology of Juglans pollenfrom the Salto river valley successions is different from that ofJuglans regia pollen, commonly found in the Italian sedimentsrecords of the last millennia.

Hamamelidaceae are represented by some pollen grains ofLiquidambar and small (20–25 mm) tricolpate undifferentiated ones.

Concerning triporate grains with protruding vestibulate pores,two different types have been found, showing differences in size,exine thickness, and in the pores morphology: one was surelyascribed to Betula, the other temptatively attributed to Rhoipteleaon the basis of the pollen features reported in many records ofMessinian and Pliocene age (e.g. Bertoldi and Castello, 1990; Bertiniand Martinetto, 2008).

Fig. 3. Stratigraphic column of Marano de’ Marsi succession (a). In column (b) is the variations of magnetic susceptibility, in (c) the variation of natural remanent magnetization atambient temperature, in (d) the characteristic palaeomagnetic component of inclination, with the polarity interpretation.

Fig. 4. Stratigraphic column of Borgorose core (a). In column (b) is the variations of magnetic susceptibility, in (c) the characteristic palaeomagnetic component of inclination. Notethat palaeomagnetic samples are unoriented, therefore the inclination is used to derive a stratigraphy of the changing polarity.

L. Sadori et al. / Quaternary International 225 (2010) 44–5748

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4. Palaeomagnetic and palaeobotanical results

4.1. Palaeomagnetic results

The low-field magnetic susceptibility values are generally low inaverage and range between 14 and 164�10�6 SI (Fig. 3b). In detail,we can subdivide the Marano de’ Marsi section into three portions(Fig. 3b). The lower portion, from 10.7 to 5.00 m height, is charac-terized by low-intensity values with a weak linear increase of themfrom 30 to 70�10�6 SI. This part is also characterized by a weakciclicity with a frequency of about 20–40 cm for each cycle (Fig. 3b).The middle-upper part, from 5.00 to 2.70 m height, the suscepti-bility shows more scattered values with relatively higher values(from 38 to 164�10�6 SI). From this height upwards, the suscep-tibility generally shows constant low values up to the contact withthe slumping where higher values are observed.

The intensity of the NRM is in the 1–20�10�3 A/m range,without any particular variation along the whole section. As alreadyseen in the susceptibility profile, also NRM profile of Fig. 3c showsconstant trend around a mean value of 8.8� 10�3 A/m and char-acterized by a ciclicity at small scale with a frequency similar to thatof susceptibility (Fig. 3c).

These variations clearly reflect the lithostratigraphic evolutionof the Marano de’ Marsi succession. In general, the magneticsusceptibility displays a small variation with low values, reflectingstable and constant input of diamagnetic grains (i.e. calcite) fromcarbonatic substrate and minor paramagnetic (clay minerals)grains during the deposition. The middle-upper part of the sectionwith higher susceptibility values includes deposits characterized bydarker clays (i.e. poorly oxidized), whereas the lower part from 10.7to 5.00 m is characterized by relatively lighter-coloured, calcite-richlacustrine sediments (Fig. 3b). The alternation between lighter (i.e.calcite-rich) and darker (organic matter rich) layers is alsoresponsible of the high frequency susceptibility variation observedat small scale (Fig. 3b). Moreover, the lacking of very high values ofsusceptibility excludes the presence of any volcaniclastic contam-ination into the palaeolake, such as pyroclastic fallout productscharacterized by high content in ferromagnetic grains.

Thermal and alternating field demagnetizations up to320–450 �C and 10–80 mT respectively were usually sufficient todemagnetize samples. This range of temperatures and magneticfield suggests the occurrence of magnetic minerals with relativelysoft coercivity, possibly iron sulphides and magnetite with variableTi-content. Both demagnetization approaches generally reveals thepresence of one stable component of magnetization, after removalof a viscous component at 120–180 �C and 5–10 mT (Fig. 5b). Thissingle component is present in 98% of the collected samples andrepresents a characteristic magnetization with positive inclinations(i.e. normal polarity) resolved in the 180–440 �C and 10–80 mTdemagnetization intervals (Fig. 5a–c). The palaeomagneticinclinations of the characteristic magnetic remanence, aftertectonic correction, range between 32� and 76� with a meaninclination of 53� (Fig. 3d).

In the Borgorose core the magnetic susceptibility values aregenerally low and range between 81 and 249�10�6 SI (Fig. 4b).These values are relatively higher than Marano de’ Marsi sectionlikely because of Borgorose sediments have a major content of clayminerals (i.e. paramagnetic fraction). The highest values are relativeto the upper portion of the core, from 540 to 870 cm depth,whereas they are constant for the remaining lower portion.

