据光明网2012年9月6日报道，中科院古脊椎动物与古人类李淳科研小组在华南海相三叠纪地层中首次发现的陆生初龙类富源滇东鳄（ Diandongosuchus fuyuanensis gen. et．nov）化石，不仅丰富了初龙类化石在亚洲的记录，而且进一步表明云...据光明网2012年9月6日报道，中科院古脊椎动物与古人类李淳科研小组在华南海相三叠纪地层中首次发现的陆生初龙类富源滇东鳄（ Diandongosuchus fuyuanensis gen. et．nov）化石，不仅丰富了初龙类化石在亚洲的记录，而且进一步表明云贵地区的海相三叠系化石动物群并非是一个单纯的海洋生物化石组合。2012年9月出版的美国《古脊椎动物学杂志》刊发了该项研究成果。展开更多
Age determinations of the Triassic lithostratigraphic units of the Yanshan belt were previously based on plant fossils and regional correlations of lithologies. The Liujiagou and Heshanggou Formations were assigned as...Age determinations of the Triassic lithostratigraphic units of the Yanshan belt were previously based on plant fossils and regional correlations of lithologies. The Liujiagou and Heshanggou Formations were assigned as the Lower Triassic, and the Ermaying Formation was regarded as the Middle Triassic. We carried out a geochronologic study of detrital zircon grains from the Triassic sandstone in the Xiabancheng and Yingzi basins in northern Hebei where the Triassic strata are exceptionally well preserved. The results show that the Liujiagou, Heshanggou, and Ermaying Formations are all Late Triassic in age. The ages of detrital zircons also revealed that the upper part of the Shihezi Formation and the overlying Sunjiagou Formation, both of which were thought to be the Middle-Late Permian units, are actually late Early to Middle Triassic deposits. This study combines the upper Shihezi and Sunjiagou Formations into a single unit termed as the Yingzi Formation. We also substitute the widely-used Liujiagou, Heshanggou, and Ermaying Formations with the Dingjiagou, Xiabancheng, and Huzhangzi Formations, respectively. Field observations and facies analysis show that the top of the Shihezi Formation is an erosive surface, marking a parallel unconformity between the Middle Permian and Lower Triassic. The Yingzi Formation is composed mainly of meandering river deposits, indicative of tectonic quiescence and low-relief landform in the Early to Middle Triassic. In contrast, the Dingjiagou, Xiabancheng, and Huzhangzi Formations are interpreted as the deposits of sandy/gravelly braided rivers, alluvial fans, fan deltas, and deep lakes in association with volcanism, thus indicating an intense rifting setting. A new Triassic lithostratigraphic division is proposed according to age constraints and facies analysis, and the results are of significance for understanding the early Mesozoic tectonic evolution of the Yanshan belt.展开更多
文摘据光明网2012年9月6日报道，中科院古脊椎动物与古人类李淳科研小组在华南海相三叠纪地层中首次发现的陆生初龙类富源滇东鳄（ Diandongosuchus fuyuanensis gen. et．nov）化石，不仅丰富了初龙类化石在亚洲的记录，而且进一步表明云贵地区的海相三叠系化石动物群并非是一个单纯的海洋生物化石组合。2012年9月出版的美国《古脊椎动物学杂志》刊发了该项研究成果。
文摘在江西修水四都镇东岭村发现了一个连续的、出露完好的二叠纪-三叠纪界线地层剖面。在剖面中有一段厚约2.1m 的地层具有指示海平面下降的岩石组构。这段地层的底部为红色的碳酸盐颗粒岩。红色是颗粒表面的红色铁染,成分为褐铁矿,是出露地表风化形成的。这层红色颗粒岩之上有约2.0 m 的去白云石化灰岩,其中保留了原来粉晶白云石的晶形。去白云石化作用是白云岩受淡水影响而发生的,指示海平面下降事件。这段地层之上是厚1m 的颗粒岩和灰泥岩,代表浅水潮下环境。其上是二叠系-三叠系的界线。这段地层之下的地层中生物丰富多样,并且有复(蜒)、钙藻等大绝灭前的生物。这段地层及其以上的地层中生物种类很少,(蜓)、钙藻等已经消失,表明集群绝灭事件开始于这段地层之下,生物大绝灭的发生与海平面下降事件的发生是基本同时的。由此认为,可能是海平面下降有关的环境剧变事件引发了二叠纪末的集群绝灭事件。
基金国家科技重大专项(编号:2016ZX05004-004,2016ZX05004006-006),国家自然科学基金项目(编号:41372121,41502004)联合资助.[Co-Funded by the Major National Science-Technology Projects of China(Nos.2016ZX05004-004,2016ZX05004006-006),and the National Natural Science Foundation of China(No.4137
基金supported by the National Natural Science Foundation of China(Grant Nos.91114204 and 40972151)
文摘Age determinations of the Triassic lithostratigraphic units of the Yanshan belt were previously based on plant fossils and regional correlations of lithologies. The Liujiagou and Heshanggou Formations were assigned as the Lower Triassic, and the Ermaying Formation was regarded as the Middle Triassic. We carried out a geochronologic study of detrital zircon grains from the Triassic sandstone in the Xiabancheng and Yingzi basins in northern Hebei where the Triassic strata are exceptionally well preserved. The results show that the Liujiagou, Heshanggou, and Ermaying Formations are all Late Triassic in age. The ages of detrital zircons also revealed that the upper part of the Shihezi Formation and the overlying Sunjiagou Formation, both of which were thought to be the Middle-Late Permian units, are actually late Early to Middle Triassic deposits. This study combines the upper Shihezi and Sunjiagou Formations into a single unit termed as the Yingzi Formation. We also substitute the widely-used Liujiagou, Heshanggou, and Ermaying Formations with the Dingjiagou, Xiabancheng, and Huzhangzi Formations, respectively. Field observations and facies analysis show that the top of the Shihezi Formation is an erosive surface, marking a parallel unconformity between the Middle Permian and Lower Triassic. The Yingzi Formation is composed mainly of meandering river deposits, indicative of tectonic quiescence and low-relief landform in the Early to Middle Triassic. In contrast, the Dingjiagou, Xiabancheng, and Huzhangzi Formations are interpreted as the deposits of sandy/gravelly braided rivers, alluvial fans, fan deltas, and deep lakes in association with volcanism, thus indicating an intense rifting setting. A new Triassic lithostratigraphic division is proposed according to age constraints and facies analysis, and the results are of significance for understanding the early Mesozoic tectonic evolution of the Yanshan belt.
