Adele Bertini

Pliocene climatic cycles and altitudinal forest development from 2.7 MA in the Northern Apennines (Italy): Evidence from the pollen record of the stirone section (∼ 5.1 to ∼ 2.2 MA)

Marine Pliocene deposits from Northern Apennines (Italy) have been submitted to palynological studies in order to obtain a floristic, vegetational, and climatic record. The history of the Pliocene land environment and climate has been reconstructed on the basis of the chronostratigraphic framework available for the Stirone section. The Zanclean is characterized by long and relatively stable subtropical to warm-temperate climatic conditions. During the Piacenzian and Gelasian, a cooling is testified by both the reduction as well as the disappearance of some mega-mesothermic elements and the increase of microthermic ones. Laminated sediments, calibrated at ca 2.8 Ma, indicate a wet period characterized by repeated warmer/cooler fluctuations. Cyclic alternations between mega-mesothermic and meso-microthermic elements, starting after ca 2.7 Ma, are characterized by the opposition of coniferous (Picea mainly) and deciduous forests elements. The major increase of Picea has been stratigraphically correlated with the maximum expansion of the Arctic ice.

Pollen record from Colle Curti and Cesi: Early and Middle Pleistocene mammal sites in the Umbro–Marchean Apennine Mountains (central Italy)

The palynological record from the Colle Curti and Cesi continental deposits has been examined in order to identify the main palaeofloristic and vegetational changes between 0.99 and 0.6–0.7 Ma. These data show a progressive increase in aridity, as well as a progressive decrease in temperature, which are associated with the transition in dominance from the 41 to 100 ka cyclicity in the Milankovitch orbital record during the Middle Pleistocene. The disappearance of Tsuga, recorded during the lower part of the Brunhes Chron, also has been related to a shift in global aridity. During the successive open vegetational phases (glacials), Chenopodiaceae and Artemisia progressively increase, whereas Cyperaceae decrease. Forest phases (interglacials) are successively dominated by Tsuga, Abies with Picea and, finally, Pinus; but all lack significant expansion of broad-leaved deciduous taxa. Palynological and sedimentological data, in addition to taphonomic interpretations, demonstrate the occurrence of several hiatuses in the lower parts of the interglacials. These hiatuses are considered to represent the palaeoenvironmental response to climatic changes affecting local sedimentological and geomorphological conditions. Copyright

The Early Messinian Velona basin (Siena, central Italy): paleoenvironmental and paleobiogeographical reconstructions

Abstract A multi-disciplinary study of the basal lacustrine succession of the Velona basin (Tuscany, central Italy) provides informations about the paleoenvironmental and paleogeographical evolution of a post-collisional basin located in the Mediterranean area. Detailed sedimentological, paleontological (molluscs, ostracods, mammals, charophytes and pollen) and geochemical analyses on biogenic carbonates were carried out on a 66-m-thick muddy–sandy succession. Integrating the vertical distribution of selected species of ostracods and molluscs with the range of the mammal assemblage it has been possible to correlate the basal succession of the Velona basin to the Early Messinian (pre-evaporitic) corresponding to the lower part of the MN 13 zone. The basal portion of the Velona filling deposits corresponds to an unstable shallow lacustrine/marshy environment, rich in aquatic vegetation, surrounded by swamps dominated by Taxodiaceae and uplands dominated by warm temperate deciduous forests. Waters were generally brackish (oligo/mesohaline), alternating with hypohaline episodes. Salinity changes recorded by the faunal assemblages do not parallel with changes in the geochemical signatures in ostracod shells and charophyte gyrogonites. Geochemistry of biogenic carbonates points to an athalassic origin of the water salinity probably linked to the dissolution of the Triassic evaporites of the basement. Thus, the absence of connections between the Velona basin and the Mediterranean Sea during Early Messinian is confirmed. Ostracods, molluscs and mammals show a central European paleobiogeographical affinity, showing that, at the time of deposition of the Velona filling deposit, the endemic Tusco-Sardinian paleobioprovince was already disrupted and the northwards connections were noticeable. On the other hand, ostracods do not show any paleobiogeographic affinity with the ostracod assemblages of the Paratethyan realm, suggesting that no links between Mediterranean and Paratethys were present at that time.

