Imp. Sardella IITTAALLIIAANN PPLLIIOO--PPLLEEIISSTTOOCCEENNEE MMAAMMMMAALL BBIIOOCCHHRROONNOOLLOOGGYY AANNDD CCOORRRREELLAATTIIOONN WWIITTHH MMAARRIINNEE SSEEQQUUEENNCCEESS:: TTHHRREEEE CCAASSEE SSTTUUDDIIEESS RRaaffffaaeellee SSaarrddeellllaa11,, CChhiiaarraa AAnnggeelloonnee22,, GGiiaannccaarrlloo BBaarriissoonnee22,, CCllaauuddiiaa BBeeddeettttii11,, EEmmaannuueellee DDii CCaannzziioo11,, FFeeddeerriiccaa MMaarrccoolliinnii22 && EEnnrriiccoo SSqquuaazzzziinnii33 1Dipartimento di Scienze della Terra, Università degli Studi “La Sapienza”, Piazzale A. Moro, 5 – 00185 Rome, Italy; 2Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre – Largo S. Leonardo Murialdo 1 – 00146 Rome, Italy; 3Museo Paleontologico “Ex Chiesa di S. Tommaso”, Vico Catina, 24 – 05100 Terni, Italy. E-mail address: raffaele.sardella@uniroma1.it SUMMARY The use of the biochronological units, based on the occurrence and evolutionary degree of the mammals, in the correlation between marine and continental sequences, in some cases enables a more detailed definition of the age of the sequences, but in other cases shows a more complex framework. In this paper three case studies will be pointed out: Mandriola (Sardinia, Early Pliocene-Middle Pliocene boundary), Lower Valdarno (Tuscany – Plio-Pleistocene boundary) and Tiberino River Basin (Umbria - Pliocene Pleistocene boundary). Biochronological criteria can be considered a very useful tool to infer age determination in the case of Mandriola fossiliferous site. The interpretation of the marine and non marine fossil record of Lower Valdarno and Tiber River Basin lead to two different scenarios: 1) the Italian peninsula can be considered as a refugium area for the Pliocene taxa, which survived until the earliest Pleistocene; 2) the age of deposits previously referred to Early Pleistocene has to be considered older (Late Pliocene). RIASSUNTO Le unità biocronologiche, basate sulla comparsa e sul grado evolutivo delle diverse associazioni a mammiferi, rappresentano un impor- tante strumento per la correlazione tra le sequenze marine e quelle continentali. In alcuni casi questa metodologia di lavoro porta a una maggiore definizione dell’età del deposito e della sequenza stratigrafica; in altri, invece, le unità biocronologiche mettono in evidenza un quadro più complesso. In questo lavoro vengono presi in considerazione tre casi di studio: Mandriola (Sardegna - passaggio Pliocene inferiore-medio), il Valdarno Inferiore (Toscana – passaggio Plio-Pleistocene) e il Bacino Tiberino (Umbria – passaggio Plio- Pleistocene). I criteri biocronologici si sono rivelati uno strumento assai utile per definire con maggior dettaglio l’età di un deposito fossilifero nel caso del sito di Mandriola. L’interpretazione dei ritrovamenti paleontologici provenienti dalle successioni marine e continentali del Valdarno inferiore e del Bacino Tiberino conducono alla definizione di due scenari: 1) la penisola Italiana come area rifugio per taxa pliocenici, qui sopravvissuti sino alle prime fasi del Pleistocene; 2) l’età di depositi in precedenza attribuiti al Pleistocene Inferiore deve essere considerata più antica (Pliocene Superiore). Keywords: Biochronology, marine/continental correlation, fossil vertebrates, Plio-Pleistocene Parole chiave: : Biocronologia, correlazioni marino-continentale, vertebrati fossili, Plio-Pleistocene Il Quaternario Italian Journal of Quaternary Sciences 1166(1), 2003, 15-20 IINNTTRROODDUUCCTTIIOONN In 1997 Gliozzi et al. published an integrated bio- chronological framework based mainly on mammal fau- nal assemblages and their evolutionary degree. Such a biochronological framework for Pliocene and Pleistocene can be considered a first step for corre- lating continental and marine sequences. The compari- son between biochronological and biostratigraphical data enables in some cases a more detailed correlation of the sequences, while in other cases such a correla- tion does not seem to fit perfectly. In this paper three case studies will be presented, illustrating those two situations. 