Organic carbon and nitrogen geochemistry of Taiwan and the northern South China Sea

While chemical weathering of silicate rocks of low-latitude arc–continent collisions has been hypothesized as a driver of global cooling since the Neogene, the role of physical weathering on carbon export and burial has largely been overlooked. In mid- to low-latitude regions, monsoon and tropical cyclone precipitation drive intense physical erosion that may contribute to terrestrial carbon export and nutrient-stimulated marine productivity. To evaluate the influence of physical erosion of an arc-continent collision on organic carbon sequestration in the adjacent ocean basin, we analyse late Miocene to early Pleistocene sedimentary and geochemical records from the Taiwan Western Foreland Basin and time-equivalent records from the northern South China Sea. Total organic carbon (TOC) and total nitrogen (TN) concentrations were determined from pulverized rock samples collected from outcrops of the Taiwan Western Foreland Basin (Chinshui Shale and the Cholan Formation), and sediment samples collected from cored intervals from the northern South China Sea (ODP Site 1146 and 1148). Samples were analyzed using elemental analysis and rock-eval pyrolysis. Organic carbon isotopic compositions (δ13Corg, ‰ relative to Vienna Pee Dee Belemnite) were also measured for both outcrop and sediment core samples by flash combustion on an elemental analyser (EA) coupled to an isotope-ratio mass spectrometer (IRMS).