SESS 0_retro e indice edi.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 THE PLEISTOCENE CALCAREOUS TUFA OF SANTA SABINA (PERUGIA, CENTRAL ITALY): STRATIGRAPHY, PALYNOLOGY AND VERTEBRATE PALEONTOLOGY Fausto Pazzaglia 1, Massimiliano R. Barchi 1, Nicoletta Buratti1, Marco Cherin1 & Marianna Ricci2 1 Dipartimento di Scienze della Terra, Università degli Studi di Perugia 2 Dipartimento di Scienze della Terra, Università degli Studi di Firenze Corresponding author: F. Pazzaglia ABSTRACT: Pazzaglia F. et al., The Pleistocene calcareous tufa of Santa Sabina (Perugia, central Italy): stratigraphy, palynology and vertebrate paleontology. (IT ISSN 0394-3356, 2011) An integrated sedimentological, geochronological, paleontological (mammal fauna) and palynological study was carried out on the calcareous tufa of Santa Sabina, outcropping in the Ellera basin (Perugia, central Italy). Previous U/Th datings on the investigated sections provided an absolute age of 115±8 ka as confirmed by the vertebrate fauna which could be biochronologically referred to the early-middle Aurelian Mammal Age. It corresponds to the MIS 5e, and to the last inter- glacial period (Eemian) characterised by wet and warm climate conditions suitable for calcareous tufa depositon. RIASSUNTO: Pazzaglia F. et al., I “calcareous tufa” pleistocenici di Santa Sabina (Perugia, Italia centrale): stratigrafia, palinologia e paleontologia a vertebrati. (IT ISSN 0394-3356, 2011) Lo studio integrato sedimentologico, geocronologico, paleontologico (fauna a vertebrati) e palinologico dei calcareous tufa di Santa Sabina, affioranti nella zona ad ovest di Perugia (Italia centrale, ha messo in evidenza la presenza di una mammalofauna riferibile all’Aureliano inferiore-medio. Questo è in accordo con quanto precedentemente indicato dalle datazioni U/Th, che hanno restituito un’età assoluta di 115±8 ka per le sezioni studiate. Questo intervallo di tempo corri- sponde all’intervallo isotopico MIS 5e e all’ultimo interglaciale (Eemiano), caratterizzato da condizioni climatiche caldo- umide, ideali per la deposizione dei calcareous tufa. Key words: Pleistocene, calcareous tufa, Santa Sabina, mammal fauna, palynology Parole chiave: Pleistocene, calcareous tufa, Santa Sabina,mammalofauna, palinologia Among terrestrial carbonates (calcareous tufa, speleothem and travertines), calcareous tufa rep- resent good proxy-indicator of environmental changes. They can be successfully approached by integrated analyses because of their multiple reli- able geochemical records. A multidisciplinary investigation was carried out on the calcaerous tufa outcropping in the Ellera basin area, located immediately west of Perugia (central Italy). The stratigraphical study and sedimentary facies analysis throughout two key sections (SSAB2 and Chiusa section) was combined with preliminary paleontological (fossil mammals) and palynological data. These data were compared with radiometric analyses carried out on SSAB2 section (PAZZAGLIA, 2008), in order to obtain a de- tailed paleoecological and chronological frame- work. The Ellera basin is a little basin bordered to the north and north-east by Mesozoic carbonate mountains, to the west by Miocene flysch hills and to the south by Pleistocene continental hills. It con- sists of a semigraben with a eastern master-fault dipping towards west and probably antithetic west- ern minor faults. The thickness of sediments (calcareous tufas, silts, clays, sands and rare grav- els) that have filled the basin is greater than 140 m. Two units separated by erosional surfaces can be observed: the Santa Sabina Unit and the San Biagio Unit. The first 22-30 m thick unit covers an area of 10 km2 and its surface appears flat, with an elevation higher in the center. The Santa Sabina Unit shows two lithofacies: PGU4a (calcareous tufa) and PGU4b (clays, silts, peats and calcareous tufa) (PAZZAGLIA, 2008). This study is focused on the characterisation of the calcareous tufa lithofacies which outcrop in the more proximal part of the Santa Sabina Unit, with respect to the Mesozoic ridge, where possible CaCO3-enriched water springs could be presuma- bly located. From bottom to top the SSAB2 section is charac- terised by the presence of a basal calcareous- siliciclastic sand level with rare lithoclasts and or- ganic laminations (40 cm thick). At the top of the sandy level there is a centimetric calcareous crust, followed by a 110 cm thick level mainly consisting of coherent micritic tufa with phytohermal clusters/ tufts and lenticular accumulations of phytoclasts. The section is closed by centimetric strata of mi- crohermal and phytoclastic tufa (40 cm thick) (Fig. 1). U/Th datings on the SSAB2 sections provided an absolute age of 115±8 ka (PAZZAGLIA, 2008). The Chiusa section is characterised by the ab- sence of microhermal facies and by the predomi- nance of decimetric to metric strata of micritic and phytoclastic tufa. The total thickness of the section is about 10 m. 161 - 163 162 In the PGU4a phytohermal tufas, previous paleon- tological data (PRINCIPII, 1930) have revealed