Integrated sedimentological, ichnological, taphonomic, and low-order sequence-stratigraphic insights into the Oligocene shoal deposits: The Coral Limestone Member, Kutch Basin, India

Integrating the ichnologic, taphonomic, and sedimentologic data enhances the accuracy of palaeoenvironmental interpretations. The integrated analysis of the Chattian-age Coral Limestone Member within the Maniyara Fort Formation in Kutch Basin focuses on understanding the palaeogeographic architecture of microfacies association and the influencing factors determining the same on a typical Late Oligocene carbonate ramp. Through distinct petrographic examination, six distinct microfacies representing outer ramp (MF1 and MF2), middle ramp (MF3, MF4, and MF5), and inner ramp (MF6) depositional settings were identified. The Member, characterised primarily by multiple carbonate coquina intervals, was further classified based on taphonomical and ichnological characteristics. Four taphofacies (TF1, TF2, TF3, and TF4) and five ichnofabrics were identified. The outer ramp exhibits massive-appearing intensely to completely bioturbated (BI 5–6) marly mudstone–wackestone lithofacies with erosional contacts. The middle ramp displays oligotrophic conditions characterised by swaley cross-stratified bioclastic packstone–rudstone beds showing an upward intensifying moderate to intense bioturbation (BI 3–5). The storm-influenced inner ramp features the crudely swaley cross-stratified rudstone shell beds and patchy coral reefs with intense bioturbation (BI 5). Intermittent non-depositional and bioerosional short-duration episodes were observed at the top of skeletal concentrations. The integrated findings mentioned above exhibit coherence and offer valuable insights into the development of carbonate ramps. Our study offers insight into the aggrading and prograding shoal deposits within the carbonate ramp settings of a Chattian tropical sea. It highlights the complex interaction of environmental factors during this period within a high-resolution sequence-stratigraphic framework, extending up to the 5th-order, reported for the first time. This study deepens our comprehension of Oligocene carbonate buildups on a global scale — a research that has received lesser recognition compared to Eocene or Miocene carbonates.