The palaeomagnetic analysis was performed on 84 samplescollected from the core. Thermal demagnetization up to380–400 �C has allowed to completely demagnetize the samples(Fig. 5d). This temperature range is similar to that of Marano de’Marsi and suggests the presence of iron sulphides and minor

amount of Ti-magnetite grains. Interpretable palaeomagneticdirections were obtained in a total of 62 out of 84 analysed samples.The magnetization component analysis retrieved from the wholecore revealed the presence of one magnetic component ofmagnetization after removal of a viscous component up to 120 �C.In most of the cases this magnetic component is characterized bypositive inclination (Figs. 4c and 5d). Most of the samples indicatespositive palaeomagnetic inclination with a mean of 48� (Fig. 4c),suggesting a normal polarity magnetozone without magneticreversals. By the contrast, very few samples show a subhorizontalor weak negative palaeomagnetic inclinations, which are appar-ently discordant with a general positive inclination. This scattercould be related to the sampling that was performed withoutconsidering bedding tilt and the azimuth of the core.

4.2. Palynological and preliminary plant macrofossils results

The preservation of the pollen grains was generally poor in bothrecords, being they generally degraded, corroded and broken; thisfact slowed the identification, making it often problematic.

Many sediment levels turned out too poor in pollen: a total of 57out of 61 pollen samples from Marano de’ Marsi and a total of 15 outof 41 from Borgorose have been selected to be represented in thediagrams on the basis of the pollen content.

The mean count of only the terrestrial spermatophytes pollenwas 304 pollen grains at Borgorose, 351 at Marano de’ Marsi. Thetotal pollen concentration of the selected pollen samples variedfrom 1900 to 129,000 pollen grains/g at Marano de’ Marsi and from9000 to 113,000 pollen grains/g at Borgorose. Pollen counts wereexpressed in percentage and in concentration values (Figs. 6 and 7).

In all, 56 pollen taxa (of which 11 herbaceous taxa in all) wereidentified at Marano de’ Marsi, 46 (of which 8 herbaceous ones) atBorgorose, excluding the spores and the algae. The scarce numberof pollen taxa found in both records can be partially explained withthe low amount of herbaceous pollen, peaking at 3% at Borgoroseand mainly ranging from 0% to 4% at Marano de’ Marsi, wherehigher NAP (Non Arboreal Pollen) percentages are found in only 5samples. The number of terrestrial spermatophytes pollen taxafound in each level varies from 15 to 39 at Marano de’ Marsi, thehighest amount of them being found in concomitance with thehighest percentage values of NAP (13%) and very low pollenconcentration values (3200 pollen grains/g) at 9.80 m. At Borgorosethe minimum number of pollen taxa (12) matches the lowestpollen concentration value (9000 pollen grains/g), the maximumone (31) is found at 6.70 m.

Even if the number of taxa in each succession shows differencesin single sample presences, the list of pollen taxa is quite similar inthe two sites, with 43 pollen taxa in common.

The ca. 11 m long pollen succession of Marano de’ Marsi, entirelydeposited during forest phases, records strong and sudden changesin forest physiognomy. Phases with overwhelming percentages ofgymnosperm pollen and medium/high pollen concentration valuesabruptly alternate with shorter sediment horizons with prevailingangiosperm trees pollen and very low pollen concentration values(Fig. 6). Neither periods showing intermediate vegetation features,nor ones with open herbaceous vegetation are recorded in thissuccession. The number of extinct arboreal pollen taxa is high (14).

The highest percentages of indeterminable pollen grains matchthe lowest pollen concentration values, and both the highestangiosperm pollen percentages and number of taxa.

Pine pollen, both P. haploxylon and P. sylvestris types, alwaysdominant in the Gymnosperms phases, is of scarce help in inter-preting the vegetational changes. Present-day data show it istransported at long distance, so pine pollen can reflect regional andnot local vegetation.

Fig. 5. Orthogonal demagnetization diagrams of the NRM of representative samples from the Marano de’ Marsi section (a, b, c) and Borgorose core (d). Closed symbols areprojections onto the horizontal plane and open symbols are projections onto the vertical plane after tectonic correction. Demagnetization steps are in �C or mT.

L. Sadori et al. / Quaternary International 225 (2010) 44–5750

Due to the poor pollen production of living spruces (Hicks,1994), Picea pollen percentages higher than 5% are taken as anindication of local presence (Huntley and Birks, 1983).

