High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea(SCS) covering the period since the Last Glacial Maximum shows that illite(29%-48%),smectite(14%-45%),chlorite(17%-28%),and ...High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea(SCS) covering the period since the Last Glacial Maximum shows that illite(29%-48%),smectite(14%-45%),chlorite(17%-28%),and minor kaolinite(6%-14%) comprise the clay mineral assemblage,and that time series variation does not present glacial-interglacial cyclicity.Provenance analysis indicates three end-member sources:almost all smectite derives from Luzon,all kaolinite is sourced from the Pearl River,and illite and chlorite originate from both the Pearl River and Taiwan.By comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS,we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity.There were three stages of provenance change.(1) During 24.1-17.5 ka BP,contributions from Taiwan and Luzon were similar(30%-40%),while that from the Pearl River was only 25%.(2) During 17.5-14.0 ka BP,the contribution from Luzon decreased rapidly to 20%-25%,while that from Taiwan increased to 35% from an average of 25% at 18 ka BP,and that from the Pearl River increased largely to 40%.(3) During the Holocene,differences in contributions from the three major provenances increased:the contribution from Luzon increased slightly and then remained at 27%-35%,that from Taiwan increased rapidly and then remained at 55%-60%,and that from the Pearl River decreased to 15%.The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production,monsoon rainfall denudation,oceanic current transport,and sea-level change.展开更多
We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases ...We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I(13.8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs(averaged 143 ng/g dry sediment weight, dsw) than isoprenoid GDGTs(averaged 36 ng/g dsw), high BIT index(branched vs. isoprenoid tetraethers) values(>0.78) and a fluctuating GDGT-0/crenarchaeol ratio(R_(0/5), varied from 0.52 to 3.81). Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas(YD)(ca. 12.9–12.2 cal kyr BP) cold event and melt-water pulse(MWP)-1B(11.5–11.1 cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value(<0.4) and increase in crenarchaeol, which marks the beginning of phase II. Afterwards, the proxies remain relatively constant, which indicates that phase II(7.9 cal kyr BP-present) is a shelf sedimentary environment with high stand of sea level. Overall, the BIT index in our record serves as a good marker for terrestrial influence at the site, and likely reflects the flooding history of the region. The TEX_(86)(Tetra Ether Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II(21.6±0.9°C, n=49). In contrast, the MBT'/CBT(Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature(MAT)(14.3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.展开更多
Archaeal and bacterial glycerol dialkyl glycerol tetraethers(GDGTs) play a unique role in discerning the biogeochemical processes and climate change in terrestrial(e.g. soil, peat, stalagmites, lakes, rivers, hot spri...Archaeal and bacterial glycerol dialkyl glycerol tetraethers(GDGTs) play a unique role in discerning the biogeochemical processes and climate change in terrestrial(e.g. soil, peat, stalagmites, lakes, rivers, hot springs) and marine environments. Organic proxies based on GDGTs(e.g. TEX_(86), MBT/CBT and BIT) have made impressive applications in the open ocean and terrestrial environments. However, the applicability of these proxies in marginal seas has not been thoroughly evaluated, which is necessary given the complexity and dynamics of these systems, such as organic matter(OM) flux, hydrodynamic conditions, and human impact. This review aims to summarize recent studies of GDGTs and GDGT-based proxies in the Chinese marginal seas(CMS), which are characterized by diverse gradient in terrigenous supplies and ocean productivity and hold rich information on climate and sea level changes, ocean current dynamics, sedimentary evolution and biogeochemical processes.展开更多
基金supported by the National Natural Science Foundation of China (40925008,40876024 and 40776027)the National Basic Research Program of China (2007CB815906)+1 种基金the Shanghai Shuguang Program (07SG23)the Shanghai Subject Chief Scientist Program (10XD1406300)
文摘High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea(SCS) covering the period since the Last Glacial Maximum shows that illite(29%-48%),smectite(14%-45%),chlorite(17%-28%),and minor kaolinite(6%-14%) comprise the clay mineral assemblage,and that time series variation does not present glacial-interglacial cyclicity.Provenance analysis indicates three end-member sources:almost all smectite derives from Luzon,all kaolinite is sourced from the Pearl River,and illite and chlorite originate from both the Pearl River and Taiwan.By comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS,we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity.There were three stages of provenance change.(1) During 24.1-17.5 ka BP,contributions from Taiwan and Luzon were similar(30%-40%),while that from the Pearl River was only 25%.(2) During 17.5-14.0 ka BP,the contribution from Luzon decreased rapidly to 20%-25%,while that from Taiwan increased to 35% from an average of 25% at 18 ka BP,and that from the Pearl River increased largely to 40%.(3) During the Holocene,differences in contributions from the three major provenances increased:the contribution from Luzon increased slightly and then remained at 27%-35%,that from Taiwan increased rapidly and then remained at 55%-60%,and that from the Pearl River decreased to 15%.The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production,monsoon rainfall denudation,oceanic current transport,and sea-level change.
