Bore-hole Well-cores Provide Evidence for Crustal Heterogeneity Beneath the Koyna-Warna Reservoir Site, Deccan Volcanic Province, India

High-resolution lithologs from four bore-well-cores KBH05 (Phansavale), KBH09 (Khadi Kolvan), KBH10 (Udgiri) and KBH08 (Paneri) from west to east have been generated. These reveal conspicuous sub-trappean heterogeneity, especially given the limited areal extent of about three hundred square kilometers enclosing them. In this contribution, a description of lithological characteristics is provided, which include the discovery of relict greenstone volcanic rocks concealed beneath the Deccan Volcanic Province from the westernmost bore- well-cores as well as a thin layer of sediments in another at the edge of the Western Ghats. Fossil imprinted ash beds of substantial thickness are observed in two of the well-cores on the Deccan Plateau. Intrusive sheets of aplite/granite within the gneisses, seen in one of the well-cores, provides compelling evidence of a reworked basement beneath the Deccan Volcanic Province. The heterogeneity reported here is consistent with patterns of selective locales of earthquake occurrences in the Koyna-Warna zone; definitive roles for reservoir triggered seismicity needs further examination.

 

Figure Caption: Lithologs referenced to MSL

Citation: Tarun C. Khanna, Kusumita Arora, Haris Raza, R. K. Chadha and Harsh K. Gupta; 2020. Bore-hole Well-cores Provide Evidence for Crustal Heterogeneity Beneath the Koyna-Warna Reservoir Site, Deccan Volcanic Province, India; JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.96, July 2020, pp.36-42