11)) IInnffeerrrriinngg aaggee ccoonnssttrraaiinnttss ttoo mmaarriinnee ssuucccceessssiioonnss bbyy mmeeaannss ooff ccoonnttiinneennttaall ffoossssiill vveerrtteebbrraatteess:: tthhee MMaannddrriioollaa ffoossssiilliiffeerroouuss ssiittee ccaassee ssttuuddyy Age determination of the various formations out- cropping in the Sinis Peninsula (western Sardinia, Italy) and their stratigraphical correlations have been for a long time a matter of debate. Actually, each formation outcrops in a very limited area, most of the time they show no visible stratigraphi- cal continuity or heteropy with other formations, and usually lacks significant fossils. Nonetheless, a revision of the lagomorph and rodent content of the Mandriola fossiliferous site (southern coast of the Capo Mannu Peninsula, northern portion of the Sinis Peninsula; Fig. 1) fixed a constraint to the age of the enclosing formations. The fossiliferous layer consists in a lens (3 m thick in its central part and approximately 10 m long) of silt and sands accumulated in a coastal lagoon (Esu, 1986). The lens lies at the base of the Capo Mannu Fm., consi- sting of various sand complexes of aeolian origin (Pecorini et al., 1974; Carboni & Lecca, 1995). The Capo Mannu Fm. overlies the shallow water marine limestones of the Calcari di Mandriola Fm. (Fig. 1), whose depositional facies becomes shallower from bot- 16 R. Sardella et al. tom to top. All the complex represents a transition from a marine littoral environment to a continental aeolian one (Carboni & Lecca, 1995). The non-marine molluscs found in the deposit unfortunately cover too wide a stratigraphical range (Pliocene; Esu, 1986) to be useful for age determination. Fossil vertebrates of the lagoonal sediments were at first illustrated in a preliminary note by Pecorini et al. (1974), who inferred an Early Pliocene age (Ruscinian, MN14; for a synoptic MN Zones - Mammal Ages - chro- nostratigraphic chart, see Esu, 1999) for the deposit due to the presence of the murid Rhagapodemus hautima- gnensis. This opinion was in later years reconsidered by other palaeontological studies (López Martínez & Thaler, 1975; Esu & Kotsakis, 1985). On the other hand, regional stratigraphy data assi- gned the Mandriola fossiliferous site to Middle Pliocene (Carboni & Lecca, 1995). The new systematic attribution of one faunal ele- ment (the murid Rhagapodemus azzarolii; Angelone & Kotsakis, 2001) has been one of the factors that led to the reconsideration of the age of the deposit. R. azzaro- lii underwent only slight morphological and morphome- tric modifications if compared with its continental ance- stor (R. ballesioi Mein & Michaux, 1970): that may demonstrate that its colonisation of Sardinia occurred a short time before the deposition of the lagoonal sedi- ments (for a synthesis on insular environment induced modifications on vertebrates see Azzaroli, 1982). The temporal distribution of R. ballesioi in central and western Europe covers part of MN14 to early MN15 (Middle-Upper Zanclean), fixing a lower age boundary for its arrival on the island. An upper limit could be established by the presen- ce of Prolagus aff. P. depereti, derived from P. depereti López, 1975, only known in late Ruscinian assemblages (MN15, late Early Pliocene – earliest Middle Pliocene). For these reasons, the arrival of these faunal ele- ments in Sardinia and the age of the Mandriola fossilife- rous site is considered to be the Zanclean-Piacenzian boundary (Angelone & Kotsakis, 2001). The difficulty in using a common biochronological tool (such as evolutionary degree of faunal elements) to compare continental faunas and insular ones, in this case has fortunately been avoided. 22)) NNeeww ppeerrssppeeccttiivveess iinn LLoowweerr VVaallddaarrnnoo ssttrraattiiggrraapphhyy bbyy mmeeaannss ooff mmaammmmaall ffaauunnaass In Lower Valdarno area (Tuscany, Italy) sediments spanning from Early Pliocene to Late Pleistocene – Holocene outcrop. The marine Pliocene cycle deposits are represented by the “Sabbie Gialle” Fm outcropping either on the left and on the right-hand side of the Arno (Fig. 2). The end of this cycle is commonly considered to be Middle Pliocene in age, as attested by the micro- paleontological content of the deposits on the left-hand side of the Arno river (Bossio et al., 1981). In this area the transgressive overlying sediments of the “Sabbie e Argille ad Arctica islandica” Fm are discordant over the Sabbie Gialle Fm. and represent the Early Pleistocene marine ingression. Another interpretation is suggested by the recent study of Casa Sgherri (Santa Croce sull’Arno, Pisa) mammal fauna and of the findings at Vinci, in the sur- roundings of Fucecchio (Firenze), on the right-hand side of the Arno, in continental sediments correlated to the post-Pliocene marine cycle of the left-hand side (Fig. 2). Germanomys sp. (Arvicolidae, Rodentia) has been found in the “Conglomerati di Vinci”. It is related to Middle to early Late