The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magn...The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magnetism, geochemistry, particle size and clay mineralogy. Higher concentrations of magnetic minerals （high Xlf） were recorded in the deep-water sediments when compared with the shallow water sediments. The magnetic mineralogy of one of the shallow water samples is influenced by the presence of bacterial magnetite as evidenced from the XARM/Xlf VS. XARM/Xfd biplot. However, the other samples are catchment-derived. The high correlation documented for Xlf, anhysteretic remanent mag- netisation （XARM） and isothermal remanent magnetisation （IRM） with Al indicates that the deep-sea surflcial sediments are influenced by terrigenous fluxes which have been probably derived from the southern Indian rivers, the Sindhu （the Indus） and the Narmada-Tapti rivers. A lower Mn concentration is recorded in the upper slope sediments from the oxygen minimum zone （OMZ） but a higher Mn/AI ratio is documented in the lower slope and deep-sea sediments. Clay minerals such as illite （24-48.5%）, chlorite （14.1-34.9%）, smectite （10.6-28.7%） and kaolinite （11.9-27.5%） dominate the sediments of shallow and deep-sea regions and may have been derived from different sources and transported by fluvial and aeolian agents. Organic carbon （OC） data indicate a low concentration in the shallow/shelf region （well oxygenated water conditions） and deeper basins （increased bottom-water oxygen concentration and low sedimentation rate）. High OC concentrations were documented in the OMZ （very low bottom-water oxygen concentration with high sedimentation rate）. The calcium carbonate concentration of the surface sediments from the continental shelf and slope regions （〈 1800 m） up to the Chagos-Laccadive Ridge show higher concentrations （average - 58%） when compared to deep basin sediments （average - 44%）. Our study demonstrates that particle size as well as magnetic grain size, magnetic minerals and elemental variations are good indicators to distinguish terrigenous from biogenic sediments and to identify sediment provenance.展开更多
本文利用2010—2019年东印度洋海洋学综合科学考察基金委共享航次数据、Argo(array for real-time geostrophic oceanography)和简单海洋再分析数据(simple ocean data assimilation,SODA),研究了赤道东印度洋次表层高盐水(subsurface h...本文利用2010—2019年东印度洋海洋学综合科学考察基金委共享航次数据、Argo(array for real-time geostrophic oceanography)和简单海洋再分析数据(simple ocean data assimilation,SODA),研究了赤道东印度洋次表层高盐水(subsurface high salinity water,SHSW)的年际变化,并探讨了其形成机制。仅限于春季的观测资料显示,来自阿拉伯海的高盐水位于东印度洋赤道断面次表层70~130m深度处,且具有显著的年际变化。基于月平均SODA资料的研究结果表明,不同时期SHSW盐度异常的变化趋势存在显著差异,2010—2015年趋势比较稳定,而2016—2019年则呈现出显著的上升趋势。通过对SHSW的回归分析表明,风场和次表层纬向流是控制该高盐水年际变化的主要因子。进一步的分析表明,赤道印度洋的东风异常导致水体向西堆积,产生东向压强梯度力,进而激发出次表层异常东向流,最终引起SHSW盐度异常升高。此动力关联在印度洋偶极子事件中尤为显著,这进一步反映了赤道东印度洋SHSW的年际变化受到印度洋偶极子的调制。展开更多
基金The magnetic instruments used for this investigation were procured through grants(DOD Sanction No.DOD/11-MRDF/1/48/P/94ODII/12-10-96)under a research project(to RS)sponsored by the erstwhile Department of Ocean Development(now Ministry of Earth Sciences),Government of India
文摘The spatial distribution patterns of surficial sediment samples from different sedimentary domains （shallow to deep-sea regions） of the eastern Arabian Sea were studied using sediment proxies viz. environmental magnetism, geochemistry, particle size and clay mineralogy. Higher concentrations of magnetic minerals （high Xlf） were recorded in the deep-water sediments when compared with the shallow water sediments. The magnetic mineralogy of one of the shallow water samples is influenced by the presence of bacterial magnetite as evidenced from the XARM/Xlf VS. XARM/Xfd biplot. However, the other samples are catchment-derived. The high correlation documented for Xlf, anhysteretic remanent mag- netisation （XARM） and isothermal remanent magnetisation （IRM） with Al indicates that the deep-sea surflcial sediments are influenced by terrigenous fluxes which have been probably derived from the southern Indian rivers, the Sindhu （the Indus） and the Narmada-Tapti rivers. A lower Mn concentration is recorded in the upper slope sediments from the oxygen minimum zone （OMZ） but a higher Mn/AI ratio is documented in the lower slope and deep-sea sediments. Clay minerals such as illite （24-48.5%）, chlorite （14.1-34.9%）, smectite （10.6-28.7%） and kaolinite （11.9-27.5%） dominate the sediments of shallow and deep-sea regions and may have been derived from different sources and transported by fluvial and aeolian agents. Organic carbon （OC） data indicate a low concentration in the shallow/shelf region （well oxygenated water conditions） and deeper basins （increased bottom-water oxygen concentration and low sedimentation rate）. High OC concentrations were documented in the OMZ （very low bottom-water oxygen concentration with high sedimentation rate）. The calcium carbonate concentration of the surface sediments from the continental shelf and slope regions （〈 1800 m） up to the Chagos-Laccadive Ridge show higher concentrations （average - 58%） when compared to deep basin sediments （average - 44%）. Our study demonstrates that particle size as well as magnetic grain size, magnetic minerals and elemental variations are good indicators to distinguish terrigenous from biogenic sediments and to identify sediment provenance.
文摘本文利用2010—2019年东印度洋海洋学综合科学考察基金委共享航次数据、Argo(array for real-time geostrophic oceanography)和简单海洋再分析数据(simple ocean data assimilation,SODA),研究了赤道东印度洋次表层高盐水(subsurface high salinity water,SHSW)的年际变化,并探讨了其形成机制。仅限于春季的观测资料显示,来自阿拉伯海的高盐水位于东印度洋赤道断面次表层70~130m深度处,且具有显著的年际变化。基于月平均SODA资料的研究结果表明,不同时期SHSW盐度异常的变化趋势存在显著差异,2010—2015年趋势比较稳定,而2016—2019年则呈现出显著的上升趋势。通过对SHSW的回归分析表明,风场和次表层纬向流是控制该高盐水年际变化的主要因子。进一步的分析表明,赤道印度洋的东风异常导致水体向西堆积,产生东向压强梯度力,进而激发出次表层异常东向流,最终引起SHSW盐度异常升高。此动力关联在印度洋偶极子事件中尤为显著,这进一步反映了赤道东印度洋SHSW的年际变化受到印度洋偶极子的调制。
