Abstract: Coral reefs in the South China Sea have developed extensively, and their growth records preserve diverse information on marine climate and environmental changes. These records serve as a crucial environmental archive. This study focuses on the Nansha Meiji Atoll 'Nanke 1 Well' (NK1) site, systematically analyzing the composition and distribution of lipid biomarker within coral reef carbonate rocks. The potential of short- and medium-chain C14~18 fatty acids for reconstructing paleoproductivity is examined, as well as their environmental significance. The results indicate that these fatty acids exhibit high resistance to diagenesis and degradation, and are closely correlated with terrestrial nutrient input, surface water productivity, and sea-level changes, thus serving as reliable proxies for reconstructing the paleoproductivity records of reef-building corals. Furthermore, aliphatic hydrocarbon assemblages with petroleum hydrocarbon signatures were identified in the 45-65m and 95-110m stratigraphic intervals. Integrating the regional tectonic setting and chronological data of Meiji Reef, these assemblages are inferred to be products of natural hydrocarbon seepage events during the Middle and Late Pleistocene, potentially triggered by the oblique arc-continent collision in the Taiwan region of China. This study provides new geochemical evidence to elucidate the evolution of paleoproductivity and the effects of natural hydrocarbon seepage on the paleoenvironment in the South China Sea coral reef region.

Key words: Meiji Atoll, Biomarkers, Productivity Indicators, Southern South China Sea