Clinoform sedimentation along the Apennine shelf, Adriatic Sea

Abstract

Sedimentation along the central Adriatic coastline of Italy results from a series of small, distributed fluvial sources (i.e., a line source), draining the Apennine Mountains. These rivers deliver ∼ 3 × 10 7 t y − 1 of sediment, contributing to the formation of a shore-parallel shelf clinoform that has developed throughout the Holocene. Across-shelf sediment accumulation rates, calculated from 210Pb (half-life 22.3 years) measurements, are greatest on the clinoform foreset (∼ 1 cm y − 1 ), which is characterized by seafloor crenulations in a few areas. However, for some cross-sections of the clinoform, accumulation rates are not significantly higher on the foreset than on the topset and bottomset, indicating that the clinoform may not be actively prograding in those areas today. Accumulation rates increase southward along the shelf and are greatest near the Gargano Peninsula (∼ 1.7 cm y − 1 ). Between Ravenna and the Gargano Peninsula, 3.1 × 10 7 t y − 1 of sediment accumulate on the Apennine shelf. Although the amounts of sediment supply and accumulation are about the same, additional Po River sediment is thought to enter the system from the north and some sediment is transported beyond the Gargano Peninsula to the south. Anthropogenic activities, particularly dam construction following World War II, have significantly impacted sedimentation in this region. Changes in 210Pb profiles document reduction in sediment accumulation. However, observations during winter 2002–2003 using the short-lived radioisotope 7Be (half-life 53.3 d) have indicated that some new sediment is delivered to the shelf during periods of elevated discharge, so dam entrapment is not complete.