K/T Transition in India Vis-a-Vis Occurrence of Mesozoic Basin in Kutch Offshore- A Study from Nannofossils

Rajesh K. Saxena
Geology Group, ONGC, Dehradun, India

K/T boundary problems and their related causes have attracted the attention of geoscientists for the last three decades. The calcareous nannofossil biochronostratigraphy events in Eastern, NW and SW offshore part of India assumes great importance for the timing of Deccan volcanism, extinction/survival of nannofossil species, their evolutionary lineages and interpretation of palaeoenvironments across K/T boundary. K/T transition is well documented in the East Coast, Assam-Arakan Basin and amply demonstrated in the Kutch offshore and Kerala offshore, which has penetrated the trap and intertrappeans.

Exceptionally well preserved and moderately diverse Late Maastrichtian -Early Danian calcareous nannofossil are described from K/T sections of Meghalaya, South Shillong (onland), Palakollu, Krishna Godavari Basin (subsurface, onland), Kutch Deep Water Offshore well and Kerala offshore well of India. Nannofossils Micula murus, M.praemurus, Lithraphidites quadratus are characteristic of Late Maastrichtian age. Early Danian nannofossil assemblage is mainly represented by Cruciplacolithus primus(small),Hornibrookina edwardsii, Neochiastozygus modestus, Prinsius dimorphosus, P.martinii, P.tenuiculum,Biscutum sp., Futyania sp., Micrantholithus sp., Neobiscutum sp. from the subsurface sediments of India. K/T boundary calcareous nannofossil biochronostratigraphic events and accompanying hiatus are related to Deccan Trap basalts of Indian subcontinent. Extinction of the calcareous nannofossils at the K/T boundary are perhaps related to period of intense volcanism and its causes in Indian subcontinent.

The availability of Late Santonian - Maastrichtian sediments from Kutch Offshore indicates the presence of Mesozoic Basin suggesting Sub-Trappean sediments is of great importance for Mesozoic deeper hydrocarbon prospects in India.