Planktonic foraminiferal succession in late Cretaceous to early Palaeocene strata in Meghalaya, India

Abstract

A roughly 10.5-m-thick succession within the Langpar Formation of the Um Sohryngkew River section, Meghalaya, India, constrained by the last occurrence of Globotruncanita stuarti and the first occurrence of Parasubbotina pseudobulloides, spans the K/T (Cretaceous–Tertiary) transition. The unit is divisible into three parts with the lower consisting of shaly limestone, weakly calcareous shale and silty shale with coal streaks. The middle part is dominated by calcareous shale with mud flakes, coprolites, burrows and pyrite nodules, followed by alternating limestone and marlite at the top. Planktonic foraminifera are rare to frequent within the unit. Based on the distribution of zonal indices, seven successive planktonic foraminiferal zones are recognized from across the K/T boundary. From base to top, these are CF4, CF3, CF2 and CF1 in the upper Maastrichtian part and Zone P0, Zone Pα and Subzone P1a in the lower Danian part. The biozones indicate that the section is biostratigraphically continuous across the K/T boundary. A similar foraminiferal succession and K/T transition is observed in the Langpar of the Cherrapunji-Mahadeo road section at a distance of over 5km. These K/T outcrops from Meghalaya provide the first record of a continuous K/T sequence in the Indian subcontinent with respect to planktonic foraminifera.