Biostratigraphy of the Plio-Pleistocene subsurface deposits to the south of Lago di Bracciano (near Rome, central Italy):: the Sabatini 9 borehole

Abstract

The paper describes the results of micropaleontological analyses of 45 samples from subsurface deposits in the Vigna di Valle area to the south of Lago di Bracciano, where deep boreholes drilled i by Enel (the Italian Electricity Authority) were located. Planktonic and benthic foram associations were analysed and studied, and the results of micropaleontological analysis confirmed the presence of thick deposits of Plio-Pleistocene age overlying Meso-cainozoic rocks. Vocanic deposits of middle-late Pleistocene unconformably cover marine deposits of the Neoautochthonous Cycle. From the biostratigraphic point-of-view, the stratigraphic sequence is complete from the Zanclean (Globorotalia puncticulata Zone) to the Santernian (Globigerina caríacoensis Zone). Bulimina etnea individuals were found in the stratigraphically highest samples. From the paleontological point-of-view sedimentation appear to have developed under lower circalittoral to infraiittoral conditions. It can be hypothesized a single regressive marine sedimentary cycle, in the studied area which started in the lower Pliocene lasting up to the Pleistocene when it ended because of the closing of the marine sedimentary basin caused by the uplifting of the mounts Sabatini area. A lava layer within the Plio-Pleistocene deposits in the studied borehole is assumed to have been deposited into a marine environment.