The succession begins with a dense gymnosperm forest (>90%,24,000–86,000 pollen grains/g) mainly composed by Pinus, Picea,Cedrus and Tsuga. The pollen assemblage is completely depleted inherbs.

A sudden change is found in the following pollen samples, justabove 10 m. This phase, with arboreal angiosperms peaking at 90%,recording the sample with the maximum number of taxa (39), withthe lowest pollen concentration values (1900 pollen grains/g), andthe highest amount of indeterminable grains (15%) covers a thick-ness of ca. 1 m. Herbs reach their maximum value, 12%, which ismainly due to the local presence of chenopods (6%). The moreabundant gymnosperm in the first of these levels is Taxodium type(3.5%), while pines lowered from 66% to 0%. A real vegetationsuccession is hardly detected: in the lower samples both deciduousand evergreen Quercus with Fagus prevail, while the followingexpansion of Carya is mainly accompanied by Ulmus and Zelkovaand the recovering of Pinus, mainly P. haploxylon type.

The successive forest period, showing similar features from ca. 9to 2.50 m, is dominated by gymnosperms, above all by P. haploxylontype, P. sylvestris type, Cedrus and Picea. The two last show a spec-ular behaviour in the first samples, where cedar attains itsmaximum percentage values (few samples around 15–16%). Tsuga,Abies and sporadic Taxodium type are present too. Mesophilousangiosperm trees of Fagaceae, Ulmaceae and Juglandaceae are stillpresent, showing almost continuous curves. The herbs are practi-cally absent. In this long phase, the presence of two increases ofangiosperm trees at 5.40 m (25%, 24,000 pollen grains/g) and5.00 m (28%, 7500 pollen grains/g), is noteworthy. From 3.40 m anexpansion of Picea, attaining 34% at 3.00 m, is recorded.

At 2.40 m a sudden and strong forest composition change isfound, and consisting in a sharp decrease (four taxa left in all) ofgymnosperms and in an expansion of angiosperms. The number oftaxa increases, the indeterminable pollen grains too, while pollenconcentration values are very low (5800 pollen grains/g), resem-bling what happened in the previous phase with angiospermdominant.

The beginning of the following forest period, at 1.30 m, is againmarked by an abrupt increase of both Picea and Pinus taxa. Angio-sperm trees pollen is suddenly reduced from 88% to 20%. Thenumber of indeterminable pollen grains is decreased, while pollenconcentration values are increased.

In the top metre, a very similar trend is again found, with anabrupt change at 1.40 m characterized by angiosperms (with theoverwhelming presence of trees, peaking at 80% and a minimum oftotal pollen concentration, 4700 pollen grains/g), followed again bya sediment layer some tens centimetres thick, mainly characterizedby pines, spruces, and cedars. The record ends with another suddenshort and important expansion of angiosperms, followed bya recover of gymnosperms.

Preliminary plant macrofossil observations evidenced thepresence of both leaves and seeds/fruits of many angiosperms andgymnosperms. There is no apparent correspondence between themacro- and microfossil record (Fig. 6). Angiosperms leaves are infact often found also in phases in which gymnosperms pollen isdefinitely overwhelming. First data indicate the presence of fossilleaves of Acer cfr. monspessulanum, C. cfr. orientalis, Hedera, Fagus,Liquidambar, Quercus, Rosa, and fruits of C. cfr. orientalis, Engelhardiaand Liquidambar. Some seeds and leaves of gymnosperms, not yetcarefully analysed, have been ascribed to Pinus and Abies.

The sediment succession drilled at Borgorose (Salto river valley,central Italy) spans 24.5 m. Pollen concentration values vary from100 to 113,000 pollen grains/g (Fig. 7). Only from 3 m to 8.2 m wasfound enough pollen to carry out pollen analyses and to preparepollen percentage and concentration diagrams. The number ofpollen taxa is very low (46) and the arboreal pollen dominant(always >97%). The number of extinct arboreal pollen taxa is ratherhigh (14), while the number of herbaceous taxa very low (8). Fernspores are seldom present. Botryococcaceae are the only algae.

