Post-Cretaceous record of larger foraminifera from the Shillong Plateau, India: an evidence of environmental recovery during Early Cenozoic

Abstract

The Late and post-Cretaceous succession of larger benthic foraminifera and planktic microfossils from the Shillong Plateau indicates events of extinction and recovery of the biotic forms. These events are interpreted using a conceptual framework involving biological responses to environmental changes caused by eustatic and climatic variations. Stratigraphic distribution shows that the Late Maastrichtian larger benthic foraminiferal assemblage disappears earlier than the planktic microfossils at the boundary interval. After their last occurrence in the Upper Maastrichtian, the larger foraminifera reappears in the carbonates of the Lakadong Formation dated by Glomalveolina primaeva as the Thanetian (P4).
 The event of the first appearance of larger foraminifera in the Shillong Plateau correlates with zone P4. When compared with other Tethyan sections (e.g., Mediterranean) where they start occurring in the strata equivalent to zone P3b, the event of their reappearance appears to be slightly delayed in the studied section. The P3b zone is the interval marked by the onsetting of habitable conditions on shelves (oligotrophic environments) and is followed by an interval (the equivalent of the P4 zone) of extensive carbonate generation, during which highly diversified larger foraminiferal assemblages evolve and become widely distributed. The Shillong assemblage, therefore, marks the phase of "expanded oligotrophy" in which recovery of carbonate platform environments occurred on a large scale on shallow neritic shelves.

Paleogene Nummulitid biostratigraphy of the Kohat and Potwar Basins in north-western Pakistan with implications for the timing of the closure of eastern Tethys and uplift of the western Himalayas

“…In addition, oriented thin sections of individual foraminiferal tests of nummulitids (Nummulites/Assilina) were also used for further identification. The taxonomy of recorded species is based on a review of the available literature with a focus of faunas from the Indian subcontinent (Nuttal 1926;Davies and Pinfold 1937;Gill 1953;Nagappa 1959;Pascoe 1963; Sarkar Raju et al 1970, Singh et al 1970, Sahni and Kumar 1974Samanta 1965Samanta , 1968Samanta , 1981Murty 1983;Jauhri 2006, Jauhri andAgarwal 2001;Mukhopadhyay 2003Mukhopadhyay ,2005Sameeni et al , 2009Afzal 2009,2011), Indo-Pacific region (Verbeek and Fennema 1896Doornink 1932;Crotty and Engelhardt 1993;Wilson 1995;and Renema 2002), Mediterranean region (Schaub 1981;Serra-Kiel et al1998) and Tertiary rocks of Middle East (Bellen et al 1959;Kalantari 1981;White 1994;Racey 1994Racey , 1995and Karim and Baziany 2007).…”

“…In the northern Spain and southern France it is representing Early Eocene (Middle Illedian 2) (Höttinger 1960, Tambareau andVillate, 1977;Robador et al 1991;Schaub 1981). In India, it represents Early Eocene (Middle Illerdian 2≈SBZ8)-Middle Eocene (Middle Lutetian 2≈SBZ15) (Jauhri 1997(Jauhri , 2006Jauhri and Agarwal 2001). It appears synchronously with N. atacicus in Europe (Schaub 1981).…”

Palaeocene Rhodophycean Algae from the Ninniyur Formation of the Cauvery Basin, southern India

“…The recovery of benthic communities in the Cenozoic was not quick and did not occur unti I the stable, stress-free, warmer, oligotrophic environments became available following the climatic warming, high sea-level, low influx of terrigenous supply, red uced upwell ing, etc. duri ng the Thanetian (Keller, 1988;Hottinger, 1987;Jauhri, 1997). The signatures of such environments are seen in the middle unit where the different animal and floral groups appear in very high diversities and show extensive development.…”

Dinoflagellate cysts from the lakadong sandstone, Cherrapunji area: biostratigraphical and palaeoenvironmental significance and relevance to sea level changes in the upper palaeocene of the Khasi Hills, South Shillong Plateau, India

“…This is also accompanied by increased telTigenous flux giving rise to stressed environments and often accompanied by reduced salinity. In such an environment, carbonate precipitation is hampered resulting in considerable loss of carbonate platform environments and the de.struction of larger foraminiferal populations (Caron & Homewood, 1983;Jauhri, 1997).…”