Amended lithostratigraphy of the Cretaceous Bagh Group, Western Lower Narmada Valley, India: A comparison with pervasive Tethyan basins

Abstract

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.