Pliocene (MN15b-16b) (Fejfar, 2001). Together with Germanomys, remains of E. ex gr. E. stenonis-senezensis have been recovered. Such a finding, even if without a specific attribution, reduces the time span to Late Pliocene (Costa San Giacomo-Olivola F.U.), since either E. stenonis Cocchi and E. senezensis Prat are widespread in western Europe in sites correla- ted with Late Pliocene and earliest Pleistocene (Alberdi et al., 1998). A few km westward in the sediments of the Massarella Unit, related to those of Vinci, the Casa Sgherri local fauna has been found (Marcolini et al., 2000; Marcolini, 2001, Marcolini, in press). Large and small mammals have been recovered and the assem- blage seems to be related to the Late Pliocene. As to large mammals, the contemporary presence of Enhydrictis ardea (Bravard), Acinonyx pardinensis (Croizet & Jobert), Sus strozzii Meneghini and Macaca sylvana florentina (Cocchi) has important biochronologi- cal meanings since such an assemblage indicates a time lapse comprised between the Costa S. Giacomo F.U. and the Olivola F.U. As to small mammals, Mimomys ostramosensis Janossy & Meulen and Fig. 1 - Location of the Mandriola fossiliferous site and lithologi- cal section of the outcrop. 1. Calcari di Mandriola Fm. limesto- nes, deeper water facies; 2. Calcari di Mandriola Fm. limesto- nes, shallower water facies; 3. first dunar complex of the Capo Mannu Fm.; p.s.l.: present sea level; dv: vertebrate deposit (not in scale) (from Carboni & Lecca, 1995, modified). Mimomys pitymyoides Janossy & Meulen are associa- ted in several Late Villanyian faunas (see discussion in: Marcolini, 2001) while all the three species M. ostramo- sensis, M. pitymyoides and M. pusillus (Méhély) have been recently recovered together in some Late Villanyian localities (i.e. Przymilowice 3, Poland) (Nadachowski, 2001). If we consider this piece of infor- mation, together with large mammals biochronological information the assemblage can be correlated with the Costa S. Giacomo to Olivola F.U., Late Pliocene in age (Marcolini, in press). On the basis of the fossil content, the basal portion of the Massarella unit and the “Conglomerati di Vinci” must be attributed to the Late Pliocene (Marcolini, 2001; in press), in accordance to the recent interpretation of the Lower Valdarno area suggested by Zanchetta et al. (1995), Zanchetta & Mazza (1996) and Marcolini et al. (2000). These authors suggest that the post-Middle 17Italian Plio-Pleistocene mammal biochronology ... Pliocene cycle in the Lower Valdarno is not entirely attri- butable to the Early Pleistocene but it could be anteda- ted to the Late Pliocene. Indeed, Zanchetta & Mazza (1996), on the basis of the finding of Anancus arvernensis (Croizet & Jobert) in sediments disconformably overlying the Sabbie Gialle Fm. and laterally continuous with the Sabbie e Argille ad Arctica islandica Fm., suggest that the lowermost part of this new cycle may be older than the base of the Early Pleistocene. The authors suggested two scenarios to justify this finding: the first hypothesis is that Anancus arvernensis, whose LAD in Italy is in the Costa San Giacomo F.U., survived until the Pleistocene Olivola F.U. (now correlated with Late Pliocene; Torre et al., 1996). The second one is that the base of the Sabbie e Argille ad Arctica cycle is older than previously believed, i.e. Late Pliocene. The authors saw the second scenario as the most acceptable. Fig. 2 - Location of the Lower Valdarno fossiliferous sites and schematic sketch of the relationships of the left-hand and right-hand Plio-Pleistocene deposits. 33)) TThhee ssoouutthh--wweesstteerrnn bbrraanncchh ooff tthhee TTiibbeerr RRiivveerr BBaassiinn ((UUmmbbrriiaa)):: aann ooppeenn aaiirr llaabb ffoorr ccoorrrreellaattiinngg ccoonnttiinneennttaall ttoo mmaarriinnee ddeeppoossiittss The Tiber River Basin is the lar- gest intramontane basin of the Apennine, in which non marine sedi- mentation took place from Pliocene up to Holocene. Modern studies give an updated picture of stratigraphy and palaeontology of its south- western branch, where the sedimen- tary successions widely crop out. Stratigraphy was depicted, among others, by Conti & Girotti (1978), Ambrosetti et al. (1989, 1995a, 1995b), Basilici (1995, 1997), Abbazzi et al. (1997). The Pliocene and Early Pleistocene deposits considered in these studies are referable to three lithostratigraphic units (Fig. 3): 1. The “Fosso Bianco” Formation, a lacustrine unit, Middle Pliocene – Late Pliocene in age. 2. The “S. Maria di Ciciliano” Forma- tion, which unconformably lies above the “Fosso Bianco” For- mation. It consists of sediments laid down in a fluvial environment characterised by different facies: meandering channel deposits with trough cross stratification, lake and swamp deposits, and paleosols. This formation has been referred to the Early Pleistocene but, as discussed in this work, the pa- laeontological data suggest the occurrence of Late Pliocene ele- ments. 