Jurassic smectite and kaolinite trends of the East European Platform: implications for palaeobathymetry and palaeoclimate

Clay minerals cannot only give information on sedimentary depositional environment but also the climate regime under which sediment was weathered. The successions of non‐marine to marine Middle and Late Jurassic strata of the East European Platform show upwards increasing contents of smectite and decreasing contents of kaolinite. There is also an increasing smectite vs. kaolinite ratio laterally, in a basinward direction within individual formations. Vertical smectite and kaolinite content curves coincide broadly with the Sahagian and Jones eustatic sea‐level curve. All this implies differential settling of smaller smectite particles offshore and larger kaolinite particles onshore. Smectite formation, preservation and supply were further enhanced as the eastwards expanding Late Jurassic arid zone of Laurasia influenced weathering conditions in the sediment source areas, to the north and east of the East European Platform.