Informatics Publishing Limited

Abstract

The abundance, survivorship and extinctions of smaller benthic foraminifera across Cretaceous/ Tertiary Boundary in a well section GS-II-A in Krishna-Godavari basin appears to be a reflection of tolerance and responses to major geological events such as basinal rise, sea level drop, hiatus and widespread Deccan volcanism. During the terminal Cretaceous the marine environment possibly suffered declining CaCO₃ level and anoxic conditions.

Towards the top of Cretaceous (Zones M -16/17), smaller calcareous benthic foraminifera show a decline in relative abundance of the order of 35 %. The relative abundance oflow O₂ tolerant arenaceous foraminifera shows a gain of 20% to 25%. A hiatus of the order of less than 8.5Ma encompasses KTB. A major transgressive phase after an anoxic stage above KTB hiatus reestablishes equable conditions for the proliferation of smaller calcareous benthic foraminifera. This relative decline of calcareous benthic foraminifera and survival abilities of arenaceous benthic foramini fera is suggestive of gradual and possibly stepwise elimination process under ecological stress over a prolonged period caused by a chain of KTB events.

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