Palaeomagnetic and rock magnetic analysis of Holocene deposits from the Adriatic Sea: detecting and dating shortterm fluctuations in sediment supply.

We present palaeomagnetic and rock magnetic results from five cores collected in the basin of the Adriatic Sea. Four cores (PRAD2-4; KS02-246; CSS00-23 and CSS00-07) were collected along a shore-parallel transect whereas the fifth core (AMC99-01) was retrieved in the central Adriatic in 250 m water depth, on the floor of the Meso-Adriatic Depression. After alternating field demagnetization, the natural remanent magnetization (NRM) directions show a characteristic and primary magnetization of the sediments that is representative of secular variation of the geomagnetic field. By combining ¹⁴C dating and the ages of magnetic inclination features, it has been possible to establish an age-depth model for all of the cores. Precise identification of the secular variation features provides a refined chronology that allows us to quantify short-term changes in sediment flux from the Adriatic catchment as well as changes in sediment routing within the basin. Rock magnetic parameters indicate a homogeneous magnetic mineralogy dominated by fine-grained magnetite. Variations in both concentration and grain-size related magnetic parameters reflect changes in sediment supply between glacial and interglacial stages, as well as changes in environmental conditions. Selective dissolution of magnetic grains is associated with the formation of sapropel S1 during the first part of the Holocene, although the duration of the anoxic interval varies between cores. A significant modification in sediment supply characterizes the late-Holocene deposits with a marked increase in sedimentation rate occurring during the last few centuries. We interpret this as a far-reaching response to the rapid construction of the modern Po delta under increasing anthropogenic impact. [ABSTRACT FROM AUTHOR]