HR: 1300h
AN: OS52C-07    [PDF]
TI: Organic carbon burial in rapidly accumulating sediments off the southwest coast of Taiwan, a mountainous island
AU: * Kao, S J
EM: sjkao@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, 128, Academia Rd., Sec. 2, Nankang, Taipei, 115 Taiwan
AU: Shiah, F K
EM: fkshiah@ccms.ntu.edu.tw
AF: 1. Institute of Oceanography, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Liu, K K
EM: kkliu@ncu.edu.tw
AF: Institute of Hydrological Sciences, National Central University, 300, Jungda Rd., Junbli, Taoyuan, 320 Taiwan
AB: Surface sediments and suspended particles were collected from the shelf to slope area off southwestern Taiwan, where the deposition condition is characterized by high sediment accumulation rate, ranging from 100 to 1300 mg cm-2 y-1. The samples were analyzed for organic carbon content, nitrogen content and their isotopic compositions (d13C and d15N). The purpose is to estimate the burial fluxes of organic carbon from the marine and terrestrial origins in the depo-center off the southwestern coast of Taiwan, a typical mountainous island. The total organic carbon contents in sediments are medium to low, ranging from 0.45 to 1.35 percent. The d13C values of sedimentary organics ranged from ­V24.8 to ­V21.2 permil showing a spatial pattern significantly influenced by terrestrial organic inputs. In contrast, the d13C values of suspended particles varied in a narrower range, from ­V22.5 to ­V20.9 permil with a mean value of ­V21.7+0.4 permil. The two end-member mixing model of isotopic compositions (terrestrial and marine organics) was used to estimate the sedimentary organic carbon derived from marine (TOCmar) and from terrestrial (TOCterr) origins. Previously reported sediment accumulation rates were correlated to their corresponding water depth such that an empirical function was established to estimate the sediment accumulation rate for a given depth in our study area. A dilution-dominated pattern of marine organic carbon was revealed from the relationship between the estimated sediment accumulation rate and TOCmar. The burial of marine organic carbon for this region ranged from 5 to 20 g C m-2 y-1 with an area weighted mean of 8 g C m-2 y-1, which is much higher than other open marine systems. Compared to the universal burial efficiency model proposed by Betts and Holland (1991), most values in our study area are higher than the assumed 54 percent upper limit indicating that rich supply of sediments around small mountainous islands may enhance the burial efficiency of sedimentary organics.
DE: 1040 Isotopic composition/chemistry
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1055 Organic geochemistry
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting