Major and trace element compositions of surface sediments from the lower Bengal Fan: Implications for provenance discrimination and sedimentary environment

Abstract

The Bengal Fan, the largest submarine fan in the world, receives a large amount of terrestrial material from the Himalayas and the Indian Peninsula, making it an ideal area for studying land-sea interactions in different time scales. Using the major and trace element compositions of 98 surface sediment samples from the lower Bengal Fan, we identified the provenances of the sediments, calculated the relative contributions of each provenance, and further assessed their controlling factors. The statistic results of the major and trace elements confirm that terrigenous materials comprise the majority on the sediment and that the study area can be divided into three depositional provinces. The main sources of sediments are the Himalayas and Indian river systems, which can be distinguished in the Fe/Al-K/Al scatter diagram. Based on calculation results of a two end-member mixing model, the relative contributions of the Himalayas and the Indian rivers are 55% and 45%, respectively. However, the spatial distributions of sediments from these two sources in the three provinces exhibit a large variation. The Himalayan contributions decrease from 63% in province I (southeast part of the study area) to 53% in province II (central part of the study area) and 45% in province III (northwest part of the study area). Correspondingly, the contributions of Indian rivers increase from province I through province III. During the high sea levels of modern time, seasonal monsoonal currents play a key role in controlling the sediments transport from South Asia continent to the lower fan.