The diagrams show rather homogeneous features, with AP(Arboreal Pollen) ranging from 97 to 99% and pollen concentrationvalues from 9000 to 113,000 pollen grains/g. Gymnosperms pollen(72–89%) is always prevailing on that of Angiosperms (Fig. 3).P. haploxylon type is always dominant and mainly accompanied byPicea, P. sylvestris type, Taxodium type, Cedrus, and Tsuga. Picea, withpollen values always between 8 and 19% (Huntley and Birks, 1983),was locally present. Deciduous oaks were always present, even ifwith low values (2–5%) and peaking at 9% only at 8.60 m. Caryashows high percentage values among the angiosperms (8%), soonafter a slight decrease of Taxodium type and Cedrus, and the start ofQ. ilex type curve. Other important arboreal angiosperm taxa areFagus (increasing in top samples), Pterocarya, Juglans, Ulmus,Hamamelidaceae. The presence of Engelhardia, Nyssa and cfr.Rhoiptelea is worth to be mentioned.

The two investigated sites from Salto river valley (central Italy)deserve some common considerations.

Fig. 6. Lithostratigraphy and pollen percentage and concentration diagrams (groups and others, top; selected taxa, bottom) of Marano de’ Marsi succession. Black dots indicatevalues lower than 2%. Pollen groups: subtropical humid forest (Taxodium type, Engelhardia, Nyssa, cfr. Rhoiptelea); temperate broad leaved deciduous forest (Carpinus betulus, Carya,Castanea, Celtis, Corylus, Hamamelidaceae undiff., Juglans, Juglandaceae undiff., Liquidambar, Pterocarya, Q. robur type, Quercus cerris type, Tilia, Ulmus, Zelkova); mid to high elevationforest (Abies, Cedrus, Picea, Tsuga, Betula, Fagus); sclerophyllous forest (Quercus ilex type, Olea); xeric elements (Ephedra and herbs minus Cyperaceae).

L. Sadori et al. / Quaternary International 225 (2010) 44–57 51

At least five common features can be found: 1) the woods foundin both successions are always very dense, with a thick forestcanopy preventing the growing of herbs, practically absent; 2) thelist of extinct taxa is the same (14 pollen types), showing the

presence of many trees at present living in subtropical Asia andnorth America; 3) no clear vegetation successions are shown atboth sites; 4) there is an indication for a pollen rain coming fromseveral vegetational belts, as it results from the mixing of montane,

Fig. 7. Lithostratigraphy and pollen percentage and concentration diagrams (groups and others, top; selected taxa, bottom) of Borgorose succession. Black dots indicate values lowerthan 2%. For pollen groups see Fig. 6.

L. Sadori et al. / Quaternary International 225 (2010) 44–5752

mesophilous, hygrophilous and hygrophilous elements; 5) thetypical alternation between steppe and forest formations, charac-terizing the glacial/interglacial cycles, is absent in both records.

On the other hand the two successions differ because at Bor-gorose gymnosperms are always overwhelming (even in poor inpollen samples not in diagram), while at Marano de’ Marsi there arestriking changes in angiosperms and gymnosperms dominances.

Concerning the presence of some arboreal taxa, few observa-tions, useful to interpret the two successions and to locate them inthe chronological scale, can be drawn. First of all, it is clear that Italyplayed an important role in preserving the biodiversity, due to thepermanence and late extinction of many subtropical taxa, ifcompared with the rest of Europe. Zelkova can be the best examplefor it: Ferguson and Knobloch (1998) reported about its extinction

in Europe during the Pliocene, probably referring to centralEuropean countries. Its late extinction in central Italy, during thelast pleniglacial (Follieri et al., 1986), and its permanence in Sicily(Di Pasquale et al., 1992; Quezel et al., 1993) is once more a strongindication of the fact that Italy showed a particular tendency inpreserving biodiversity. There are also evidences of diachronicextinctions of many taxa in Italy, probably along a north-southgradient (Bertini, 2003).

The decrease and disappearance of Taxodium type pollen fromsome Italian pollen records was once considered a good element toput the marker between Pliocene and Pleistocene (Lona et al., 1969;Lona and Bertoldi, 1972), but more recent data, which arecontributing to fill a knowledge gap on the period, show thepersistence of this pollen type during the Lower Pleistocene

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(Bertini, 2003; Ravazzi, 2003; Fusco, 2007) and even at the Lower-Middle Pleistocene boundary (Capraro et al., 2005). On the otherhand, the macrofossil record indicates the persistence of permin-eralized wood of Taxodium in Rome, at Cava Bianca, around 450,000years BP (Follieri and Magrı, 1961).

The final disappearance of Tsuga specifically seems to haveoccurred during the early part of the Brunhes chron and has beenrelated (e.g. Bertini, 2000) to the shift in global aridity that occurredduring the 41 ka to 100 ka Middle Pleistocene climatic cyclicitytransition. Tsuga is still found in southern Italy at Valle di Manche(Capraro et al., 2005) after the Matuyama/Brunhes boundary.

