Provenance and Tectonic Setting of the Neogene Clastic Sedimentary Rocks in the Offshore Bay of Bengal, Bangladesh

ABSTRACT The offshore Bengal Basin experienced sedimentation due to the interaction between the Indo‐Asian collision and the amalgamation of Indo‐Burma. To infer the provenance, paleoweathering and tectonic evolution of the Neogene sedimentary rocks from the Sangu Gas Field in the Bay of Bengal, Bangladesh, this study presents a new set of whole‐rock geochemical and detrital zircon U–Pb data. Major and trace element geochemistry indicates that these Neogene sediments originated from an active continental margin (ACM) tectonic environment associated with the recycled orogen, aligning well with the sandstones' quartz‐feldspar‐lithic composition. The geochemical characteristics and elemental ratios of the Neogene sedimentary rocks [e.g., Eu/Eu* (0.55–0.58), (La/Lu) N (9.2–10.0), La/Sc (2.30–3.98) and (La/Yb) N (8.46–10.03)], indicate a primary origin from felsic source rocks. The source rocks are dominantly granites that had undergone mild to moderate chemical weathering. The U–Pb ages of the Pliocene Tipam Group and the Miocene Surma Group range from 22.49 to 2794.45 and 28.04 to 3168.21 Ma, respectively. The sandstones of the Tipam and Surma groups exhibit a notable zircon age peak at around 440–620 Ma, which bears similarities to the Tethyan Himalaya (TH), Upper Lesser Himalaya (ULH) and Indo‐Burman Ranges (IBR). The secondary peaks at ~1500–2000 Ma correspond to the Lesser Himalaya (LH) ages. The additional subordinate peaks at ~700–1200 Ma reflect the age of the Higher Himalaya (HH). The notable increase in the younger detrital zircon (< 200 Ma) populations was observed in the Tipam Group samples (~22%). These additional young zircons were possibly derived from the recycled Paleogene arc of the Indo‐Burma Ranges that might have originated from the Burma magmatic arc.