末次冰期以来南海东北部陆源有机碳埋藏通量演变:海平面和季风驱动

SEA LEVEL CHANGE AND MONSOON DOMINATED EVOLUTION OF TERRIGENOUS ORGANIC CARBON BURIAL FLUX IN THE NORTHEASTERN SOUTH CHINA SEA SINCE THE LAST GLACIAL

大陆边缘盆地是大陆风化剥蚀产物的主要沉积汇,其中有机碳的埋藏通量及其控制机制的研究对于理解全球碳循环具有重要科学意义。本研究基于南海东北部台西南盆地TWS-1岩芯的AMS14C测年、总有机碳、总氮含量和稳定碳同位素组成的分析,探讨了末次盛冰期23ka BP以来南海东北部陆源有机碳的来源、历史和影响机制。与潜在物源端元对比表明,台湾是研究站位沉积物陆源有机碳的主要物源,相对海源其贡献比例约为58%,陆源物质可能主要通过海底峡谷水道和低海平面时期陆架河流输入。重建的陆源有机碳通量在末次冰消期早期(19-13kaBP)和中全新世(7-4ka BP)期间有两个峰值,分别约0.16g/(cm^2·ka)和0.09g/(cm^2·ka)。综合分析表明,二者分别受控于冰期低海平面时期增强的陆架风化剥蚀和全新世季风强盛期降水驱动的古台湾岛剥蚀。我们的工作表明冰期-间冰期循环中海平面和季风分别驱动的大陆边缘有机碳埋藏可能对全球碳循环和大气CO2浓度演变有重要影响。

The continental margin basin is the main sedimentary sink of the products of continental weathering and erosion. The burial of organic carbon is of great scientific significance for understanding the global carbon cycle. This study is based on the analysis of AMS14 C dating, total organic carbon, total nitrogen content, and stable carbon isotope composition of the Core TWS-1 in the Taixinan Basin of the northeastern South China Sea to reveal the source, history, and driven force of terrigenous organic carbon in the study area since the last glacial. Comparison with potential source end-members shows that Taiwan Island was the main source of terrigenous organic carbon to the study site, contributing 58% of the total. The terrigenous materials were mainly transported through submarine canyon channels and shelf rivers during the sea level low-stands. The reconstructed terrigenous organic carbon flux shows two peaks of 0.16 g/(cm^2·ka) during the early deglaciation(19-13 ka BP) and 0.09 g/(cm^2·ka) during the middle Holocene(7-4 ka BP). The comprehensive analysis showed that the two peaks were controlled by the enhanced erosion of the continental shelf during the glacial low sea level stands and the intensified erosion in ancient Taiwan Island driven by precipitation during the Holocene maximum monsoon period. Therefore, we believe that the burial of organic carbon in continental margin driven by sea level change and monsoon during the glacial-interglacial cycle may have considerable effects on the global carbon cycle and the evolution of atmospheric CO2 concentration.