Last Zelkova species became extinct around 30,000 years BPin central Italy (Follieri et al., 1986). Its presence is documented inthe last pleniglacial sediments filling the Corvaro intermontanebasin (Chiarini et al., 2007), located to the north east of the Saltoriver valley. No univocal data for Celtis diffusion are available.Nowadays Celtis australis, considered native of Italy, is a sporadictree in the peninsula. It is rarely found in Italian Pliocene and lowerPleistocene fossil records and never present in the last 300,000years pollen record from Valle di Castiglione, central Italy(Follieri et al., 1988).

Carya and Pterocarya are both at present extinct in Italy, beingtheir diffusion area restricted to north America and Asia. Theextinction of Carya in Italy seems to have happened during theMiddle Pleistocene, but the precise date of its disappearance wasnot established, due to the lack of continuous records for the period.At Carsoli, few km away from Salto river valley, a fossil perminer-alized wood of Carya dated at around 530,000 years BP wasdetermined (Giardini and Sadori, unpublished data). The lastoccurrence of Pterocarya pollen, whose macrofossils (both leaf andfruit) last find is from the middle Pleistocene lake of Riano Romano(Rome, central Italy) dated at around 320,000 years BP (Follieri,1958), was found at Valle di Castiglione (Rome, central Italy) around220,000 years BP (Follieri et al., 1988).

Recently some doubts were raised on the presence of Rhoipteleain the Italian palaeoflora because its macrofossils were never foundin Europe. Notwithstanding, this pollen type, featuring someNeogene records, was not found so far in Pleistocene and in LatePliocene ones. In the long Stirone record (Bertini, 2001) it is notrecorded in the uppermost part, since the Piacenzian.

5. Discussion

The two pollen records from the Salto river valley show thepresence of 14 pollen taxa at present extinct in peninsular Italy andin whole continental Europe. The extinction of most of these taxawas not clearly established yet in Italy, and appears not to havebeen contemporary.

In both successions, during the phases with prevailinggymnosperms (Figs. 6 and 7), altitudinal microthermic elementslike Picea, Tsuga (in some way also Abies can be included) are foundmixed with mesothermic taxa like Taxodium type (Sequoia presencewas excluded on the base of pollen morphology) demanding morehumidity. Pollen grains of Cathaya were identified with certaintyin the same periods in which P. haploxylon type is the over-whelming taxon.

During the phases with prevailing angiosperms of Marano de’Marsi (Fig. 6) and those showing an angiosperm expansion atBorgorose (Fig. 7), elements requiring yearly humidity like Nyssa,Engelhardia and cfr. Rhoiptelea are found together with treestolerating seasonal contrasts such as Q. robur type, Fagus, C. betulus,O. carpinifolia/C. orientalis, Ulmus, Zelkova, Juglans, Carya, Pterocarya,Acer, Tilia, Betula, Liquidambar and Mediterranean trees such asQ. ilex type and Oleaceae. Herbs are very rare, with sparse grains ofsteppe elements like Artemisia.

The contemporary presence of taxa at present showing differentecological requirements and living at different altitudes, and theabsence of clear vegetational successions, indicate that the pollenrain was coming from different vegetational belts, suggesting thatthe Apennine chain was already playing an important role. It isclear that the alternating presence of humidity demanding treeslike Taxodium type and Nyssa are the local expression of an envi-ronmental change found in all the altitudinal vegetation beltssurrounding the ancient basin. The rapid and consistent alterna-tions found at Marano de’ Marsi between conifer forests anddeciduous angiosperms ones, induce to consider that a consistentchange in vegetation occurred. The vegetational phases featured byaltitudinal gymnosperms at Marano de’ Marsi can be probablyconsidered deposited during glacial periods. In northern Italy, infact, the glacial/interglacial cycles since the Gelasian (Bertini, 2003)were characterized by arboreal phases with gymnosperms andangiosperms alternately dominating, and not by steppic andarboreal phases like in southern coastal Italian areas (Combourieu-Nebout et al., 2004), Anyway it must be evidenced that themacrofossil record shows abundance of angiosperms even inperiods with overwhelming gymnosperm pollen (Fig. 6).

