Composition in the continental margin surface sediments from the Ross Sea to the Amundsen Sea (West Antarctica) – Relation to modern environmental condition
WANG Jiakai 1,3, LI Tiegang 2,3,4*, TANG Zheng 2,4, XIONG Zhifang 2,4, LIU Yanguang2,4, CHEN Zhihua 2,4 & CHANG Fengming 1,3,4
1 Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;
2 Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural and Resources, Qingdao 266061, China;
3 University of Chinese Academy of Sciences, Beijing 100049, China;
4 Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
Abstract: Shelf and coastal sediments usually using multiple proxies such as productivity and organic geochemical proxies, with trace element (TE) enrichment, to characterize their modern productivity, nutrient level, and redox conditions. The environmental conditions in the shelf and coastal region along the Ross Sea to Amundsen Sea have changed rapidly in recent decades under the global warming condition. However, the marine productivity and sedimentary redox history in these regions are poorly known. Paleoenvironment archives, including bulk sedimentary elemental enrichment factors, can provide insight into past and future environmental changes in this climatically sensitive region. This study provides redox-sensitive TE (Mn, Ni, Cu, U, P, Mo, Co, V, Zn, and Cd), productivity-related proxies (total organic carbon and opal), with total nitrogen and CaCO3, content in bulk surface sediments from these regions. The organic chemical proxies from the shelf and coastal region of the Ross and the Amundsen sea show that the higher productivity affiliate with the nutrient-rich deepwater upwelling region. Also, the upwelling of weak corrosive deepwater may benefit the preservation of CaCO3, and the formation of more corrosive dense shelf water near the coastal region (coastal polynya) may limit the preservation of CaCO3 in modern sedimentary conditions. Redox-sensitive TEs (Mn, Co, and U) enrichment factors suggest no oxic and anoxic conditions in the study area. However, the redox-sensitive TE (Cd) enrichment factor indicates that the suboxic sedimentary redox condition generally exists in the study area due to high primary productivity and organic matter preservation/decomposition. Other redox-sensitive TEs (P, Ni, Cu, V, and Zn) enrichment factors and the correlation between these elements/Ti with productivity and nutrient proxies indicate the organic matter decomposition process and massive phytoplankton biomass bury. Moreover, this process resulting in different enrichment patterns, which enrich in P, Mo, and Zn but deplete in Ni, Cu, and V. In the future, more surface samples and bottom current energy-related proxies around the continental margin of the Antarctic will prepare for further illustration about the influence of organic matter decomposition and oxygen-riched water ventilation on the modern sedimentary environment, and the influence of sedimentary environment on the distribution pattern of the productivity and nutrient-related proxies, and TEs’ concentration in the bulk sediments of Southern Ocean.
Keywords: redox, nutrient, productivity, shelf and coastal region, offshore of Ruppert and Hobbs coast, Ross Sea, Amundsen Sea