Himalayan Geology, Vol. 41 (1), 2020, pp. 11-20, Printed in India
Provenance, Weathering, Tectonic setting and Palaeo-oxygenation condition of the Cretaceous Calcareous Grey Shale (CGS) from the Kallakudi Dalmia Limestone Quarry No:II, Uttatur group, Trichinopoly, Tamilnadu, India
A.V. UDAYANAPILLAI1, VELMAYIL PERUMAL2*, S.ARMSTRONG-ALTRIN JOHN3
1,2Department of Geology, Alagappa University, Karaikudi, Tamilnadu, 630003, India
3Unidad de Process Oceanicosy Costeros, Instituto de Cienciasdel Mary Limnologia, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, 04510 Mexico D.F., Mexico
*Email (Corresponding author):geo6perumal@gmail.com
Abstract: The Cretaceous Calcareous Grey Shale (CGS) is an inter-bedded formation between the Cretaceous Dalmiapuram Limestone formation of Uttatur group and Proterozoic basement rocks in Kallakudi Dalmia Limestone quarry No II. Shale samples were analyzed for major, trace and rare earth elements to find out their weathering condition, provenance, tectonic setting and palaeo-oxygenation conditions. The shale has high concentration of SiO2, Al2O3, CaO, Fe2O3,Cr, Ni, Zr, Ba and Sr with Light Rare Earth Elements (LREE). Geochemical data suggests that the CGS is evolved from a felsic source and that the enrichment of CaO and Sr contents in CGS is due to the presence of Cretaceous marine invertebrate fragments in the shale samples. The Al2O3/TiO2 ratio and Th/Co vs La/Sc plot confirms that the CGS was derived from the felsic source rocks. The Eu/Eu* vs (Gd/Yb) plot also indicates that the CGS is derived from the Proterozoic basement rocks of felsic composition. The tectonic discrimination diagram revealed the continental rift setting. The U/Th,V/Cr,Ni/Co and Cu/Zn ratios indicate that CGS was formed under both oxidizing and sub-oxidizing conditions.
Keywords: Geochemistry, Shale, Provenance, Tectonic setting, Uttatur Group, Palaeo-oxygenation, Ariyalur.
