Significance of random illite-vermiculite mixed layers in Pleistocene sediments of the northwestern Atlantic Ocean

The clay mineralogy of Pleistocene sediments of eleven sediment cores at th ree ODP sites from 30 degrees N to 60 degrees N northwestern Atlantic Ocean has been investigated. The sediments are characterized by the presence of random illite-vermiculite mixed layers (I-V) (up to 32% of the clay mineral assemblage). The I-V clays are much more abundant during interglacial peri ods than during glacial ones. They are attributed to detrital supply throug h erosion of high-latitude continental areas from which they are derived ma inly from chemical weathering of micaceous phyllosilicates. Their spatial d istribution and the specific conditions for their formation through weather ing suggest that I-V mixed layers are mainly derived from the Canadian Shie ld. They were transported From their source to marine deposition areas by r ivers, deep water masses or nepheloid layers. Due to the specific condition s required For the Formation of I-V, its occurrence and abundance are used as a palaeoclimate and palaeocirculation proxy for northwestern Atlantic Pl eistocene sediment.