The role of foraminifera as indicators of the Late Pleistocene-Holocene palaeoclimatic fluctuations on the deltaic environment: The example of Tiber delta succession (Tyrrhenian margin, Italy)

摘要

The palaeoclimatic and palaeoenvironmental reconstruction of the last 39.0 kyr of the central Tyrrhenian shelf are presented in this paper. Micropalaeontological, sedimentological and stable isotopic data integrated by radiocarbon dates were determined from three cores drilled in the Tiber delta sequence (TDS), which constitutes one of the most complete Late Quaternary high-frequency depositional sequences in the Mediterranean area. Short-period climate variations that induced short-period events caused changes in the Tiber run-off and increased the sediment supply and grain size in the delta system. The three cores, with different thicknesses, record all the system tracts forming the TDS. Three intervals corresponding to the Early and Late Lowstand, Transgressive and Highstand System Tracts (TSTand HST) were recognised. The first is characterised by shoreface/inner shelf deposits and corresponds to a general cooling period characterised by short warmer periods (approximately 1.0 kyr), confirming the climatic variability of MIS 3/MIS 2. A very condensed deposition affected the second interval, which is characterised by a very low sedimentation rate corresponding to the TST of TDS. The third interval, corresponding to Holocene shelf deposits, shows small climatic oscillations that mark an enhanced seasonality typical of the modern Tyrrhenian regime. At the millennial scale, two warm intervals (Copper Age and Late Bronze Age/II century AC) alternating with two cold humid intervals (Bond cycle B3/RCC: 4.2-3.8 kyr BP of Mayewski events and the Little Ice Age) have been recognised.