TOWARDS THE LOWERING OF THE PLIOCENE/PLEISTOCENE BOUNDARY TO THE GAUSS-MATUYAMA REVERSAL

Abstract The present Pliocene/Pleistocene boundary is at the top of the Olduvai normal subchron. Many data now favour the lowering of the Pliocene/Pleistocene boundary to the Gauss-Matuyama reversal. This affords an opportunity to give to the boundary a more global significance in keeping with recent evidence.

Messinian‐Zanclean vegetation and climate in North‐Central Italy

A palynological study was carried out on four Italian Miocene‐Pliocene sections ranging in age from uppermost Tortonian to Zanclean located on the Adriatic side of the North‐Central Apennines. The study documents the Mediterranean isolation, the salinity crisis (s.s), the “lago‐mare”; event and the re‐establishment of open‐marine conditions in the Mediterranean at the beginning of the Pliocene. From a climatic point of view, a transition from subtropical/warm‐temperate conditions during the Messinian to warm‐temperate/temperate conditions during the Zanclean is recorded. The presence of a lower thermic level, with respect to the Messinian, the re‐establishment of open‐marine conditions and the uplift of the Apennines were major factors controlling paleoenvironmental variations during the Zanclean. The latter is also characterized by cyclic temperature oscillations. Correlations with coeval sections in the Mediterranean area confirm the existence of latitudinal climatic gradients within the studied area.

The Late Pliocene Site of Poggio Rosso (Central Italy): Taphonomy and Paleoenvironment

Abstract Taphonomic, paleobiological, and paleoecological analyses have been conducted on a rich bone accumulation on Poggio Rosso in the Upper Valdarno basin (Tuscany, central Italy). Fossil mammalian remains from the Upper Valdarno, including the type specimens of important European Villafranchian taxa, have been collected from the Renaissance through the present, mostly with little concern for stratigraphy. Because the specimens, elements, skeletal parts, and even entire skeletons generally were found in isolation, a great deal of information on taxonomic co-existence, population dynamics, proportions of limb segments, and other metrics, was precluded. The discovery of the latest Pliocene Poggio Rosso site, where bones are preserved in a sandy floodplain bed, has provided opportunity to rectify these omissions. The bone accumulation largely consists of limb bones (mostly articulated) and skulls, many of which are associated with mandibles. Axial skeletal elements are strongly underrepresented. Several bones were bimodally oriented. The specimens are slightly weathered, and have common bite and gnaw marks. Some coprolites also occur. Because of its complex genesis, Poggio Rosso does not match conventional taphonomic categories. The bimodal arrangement of the elements and sedimentologic evidence indicate that an unconfined flood flow contributed to the assemblages final arrangement. The role of carnivores, however, was far more substantial. The occurrence of skulls, limb bones, bite and gnaw marks, and coprolites and the comparative rarity of axial skeletal parts, attest to the presence and activity of carnivores—hyenas in particular, represented in the Upper Valdarno by Pachycrocuta brevirostris. Poggio Rosso thus is a sort of den with characteristics of a kill site. The proportionally high amount of carnivore remains, especially skulls, intimates that the hyaenids might have had cubs at the time. General wastage and incompletely consumed carcasses indicate surplus killing as well as actively transported prey elements; all of which, along with specific paleobiological speculations, suggest that the bone accumulation was formed by a cooperative group of hyenas preying on debilitated game populations in a moment of great environmental stress (possibly a period of drought). Sedimentological and palynological analyses confirm arid environmental conditions and reveal that the bones accumulated over a short time. Moreover, these same data indicate that the changes in the floodplain occurred during a major climatic fluctuation, with an increasingly arid phase that ended close to the fossil-bearing layer, which was then followed by wetter conditions.

Orbitally forced paleoenvironmental and paleoclimate changes in the late postevaporitic Messinian of the central Mediterranean Basin

