Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

N. Malarkodi ¹, S. J. Patel ², P. J. Fayazudeen ¹, U. B. Mallikarjuna ³

Affiliations
1 Department of Geology, Bangalore University, Bangalore - 560 056, IN
2 Department of Geology, M.S. University, Baroda - 390 002, IN
3 Geology Division, Civil Engineering Department, Islamiah Institute of Technology, National Park Road, Bangalore - 560076., IN

Abstract

Sediments of Manaveli Formation (Palaeocene) are studied from the Thondaimanattam quarry section and Manaveli section of the Pondicherry area, which comprises of bioturbated arenaceous limestone-shale and shaly-sandstone sequences respectively. These sediments consist of high density and low diversity trace fossil genera which includes Lanicodichnus, Ophiomorpha, Planolites, Palaeophycus, Skolithos, Thalassinoides, and Polychaetes tubes. The abundance of horizontal structures of the Thondaimanattam quarry section indicate low to moderate wave and current energy in fully marine subtidal environments while the presences of vertical structures of the Manaveli section indicate moderate to high wave and current energy in the marginal marine environment of deposition for the Palaeocene sediments of the Pondicherry area.

Keywords

Trace Fossils, Palaeocene, Palaeoenvironment, Pondicherry.

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N. Malarkodi ¹, G. Keller ², P. J. Fayazudeen ¹, U. B. Mallikarjuna ³

Affiliations
1 Department of Geology, Bangalore University, Bangalore - 560 056, IN
2 Department of Geosciences, Princeton University, Princeton, NJ, 08544, US
3 Civil Engineering Department, Geology Division, Islamiah Institute of Technology, National Park Road, Bangalore - 560076, IN

Abstract

Intertrappean beds exposed between upper and lower traps of the Government and Sunnamrayalu quarries of Rajahmundry were analyzed based on benthic and planktic foraminifera, ostracodes and algae observed in thin sections. Planktic foraminifera indicate deposition occurred in the early Danian Parvularugoglobigerina eugubina (P1a) zone shortly after deposition of the lower trap flows. The most diverse planktic assemblages were deposited in limestones of the middle intertrappean interval and indicate an upper P1a age, or subzone P1a(2), as marked by the co-occurrence of P. eugubina, Globoconusa daubjergensis, Parasubbotina pseudobulloides and Subbotina triloculinoides. Reworked late Maastrichtian planktic foraminifera are common in a limestone interval and suggest erosion of uplifted Cretaceous sediments. Benthic foraminiferal assemblages indicate deposition occurred predominantly in shallow inner shelf to brackish environments. Similarly, ostracodes indicate variable environments ranging from inner neritic to brackish with fresh water influx, as also indicated by the presence of fresh water algae. These data confirm an overall deepening from restricted shallow marine to estuarine, lagoonal and finally open marine conditions followed by abrupt emersion and paleosoil deposition prior to the arrival of the upper trap flows at or near the base of C29n.

Keywords

Foraminifera, Ostracodes, Danian, Intertrappean, Rajahmundry, Andhra Pradesh.

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