Abstract: Cretaceous globally relative sea level rise caused expansive epeiric seas that formed vast carbonate platforms, preserving signatures of marine transgression and regression. The Narmada basin in the central India is a repository of such deposit in the Bagh Group, which bears the evidence of late Cretaceous inundation of the Indian subcontinent. A combined facies, petrography and isotope geochemistry reveal an extensive pedogenic alteration of platform carbonate deposit of the Upper Cretaceous Bagh Group in the western Narmada basin in central India. The highly fossiliferous carbonate sequence of the Bagh Group consists of two Formations, the Nodular Limestone Formation at the base, and the Bryozoan Limestone Formation at top. The Nodular Limestone Formation comprises primarily of mudstone and wackestone, with relics of bioclasts such as gastropods, echinoderms, molluscs, forams and calcispheres, reflecting a low-energy supratidal to upper intertidal environment of deposition. Prolonged pedogenesis leads to pervasive micritization, brecciation, desiccation and recrystallization. The overlying Bryozoan Limestone, dominated by packstone and planar laminated rudstone with bryozoans, gastropods, echinoderms/echinoid spines, and molluscs, indicates deposition within the lower intertidal environment with moderately high-energy conditions. Abundant meniscus cement and biomolds suggest meteoric vadose diagenetic modification, whereas, intense secondary micritization of sediments indicates prolonged calichification. The Nodular Limestone Formation is overall deepening upward and it represents the upper part of a TST, the lower part of the same TST incorporating the Nimar Formation. The glauconite bed within the Bryozoan Limestone Formation indicates top of the transgressive systems tract (TST). The stratigraphic condensation at the top of the transgressive systems tract has allowed the Formation of glauconite. The overlying Lameta Formation indicates shallowing upward trend and it represents a highstand systems tract (HST). The boundary between the TST and HST roughly coincides with the boundary between the Bryozoan Limestone Formation and Lameta Formation. The δ13C and δ18O ratios of both Nodular Limestone and Bryozoan Limestone formations are depleted than the normal marine values, indicating an extensive diagenetic resetting of the carbonates. While the meteoric cement is depleted in both δ13C and δ18O ratio, the burial cement shows a decrease of δ18O at constant δ13C. The pedogenetic horizons within the Bagh carbonates bear subtle evidence of subaerial exposures within the overall transgressive Bagh Group.

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