Petrography and stable isotopic variations in Dalmiapuram Formation of Cauvery Basin, South India: implication on OAE1d

Abstract

Petrography, carbon and oxygen isotopic study was carried out to interpret isotopic variations on the predominant carbonate sequence of the Dalmiapuram Formation of the Cauvery Basin, South India. The common petrographic types identified in the Dalmiapuram Formation range from wackestone to boundstone. The gray shale and limestone members show large variations in d 13 C and d 18 O values (Gray shale member: ?1.44 to ?2.40 % VPDB, -3.05 to -5.92 % VPDB, respectively; Limestone member: -6.07 to ?2.93 % VPDB; -7.08 to -0.39 % VPDB; respectively). In the present study, the carbon and oxygen values are not correlated, which supports the fact that these limestones retain their primary isotopic signatures. In carbon isotope curve, one negative shift is identified in the gray shale member and a positive isotopic excursion is detected in the coral algal limestone (CAL). The observed positive isotopic excursion in the lower part of the CAL correlates with OAE1d and suggests the global nature of the late Albian OAE1d in the Cauvery Basin.

Major and trace element characterization of Oceanic Anoxic Event 1d (OAE 1d): Insight from the Umbria-Marche Basin, central Italy

“…In fact, the OAE 1d carbon isotope anomaly has been identified worldwide in variable depositional settings, thus suggesting a potential global extent of this event. In particular, it has been widely recognized in the western Tethys Ocean (Erbacher and Thurow, 1997;Gale et al, 1996;Stoll and Schrag, 2000;Strasser et al, 2001;Bornemann et al, 2005;Reichelt, 2005;Sprovieri et al, 2013;Gambacorta et al, 2015;Giorgioni et al, 2015;Bąk et al, 2016;Gyawali et al, 2017), in the eastern Tethys Ocean (Vahrenkamp, 2013;Zhang et al, 2016;Wohlwend et al, 2016;Hennhoefer et al, 2018;Yao et al, 2018;Navidtalab et al, 2019), in the northern Tethys (Melinte-Dobrinescu et al, 2015), in the Atlantic Ocean (Wilson and Norris, 2001;Nederbragt et al, 2001;Petrizzo et al, 2008;Ando et al, 2010), in the Pacific Ocean (Takashima et al, 2004;Robinson et al, 2008;Navarro-Ramirez et al, 2015;Rodriguez-Cuicas et al, 2019, 2020, in the Western Interior Seaway (North America) (Gröcke et al, 2006;Gröcke and Joeckel, 2008;Scott et al, 2013;Richey et al, 2018), in the Boreal Realm (Mitchell et al, 1996;Bornemann et al, 2017), and in the Indian Ocean (Madhavaraju et al, 2015).…”