Polycyclic Tectono‐Sedimentary Evolution of the Upper Assam Basin, Northeast India: A Synthesis of Foreland Basin Development

The Upper Assam Basin, forming the eastern segment of the Assam–Arakan Basin in northeast India, preserves an exceptional record of passive‐margin, marine shelf and foreland basin evolution associated with convergence between the Indian, Eurasian and Burmese plates. Although previous investigations have significantly advanced understanding of its tectonic evolution, stratigraphy, sedimentology, structural geology, petroleum systems and crustal architecture, these components have rarely been integrated within a unified tectono‐sedimentary framework. This study presents a process‐based tectono‐sedimentary synthesis of the polycyclic evolution of the Upper Assam Basin by integrating published geological, stratigraphic, sedimentological, structural, geophysical and petroleum datasets. Basin evolution is reconstructed through eight successive stages, comprising Precambrian basement inheritance, Late Cretaceous passive‐margin development, Palaeocene marine transgression, Eocene carbonate‐platform evolution, Late Eocene foreland basin initiation, Oligocene deltaic progradation, Miocene molasse deposition and Plio–Quaternary basin modification. The synthesis shows that progressive India–Asia convergence, increasing Himalayan loading and Indo–Burman deformation gradually transformed the passive‐margin system into a flexural foreland basin, reorganising accommodation‐space generation, sediment routing, depositional environments, provenance, structural architecture, burial history and thermal evolution. These coupled geological processes are integrated into a process‐based evolutionary model that interprets the Upper Assam Basin as a dynamically evolving tectono‐sedimentary system in which lithospheric deformation governed basin subsidence, sediment dispersal, depositional architecture, diagenetic evolution and thermal maturation over geological time. The proposed framework provides a geological basis for understanding the evolution of hydrocarbon systems, reservoir quality, geothermal resources, groundwater occurrence and geological carbon storage, while offering a conceptual framework for investigating comparable polycyclic foreland basins developed along active continental margins.