The pollen succession from Marano de’ Marsi shows in fact someproblematic aspects, probably linked to taphonomical processes.The pollen samples with angiosperm trees dominating show thehighest number of taxa and the lowest pollen concentration values(Fig. 6). It is hard to explain this scarce presence of pollen, alsopointed out by pollen grains deterioration both in shape and inexine, in the same levels. Moreover, these pollen samples withangiosperms over than 90%, are preceded and followed by stratawith very different pollen assemblages, with prevailing gymno-sperms. There is no evidence of such strong and abrupt changes inother pollen records. This is an important clue to warn that someproblems occurred in sedimentation. Palynology, evidencing thelack of specific phases of vegetational successions, can in fact be ofhelp in singling out the presence of possible hiatuses. Bertini (2000),in fact, considered the possibility that sediment gaps occurred in thepollen record from Colle Curti (central Italy), despite the lack ofdefinitive sedimentological evidence, just on the basis of theabsence of vegetational phases of potential interglacial status.

Magnetic susceptibility profile seems to rule out the possibilitythat enhanced erosion in the catchment area of Marano de’ Marsicould have caused such strong decreases in pollen concentration. Inorder to examine the possibility of sediment gaps, not indicated bythe macroscopic observation of the stratigraphic succession, care-fully conducted in the outcrop for a width of some metres, thinsection analyses at key-depths were performed. These showed thealternation of quite similar lithologies, from clayey marls to siltyclaystones, and the presence of likely erosional disconformities ofa low order, ranging from the zeroth-order (lamination surface) tothe first-order (set bounding surface) sensu Miall (2006), consistentwith the sedimentary environment.

The chronological framing of the two sediment successions is notan easy task, being absent either animal fossils or other clear strati-graphic constraints. The two records are not likely to be quitecontemporary, as they do not show exactly the same vegetationalphases. By the way they show a quite similar floristic list (43 commontaxa, same extinct arboreal pollen taxa) and they can be set against thebackground of the same period. The help in defining this time periodcan derive from either magnetostratigraphy or palynostratigraphy.The sediments of both sites show normal magnetic polarity. Thepresence and abundance of many pollen taxa related to trees, whosepresent-day relicts live in subtropical regions of Asia and NorthAmerica, induce to exclude the possibility to frame the pollen recordsin the normal polarity Jaramillo subchron, even if Italy shows peculiarfeatures, as provided refugia to many ‘‘exotic plants’’. Near Crotone, in

L. Sadori et al. / Quaternary International 225 (2010) 44–5754

southern Italy (Fig. 8), at the transition between Early and MiddlePleistocene, in fact, Capraro et al. (2005) observed the persistence ‘‘ofthe major ‘Tertiary’ taxa (such as Taxodium, Carya, Pterocarya, Liquid-ambar, Tsuga, Cedrus)’’, but with very low amounts. In the twosuccessions from Salto river valley the important amount of the justmentioned taxa, beside the presence of Cathaya, Engelhardia, Nyssa,cfr. Rhoiptelea, and Hamamelidaceae undiff. is taken as an indication ofan older age. The Early Pleistocene record from Scoppito, central Italy(Magri et al., 2010) deposited towards the end of the period, and fewkilometres away from Salto river valley, lacks all the last mentionedtaxa. Moreover in the pollen successions of Salto river valley there isno evidence of the relevant glacial/interglacial oscillations thatoccurred in the last 1 million years (Ruddiman et al., 1989; Raymoet al., 1997; Leroy, 2007), when the pattern of the orbitally drivencycles had changed from obliquity to eccentricity.

A short lacustrine sediment record pertaining to the Mon-teleone Sabino Unit (Cosentino et al., in press), outcropping nearFara in Sabina, few tens of km to the west of the Salto river valley,was ascribed to the Late Pliocene (Barisone et al., in press) on thebasis of the pollen assemblage (e.g. for the presence of Symplocos,Nyssa, Hamamelidaceae undiff.), the middle Villafranchianmammal remains within the same stratigraphic unit, and the

Fig. 8. Sites mentioned in the text. 1. Leffe (Muttoni et al., 2008); 2. Stirone (Bertini, 2001); 3(Fusco, 2007); 6. Ponte a Elsa (Valleri et al., 1990); 7. Santa Barbara (Bertini, 2002) and Pogg2000) and Dunarobba (Biondi and Brugiapaglia, 2000; Martinetto, 2001b; Vassio et al., 20press); 11. Carsoli (Giardini and Sadori, unpublished); 12. Scoppito (Magri et al., 2010); 13. CaValle di Castiglione (Follieri et al., 1988); 14. Valle di Manche (Capraro et al., 2005) and V(Combourieu-Nebout et al., 2004).

lateral heteropic relations with the coastal marine deposits of theTorre Baccelli Unit (Cosentino et al., in press), recently ascribed tothe Late Pliocene (Cosentino and Fubelli, 2008).