2. The “Chiani-Tevere Formation”, a marine unit widely outcropping along the Middle Tiber Valley and bordering on the “S. Maria di 18 Ciciliano” Formation by means of the interfingering of their sediments. The “Chiani-Tevere” Formation is mostly Early Pleistocene, with only in a few sites a Gelasian age. The total thickness exceeds 300 m and the heteropy to the “S. Maria di Ciciliano” Formation occurs where its strata are Santernian in age (Mancini et al., in press). Up to 15 years ago the only important large mam- mal finding in the south-western branch of the Tiber River Basin was the almost complete skeleton of Stephanorhinus etruscus (Falconer) coming from Capitone (Ambrosetti, 1972). In the following years a new research campaign enabled a more detailed defini- tion of the stratigraphy of continental deposits outcrop- ping in the area as well as the discovery of many verte- brate sites. In the area near Terni and Montecastrilli the “S. Maria di Ciciliano” Formation outcrop (Basilici, 1995; 1997). This formation is heteropic to the marine Chiani- Tevere Formation, which is mostly of Santernian age (Mancini et al. in press), thus it has traditionally be refer- red to Early Pleistocene. Recent discoveries in the Terni area suggest the occurrence of more fossiliferous levels different in composition and age. In the fluvial deposits exposed in this area three mammal faunal assemblages have been collected until now. The older one comes from Torre Picchio and inclu- des a great number of vertebrates, coprolites, freshwa- ter molluscs, ostracods and plants (woods, fruits and seeds) (Girotti et al., in press). Vertebrates are represented by large and small mammals, rare birds, reptiles, amphibians and some fishes. Among the mammals Prolagus sp. Oryctolagus lacosti (Pomel), Mimomys medasensis Michaux, ?Mammuthus meridionalis (Nesti), Stephanorhinus cf. S. etruscus (Falconer), Equus stenonis Cocchi, Sus strozzii Meneghini, Eucladoceros dicranios (Nesti) vel ctenoides (Nesti), Axis nestii (Major), Bovoidea (?Gallogoral sp.), Leptobos vallisarni Merla vel L. etru- scus (Falconer), Mustelidae indet. (?Baranogale sp.), Canis cf. C. arnensis Del Campana, ?Homotherium cre- natidens (Fabrini) have been found. This faunal assem- blage shows transitional features between Costa S. Giacomo F.U. and Olivola F.U., with the contemporary occurrence of Mimomys medasensis (recorded herein for the first time outside Spain), ?Baranogale sp. (similar in size with the middle Villafranchian European speci- mens), ?Gallogoral sp., Axis nestii and Leptobos etru- scus. Another faunal assemblage comes from Villa S. Faustino and Colle S. Andrea, near Massa Martana (Ambrosetti et al., 1995a) and it is referable to the late Villafranchian. At Villa S. Faustino the fossil mammals mainly come from the sandy deposits (Ambrosetti et al., 1995; Sardella et al., 1995) and include: Castor sp., Elephantidae indet., Stephanorhinus etruscus, Equus stenonis, Sus strozzii, Axis nestii, Cervidae indet., Leptobos sp. (vallisarni vel etruscus), Megantereon cul- tridens (Cuvier, partim). At Colle S. Andrea Pachycrocuta cf. P. brevirostris (Aymard) Cervidae indet., Leptobos cf. L. vallisarni, Castor sp. occur. The paleontological analysis of these sites suggests they are coeval and to refer the faunas to the Tasso F.U. The third assemblage comes from Colle S. Umano and includes large mammals referable to the late Villafranchian-earliest Galerian (Early Pleistocene). The faunal list includes a large sized equid referable to Equus ex gr. E. bressanus-suessenbornensis, a bovid with bisontine features (Bison vel Leptobos), Hippopotamus antiquus Desmarest and Axis eurygonos (Azzaroli). The presence of different mammal faunas in the south-western branch of the Tiber River Basin suggests a more complex framework for the stratigraphy of the “S. Maria di Ciciliano” Formation. The faunal assembla- ge coming from Torre Picchio shows more “archaic” fea- tures (Mimomys medasensis, Axis nestii, the possible R. Sardella et al. Fig. 3 - Location of the Tiber River basin and schematic sketch of the stratigraphy: fA - Acquasparta Formation (Early Pleistocene); 4, fSMC - S. Maria di Ciciliano Formation (Early Pleistocene-?Late Pliocene); fPN - Ponte Naia Formation (Late Pliocene); fFB - Fosso Bianco Formation (Middle-Late Pliocene); PS - pre-Pliocene substratum. 