Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor int...Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.展开更多
The Burma Terrane has yielded some of the earliest pieces of evidence for monsoonal rainfall in the Bay of Bengal.However,Burmese ecosystems and their potential monsoonal imprint remain poorly studied.This study focus...The Burma Terrane has yielded some of the earliest pieces of evidence for monsoonal rainfall in the Bay of Bengal.However,Burmese ecosystems and their potential monsoonal imprint remain poorly studied.This study focuses on the late Eocene Yaw Formation(23°N)in central Myanmar,which was located near the equator(c.5°N)during the Eocene.We quantitatively assessed the past vegetation,climate,and depositional environments with sporomorph diagrams,bioclimatic analysis,and sequence biostratigraphy.We calculated the palynological diversity and drew inferences with rarefaction analysis by comparing with four other middle to late Eocene tropical palynofloras.Palynological results highlight a high floristic diversity for the palynoflora throughout the section formed by six pollen zones characterized by different vegetation.They indicate that lowland evergreen forests and swamps dominated in the Eocene Burmese deltaic plains while terra firma areas were occupied by seasonal evergreen,seasonally dry,and deciduous forests.This vegetation pattern is typical to what is found around the Bay of Bengal today and supports a monsoon-like climate at the time of the Yaw Formation.Bioclimatic analysis further suggests that in the late Eocene,the Yaw Formation was more seasonal,drier,and cooler compared to modern-day climate at similar near-equatorial latitude.More seasonal and drier conditions can be explained by a well-marked seasonal migration of the Intertropical Convergence Zone(ITCZ),driver of proto-monsoonal rainfall.Cooler temperatures in the late Eocene of central Myanmar may be due to the lack of adequate modern analogues for the Eocene monsoonal climate,while those found at other three Eocene Asian paleobotanical sites(India and South China)may be caused by the effect of canopy evapotranspirational cooling.Our data suggest that paleoenvironmental change including two transgressive-regressive depositional sequences is controlled by global sea level change,which may be driven by climate change and tectonics.The high diversity of the Yaw Formation palynoflora,despite well-marked seasonality,is explained by its crossroads location for plant dispersals between India and Asia.展开更多
基金funded by the fellowship of the China Postdoctoral Science Foundation(No.2020M682134)the National Natural Science Foundation of China(Nos.41872149,42076220)the Shandong Postdoctoral Innovation Research Project。
文摘Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.
基金the China Scholarship Council(CSC grant 201604910677)the University of Amsterdam+1 种基金the European Research Council Consolidator Grant(MAGIC 649081)the ANR grant ANR-19-ERC7-0007.
文摘The Burma Terrane has yielded some of the earliest pieces of evidence for monsoonal rainfall in the Bay of Bengal.However,Burmese ecosystems and their potential monsoonal imprint remain poorly studied.This study focuses on the late Eocene Yaw Formation(23°N)in central Myanmar,which was located near the equator(c.5°N)during the Eocene.We quantitatively assessed the past vegetation,climate,and depositional environments with sporomorph diagrams,bioclimatic analysis,and sequence biostratigraphy.We calculated the palynological diversity and drew inferences with rarefaction analysis by comparing with four other middle to late Eocene tropical palynofloras.Palynological results highlight a high floristic diversity for the palynoflora throughout the section formed by six pollen zones characterized by different vegetation.They indicate that lowland evergreen forests and swamps dominated in the Eocene Burmese deltaic plains while terra firma areas were occupied by seasonal evergreen,seasonally dry,and deciduous forests.This vegetation pattern is typical to what is found around the Bay of Bengal today and supports a monsoon-like climate at the time of the Yaw Formation.Bioclimatic analysis further suggests that in the late Eocene,the Yaw Formation was more seasonal,drier,and cooler compared to modern-day climate at similar near-equatorial latitude.More seasonal and drier conditions can be explained by a well-marked seasonal migration of the Intertropical Convergence Zone(ITCZ),driver of proto-monsoonal rainfall.Cooler temperatures in the late Eocene of central Myanmar may be due to the lack of adequate modern analogues for the Eocene monsoonal climate,while those found at other three Eocene Asian paleobotanical sites(India and South China)may be caused by the effect of canopy evapotranspirational cooling.Our data suggest that paleoenvironmental change including two transgressive-regressive depositional sequences is controlled by global sea level change,which may be driven by climate change and tectonics.The high diversity of the Yaw Formation palynoflora,despite well-marked seasonality,is explained by its crossroads location for plant dispersals between India and Asia.
