Northeastern Section - 56th Annual Meeting - 2021

Paper No. 18-3
Presentation Time: 2:15 PM


CHANG, Queenie1, HREN, Michael1, LIN, Andrew2, TABOR, Clay1, YU, Shun-Wen3, ELEY, Yvette4 and HARRIS, Gregory1, (1)Department of Geosciences, University of Connecticut, 354 Mansfield Rd Unit 1045, Storrs, CT 06269-1045, (2)Department of Earth Sciences, National Central University, Taoyuan, 32001, Taiwan, (3)Exploration and Development Research Institute, CPC Corporation, Miaoli, 360, Taiwan, (4)School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom

Fluvial sediments are important archives of paleoenvironments, but variations in sediment production and transport processes greatly influence sediment geochemistry and resultant interpretations of ancient conditions. Sedimentary records of orogenic belt in tectonically-active tropical regions characterized by high precipitation rates, rapid erosion, and short sediment residence times may be particularly sensitive to these surface processes. To examine climatic and geomorphic controls on isotope geochemical signatures of fluvial sedimentary archives, we present the leaf-wax n-alkanes hydrogen and carbon isotope (δDn-alkane and δ13Cn-alkane) records from two sediment cores collected in onshore and offshore of the Gaoping river-submarine canyon system in southwestern Taiwan. These records span the last ~26 kyr and provide the information about the temporal and spatial differences in the geochemical signal within a source-to-sink system. The results show that the records of the offshore core which is distal to the orogeny reflects predominantly the environmental variation due to climate change through the glacial-interglacial transition. From Last Glacial Maximum (LGM) to present, the δ13Cn-alkane of the offshore core decreased by ~1.5-2.0‰ and the δDn-alkane increased by ~10-15‰. These variations reflect the biologic responses to global atmospheric δ13Catm and pCO2 increase and precipitation δDprecip changes associated with regional warming due to deglaciation. The onshore core records have captured the same environmental signal variation through time, but the δ13Cn-alkane are systematically larger and δDn-alkane smaller than the offshore core, which may be because it is proximal to the orogeny and has higher catchment integration elevation. ­­Our findings demonstrate that in tropical mountain system, isotopic variations in sedimentary records will most strongly reflect changes to catchment integration of sediments and organic materials, highlighting the critical role that depositional setting plays in controlling geochemical records of paleoenvironment.