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

A. K. Ray ¹, C. C. Ghosh ¹, S. Nag ¹

Affiliations
1 Geology Department, Presidency College, Calcutta 700 073, IN

Abstract

Alveolina of Kutch Middle Eocene limestones and marls is identified as A. elliptica var. nuttalli. The variety is shown to have a characteristic shape (expressed as a ratio of polar and equatorial diameters), and more or less fixed number of flosculinised whorls; the variation in the development of non-flosculinised whor1s on the flosculinised ones is attributed to an ontogenetic development correlated with size increase. The variety shows a clear case of lateral facies variation, occurring in two 'apparent' horizons in deeper parts of the basin with vertical absence in between, but continuing throughout the rock unit in marginal shallower parts. The facies-governed nature of this larger benthic foraminiferal species and its presence in the Kutch Paleogene sequence without the earlier glomalveoline forms are considered important aspects in stratigraphic studies.

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S. Sarangi ¹, A. Sarkar ¹, S. K. Bhattacharya ², A. K. Ray ³

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad-826004, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad-380009, IN
3 Department of Geology, Presidency College, Calcutta-700073, IN

Abstract

High resolution oxygen isotope analysis of samples from two different Eocene Oligocene Boundary (EOB) sections of Wagapadhar and Waior of Kutch area and their correlation with DSDP sites indicate continuity of sedimentation at these sites. A rapid cooling of -6°C across the EOB, synchronous with extinction of Eocene larger benthic foraminifera, is also observed.

Keywords

Isotope, Eocene-Oligocene Boundary, Kutch, Gujarat.

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