Clay Mineral Composition and Transport Pattern of Surface Sediments in the Ganges Submarine Delta

Abstract

The Ganges Submarine Delta is a key area for the interaction between land and sea in the northeastern Indian Ocean. Studying the distribution, provenances, and transportation of sediments in the Ganges Submarine Delta, is of great importance to reveal the sedimentary environment characteristics in this area and deepen the understanding of the "source-sink" system of sediment in the northeastern Indian Ocean. We analyzed the grain size and clay mineral content of 84 surface sediments in the Ganges Submarine Delta with aim to reveal the provenances and transport patterns of fine-grained sediments. The results show that the illite has the highest content (~66%), followed by chlorite, kaolinite, and smectite (~18%, 11%, and 5%, respectively). Illite content generally shows a decreasing trend from north to south. Smectite exhibits higher content in the northwest and lower content in the southeast, while chlorite displays opposite characteristics with smectite. The high-content kaolinite is mainly distributed in the southern area. Based on spatial cluster analysis of four clay minerals, the study area can be divided into two provinces: province I is located in the northern area, where the clay mineral assemblage is very similar to that of Ganges-Brahmaputra rivers; Province II is located in the southern area with deep-water, where the clay mineral characteristics have changed due to the mixing of material originating from the Indian Peninsula. Illite/(smectite+chlorite+kaolinite) and kaolinite/illite are used to discuss the sediment transport paths in the two provinces. We inferred that the Himalayan material is widely distributed throughout the study area, and mainly transported from the estuary to the southwestern area under the combined influence of tides, plume, and monsoons. Meanwhile, the Mahanadi river’s sediments are transported from southwest to northeast under the influence of the southwest monsoon, affecting the sediment composition in province II.

Keywords: sediments, grain size, clay minerals, provenances, transport paths, Ganges Delta