A c. 50 m thick section located in the Crotone Basin (southern Italy) was investigated using oxygen isotopes, pollen and planktonic foraminifera. The section records two complete transgressive-regressive cycles mainly driven by glacio-eustasy. Biostratigraphy and oxygen isotope chronology indicate that the section spans from Marine Isotope Stage (MIS) 22 (c. 0.87 Ma) to MIS 18.3 (c. 0.73 Ma), thus straddling the Matuyama-Brunhes (M-B) boundary which occurs in the middle of MIS 19. The rich pollen assemblages provide a unique record of the vegetation in the central Mediterranean during the Early-Middle Pleistocene climatic transition. Interglacials are characterized by a mesothermic vegetation similar to the present day, whereas a rain-demanding conifer forest dominates the glacials of MIS 20 and MIS 18. This is unexpected because it is generally considered that during the Pleistocene, glacials in central Mediterranean were characterized by steppe (arid) conditions. By contrast, arid conditions occur during the deglaciations. These results are inconsistent with the widespread practice of linking glacials with arid conditions in the central Mediterranean during Pliocene and Early Pleistocene times. This study emphasizes the need to establish more accurate land-sea correlation.

No abstract

No abstract

Climate change has traditionally played a secondary role in the literature behind eustasy and tectonics, with eustasy regarded as the main controlling factor in development of sedimentary sequences. Here, we emphasize the role of the interaction of climate-modulated sediment supply and sea-level change, particularly its potential impact on sequence development. We discuss a case history from the lower–middle Pleistocene of the highly subsiding Valle di Manche shelf area (Crotone Basin, Calabria, southern Italy), where a stack of cyclothems spanning from late Marine Isotope Stage (MIS) 22 to full MIS 18 preserves a full record of eustatic cycles, glacials included. Tectonics certainly played a critical role in the creation of local accommodation, ultimately controlling the preservation of an almost complete sedimentary record. However, its role as a factor controlling the sediment flux on Milankovian scale can be ruled out. Direct comparisons between data concerning δ18O, pollen, and physical stratigraphy demonstrate that climate-induced changes in sediment load caused significant deviations from the predicted timing and magnitude of the responses to sea-level changes in the traditional sequence model. A phase lag occurred in the timing of systems tracts, leading to a significant delay of one-quarter of a sea-level cycle. Specifically, climate-driven sediment discharge during sea-level rise triggered progradation of shelf-margin wedges, which should thus be considered lowstand in their architecture and "transgressive" in their timing. This was generated by a shift toward drier conditions, leading to extensive deforestation and consequent lowering of the threshold for slope erosion and mass-wasting processes in the source area. Due to the reduced extent of the transfer zone, sedimentary signals were conveyed rapidly from source to sink with little apparent attenuation, suggesting that the Milankovitch-scale climate changes can lead to rapid source-to-sink responses on tectonically active margins fed by high-gradient, short-headed streams. The studied case history demonstrates that the impact of Milankovitch-scale climatic forcing on sediment supply in an icehouse world can be more supluential than sediment redistribution due to corresponding sea-level fluctuations. These findings emphasize that a reconstruction of the timing of systems-tract development with respect to sea-level changes based on a sequence-stratigraphic approach may be misleading, whenever independent chronological and climatic constraints are not available

No abstract