Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the...Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the gas hydrate decomposition events since the late Quaternary under the conditions of methane seepage. The results show that： 1） the δ13C values of the benthic foraminiferan Uvigerina spp. （size range of 0.25-0.35 ram） are from -0.212% to -0.021% and the δ180 values of the planktonic foraminiferan Globigerinoides ruber （size range of 0.25-0.35 ram） are from -0.311% to -0.060%; 2） three cores （ZD2, ZD3 and ZS5） from the bottom of a hole are aged for 11 814, 26 616 and 64 090 a corresponding to the early oxygen isotope stage （MIS） Ⅰ, Ⅲ and Ⅳ final period, respectively; 3） a negative-skewed layer of carbon isotope corresponds to that of MIS II （cold period）, whose degree of negative bias is -0.2%0; and 4） the δ13C compositions of foraminiferans are similar to those of the Blake Ridge and the Gulf of Mexico sediments of the late Quaternary. According to the analysis, the reasons for these results are that the studied area is a typical area of methane seep environment in the area during MIS II due to the global sea-level fall and sea pressure decrease. Gas hydrate is decomposed and released, and a large number of light carbon isotopes of methane are released into the ocean, dissolved to inorganic carbon （DIC） pool and recorded in the foraminiferan shells. A pyrite layer developed in the negative bias layers of the foraminiferans confirms that the δ13C of foraminiferans is more affected by methane and less by the reduction of marine productivity and early diagenesis. The use of foraminiferan δ13C could accurately determine late Quaternary hydrate release events and provide evidence for both reconstructing the geological history of methane release events and exploring natural gas hydrate.展开更多
Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and easte...Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and eastern Indian Ocean （IO） duringApril 5-16 of 2011. The in situ Chl a concentration and carbon fixation showed decreasing trends from high to low latitudealong the three transects, while the photosynthetic rate of phytoplankton estimated from 14C incorporation displayed no simplevariation with latitude. Chl a concentration and carbon fixation in the IO water was lower than that in the JS water. Highersalinity and lower contents of dissolved inorganic nitrogen （DIN） and silicate （SiO3^2-） characterized the IO water as comparedto the SCS or JS water, and the PO4^3- content was lower in the IO water than in the SCS or JS water in most cases. Our resultsalso indicate the importance of DIN and SiO3^2- concentrations for the geographical changes in phytoplankton biomass andprimary productivity among the three regions.展开更多
高分辨率地震资料显示,南海北部西沙海域碳酸盐台地周缘广泛发育水道沉积体系。礁缘水道底界面表现出强反射特征,内部充填弱-强、连续性好的地震相,可见底部杂乱反射特征;斜坡水道在地震剖面上表现为横向上连续发育的"V"型特...高分辨率地震资料显示,南海北部西沙海域碳酸盐台地周缘广泛发育水道沉积体系。礁缘水道底界面表现出强反射特征,内部充填弱-强、连续性好的地震相,可见底部杂乱反射特征;斜坡水道在地震剖面上表现为横向上连续发育的"V"型特征,且下切深度较浅。西沙隆起与广乐隆起之间的南北向低洼地带发育大型深水水道,并且受古地貌高点影响,水道分为南北两个分支。北分支水道可分为5期,且水道迁移现象明显;南分支水道可分为4期,水道以充填强振幅、连续性好的浊流沉积体和弱振幅、杂乱的块体搬运体系(Mass Transport Deposits,MTDs)为特征,每期水道均表现出侵蚀-充填-废弃的旋回性。分析认为西沙碳酸盐台地周缘水道沉积物源来自西沙隆起和广乐隆起的碳酸盐台地和生物礁碎屑及由火成作用产生的火成岩碎屑。西沙-广乐碳酸盐台地水道相互贯通,构成台地-斜坡-深水的水道沉积体系,为碳酸盐岩、生物礁及火山碎屑向台地周缘输送提供了良好的通道。展开更多
对南海北部陆坡Site4B站位末次冰盛期晚期至全新世(30~120cm)长链脂肪醇分布及碳同位素组成进行讨论,结果表明,长链脂肪醇碳优势指数(CPI,10.49~24.56)、平均碳链长(ACL,28.91~29.99)以及平均碳同位素组成(–28.85±0.97‰~–32.92&...对南海北部陆坡Site4B站位末次冰盛期晚期至全新世(30~120cm)长链脂肪醇分布及碳同位素组成进行讨论,结果表明,长链脂肪醇碳优势指数(CPI,10.49~24.56)、平均碳链长(ACL,28.91~29.99)以及平均碳同位素组成(–28.85±0.97‰~–32.92±1.38‰)均反映了陆源C3植物来源,代表了沉积物中陆源输入。Site4B站位末次冰盛期末至晚更新世末(65~102cm,19.343~11.636ka BP)普遍较低的陆源输入均响应了大规模的冰融水事件19ka-MWP、MWP-1A、MWP-1B(melt water pulse,MWP)和暖气候事件(B/A事件),不具冰期/间冰期旋回变化特征。在末次冰盛期晚期(102~120cm)和全新世(30~60cm,10.490~约7.104 ka BP)陆源输入的旋回变化均反映了加强/减弱的冬季风/夏季风旋回变化,其中在末次冰盛期晚期记录一次冬季风最强事件,在早全新世至9.940ka BP记录一次夏季风最强事件。通过Site4B站位末次冰盛期末至晚更新世末(19.343~约11.636 ka BP)千年尺度陆源输入分布特征和全球冰期/间冰期旋回气候变化的对比,发现不具明确的区域对比性,可能受到低纬地区局地环境的作用所致。展开更多
基金Project(40976035) supported by the National Natural Science Foundation of ChinaProject(2009CB219501) supported by the National Basic Research Program of ChinaProject(908-ZC-I-07) supported by the Special Program of Comprehensive Survey and Assessment Offshore China Sea
