GSM Technical talk (in collaboration with the Geology Programme, UKM): “Signature of mass mortality of fauna and high temperature pressure event preserved in Late Cretaceous bone bed of Fatehgrah Formation of Barmer Basin, India.” - Mathur C.S., PhD (J.N.V. University, Jodhpur. India)

Event Code : GSMTT 10-4-2017 Venue Name : Geology Program Meeting Room, Geology Building, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi Host Name : Coordinator Name : Date From : 2017-10-04

Talk begins at: 11.00 a.m.Tea will be provided at 10.30 a.m.

ABSTRACT

Bone bed of Fatehgarh Formation (FGF) is an important entity of the petroliferous BarmenrBasin, western Rajasthan, India as it preserved signatures to endorse various global events such as Late Cretaceous phosphogenesis, K/T boundary, mass extinction of fauna, and unusual impact event. The 12 meter thick phosphorite facies of FGF display almost all spectrums of phosphorite types and representing global Late Cretaceous phosphogenic event in N-W India. Among these types, the 15 cm thick bone bed (event bed) is a principle phosphorite facies of FGF. It is characterized by their significant biogenic and unusual magnetic framework elements. The biogenic framework elements include vertebrae, dental plates, teeth, spines and scales of microvertibrates along with teeth, bones, bone fragments, cranium, vertebrae, phosphatic dungs of crocodile, dinosaur and turtles. Maastrichian age is suggested from the close faunestic association of biota of the bone bed which represent near shore marine. The five cms. thin,discontinuous layer in the topmost part of the bone bed represent the K/T boundary which is characterized by the presence of ejecta material including magnetic spherules, fine magnetic dusts and microbracciated matrix. The petrographic and geochemical analysis of these high temperature pressure objects indicate impact event that brought significant biological changes perhaps Mass extinction of the Fatehgarh biota. To recognize impact structure, at first instance, geomorphologically, the potential candidate in western India, seems to be Siwana Ring Complex (SRC) which is situated about 130 Kms from Barmer city.

The SRC is composed of rings of granites nestling around Siwana and covers an area of 290 km2. To recognize, it as impact crater, following evidences are significant:Mathur et al., (2009) and Tripathi et al., (2010) reported the presence of coesite and stishovite minerals from the magnetic particles recovered from the SRC. Additionally, the deformational field features such as shatter cones, impact melt and lithic breccias,pseudotachylite, impact melt sheets and microscopic features such as diaplectic glasses; planar deformation features (PDFs) in minerals, diagnostic textures and microstructures of the impact melt. These evidences are diagnostic target rock deformation features derived due to an impact at SRC (Mathur 2016, under communication).