Terrestrial flux in sediments from the Okinawa Trough estimated using geochemical compositional data and its response to climate changes over the past 35000 a

摘要

Terrestrial supply to marginal seas is a function of interaction between land and ocean in response to climate changes.Terrestrial flux in sediments,therefore,is potential not only to reflect the paleoceanographic evolution of sedimentary basin,but also to reveal the paleoclimatic changes in source regions.Sediments from the Okinawa Trough were quantitatively partitioned into terrestrial,volcanic and biogenitic end members using constrained least-squares technique for geochemical compositional data.Combined with the density of bulk sediments and sedimentation rate,the terrestrial flux in sediments from the Okinawa Trough since the last 35 000 a was estimated.Based on surface seawater temperature(SST) and sea level changes over the past 35 000 a,the response of terrestrial flux to the climate changes was discussed.It is demonstrated that the terrestrial supply to the Okinawa Trough mainly derived from Chinese landmass via the Changjiang(Yangtze) River and controlled by sea level changes.During the post-glaciation,the terrestrial flux was the lowest in response to the highest sea level stand.During the last glacial maximum(LGM),the terrestrial flux was not so high as previously expected,indicating the arid climatic condition in source region was responsible for lowering the Changjiang River's runoff during that time.During the deglaciation,the terrestrial flux increased in response to a quick rising of the sea level,probably implicating occurrence of down-slope transport.The four events characterized by slight increase in terrestrial flux exactly correspond to the LGM,Heinrich events(H1,H2,H3),respectively.