Apurva D. Shitole

The Narmada Basin in west‐central India forms the northern part of the Central Indian Tectonic Zone (CITZ). The Cretaceous Bagh Group rocks of the Western Lower Narmada Valley (WLNV) succession was studied for sedimentary facies analysis and ichnology. Textural and mineralogical characteristics along with primary and secondary sedimentary structures revealed 11 lithofacies, of which the calcareous sandstone, fine‐grained sandstone‐siltstone‐shale and sandy/silty allochemic limestone lithofacies are highly bioturbated. WLNV contains a well‐preserved, less diverse, and relatively abundant ichnofauna; a total of 24 ichnospecies belonging to 15 ichnogenera with pseudotrace fossils are identified and described. The trace fossils belong to the Skolithos, Cruziana and Glossifungites Ichnofacies. The Skolithos Ichnofacies suggest an upper shoreface environment with moderate‐to‐high energy conditions and shifting substrate; the Cruziana Ichnofacies suggest a lower shoreface environment with low‐to‐moderate sedimentation rates and energy conditions and the Glossifungites Ichnofacies suggest dewatering of sediments and a slow rate of sedimentation. Early ichnological studies in the different Tethys‐related Cretaceous basins of the Indian subcontinent (Eastern Lower Narmada Valley, Kachchh, Cauvery, Jaisalmer, Barmer and Saurashtra) primarily focused on identifying the trace fossils, describing the new species and interpreting them in relation to trace producers and depositional environment. However, many of the ichnogenera and ichnospecies established from these basins need special attention because they either have been described as invalid, revised or assigned an unclear taxonomic status. The Cretaceous trace fossils reported to date from these basins are compiled along with their paleoenvironmental interpretation. The study also discusses the present status of the ichnogenera and ichnospecies names of the trace fossils reported to date from these basins. These data can be further used to enhance our understanding of how paleoenvironmental conditions control the distribution of trace‐making communities across space and time.

The evolution of the Narmada, Saurashtra, and Kachchh basins in the western margin of the Indian Craton is associated with the Middle Jurassic segmentation of Gondwana. The Narmada Basin was evolved during the Early Cretaceous and preserved a thick clastic and non‐clastic sequence of the Bagh Group. The succession lies unconformably on the Precambrian rocks, and a complete sequence is exposed in the Western Lower Narmada Valley (WLNV). Until now, it has been described using various informal lithostratigraphic units emphasizing local lithic characters, which have no relevance with the stratotypes and do not fit into the concept of the International Subcommission on Stratigraphic Classification (ISSC). In the present study, the Bagh Group succession is mapped across the Lower Narmada Valley (LNV) and correlated between sections. The units in WLNV were revised and redefined assigning the stratotypes as per the ISSC. The amended lithostratigraphy of the Bagh Group comprises five formations, viz. Songir, Vajepur, Bilthana, Nodular Limestone, and Uchad. The Uchad Formation is a newly recognized youngest unit and is subdivided into the Narmada sandstone and the Men Nadi Limestone members. The lithological and palaeontological evidences indicate that the Bagh Group succession of the WLNV developed in a fluvio‐marine environment during the Berriasian? (Neocomian) to Coniacian age. The Cretaceous succession of the WLNV is also compared with the pervasive Tethyan basins, including the Eastern Desert (Egypt), Saurashtra–Kachchh (India), Mahajanga (Madagascar), and Carnarvon (Australia). The Albian–Coniacian lithostratigraphy of the Narmada Basin is comparable to the Eastern Desert, although located at different palaeolatitudes, which suggest similar eustatic and tectonic conditions. It also shows a similar sedimentation pattern compared with the adjoining Saurashtra Basin during the Cenomanian–Coniacian. However, it differs from the Kachchh, Mahajanga, and Carnarvon basins, which can be attributed to different palaeolatitudes, as well as the development of rift‐related events. The deposition of the Bagh Group in WLNV terminated with the separation of the Indian Plate from Madagascar and the outpouring of flood basalts during the Coniacian.