Kaolinite peaks in early Toarcian profiles from the Polish Basin –an inferred record of global warming

Paweł Brański

Abstract


In lower Toarcian clay deposits (Ciechocinek Fm., VIII depositional sequence of the Lower Jurassic) from three boreholes from the Polish Basin, illite-dominated sedimentation representing the lower part of studied interval was interrupted by enhanced kaolinite input.Levels of high kaolinite/illite ratio at the VIIIb/VIIIc parasequence boundary suggest strong continental weathering in a humid-subtropical to tropical climate related to the phase of the early Toarcian global warming recorded at the top of the tenuicostatum Zone and correlated with isotope curves from a number of European sections. Kaolinite enrichment may be locally enhanced by reworking ofpre-Jurassic kaolinitic rocks and differential settling. Diagenetic processes were not sufficient enough to transform the initial kaolinite,but may have altered smectite and mixed-layers into illite and/or chlorite.

Keywords


lower Toarcian; Ciechocinek Fm.; Polish Basin; kaolinite content; palaeoclimate; global warming

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