Provenance of Clay Minerals in Core Sediments of Krishna River Delta, East Coast, India

ABSTRACT This study focuses on the sources and processes that control the formation, evolution, and transport of clay minerals in the Krishna River Delta. The analysis of sediment cores shows a clear dominance of smectite across all cores, with the highest proportion in Turumella (88%), followed by Ponnapalli (87%), Inturu (84%), and Nizampatnam (82%). Kaolinite is most abundant at Inturu (13%), while illite reaches its maximum concentration in Nizampatnam (8%) and Ponnapalli (7%). Chlorite is present only in minor amounts, accounting for about 2% in Inturu and Nizampatnam and 1% in Turumella and Ponnapalli. These variations in clay mineral content reflect both the geological setting and the intensity of weathering processes in the drainage basin. Smectite is mainly derived from the weathering of basaltic rocks belonging to the Deccan Traps, which are widespread in the catchment area. Illite, on the other hand, is linked to Archaean rocks and is typically associated with physical weathering under colder and more arid conditions. The presence of kaolinite and chlorite points to chemical weathering, where different ions are released in stages: Mg, Ca, Na, Sr, and K during bisealisation; Fe, Cu, Ni, Mn, and Co during monosialitisation; and finally, silica removal during alitisation. A ternary diagram plotting illite+chlorite, kaolinite, and smectite clearly highlights the strong influence of lithology on clay mineral assemblages. The study shows that the composition of clay minerals in the Krishna River delta is shaped by a combination of source rock characteristics and weathering regimes, offering valuable insights into sediment provenance and depositional processes in this important fluvial-deltaic system.