Provenance of terrigenous sediments in the central Bay of Bengal and its relationship to climate changes since 25\u2009ka

Jingrui Li,Hui Zhang,Xuefa Shi,Aimei Zhu,Shengfa Liu,Narumol Kornkanitnan,Jingjing Cui,Min-Te Chen,Somkiat Khokiattiwong

doi:10.1186/s40645-020-00328-0

Abstract

Lithogenic grain-size, geochemical elements of core sediments from the central Bay of Bengal (BoB) were analyzed to identify sediment provenance and explore the regional “source-sink” processes since 25 ka. Based on the geochemical compositions of core BoB-88, relative contributions of three end-member sources (Himalayan, Myanmar, Indian Peninsula) were calculated and support the general understanding that Himalayan sources were dominant since the last glacial period, which could reach 70% on average in our study. However, sediments from the Indian Peninsula and Myanmar also contributed nonnegligible materials to the central BoB since 25 ka, especially the former shows an obvious increase since 7.5 ka, which was neglected in the previous studies. To trace the sedimentary processes of different provenance terrigenous materials and reveal their response to climate changes, four typical stages with obvious provenance percent variation, including the Last Glacial Maximum period (LGM), Heinrich 1 (H1), Early Holocene Climate Optimum (EHCO), and mid-late Holocene period, were highlighted and discussed. Sea-level change played a dominant role in the glacial-interglacial scale by controlling the transition of deposition center between the shelf/subaquatic delta and the Bengal Fan, especially for sediment from the Himalayan source, exerting influence on contributions from different provenance end-members between the Holocene and the last glacial period. The opposite directions of the southwest and northeast monsoon current in the BoB have a significant influence on the transfer of the Indian Peninsula and Myanmar materials to the studied core, which led to an increase of up to 11% than the average of the Indian Peninsula and a decrease of up to 9% than the average of the Myanmar source during the Holocene. The balance between sea level (limited transport to the deep sea) and ISM (improved erosion production and output to the BoB) during the mid-late Holocene period maintained the stability of Himalayan source percent. Due to the control of the ISM variations, the Himalayan source showed a decrease of up to 20% and 21% than average during the LGM and H1 period, respectively, and an increase of up to 14% than average during the EHCO. The Myanmar source exhibited fluctuations around the average value during the LGM period, but an obvious increase of up to 21% during the H1 period and a decrease up to 8% during the EHCO, while the Indian Peninsula source percent showed little variations during the LGM and H1, but a decrease of up to 6% during the EHCO. Obvious 1/4 processional and millennial periodic changes (5.0 kyr and 1.1 kyr) of contribution proportions from three end-members provide additional evidences for the climate control on the regional source-sink processes and proved the controlled mechanisms of the orbital parameters and possible influence from the solar activity on millennial scales.

Highlights

The Bay of Bengal (BoB), which is in the northeastern Indian Ocean, is one of the major deposition areas for eroded materials from the Tibetan Plateau and Himalaya Mountains (Kolla and Biscaye 1973, France-Lanord et al 1993; France-Lanord and Derry 1994, Colin et al 1999, Kessarkar et al 2005; Galy et al 2007; Phillips et al 2014b)
The continuous sedimentation during the Late Quaternary in the Bengal Fan mainly deposits from the turbidity overflowing and the suspension materials setting (Curray et al 2003; Curray 2014), they are characterized by finer size and dominated silt fractions (Weber et al 1997; Li et al 2017a; Li et al 2017b; Li et al 2018), and these sedimentation has been regulated by complex controlling factors like changing terrigenous sediment supply, sea level, oceanic circulation and the intensity of the Indian monsoon (Colin et al 1999; Curray et al 2003; Phillips et al 2014b; Joussain et al 2016)
The results showed that enrichment factor (EF) was in a narrow range from 0.7 to 2.0 (Fig. 4), indicating that sediments of core BoB-88 were close to the composition of Upper continental crust (UCC) and mainly from the crust source; discrimination function (DF) results showed that three potential sources all have a close relationship with the sediment of the core BoB-88 (DF < 0.5, and DFHimalayan < DFMyanmar < DFIndian Peninsula) (Fig. 4), which proved three end-members might be more reasonable for sediment provenances in the central BoB

Summary

Introduction

The Bay of Bengal (BoB), which is in the northeastern Indian Ocean, is one of the major deposition areas for eroded materials from the Tibetan Plateau and Himalaya Mountains (Kolla and Biscaye 1973, France-Lanord et al 1993; France-Lanord and Derry 1994, Colin et al 1999, Kessarkar et al 2005; Galy et al 2007; Phillips et al 2014b). Tripathy et al (2014) used major and trace elements combined with factor analysis estimating the contribution of different provenances to the SK187/PC33 core sediments in the western Bengal Fan and indicated a result of 66% and 34% from the Himalayan and peninsular Indian rivers respectively to the core site through the last glacial period.

Results

Conclusion