Biomarkers reveal the terrigenous organic matter enrichment in the late Oligocene—early Miocene marine shales in the Ying-Qiong Basin, South China Sea

• Published in: Acta oceanologica Sinica Vol. 42; no. 3; pp. 31 - 53
• Main Authors: Ding, Wenjing, Li, Youchuan, Lei, Lan, Li, Li, Yang, Shuchun, Yang, Yongcai, Hou, Dujie
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2023; Springer Nature B.V; School of Natural Sciences,Macquarie University,Sydney 2109,Australia; China National Offshors Oil Corporation(CNOOC)Research Institute Co.,Ltd.,Beijing 100028,China; School of Energy Resources,China University of Geosciences,Beijing 100083,China%China National Offshors Oil Corporation(CNOOC)Research Institute Co.,Ltd.,Beijing 100028,China%CNOOC International Limited,Beijing 100028,China%School of Energy Resources,China University of Geosciences,Beijing 100083,China
• Subjects: Alkanes; Angiosperms; Biomarkers; Carbon content; Climatology; Earth and Environmental Science; Earth Sciences; East Asian monsoon; Ecology; Engineering Fluid Dynamics; Enrichment; Environmental Chemistry; Flora; Humid climates; Marine & Freshwater Sciences; Miocene; Molecular weight; Monsoon intensity; Ocean floor; Oceanography; Oligocene; Organic carbon; Organic matter; Sea floor spreading; Sea level changes; Seafloor spreading; Shales; Summer monsoon; Total organic carbon; South China Sea; tropical/subtropical plants; higher plant-derived biomarkers; East Asian monsoonal climate; total organic carbon
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-022-2081-6

The increase of total organic carbon content of the late Oligocene—early Miocene terrigenously-dominated marine shales in the shallower depth intervals was reported in the Ying-Qiong Basin, South China Sea. The organic enriched lower Sanya Formation shales (early Miocene) have biomarker characteristics of tropical/subtropical plants, with abundant high molecular weight n-alkanes, angiosperm-derived oleanane, rearranged oleananes I, II, II, tricyclic/tetracyclic terpanes including des-A-oleanane, X, *, Y, Z, Z1 and bicadinanes W, T, T1, R. The biomarker characteristics are suggestive of larger influx of the dominant tropical/subtropical angiosperms in flora under a warming and more humid climate during depositions of the lower Sanya Formation (early Miocene) than the older Lingshui Formation (late Oligocene). The tropical/subtropical angiosperm input was thought as the prime control of terrigenous organic matter enrichment relative to the redox condition, and the coeval sea level changes and seafloor spreading in the South China Sea. Enrichment of the terrigenous organic matter in the early Miocene shales is likely in association with the coeval peak East Asian summer monsoon intensity in the South China Sea.