COUPLED ROLE OF CLIMATE AND TECTONICS IN THE DEPOSITION OF THE LATE QUATERNARY SEDIMENTARY SEQUENCE IN THE SOUTHERN MARGIN OF THE CENTRAL GANGA PLAIN, INDIA

Abstract

The Ganga Plain’s sedimentation is primarily controlled by Himalayan tectonics, variations in monsoon intensity, and glacier size. However, the significance of intrabasinal tectonics, which is an interplay of the Himalaya tectonics and basement tectonic configuration of the Ganga Plain, in comprehending the late Quaternary Ganga Plain sedimentation remains unclear. In this study, the sediment provenance and extent of weathering experienced by the sediments are studied using the mineralogical and geochemical (major, trace, and rare earth elements) composition of a sedimentary cliff sequence exposed at the Ramnagar locality near the cratonic peripheral bulge in the southern Ganga Plain. In the Ramnagar cliff sediment section, two sediment packages, designated SP-A and SP-B, are identified based on mineralogy, texture, and geochemistry. These packages of sediments show mild chemical weathering and distinct geochemical compositions. The lower part (SP-A) of the Ramnagar cliff section is characterized by higher contributions from mafic sources (pyroxene, feldspar, and mica as dominant minerals), while the upper part (SP-B) is predominately derived from felsic sources (mica and feldspar as dominant minerals), which are supplied via the peninsular and the Himalayan rivers, respectively. The southern part of the central Ganga Plain shows evidence of a shift in the sediment provenance from mafic to felsic source rock at 40 ka. This study demonstrates how weathering and sedimentation are controlled by both regional tectonics and climate in the southern margin of the central Ganga Plain.; The Director of the BSIP, Lucknow, is thanked by the authors for providing all infrastructural (SAIF) and administrative support to complete the assignment. This work is a part of MY’s doctoral thesis, supported by the funding received from the University Grants Commission (CSIR-UGC JRF fellowship, Roll No. 207693) and recorded as BSIP/RDCC/Publication no. 24/2024-25. The authors also thank Dr. Sheikh Nawaz Ali, Dr. Arvind Kumar Singh, Dr. Naimisha Vanik, Harshita Srivastava, Dr. Masud Kawsar, and Dr. Abhisek Kumar for their constructive suggestions that helped to make the manuscript better. UKS is thankful to the Head of the Department of Geology for providing the working facilities of the Department. We thank editor Dr. Kathleen Marsaglia, Associate Editor Dr. Alberto Resentini, and anonymous reviewers for constructive comments on our manuscript. Ó 2024, SEPM (Society for Sedimentary Geology)