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Abstract: A high resolution analysis of the clay–mineral content of sediments of the Cariaco Basin spanning the last climatic cycle was performed in order to determine how the detrital sedimentation in the basin records climatic oscillations at various timescales. At the scale of glacial–interglacial cycles, the clay–mineral content records changes in the geographic origin of the detrital supply, from a dominantly kaolinite- and smectite-rich southern source during glacial to a more illite-rich northerly source during interglacials. Though possibly influenced by eustatic variations, these changes mostly reflect the latitudinal fluctuations of the intertropical convergence zone (ITCZ). The Eemian shows an increased contribution from the northern source compared to the Holocene. During MIS3, seasonality modulates the effect of ITCZ position and leads to increased smectite contribution. Fluctuations of the smectite and kaolinite contents during Dansgaard/Oeschger cycles reflect changes of runoff intensity. Enhanced supplies in kaolinite during Heinrich-like events and stadials also suggest remobilizations of sediments deposited on the Unare platform resulting from rapid sea-level variations. The Younger Dryas is characterized by a significantly different clay–mineral association reflecting a drastic modification of terrigenous supply. An eolian contribution would explain this peculiar mineralogy, although local contributions cannot be ruled out. A similar event is noted at the MIS6-5 transition pointing for the occurrence of a Younger Dryas–like episode during Termination II. [Copyright &y& Elsevier]

The Middle Volgian Kashpir Oil Shales Formation, located on the Russian Platform, is a lateral equivalent of the North Sea and West Siberian petroleum source rocks. In the Volga Basin, this formation is 6 m thick and shows alternations of marls and black shales. The organic carbon content is often higher than 1%, although bioturbation and benthos are abundant, even in the black shales. In the marls, highly degraded organic matter (OM) dominates, while aliphatic, sulphur-rich OM is dominant in the black shales. The combination of sedimentological and geochemical studies allowed to determine that the redox conditions of the sediment regularly fluctuated from oxic to anoxic, under relatively productive waters, while climatic conditions were increasingly arid. It is proposed that OM deposition occurred in relation to the increasing aridity, through the combination of recurrent disruption of salinity stratification and aeolian supply of iron, which both promoted phytoplankton productivity. [Copyright &y& Elsevier]