Well-preserved graptolites of the genus Kiaerograptus are first reported from the upper Tremadocian Yinchupu Formation in the Nanba section,Yiyang,Hunan Province,South China,including four species,i.e.,Kiaerograptus l...Well-preserved graptolites of the genus Kiaerograptus are first reported from the upper Tremadocian Yinchupu Formation in the Nanba section,Yiyang,Hunan Province,South China,including four species,i.e.,Kiaerograptus lauzonensis(Erdtmann,1966),Kiaerograptus stoermeri(Erdtmann,1965),Kiaerograptus cf.supremus?Lindholm,1991,and Kiaerograptus sp.,which are robust in form.Based on these new specimens,the Kiaerograptus biozone is established for the first time in South China,increasing the late Tremadoc graptolite biozones in South China from four to five,in ascending order as follows:the Adelograptus tenellus biozone,the Aorograptus victoriae biozone,the Kiaerograptus biozone,the Sagenograptus murrayi biozone,and the Hunnegraptus copiosus biozone.A review of the occurrence records for robust Kiaerograptus species worldwide reveals that the distribution is restricted to the Aorograptus victoriae biozone and Kiaerograptus biozone in the late Tremadocian.This limited stratigraphical distribution makes Kiaerograptus a valuable taxon for precise biostratigraphical correlation at both the regional and global scales.展开更多
This study provides an overview and discussion of controls on the distribution of organic reefs during the Early Ordovican Period, in the Yangtze Platform, a region of epicontinental sedimentary rocks in South China. ...This study provides an overview and discussion of controls on the distribution of organic reefs during the Early Ordovican Period, in the Yangtze Platform, a region of epicontinental sedimentary rocks in South China. The Yangtze Platform was located in low latitudes during the Early Ordovician and recorded rich and diverse reefs through that time. During the late Tremadocian Epoch, dolomitic and stratiform stromatolites were common in supratidal to intertidal zones of the western Yangtze Platform, while columnar stromatolites formed in deeper waters of the eastern Yangtze Platform. Skeletal-dominated reefs occurred in upper subtidal settings of the central Yangtze Platform. A transition from microbial-dominated to metazoan-dominated reefs with shallowing-upward cycles was evident, indicating that the composition of the main reef-builders was driven mainly by water depth.Increasing metazoan competition during the Great Ordovician Biodiversification Event reduced the abundance of microbial reefs. Sufficient nutrient supply is interpreted to have promoted development of skeletal-dominated reefs locally in shallow settings in the central Yangtze Platform, especially represented by the expansion of abundant solitary fossils of lithistid sponges and Calathium. High salinity environmental settings facilitated the bloom of stromatolites in near-shore locations. Low oxygen content in deep subtidal settings may have led to the absence of skeletal reefs in these habitats, so the mass occurrences of stromatolites was located in the shallower-water central and eastern platform. No keratose sponge-bearing stromatolite can be confirmed across the platform during this interval.展开更多
基金supported in part by the National Key Research and Development Program(Grant Nos.2022YFF0800302)the Natural Science Foundation of China(Grant Nos.42072005,42172035)+2 种基金the China Geological Survey Project(Grant Nos.DD20221649)UNESCO:IUGS IGCP project 735“Rocks and the Rise of Ordovician Life:Filling knowledge gaps in the Early Palaeozoic Biodiversification”the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB26000000)。
文摘Well-preserved graptolites of the genus Kiaerograptus are first reported from the upper Tremadocian Yinchupu Formation in the Nanba section,Yiyang,Hunan Province,South China,including four species,i.e.,Kiaerograptus lauzonensis(Erdtmann,1966),Kiaerograptus stoermeri(Erdtmann,1965),Kiaerograptus cf.supremus?Lindholm,1991,and Kiaerograptus sp.,which are robust in form.Based on these new specimens,the Kiaerograptus biozone is established for the first time in South China,increasing the late Tremadoc graptolite biozones in South China from four to five,in ascending order as follows:the Adelograptus tenellus biozone,the Aorograptus victoriae biozone,the Kiaerograptus biozone,the Sagenograptus murrayi biozone,and the Hunnegraptus copiosus biozone.A review of the occurrence records for robust Kiaerograptus species worldwide reveals that the distribution is restricted to the Aorograptus victoriae biozone and Kiaerograptus biozone in the late Tremadocian.This limited stratigraphical distribution makes Kiaerograptus a valuable taxon for precise biostratigraphical correlation at both the regional and global scales.
基金supported by the China Geological Survey Project (Grant No.DD2019823)the Natural Science Foundation of China (Grant No. 41702003)+1 种基金the Youth Innovation Promotion Association of CAS (2019310)the special fund for strategic pilot technology Chinese Academy of Sciences(Type B, Grant No. XDB26000000)。
文摘This study provides an overview and discussion of controls on the distribution of organic reefs during the Early Ordovican Period, in the Yangtze Platform, a region of epicontinental sedimentary rocks in South China. The Yangtze Platform was located in low latitudes during the Early Ordovician and recorded rich and diverse reefs through that time. During the late Tremadocian Epoch, dolomitic and stratiform stromatolites were common in supratidal to intertidal zones of the western Yangtze Platform, while columnar stromatolites formed in deeper waters of the eastern Yangtze Platform. Skeletal-dominated reefs occurred in upper subtidal settings of the central Yangtze Platform. A transition from microbial-dominated to metazoan-dominated reefs with shallowing-upward cycles was evident, indicating that the composition of the main reef-builders was driven mainly by water depth.Increasing metazoan competition during the Great Ordovician Biodiversification Event reduced the abundance of microbial reefs. Sufficient nutrient supply is interpreted to have promoted development of skeletal-dominated reefs locally in shallow settings in the central Yangtze Platform, especially represented by the expansion of abundant solitary fossils of lithistid sponges and Calathium. High salinity environmental settings facilitated the bloom of stromatolites in near-shore locations. Low oxygen content in deep subtidal settings may have led to the absence of skeletal reefs in these habitats, so the mass occurrences of stromatolites was located in the shallower-water central and eastern platform. No keratose sponge-bearing stromatolite can be confirmed across the platform during this interval.
