Controls on detrital sedimentation in the Cariaco Basin during the last climatic cycle: insight from clay minerals

• High resolution analysis of clay minerals in Cariaco sediments of the last ∼130 ka.
• Clay content reflects changes of detrital sources around the basin.
• Changes in clay sources mainly relate to fluctuations of ITCZ and related rainbelt.
• Seasonality modulates runoff and the clay content.
• Latitudinal position of summer ITCZ during last climate cycle is traced.

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.