A rapid clay-mineral change in the earliest Priabonian of the North Sea Basin?

In the Eocene to Oligocene transitional strata in Belgium, clay mineral associations vary in response to the climatic evolution and to tectonic pulses. Decreasing smectite to illite ratios and the systematic occurrence of illite-smectite irregular interlayers are consequences of a cooling climate. A marked increase in kaolinite content occurs just after a major unconformity formed at the Bartonian/Priabonian boundary and consequently is...