19 occurrence of a middle sized bovid) compared to that from Colle S. Umano (Axis eurygonos, large bison-like bovid, etc…), with typical Early Pleistocene elements. Biochronological considerations suggest a wider time span for the continental succession of “S. Maria di Ciciliano” Formation (Late Pliocene-Early Pleistocene). The biochronology of this faunal assemblages and its significance in the stratigraphy of the Tiber River Basin is discussed in detail in Girotti et al. (in press), where two possibilities have been pointed out: to assign a Late Pliocene age to the fossiliferous deposit, with the first occurrence of species that will be very common during the Early Pleistocene times (e.g. Axis nestii, Leptobos etruscus) or to consider peninsular Italy as a refugium area, in which some vertebrates, molluscs and plants of Pliocene origin survived in the Early Pleistocene (see conclusions). CCOONNCCLLUUSSIIOONNSS The use of the biochronological units, based on the occurrence and evolutionary degree of mammals, for the correlation of marine and continental sequences, in some cases enables a more detailed definition of the age of the sequences, but in other cases shows a more complex framework. The Mandriola fossiliferous site is an emblematic example of how biochronological criteria can be succes- sfully used to infer age determination. Moreover, in this case it has been possible to apply continental European biochronological framework to the study of insular faunas. The interpretation of the marine and non marine fossil record of Lower Valdarno and Tiber River Basin (related to the Plio-Pleistocene transition) lead to two different scenarios: 1) the Italian peninsula can be con- sidered as a refugium area for the Pliocene taxa, which survived until the earliest Pleistocene; 2) the age of deposits previously referred to Early Pleistocene has to be considered older (Late Pliocene). The latter interpretation fits well with the strati- graphy of the right-hand side of the Lower Valdarno and of the Upper Valdarno and also with the palaeomagnetic analyses of Ambrosetti et al. (1975) and Bedini et al. (1981) recognising the subchron Reunion (2-2.2 Ma) within the sediments of the “Sabbie e Argille ad Arctica“ of the Colline Pisane. Moreover, this interpretation is confirmed by our recent findings of Vinci and Casa Sgherri that enable a correlation of the “Conglomerati di Vinci” and the Massarella Unit with the “Sabbie e Argille ad Arctica”, since all of them bear mammals of the Costa San Giacomo-Olivola F.U. The mammal faunas from the south-western branch of the Tiber River basin show differences in composition and can be referred to Costa S. Giacomo- Olivola F.U. (Torre Picchio), Tasso F.U. (Villa S. Faustino-Colle S. Andrea) and Farneta F.U. (Colle S. Umano) respectively. Such palaeontological data sug- gest a wider time span (Late Pliocene-Early Pleistocene) for the continental “S. Maria di Ciciliano” Formation. An age attribution for this formation other than Early Pleistocene is therefore problematic, both from a geologic and a stratigraphic point of view. From the geological point of view, the “S. Maria di Ciciliano” Formation is heteropic to the marine Chiani Tevere one, which is prevailingly Santernian in age and lies unconformably on the Middle Pliocene cycle: only in some areas of structural lowering it passes inferiorly and continuously to Late Pliocene strata, but before the heteropic episodes. In order to find a solution to these still open pro- blems a detailed analysis of the stratigraphy, of the local tectonics of the fossiliferous marine and non marine deposits, and the taphonomy of the mammal remains has to be considered. AAKKNNOOWWLLEEDDGGEEMMEENNTTSS We wish to thank two anonymous referees for their critical comments on the manuscript, T. Kotsakis, O. Girotti and M. Mancini for the useful discussions and the suggestions. This work is supported by IGAG (Istituto di Geologia Ambientale e Geoingegneria) - C.N.R. RREEFFEERREENNCCEESS Abbazzi L., Albianelli A., Ambrosetti P., Argenti P., Basi- lici G., Bertini A., Gentili S., Masini F., Napoleone G. & Pontini M.R. 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