基金supported by the National Key Basic Research Program of China (Grant No. 2013CB955703), National Key Basic Research Program of China (Grant No. 2013CB429701)the National Natural Science Foundation of China (Grant No. 91028005)+4 种基金the China Geological Survey (Grant No. GZH201100203)the Fundamental Research Funds for the Central Universitiesthe "National Thousand Talents" Program through the State Key Laboratory of Marine Geology at Tongji Universitythe DFG to GJMV Heisenberg Grant (Grant No. VE486/2-2)the Project of Shanghai Engineering Research Center of Hadal Science and Technology (Grant No. 14DZ2250900)
文摘We reconstruct the environmental evolution of the East China Sea in the past 14 kyr based on glycerol dialkyl glycerol tetraethers(GDGTs) in a sediment core from the subaqueous Yangtze River Delta. Two primary phases are recognized. Phase I(13.8–8 cal kyr BP) reflects a predominantly continental influence, showing distinctly higher concentrations of branched GDGTs(averaged 143 ng/g dry sediment weight, dsw) than isoprenoid GDGTs(averaged 36 ng/g dsw), high BIT index(branched vs. isoprenoid tetraethers) values(>0.78) and a fluctuating GDGT-0/crenarchaeol ratio(R_(0/5), varied from 0.52 to 3.81). Within this interval, temporal increases of terrestrial and marine influence are attributed to Younger Dryas(YD)(ca. 12.9–12.2 cal kyr BP) cold event and melt-water pulse(MWP)-1B(11.5–11.1 cal kyr BP), respectively. The prominent transition from 8 to 7.9 cal kyr BP shows a sharp decrease in BIT index value(<0.4) and increase in crenarchaeol, which marks the beginning of phase II. Afterwards, the proxies remain relatively constant, which indicates that phase II(7.9 cal kyr BP-present) is a shelf sedimentary environment with high stand of sea level. Overall, the BIT index in our record serves as a good marker for terrestrial influence at the site, and likely reflects the flooding history of the region. The TEX_(86)(Tetra Ether Index of tetraethers consisting of 86 carbons) proxy is not applicable in phase I because of an excess terrestrial influence; but it seems to be valid for revealing the annual SST in phase II(21.6±0.9°C, n=49). In contrast, the MBT'/CBT(Methylation of Branched Tetraethers and Cyclization of Branched Tetraethers) proxy appears to faithfully record the annual mean air temperature(MAT)(14.3±0.63°C, n=68) and presents an integrated signal over the middle and lower Yangtze River drainage basin.
基金supported by the Project of Shanghai Engineering Technology Research Center of Hadal Science (Grant No. 14DZ2250900)the Joint Project of Shanghai "Shutong" Hadal Science and Technology Special Foundation and Shanghai Ocean University Discipline Construction (Grant No. HAST-S-2015-01)+1 种基金the National Key Basic Research Program of China (Grant No. 2013CB955703)the South China Sea-Deep Program of the Natural National Science Foundation of China (Grant Nos. 91028005 & 91428308)
文摘Archaeal and bacterial glycerol dialkyl glycerol tetraethers(GDGTs) play a unique role in discerning the biogeochemical processes and climate change in terrestrial(e.g. soil, peat, stalagmites, lakes, rivers, hot springs) and marine environments. Organic proxies based on GDGTs(e.g. TEX_(86), MBT/CBT and BIT) have made impressive applications in the open ocean and terrestrial environments. However, the applicability of these proxies in marginal seas has not been thoroughly evaluated, which is necessary given the complexity and dynamics of these systems, such as organic matter(OM) flux, hydrodynamic conditions, and human impact. This review aims to summarize recent studies of GDGTs and GDGT-based proxies in the Chinese marginal seas(CMS), which are characterized by diverse gradient in terrigenous supplies and ocean productivity and hold rich information on climate and sea level changes, ocean current dynamics, sedimentary evolution and biogeochemical processes.
