Sediment Provenance of the Nansha Trough Since 40 ka B.P. in the South China Sea: Evidence From δ13Corg, TOC and Pollen Composition

Abstract

Geochemical proxies in organic matter (OM) are considered to be reliable proxies for deciphering types of paleo-vegetation (C3 plants and C4 plants) and their abundance. The contributions of total organic carbon (TOC), stable carbon isotopes (δ 13 C org), total nitrogen (TN) and organic carbon to total nitrogen ratios (C/N) were obtained from a gravity core NS07-25 (6 • 39.945 ′ N, 113 • 32.936 ′ E, water depth 2006 m), extracted from the southern South China Sea (SCS). These data were used to reconstruct the climate changes of the Nansha Trough since 40 ka B.P. by comparing them with pollen data from the same core, and this comparison provides better sediment provenance details in the study area. During the periods between 37 and 27 ka, and from 12.5 ka to modern day, the majority of terrestrial sediment received from Borneo, and some climatic events have been governed by aeolian fluxes from mid-latitude areas (mainland China). These periods were relatively humid, compared to 27-12.5 ka, where the majority of terrestrial sediment came from the Sunda Shelf through riverine pathways. This study serves as the first study to correlate deep oceanic pollen and geochemical proxies in order to identify the weaken terrestrial OM signals in the deep ocean.

Holocene sediment source analysis and paleoclimatic significance of core KZK01 from the eastern part of the Beibu Gulf

“…It receives sediments from Hainan, Guangxi, the Pearl River, Taiwan, Vietnam, and the Red River and other source areas, and the combined influence of the multi-level current system, the East Asian monsoon, and hydrodynamic conditions make the sediment transportation and deposition process in the bay very complex (Zhou et al, 2014;Zhang et al, 2015;Liu et al, 2016). Identifying the sources of sediments is of great significance in reconstructing the evolution of sedimentary environments and paleoclimate reconstruction (Thilakanayaka et al, 2019;Liu et al, 2021). However, geochemical information can be lost during weathering and denudation as well as during the deposition of sediments from different source areas, and multiple methods should be adopted for comprehensive source analysis (Cao et al, 2018;Xu and Jiang, 2019).…”