Transgressive offshore deposits on the central Adriatic shelf: architecture complexity and the record of the younger dryas short-term event

Abstract

The late-Quaternary transgressive deposits on the Central Adriatic shelf are as much as 25 m thick. This transgressive record includes an "out-of-sequence" prograding deposit that is sandwiched between two landward-stepping units composed of offshore mud. Sedimentologic, paleontologic, and magnetic susceptibility data, with calibrated AMS 14C dates allow to ascribe this progradational unit to the Younger Dryas short-term event. This progradational unit on the shelf correlates with a 1-m-thick deposit, characterized by increased sediment accumulation rates, within the continuous marine section of the adjacent slope basin (the Meso Adriatic Depression). The prograding unit within the transgressive record (TST) is up to 18 m thick and shows a composite geometry. The surface at the top of the unit is erosional across the inner shelf marking a phase of decreased supply and increased reworking on the sea floor. On the outer shelf, this upper surface merges with the downlap surface at the base of the progradational unit. In this area, cores cross-cutting through the erosional surface document a gap of as much as 4 ka (between 13 and 9 14C ka BP) caused by erosion of older units during the Younger Dryas interval and subsequent condensed deposition above it.