Geological and paleooceanological significance of psephite from the cretaceous-cenozoic deposits from the near-pole part of the Lomonosove ridge

Abstract

The article gives a characteristic of the psephitic material obtained in the IODP-302 well on the Lomonosov Ridge. We provide data on the shape of rock fragments, their roundness, petrographic composition and distribution over lithological units of the well. It is shown that the major part of the psephites was delivered to the drilling point with ice, but several samples have a local origin and characterize the composition of the Mesozoic rocks. The roundness of the psephites consistently deteriorates in the younger enclosing sediments. The paper presents arguments that link this trend with the intensification of the ice regime. The consequence of the ice cover increase is the shortening of the time of psephites occurrence in the wave-surf zone, where large-sized material is rounding, by activating the “anchor” mechanism of the rock fragments capture. The level of change in petrographic associations of psephites generally coincides with the level of change in the association of heavy minerals, which is a consequence of the appearance of more distant sources areas. It is shown that the “paleo–trans–polar” ice drift system began to function in the middle Miocene. The paper draws conclusions about the evolution of the ice regime in the Arctic Ocean during the Cenozoic.