The Hongshuizhuang Formation is a Meso-Neoproterozoic high-quality source rock in the North China Craton(NCC),comprising abundant organic matter.The present study focuses on the analysis of the Hongshuizhuang Formatio...The Hongshuizhuang Formation is a Meso-Neoproterozoic high-quality source rock in the North China Craton(NCC),comprising abundant organic matter.The present study focuses on the analysis of the Hongshuizhuang Formation in the Zhoukoudian area of the Jingxi sag,discussing its genesis and mechanisms of organic matter enrichment through geological and geochemical methods.The Hongshuizhuang Formation is divided into three members from bottom to top respectively as the lower,middle and upper member.Trace elements analysis indicate that the Hongshuizhuang Formation developed restricted neritic facies in an extensional environment within a continental island arc under a post-orogenic background.The lower and upper members were deposited in a relatively shallow,strongly retained water mass within a suboxic and saline environment influenced by subhumid climate,while the middle member was deposited in an anoxic deep-water environment with relatively low salinity and weak restrictions.The PAAS-normalized rare earth element distributions of the middle and upper members show an enrichment of LREEs and a depletion of HREEs,and a low mean Y/Ho ratio with a positive Eu anomaly,indicating that the regional deposition has been affected by hydrothermal fluids.The negativeδ13 C andδ18 O values and the positive87 Sr/86 Sr values confirm that the deposition of the middle and upper members was accompanied by crustal hydrothermal activities.Accumulation of organic matter and enrichment of Baxsand P indicate that productivity is the basis of organic matter enrichment in the Hongshuizhuang Formation,where high-quality source rocks are concentrated in the middle member.In addition,reduced water mass controls the preservation of organic matter.Hydrothermal activity,humid climate,and salinity support a higher primary productivity and the formation of reduced water masses.However,due to limitations in depth,the high-quality source rocks in the Jingxi sag are thinner than the Jibei sag.展开更多
Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil h...Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally,or to comparing the width of the hemispheres.In the present study,using 3D laser scanning,we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus,dated to 0.4-0.8 Ma.Compared with modern endocasts,we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens.However,the relative hemisphere volumes against surface areas differed between the two groups.When comparing the relative sizes between the left and right hemispheres,the ZKD specimens exhibited a greater variation than in the modern humans;there were no differences in the two hemispheres in the ZKD specimens,while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere.These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution.These anatomical changes are likely related to the origin of human brain lateralization.展开更多
基金Fundamental Research Funds for the Central Universities of China(35832019010)National Natural Science Foundation of China(41802169)。
文摘The Hongshuizhuang Formation is a Meso-Neoproterozoic high-quality source rock in the North China Craton(NCC),comprising abundant organic matter.The present study focuses on the analysis of the Hongshuizhuang Formation in the Zhoukoudian area of the Jingxi sag,discussing its genesis and mechanisms of organic matter enrichment through geological and geochemical methods.The Hongshuizhuang Formation is divided into three members from bottom to top respectively as the lower,middle and upper member.Trace elements analysis indicate that the Hongshuizhuang Formation developed restricted neritic facies in an extensional environment within a continental island arc under a post-orogenic background.The lower and upper members were deposited in a relatively shallow,strongly retained water mass within a suboxic and saline environment influenced by subhumid climate,while the middle member was deposited in an anoxic deep-water environment with relatively low salinity and weak restrictions.The PAAS-normalized rare earth element distributions of the middle and upper members show an enrichment of LREEs and a depletion of HREEs,and a low mean Y/Ho ratio with a positive Eu anomaly,indicating that the regional deposition has been affected by hydrothermal fluids.The negativeδ13 C andδ18 O values and the positive87 Sr/86 Sr values confirm that the deposition of the middle and upper members was accompanied by crustal hydrothermal activities.Accumulation of organic matter and enrichment of Baxsand P indicate that productivity is the basis of organic matter enrichment in the Hongshuizhuang Formation,where high-quality source rocks are concentrated in the middle member.In addition,reduced water mass controls the preservation of organic matter.Hydrothermal activity,humid climate,and salinity support a higher primary productivity and the formation of reduced water masses.However,due to limitations in depth,the high-quality source rocks in the Jingxi sag are thinner than the Jibei sag.
基金supported by the National Natural Science Foundation of China (40972017)the Knowledge Innovative Program of the Chinese Academy of Sciences (KZCX2-YW-159 and XDA05130100)the International Cooperation Program of MST of China (2009DFB20580)
文摘Endocasts are important materials used for the study of human brain evolution,and allow examination of the external features of brain anatomy from the inside the cranium.Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally,or to comparing the width of the hemispheres.In the present study,using 3D laser scanning,we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus,dated to 0.4-0.8 Ma.Compared with modern endocasts,we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens.However,the relative hemisphere volumes against surface areas differed between the two groups.When comparing the relative sizes between the left and right hemispheres,the ZKD specimens exhibited a greater variation than in the modern humans;there were no differences in the two hemispheres in the ZKD specimens,while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere.These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution.These anatomical changes are likely related to the origin of human brain lateralization.
