Studio geologico-paleontologico della evoluzione paleoambientale della costa molisana nel corso del tardo Pleistocene-Olocene con particolare riguardo alla trasgressione versiliana

A multidisciplinary study comprising geomorphological, stratigraphical, paleontological, palynological and geochronological analyses has been carried out on sedimentary successions coming from two sectors of the Molise coastal area: the area of the Trigno river mouth and the area of the harbour of the Termoli city. The analyses were made on 6 core successions, three of which were drilled within the sea, some hundreds of meters from the current shoreline, in the area of the Trigno river mouth, and the other three on the beach, very near to the actual shoreline, in the area of the harbor of Termoli. The obtained results allowed us to reconstruct several stages of the palaeoenvironmental evolution of the study areas during Late Pleistocene and Holocene. The paleontological analyses were fundamental to reconstruct the palaeoenvironments in general, and to point out in particular several palaeo-bathymetric variations related alternatively to regressive and transgressive trends controlled by climatic changes occurred during the last 8000 years. In the area of the Trigno river mouth, during the Last Glacial Maximum, fluvial dynamics and erosion in particular gave origin to a very heterogeneous palaeo-topographical setting. After the Last Glacial Maximum (LGM), about 20000 years ago, fluvio-palustrine environments populated by non-marine fauna evolved and persisted for about 1000 years, giving way to a clayey-silty sedimentary sequence. At this time the sea level was about 100 m below the modern sea level and the shoreline located some tens of km more seawards. The next reconstructed evolutionary stage of this area is related to the progressive sea level rise and the Post-Glacial Holocene marine transgression. First, lagoonal-like, seaward open environments evolved. Successively, about 8000 years ago, marine, environments evolved, characterized by typical shoreface features and deposition of fossil-rich sands. These environments were populated by typical infalittoral fauna. In the first stage, the palaeo-bathymetries were very low and the sea level was about 11-12 m below the modern sea level. Immediately after, palaeo-bathymetries increased and the shoreline and related coastal-marginal environments moved further landward. Afterwards, the palaeo-bathymetries decreased again, allowing to identify a regressive trend most likely referring to the climatic cooling occurring about 6800-7000 years ago. At this period the sea level was at about 7,5/8,0 m below the present one. After the optimum climaticum, about 6000 years ago, the coastal and marine environments moved seaward and the palaeo-bathymetries decreased again, probably in response to a new phase of climatic cooling, tentatively related to the beginning of the Neoglaciation that started 5000-5500 years ago. The sea level during this period was about 4/5 m below the modern one. The next stage of environmental evolution is characterized by the persistence of littoral environments and various slight oscillations of the shoreline. At this period a fluvio-deltaic environment evolved giving way to phases of temporary emersion and consequent pedogenesis. The youngest portion of the examined sedimentary successions are related to the modern coastal setting, while sediment intervals referring to the Little Ice Age are lacking due to the consistent retreat (ca. 700 m) that has affected the coast line during the last century. The results obtained for the second study area, located immediately south to the harbour of Termoli are still preliminary and evidence a rather complicated and heterogeneous palaeoenvironmental evolutionary setting. The study allowed to identify various landward and seaward shifts of the shoreline during the Late Pleistocene and the Holocene giving rise to various stages of emersion during which the sediments partially underwent pedogenesis.. The arrival of the Holocene marine transgression in this study area corresponds to the period when sea level was about 11 m below the modern one. This evidence is in good agreement with the data obtained in the area of the Trigno mouth where the sea arrived near the present coast about 8000 years ago when the sea level was 11-12 m below the modern one. In the Termoli area several shoreline oscillations occurred before the Holocene marine transgression could be identified. At present it is not possible to precise the chronology of this oscillations which, however, took place certainly before the Last Glacial. The present study is the first one that deals specifically with the late Pleistocene and Holocene evolution of the Molise coast. The obtained results which are, we believe, very significant, are surely preliminary but may represent an important basis for further near-future studies on this thematic. Such studies, in fact, may contribute significantly to develop a more wider and detailed frame of knowledge also in relation to climate controls, taking in consideration sedimentary and morphologic data coming frorm other sectors of the Molise coast and, in particular, the outcropping morpho-sedimentary evidences which refer to the Middle and Late Holocene progradation of the Molise coast.