Linee di riva del Pleistocene Inferiore sul versante sinistro della media valle del F. Tevere

Abstract

Marine sediments dating to Pliocene and Pleistocene outcrop on the left side of the River Tiber Valley to the north of Rome, unconformably lying on the sediments of the Amelia, Narni and Sabina mountain range in the Apennines. Evidence of Quaternary shorelines, such as borings by lithophagous organisms, wave-cut notches and paleeobeaches, are described all along these mountains. Shorelines are identified at various altitudes; their increasing altitude perpendicularly to the coast indicates a marine ingression in the Early Pleistocene. There is no evidence that the highest sea level stand identified has constant altitude along the entire range, and difference in elevation among highest shoreline traces is explained as resulting from tectonic displacements. Coarse-grained clastic sediments of continental origin from the emerged mountain slopes are interbedded with marine sediments and show, at the base and near the top, traces of wave action and of borings by lithophagous organisms. The lowest shoreline is attributed to a low sea-level stand, which would be consequent to a climate deterioration that might have caused the production of coarse-grained detrital deposits. The highest shoreline, the trace of which is visible both on continental deposits and on the substratum, indicates the maximum level of the Early Pleistocene sea before its definitive retreat from the area.