Chemo- and biostratigraphy of the Cretaceous Dalmiapuram Formation, Uttatur Group, Kallakudi II section, Cauvery Basin, South India

The Cauvery Basin at the southeastern tip of the Indian plate was an Albian to Danian marine embayment. The Dalmiapuram Formation is composed of bioclastic wackestone and coral boundstone. Benthic foraminifera and calcareous algae are relatively common in the Dalmiapuram Formation. The fossils support an age range of upper Albian to Cenomanian, which complements previously reported nannofossils that suggest an early Albian to Turonian age. The low diversity assemblage of foraminifera and calcareous algae and other organisms in the Dalmiapuram Formation is characteristic of a near-shore carbonate shelf or ramp. The low diversity and abundance of planktic species with coral and coral-algal buildups suggests more offshore conditions, probably within storm wave-base. The δ 13 C and δ 18 O values vary greatly. The absence of correlation between Mn and Sr indicates that these limestones retain their primary isotopic signatures. Gray shale/limestone unit has positive carbon isotope excursion (CIE) of ~ 0.8 to 1.0‰ that correlate with OAE 1c event. Similarly, significant positive CIE noticed in the lower part of the coral algal limestone is attributed to OAE 1d event. This suggests that oceanic conditions that created deep-water low oxygen conditions affected the shallow-water photic zone.