文摘Carbon and oxygen isotope and dating analyses of foraminiferan in sediment cores collected from three different areas of the northern slope of the South China Sea were conducted, in order to examine the records of the gas hydrate decomposition events since the late Quaternary under the conditions of methane seepage. The results show that： 1） the δ13C values of the benthic foraminiferan Uvigerina spp. （size range of 0.25-0.35 ram） are from -0.212% to -0.021% and the δ180 values of the planktonic foraminiferan Globigerinoides ruber （size range of 0.25-0.35 ram） are from -0.311% to -0.060%; 2） three cores （ZD2, ZD3 and ZS5） from the bottom of a hole are aged for 11 814, 26 616 and 64 090 a corresponding to the early oxygen isotope stage （MIS） Ⅰ, Ⅲ and Ⅳ final period, respectively; 3） a negative-skewed layer of carbon isotope corresponds to that of MIS II （cold period）, whose degree of negative bias is -0.2%0; and 4） the δ13C compositions of foraminiferans are similar to those of the Blake Ridge and the Gulf of Mexico sediments of the late Quaternary. According to the analysis, the reasons for these results are that the studied area is a typical area of methane seep environment in the area during MIS II due to the global sea-level fall and sea pressure decrease. Gas hydrate is decomposed and released, and a large number of light carbon isotopes of methane are released into the ocean, dissolved to inorganic carbon （DIC） pool and recorded in the foraminiferan shells. A pyrite layer developed in the negative bias layers of the foraminiferans confirms that the δ13C of foraminiferans is more affected by methane and less by the reduction of marine productivity and early diagenesis. The use of foraminiferan δ13C could accurately determine late Quaternary hydrate release events and provide evidence for both reconstructing the geological history of methane release events and exploring natural gas hydrate.
基金National Natural Science Foundation of China(41206132,41276162,41130855)Chinese Academy of Sciences Strategic Pilot Science and Technology(XDA11020202,XDA05030403)+2 种基金National Project of Basic Sciences and Technology(2012FY112400,2013FY111200)Chinese Academy of Sciences Knowledge Innovation Program(SQ201115)Natural Science Foundation of Guangdong Province(S2011040000151)
文摘Results are presented about the changes in chlorophyll a density, carbon fixation and nutrient levels in the surfacewaters of three transects of the southern South China Sea （SCS）, northern Java Sea （JS） and eastern Indian Ocean （IO） duringApril 5-16 of 2011. The in situ Chl a concentration and carbon fixation showed decreasing trends from high to low latitudealong the three transects, while the photosynthetic rate of phytoplankton estimated from 14C incorporation displayed no simplevariation with latitude. Chl a concentration and carbon fixation in the IO water was lower than that in the JS water. Highersalinity and lower contents of dissolved inorganic nitrogen （DIN） and silicate （SiO3^2-） characterized the IO water as comparedto the SCS or JS water, and the PO4^3- content was lower in the IO water than in the SCS or JS water in most cases. Our resultsalso indicate the importance of DIN and SiO3^2- concentrations for the geographical changes in phytoplankton biomass andprimary productivity among the three regions.
文摘高分辨率地震资料显示,南海北部西沙海域碳酸盐台地周缘广泛发育水道沉积体系。礁缘水道底界面表现出强反射特征,内部充填弱-强、连续性好的地震相,可见底部杂乱反射特征;斜坡水道在地震剖面上表现为横向上连续发育的"V"型特征,且下切深度较浅。西沙隆起与广乐隆起之间的南北向低洼地带发育大型深水水道,并且受古地貌高点影响,水道分为南北两个分支。北分支水道可分为5期,且水道迁移现象明显;南分支水道可分为4期,水道以充填强振幅、连续性好的浊流沉积体和弱振幅、杂乱的块体搬运体系(Mass Transport Deposits,MTDs)为特征,每期水道均表现出侵蚀-充填-废弃的旋回性。分析认为西沙碳酸盐台地周缘水道沉积物源来自西沙隆起和广乐隆起的碳酸盐台地和生物礁碎屑及由火成作用产生的火成岩碎屑。西沙-广乐碳酸盐台地水道相互贯通,构成台地-斜坡-深水的水道沉积体系,为碳酸盐岩、生物礁及火山碎屑向台地周缘输送提供了良好的通道。
文摘对南海北部陆坡Site4B站位末次冰盛期晚期至全新世(30~120cm)长链脂肪醇分布及碳同位素组成进行讨论,结果表明,长链脂肪醇碳优势指数(CPI,10.49~24.56)、平均碳链长(ACL,28.91~29.99)以及平均碳同位素组成(–28.85±0.97‰~–32.92±1.38‰)均反映了陆源C3植物来源,代表了沉积物中陆源输入。Site4B站位末次冰盛期末至晚更新世末(65~102cm,19.343~11.636ka BP)普遍较低的陆源输入均响应了大规模的冰融水事件19ka-MWP、MWP-1A、MWP-1B(melt water pulse,MWP)和暖气候事件(B/A事件),不具冰期/间冰期旋回变化特征。在末次冰盛期晚期(102~120cm)和全新世(30~60cm,10.490~约7.104 ka BP)陆源输入的旋回变化均反映了加强/减弱的冬季风/夏季风旋回变化,其中在末次冰盛期晚期记录一次冬季风最强事件,在早全新世至9.940ka BP记录一次夏季风最强事件。通过Site4B站位末次冰盛期末至晚更新世末(19.343~约11.636 ka BP)千年尺度陆源输入分布特征和全球冰期/间冰期旋回气候变化的对比,发现不具明确的区域对比性,可能受到低纬地区局地环境的作用所致。