the presence of leaves and stems of Poaceae (Arundo sp., Phragmites sp.) and Cyperaceae (Carex?). In the micritic tufa abundant lacustrine molluscs (PRINCIPI, 1930), ostracods and oogons of Characeae have been found (PAZZAGLIA, 2008). Some of the sedimentological data recorded from SSAB2 section reveal a partial fluvial origin of the deposits (i.e. siliciclastics inputs, presence of mi- crohermal facies, current structures). These evi- dences are absent in the Chiusa section. So, the facies association of the examined sections sug- gests a gradual passage from fluvio-palustrine to fully palustrine conditions from north (SSAB2 sec- tion) to south (Chiusa section), as the distance from the Mesozoic carbonate ridge increases. Fossil vertebrate finds from Pleistocene travertine s.l. deposits are rare in Europe. The most impor- tant site is Weimar-Ehringsdorf (Germany), that has provided a diverse vertebrate collection, in- cluding fish, amphibians, reptiles, birds and mam- mals (SCHÄFER et al., 2007). The first report about the presence of mammalian fossils from the “travertines” near the village of Ellera was written by BONARELLI (1900), who generically cited “hippopotamus remains”. Later, PRINCIPI (1930) published a more complete description of the “travertine” outcrops near Ellera, where he listed and synthetically described the mammals. Prin- cipi’s collection from Ellera was long reported missing, but it was recently found again in the warehouse of the “Soprintendenza per i Beni Ar- cheologici per l’Umbria”. The mammal fauna from Ellera was collected at the beginning of the 20th century. Unknown is the stratigraphic origin of the fossils: PRINCIPI (1930) wrote that they became from “travertine” near “Rosci’s house”, a farm still there, near Chiusa section. The type of carbonatic encrustations on the fossil bones are comparable with the facies outcropping at Chiusa section. Because of the high rate of sedimentation of the calcareous tufa (i.e. PENTECOST & WHITTON, 2000), it could be reasona- bly supposed that the mammal remains form a chronologically homogeneous assemblage. The collection is poor in terms of quantity of fossil material, but it is characterised by a quite abundant paleodiversity. The most represented taxon is Bos primigenius. Four isolated molar teeth (two lower and two upper), a left astragalus, the distal end of a metacarpal, the proximal end of a radius, the proximal end of a femur, and lots of other frag- ments were identified. Elephas antiquus is repre- sented by fragments of molar teeth and tusks. The tip of a little tusk is still partially embedded in a block of very compact tufa. The distal end of a tibia belongs to a medium size cervid and is mor- Fig. 1, SSAB2 section, with indication of the 8 samples taken for palynological analysis. Sezione SSAB2, con indicazione degli 8 campioni raccolti per le analisi palinologiche. F. Pazzaglia et al. 163 Ms. received: Testo ricevuto il phometrically compatible with Cervus sp.. Four lateral teeth (p4, m1, m2, m3) can be rather related to a smaller, Dama-like form. Cervidae are also represented by a dorsal vertebral centrum, lacking of the anterior and posterior epiphysis, thus re- ferred to a young animal. Other Artiodactyla re- mains are a right m2 of Sus scrofa and some teeth fragments of Hippopotamus sp.. Perissodactyla are represented by a tooth fragment and an astra- galus of Stephanorhinus sp.; further analysis of the latter bone will probably allow to determine the rhi- noceros species. The only remain belonging to a Carnivore is a left p4 of Ursus spelaeus. The mam- mal fauna is typical of a forested landscape on the whole, with the presence of quite large palustrine and/or lacustrine habitats (because of the occur- rence of Hippopotamus sp.) as revealed by sedi- mentological inferences, and other paleontological data (plants, molluscs, and ostracods). Although palynological processing of carbonates is still generally discouraged because considered as unfavourable lithotypes, some literature reveals that calcareous tufa could be palynologically pro- ductive and often suitable for pollen analysis (i.e. BURJACHS & JULIÀ, 1994; VERMOERE et al., 1999). A palynological investigation was carried out on 8 samples taken from the SSAB2 section (Fig. 1). The section was sampled with a variable interval (max. 60 cm) from both micritic and phytohermal facies. Standard chemical and physical treatments were employed to remove most of the mineral sediment and to concentrate pollen grains in the residue. Pollen analyses are in progress to define vegetational and climatic conditions during carbon- ate deposition. Although most of the fossil material from Ellera is fragmentary and some of the speci- mens have not been thoroughly examined yet, the finds allowed to infer some biochronological and paleoecological conclusions. The mammal collec- tion could be biochronologically referred to the early-middle Aurelian Mammal Age, as previously suggested by a radiometric dating (115±8 ka, PAZ- ZAGLIA, 2008). 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