The northern sector of the Malay Basin has long been underrepresented,leaving a gap in the understanding of its paleoenvironmental evolution.In addressing this gap,detailed biostratigraphic analysis based on palynolog...The northern sector of the Malay Basin has long been underrepresented,leaving a gap in the understanding of its paleoenvironmental evolution.In addressing this gap,detailed biostratigraphic analysis based on palynology and foraminifera from two wells,i.e.,Tj-1 and Tp-1,has been conducted to reconstruct the paleoenvironment during the Miocene age.The factors influencing their distribution were analyzed using a sequence biostratigraphic approach,complemented by environmental parameters such as grain size and organic matter content,supported by seismic and gamma ray logs.The findings reveal significant differences in the faunal distribution of the inner shelf and delta front between the two studied wells.The inner shelf in Tj-1 well is dominated by Asterorotalia pulchella and the accessory species Pseudorotalia schroeteriana.Whereas Tp-1 well,is dominated by Pseudorotalia schroeteriana,but Asterorotalia pulchella is absent.For delta front species,Bigenerina sp.and Reophax sp.are found throughout Tp-1 well.However,in Tj-1 well,the dominant assemblages are Bigenerina sp.and Miliammina sp.during Serravallian to Tortonian,and Cavarotalia annectens from Tortonian to Messinian.Furthermore,our study identifies a major transgressive-regressive(T-R)event during Langhian to Serravallian period,inferred from stratigraphic dating using the standard palynological zonation of Malay Basin('PR'zone)with the age according to VIM(Vietnam-Indonesia-Malaysia)and SEA(Southeast Asia)cycles,which also highlights unconformities.This suggests that tectonic events have led to distinct fauna provinces within the Miocene biostratigraphic assemblages.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 Malaysia—Thailand Joint Authority (MTJA) Cess Fund,under the grant number IF064-2019 managed by UPGP of UM
文摘The northern sector of the Malay Basin has long been underrepresented,leaving a gap in the understanding of its paleoenvironmental evolution.In addressing this gap,detailed biostratigraphic analysis based on palynology and foraminifera from two wells,i.e.,Tj-1 and Tp-1,has been conducted to reconstruct the paleoenvironment during the Miocene age.The factors influencing their distribution were analyzed using a sequence biostratigraphic approach,complemented by environmental parameters such as grain size and organic matter content,supported by seismic and gamma ray logs.The findings reveal significant differences in the faunal distribution of the inner shelf and delta front between the two studied wells.The inner shelf in Tj-1 well is dominated by Asterorotalia pulchella and the accessory species Pseudorotalia schroeteriana.Whereas Tp-1 well,is dominated by Pseudorotalia schroeteriana,but Asterorotalia pulchella is absent.For delta front species,Bigenerina sp.and Reophax sp.are found throughout Tp-1 well.However,in Tj-1 well,the dominant assemblages are Bigenerina sp.and Miliammina sp.during Serravallian to Tortonian,and Cavarotalia annectens from Tortonian to Messinian.Furthermore,our study identifies a major transgressive-regressive(T-R)event during Langhian to Serravallian period,inferred from stratigraphic dating using the standard palynological zonation of Malay Basin('PR'zone)with the age according to VIM(Vietnam-Indonesia-Malaysia)and SEA(Southeast Asia)cycles,which also highlights unconformities.This suggests that tectonic events have led to distinct fauna provinces within the Miocene biostratigraphic assemblages.
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.
