Cretaceous/Palaeogene boundary transition induced lattice defects in illite and kaolinite associated with the Um-Sohryngkew river section, Meghalaya, India (original) (raw)

Solid Earth Sciences, 2020

Abstract

Cetaceous-Palaeogene Boundary (KPB) transition records restricted to a unique, continuous, late Maastrichtian-early Danian, shallow marine Um Sohryngkew river succession (bearing planktonic foraminifers' CF4 to P1a biozones) have not been studied in detail. Earlier studies sub-divided it into lower, middle and upper parts, defined by the dominance of illite> illite/smectite; illite>kaolinite> montmorillonite and kaolinite > montmorillonite assemblages, respectively. However, limited studies were carried out on the KPB transition events, particularly for those reproduced in the illite (C2/m) and kaolinite (P1) lattice structures. Thus, illite a nd kaolinite cell parameters and interatomic distances have been studied to understand KPB transition events. For this purpose, layer-wise clay (0.2–2 μm) separates were analyzed by X-ray diffraction method and subjected to Rietveld refinement. Obtained data show substantial expansion in the c-axis of the kaolinite grains assoc...

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