Paleoenvironmental and paleoclimate changes that occurred during the late postevaporitic stage of the Mediterranean Basin in the Messinian foreland domain of the Adriatic region offer a new perspective on the relationship between orbital forcing and climate response. The magnetic susceptibility record of the Fonte dei Pulcini A section (Maiella Mountains, Italy) allows us to orbitally tune the record between 5.394 and 5.336 Ma and to temporally constrain the paleoenvironmental and paleoclimate changes evidenced by quantitative paleontological (palynomorphs, ostracods, and calcareous nannofossils), stable isotope (δ 18 O and δ 13 C), and X-ray diffraction (XRD) analyses. The base of the Fonte dei Pulcini A section is characterized by Paratethyan ostracods and dinocysts, which point to the late Messinian Lago-Mare biofacies ( Loxocorniculina djafarovi zone) of the Mediterranean Messinian stratigraphy. From paleontological and geochemical (δ 18 O) analyses, there is no evidence of a marine incursion in the Fonte dei Pulcini A section. The major changes in terms of paleodepth, paleosalinity, evaporation versus precipitation, aridity versus humidity, and reworking processes occurred in the upper part of the Fonte dei Pulcini A section, during the last Messinian insolation cycle (i-cycle 511/512), which is characterized by high-amplitude oscillations. In contrast, the lower part of the Fonte dei Pulcini A section, which was deposited during relatively low-amplitude insolation cycles, is characterized by more stable environmental conditions. Comparing summer insolation with the paleoenvironmental changes at the Fonte dei Pulcini A section, we identify delays of several thousands of years between orbital forcing and climate response.

Late Pliocene vegetation and climate in Central Italy : High-resolution pollen analysis from the Fosso Bianco succession (Tiberino Basin)

Palynological analyses from the long and continuous Fosso Bianco sedimentary succession delineate the paleoenvironmental history of the continental deposits from the Tiberino basin, during the Gelasian. The floristic and vegetational data fill the palynological gap in Central Italy for a period of ca 400 kyr, between the 100 and 82 isotopic stages. The response of the vegetation to the glacial-interglacial cycles is testified by a competition between a coniferous forest dominated by Picea and a thermophilous forest characterized by deciduous elements and Taxodiaceae. A competition between the thermophilous forest and the steppe associations is not so evident as recorded in some sites from the Mediterranean area, though herbs show repeated phases of expansion.

Cesi, an early Middle Pleistocene site in the Colfiorito Basin (Umbro-Marchean Apennine), central Italy

Near the village of Cesi, at the head of the Chienti River, in the Colfiorito Basin (Umbro-Marchean Apennines, central Italy), fluvio-lacustrine deposits have yielded mammal fossil remains. The results of a multidisciplinary investigation indicate that the vertebrate-bearing sediments date about 700 ka and accordingly provide a fossil assemblage for the Middle–Late Galerian. Palynological investigations carried out from sediments underlying the fossiliferous level suggest predominantly cold and dry conditions, whereas the fauna suggests a slight climatic amelioration towards cool and moist conditions in the uppermost part of the sequence.

Climate and vegetation in the Upper Valdarno Basin (central Italy) as a response to Northern Hemisphere insolation forcing and regional tectonics in the late Pliocene-early Pleistocene

The pollen record from the Upper Valdarno contributes to the documentation of the main palaeonvironmental changes in one of the best known basins of the Northern Apennines where lacustrine and fluvial sediments deposited since 3.3 Ma. During the Piacenzian the lacustrine system (CSBb of the Castelnuovo dei Sabbioni Synthem) was characterized by the expansion of swamp formations where humid, subtropical to warm temperate forest taxa largely spread. Such assemblages suffer a major decrease under the effect of a gradual cooling since about 2.8 Ma, as testified by the spread of altitudinal coniferous taxa. However, repeated resurgences of subtropical forest taxa have been recorded in the overlain fluvio-deltaic sandy deposits (CSBc), from 2.7 Ma onwards. The first notable expansion of a dry-climate vegetation type consisting of mostly treeless open herbaceous vegetation has been observed in the lower portion of VRC fluvio-lacustrine deposits (Montevarchi Synthem); in fact, the major pulse of Artemisia in the aeolian sands of Rena Bianca is associated to the first glacial cycles that occurred after 2.6 Ma and the tectonic phase that involves the CSB lacustrine deposits.Both climate and tectonics strongly interplay driving the changes in the structure and floral composition of wetlands associated to successive depositional environments. Since 2.6 Ma swamps notably change in structure, with a large reduction of subtropical taxa especially Ta xodium/Glyptostrobus type and the progressive expansion of warm temperate forest taxa. At the same time, marshes expanded with plants able to resist in dynamic environments affected by river action. The palynological documentation of the glacial/interglacial cycles (G/I) younger than 1.7 Ma becomes ever more discontinuous when the effects of tectonics and climate (including the associated interactions) promote successive erosional processes during the emplacement of the lower portion of UFFa (ciottolami di Laterina, Auctt.; Torrente Ciuffenna Synthem). The age of the latter still controversial could fall within an interval of time including the Mid-Pleistocene transition.