The marine sections from Valle Ricca at Monterotondo (Urbanet al., 1983; Arias et al., 1990) near Rome, whose chronologicalframing was subject of scientific discussion (Carboni et al., 1993),and which are possibly ascribable to the Middle Pliocene–EarlyPleistocene long time period, show some similarities with the Valledel Salto successions. In the investigated period, according to theauthors covering some hundreds thousands of years, a very denseforest cover with gymnosperms (mainly Pinus, both haploxylon anddiploxylon, Abies, Picea, Tsuga, Cedrus and Taxodiaceae) is found.Herbs are very rare, and arboreal angiosperms expansions too,being the last mainly represented by Quercus, Ulmus, Carya andPterocarya. Sparse grains of Nyssa, Liquidambar, Aesculus andEucommia are present too.

If minor periods with normal polarity are excluded on the basisof their short duration, the possibility that the successions weredeposited during the subchrons Olduvai, Reunion (Late Pliocene),or Gauss (Middle Pliocene) has to be taken in consideration.

To this purpose some comparisons with pollen data availablefrom Italian marine and continental records were carried out. The

. Sesta Godano (Bertoldi and Castello, 1990); 4. Sarzana (Bertoldi et al., 1994); 5. Lamoneio Rosso (Mazza et al., 2004; Bertini et al., 2010); 8. Fosso Bianco (Pontini and Bertini,

08); 9. Colle Curti and Cesi (Bertini, 2000); 10. Monteleone Sabino (Barisone et al., inva Bianca (Follieri and Magrı, 1961), Valle Ricca (Urban et al., 1983; Arias et al., 1990) andrica-Semaforo (Combourieu-Nebout et al., 1990; Klotz et al., 2006); 15. Punta Piccola

L. Sadori et al. / Quaternary International 225 (2010) 44–57 55

stratigraphic position of many of them is however sometimesdubitatively assessed by the authors, lacking an univocal referencechronology for the Plio-Pleistocene series.

Even if Italy numbers most of the European palynological conti-nental sites covering the Late Pliocene and the Early Pleistoceneperiods (see Bertoldi, 1990; Bertini, 2002, 2003; Fusco, 2007, 2010;Leroy, 2007), a clear correspondence between the Salto river valleysuccession and other Italian Pliocene and Pleistocene successions isnot easily found. The records from Marano de’ Marsi and Borgoroseshow a reduced number of taxa, even if generally, although coveringshort and uncalibrated intervals of time, continental successionspreserve a rich palynoflora (e.g. Bertini, 2001). Moreover the pollenassemblage shows an intriguing peculiarity, consisting in the pres-ence of an ‘‘old taxa’’ such as cfr. Rhoiptelea. By the way the absence oftaxa like Sequoia type, Palmae, Celastraceae, Cyrillaceae, that aregenerally found with Rhoiptelea, and indicating an Early and MiddlePliocene age, is noteworthy. The absence of Sciadopytis, Symplocos,Eucommia, and Sapotaceae pollen, that are found (though sporadi-cally) also in Early Pleistocene Italian sediment records, has to bepointed out too.

A Middle Pliocene age, consistent with the possibility to framethe investigated succession during the Gauss chron, seems there-fore not very probable for the floristic assemblages of Salto rivervalley, at the present state of the knowledge. The two pollenrecords of central Italy lack, in fact, of many subtropical taxa foundin marine and continental Italian successions (Fig. 8) like SantaBarbara, (Bertini and Roiron, 1997; Bertini, 2002), Stirone (Bertini,2001), Sarzana (Bertoldi et al., 1994), Sesta Godano (Bertoldi andCastello, 1990), Ponte a Elsa (Valleri et al., 1990), Punta Piccola(Combourieu-Nebout et al., 2004). Apart the presence of cfr.Rhoiptelea, the investigated records from central Italy show moresimilarities with the younger successions of Lamone (Fusco, 2007),Leffe (Ravazzi and Rossignol Strick, 1995; Ravazzi and Moscariello,1998; Ravazzi, 2003; Muttoni et al., 2008), Upper Valdarno (Bertiniet al., 2010) and the composite succession of Vrica-Semaforo (e.g.Combourieu-Nebout et al., 1990; Klotz et al., 2006). A good corre-spondance is also found with the uppermost part of the pollendiagram of Fosso Bianco succession (Pontini and Bertini, 2000),located close to Dunarobba fossil forest, in the Tiberino Basin, andreferred to the Upper Pliocene.

