Palaeoecological Insights From Transitional Environments: Marginal‐Marine and Terrestrial Trace Fossils From the Cretaceous Interval of the Jaisalmer Basin, India

ABSTRACT The integration of ichnological, sedimentological, and palaeopedological evidence provides critical information regarding the marine‐to‐terrestrial transition and intermittent subaerial exposures in marginal‐marine settings. This study presents the palaeoenvironmental transition from marine to continental depositional regimes within a tide‐influenced deltaic system from the Lower Cretaceous Pariwar Formation of the Jaisalmer Basin, western India. The ca. 50 m‐thick outcrop records a locally occurring marginal‐marine ichnoassemblage of Rosselia socialis , Conichnus conicus, and Ophiomorpha nodosa . This assemblage is overprinted by the dominant continental biogenic structures, including rhizoliths, termite nests ( Termitichnus schneideri , Vondrichnus planoglobus ), and lungfish aestivation chambers. A detailed ichno‐sedimentological facies analysis led to the identification of tidal rhythmites, tide‐influenced distributary‐channel deposits, and pedogenised sandstones, which point towards the successive phases of inter‐ and sub‐tidal flat development and filling of active and abandoned channels. The superposition of the terrestrial trace‐fossil suite over the marginal‐marine and the upwards intensification of such superposition reveal a progressive shallowing‐up trend implying a deltaic progradation amidst the low‐order base‐level fluctuations. Rhizolith morphotypes (viz., Types 1–3) testify to a variability in the root systems and the palaeohydrologic conditions; for example, the complex network of isopteran nests and lungfish burrows indicates the semi‐arid climatic and the seasonal desiccation episodes. The ichnofacies analysis reveals the dominance of Rosselia and Termitichnus ichnofacies. This illustrates the ecological convergence of marginal‐marine macrobenthic and terrestrial infauna in response to the primarily autogenic environmental fluctuations across the marine–terrestrial transition zone. This integration of ichnology and sedimentology defines the sequence‐stratigraphic and palaeoenvironmental framework for the Cretaceous sequence of the Indian northwestern inner shelf close to the basin margin.