Lithology, petrography, microfacies, environmental history and hydrocarbon prospects of the Kallankurichchi Formation (Upper Cretaceous, Ariyalur Group, South India)
by Muthuvairavasamy Ramkumar, Salem
RAMKUMAR, M. (2004): Lithology, petrography, microfacies, environmental history and hydrocarbon prospects of the Kallankurichchi Formation (Upper Cretaceous, Ariyalur Group, South India. Freiberger Forschungshefte, C 502: Paläontologie, Stratigraphie, Fazies (12): 77-100; Freiberg.
The Kallankurichchi Formation of Ariyalur Group (Upper Cretaceous, Tamil Nadu State, India) represents thick limestone deposits with very high proportion of faunal remains. Its faunal diversity and abundance attracted considerable attention of paleontologists from all over the World and as a result, a wealth of literature on fossil composition of the formation exists. However, owing to the many changes in lithological and facies characteristics of this formation, often the workers find it difficult in the field to identify and corroborate lithological and facies descriptions in the literature. This paper attempts to fill the gap through detailed lithological and facies variations along with petrography towards interpretation of depositional environments. Compilation of field and petrographic data revealed that the formation was deposited in facies belts 2, 6 and 7 under SMF types 8, 10, 11, 12 16 and 18 according to the facies classification of WILSON. Deposition of this formation took place in a distally steepened ramp setting under normal saline, warm, well-mixed open sea conditions with low-moderate depositional energy and rate. Owing to the recent oil find in areas nearby and occurrence of bitumen residues in this formation, this paper examines also the plausibility of organic carbon preservation and maturation. It is brought out that although the depositional environments supported luxurious biotic diversity and abundance, owing to the biological factors, prolonged exposure of sediments at sediment-water interface, followed by extensive diagenetic transformations under open system, preservation and maturation of organic matter contained in the sediments were poor and the possibility of locating commercial quantities of hydrocarbon in this formation is remote.