It has anyway to be precised that the list of taxa from the Saltoriver valley successions is shorter than those of other sites andshows some minor differences, that could be possibly explained notonly with the lack of herbs (that could be anyway a possible indi-cation of an older age than the Late Pliocene), but also withdifferent local environmental conditions. These last could alsoexplain the permanence of cfr. Rhoiptelea, probably suggesting that,similarly to what (as already mentioned in this text) happened indifferent geological periods in central Italy for many taxa like Carya(Giardini and Sadori, unpublished data), Zelkova (Follieri et al.,1986), and many gymnosperms (Follieri and Magrı, 1961), it was fora long time preserved in the central Apennine area.

To better define the age of the Salto river valley successions therole of P. haploxylon/Cathaya, showing very high percentages in theinvestigated record, was checked. At Stirone (Bertini, 2001), in thenorthern Apennines, the above mentioned taxon show a significantincrease from the Upper Piacenzian, followed by a progressivedecrease during the Gelasian. On the contrary, at Vrica (Combour-ieu-Nebout and Vergnaud-Grazzini, 1991; Klotz et al., 2006) wherethe record starts at ca. 2.48 Ma, and Pinus is always overwhelming,Cathaya shows a very high amount, especially from 1.92 and 1.74 Ma.

On the basis of these considerations, the investigated recordscan be probably ascribed to the Late Pliocene, being they depositedin one of the normal polarity subchrons, such as Reunion or Olduvaiones. Taking into account the short duration of Reunion subchron

(w10 ka) and the striking changes in forest composition of Maranode’ Marsi (possibly recording portions of long climatic cycles), it islikely that the two investigated successions were deposited duringthe Olduvai subchron.

In absence of an independent chronology and of a clear recon-struction of the vegetation history of the region, we cannot,however, definitely rule out the possibility that both recordsdeposited during the Gauss chron. The only element favouring thishypothesis, besides the already discussed presence of cfr. Rhoipte-lea, could be however the thick forest canopy that always preventedthe expansion of herbs, typical of Middle Pliocene pollen records.

6. Conclusions

The lacustrine deposits of Salto river valley, belonging to a morecomplex depositional system including alluvial and deltaic facies,show a pollen content, which was mostly tree airborne pollen, bothlocally growing and coming from vegetation belts distributed atdifferent elevations. Such consideration, suggesting that in thesurrounding areas already existed mountain reliefs, is consistentwith the presence of coarse-grained alluvial facies in the deposi-tional system.

No traces of the vegetation alternations of glacial/interglacialperiods, as known for the southernmost areas of Italy, are found,being herbs almost absent. This fact, together with the presence ofmany taxa extinct in Italy and living nowadays in subtropical areasof the northern hemisphere outside Europe, suggest a Late Plioceneor an Early Pleistocene age. The second possibility is anywayexcluded for the normal polarity of both records.

The two investigated successions correlate on the whole bothpalynologically and magnetostratigraphically, showing a verysimilar floristic assemblage (same list of extinct arboreal taxa) andthe same magnetic properties.

A preliminary macrofossils study from the Marano de’ Marsioutcrop supports and integrates pollen analysis, though pointingout some taphonomical discrepancies. On the basis of the planttaxa and normal polarity of the sediments, the hypothesis that thetwo records deposited in a similar age and come from the samelacustrine basin, is advanced, according to the geological data.

The period in which this ancient basin was active, as well as itsextension and shape, cannot be reconstructed in detail: after thesedimentation of the Marano de’ Marsi unit, the development ofthe small Corvaro depression during the Early Pleistocene actuallycaused the extinction and the subsequent dissection of the ancientbasin itself. Nevertheless, palaeobotanic and palaeomagnetic datahighlight that the two studied records, lacking of helpful faunasremnants, formed during a normal polarity interval and probablycan be ascribed to the Olduvai subchron (Late Pliocene).

This paper is one evidence more that the development ofpalaeoenvironmental research and of chronological tools, is moreand more demanding independent data to frame past records.

Acknowledgments

The authors are indebted to E. La Posta for helpful assistance inthe field work and to F. Cifelli for palaeomagnetic sampling.

A special thank to A. Bertini for help in pollen identification ofproblematic taxa, for useful discussion and continuous stimulus.We are grateful also to E. Martinetto for advice in macrofossildetermination of Marano de’ Marsi specimens.

The authors acknowledge the reviewers D. Cosentino and F.Diniz who highly contributed to improve the article.

The sediment sampling was carried out in Meschini and Nicolaiestates.

L. Sadori et al. / Quaternary International 225 (2010) 44–5756

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