Stratigrafia dei depositi pleistocenico-olocenici dell’area costiera di Metaponto compresa fra Marina di Ginosa ed il Torrente Cavone (Italia meridionale): carta geologica in scala 1:25.000

In order to improve the geological and stratigraphic knowledge of the Metaponto coastal area a detailed geological survey has been performed between Marina di Ginosa (Taranto) and Cavone river (Matera). Furthermore, a facies analysis either along stratigraphic sections or on cores obtained from five continuously-cored boreholes, drilling in the Holocene and middle – upper Pleistocene deposits up to 120 m of depth, has been carried out. The outcropping deposits have been distinguished in: upper Pleistocene “sandy-conglomeratic deposits of the regressive coastal prisms” and Holocene “Metaponto plain deposits”. The first deposits are subdivided into three lithostratigraphic units. The first two units have a thickness variable up to 15 m, and are represented by sandy-conglomeratic prisms resulting from the interplay between sea-level fluctuations and regional uplift; they are referred to “sabbie e conglomerati di Policoro” and “sabbie e conglomerati di Masseria Ricotta”, showing facies features of shoreface passing upward to continental environments. The third unit, up to 2 m thick, is an “eluvial product”, made up of reddish sands with gravelly layers unconformably and discontinuously overlaying the previous deposits. The Holocene “Metaponto plain deposits” have been distinguished in: “continental deposits” and “transitional deposits”. Continental deposits are represented by mainly some meters thick fine- to coarse-grained sediments of eluvial, fluvial, lacustrine and palustrine environments. Transitional deposits are represented by some meters thick sandy and silty Holocene beach-dune systems (modern and ancient) and sandy and clayey-silty deltaic systems (modern and ancient). The buried deposits of the Metaponto coastal area have been distinguished in three units thanks to the facies analysis and mainly to the recognition of two important erosional surfaces. The lower unit (called substratum), found beginning from a depth variable from 13 m to 44 m moving seaward, is at least 76 m thick and made up of clayey-silty deposits, with interbedded sandy beds passing landward and upward to sandy and/or sandy-gravelly deposits. The lower boundary was not found, whilst the upper boundary is represented by an erosional surface (SE) highlighted by a lag deposit. The facies features of these deposits can be referred to offshore passing upward to shallow marine environments. The age is middle - late Pleistocene. The intermediate unit is bounded both on bottom and on top by erosional surfaces (SE and ST). This intermediate upper Pleistocene wedge-shaped unit, called “Metaponto buried plain deposits”, pinches out landward, passing from about 7 m to 0 m in thickness. It is made up of sandy-gravelly deposits of continental to shallow marine environments. The third upper unit erosionally overlies both the previous unit and the substratum by the ST surface. This unit is made up of sands and gravelly sands, and its thickness varies from 13 m to 48 moving seaward, and has been attributed to the progradation of a beach system, laterally linked to a deltaic system, and passing seaward to an offshore system. A lamellibranch shell yielded a not calibrated 14C age of 7.572±50 yr BP for these deposits. The overall collected data allow us to draw a geological map on 1: 25.000 scale that provides a new stratigraphic framework of the outcropping Metaponto plain deposits. Furthermore, the geological sections obtained also utilizing the boreholes allow us both to reconstruct the geometry of the buried deposits and to outline the evolutionary history of the Holocene transgressive prism along the coastal study area.