Environmental change and process of mass extinction of Paleozoic oranisms in Yangtze Block during Late Paleozoic to Early Mesozoic time

扬子地块晚古生代-早中生代环境变化与古生代生物大绝灭过程本项目的主要目的是研究二叠纪末环境变化与古生代生物大绝灭过程。通过对扬子地块二叠纪-三叠纪连续地层层序的研究，重点阐明了珊瑚、放射虫、牙形石和镰刀虫等大小化石的垂向分布规律。此外，我们还对扬子地块上的黔西和桂中-桂西地区的二叠-三叠系沉积环境进行了重建。本研究选取了贵州1-7、广西8-12两个剖面进行研究.臭祖山（安顺以北17公里），G-H-I，20米; 2. Maoshachin（紫云以南34 km），D-G-I，400米; 3.赛洼（紫云南18 km），P3，1100米;大津町（贵阳），E-G-H-I，240米; 5.都拉营（贵阳），C ...更多信息 -E-G-I-J，40 m + ; 6.大旺沙（贵阳南85公里），D-G-I-K，220米; 7.那水（罗甸西南40公里），D3-T1 ; 8.东天岩（柳州以南20 km），A-B，40 m + ; 9.牛木坪（柳州东北10 km处），F-H，200 m + ; 10.里那浪（平果东北偏东20公里），D3-T1，450米以上; 11.茨坪（平果西北20公里），A-C-F-K，70米以上; 12. Guofualungchiu（平果以西20 km），P-T1，50 m+（A）Chibsia组[P21] ;（B）Kufebg组。：（C）茅口组。[P2，2] ;（D）吴家坪组;（E）龙潭组。：（F）Hoshan组。[P31]（G）长兴组;：（H）Talung Fm. [P32]（I）Tayeh Fm.：（J）叶朗组（Yehlang Fm.）：（K）罗楼组[T11]在每个剖面中，进行了岩石和生物地层学研究，并对化石和沉积岩进行了系统取样。上二叠统可划分为碳酸盐岩相、碎屑岩-改造碳酸盐岩相、碎屑岩-硅质岩相三种岩相，分别相当于台地相、斜坡相和盆地相沉积。最上部的二叠统被下三叠统碎屑岩整合覆盖。沉积相龙潭组为三角洲成因的向上变粗层序，偶见潮坪沉积。钙质浊积岩相局部表现为旋回沉积，表现为向上减薄的叠置层序。下三叠统碎屑岩相为浅海沉积，普遍存在丘状交错层理。生物相中二叠世的皱纹珊瑚很常见，但在上二叠世（吴家坪组和长信组）则很稀少。珊瑚是相依赖的，在分类组成方面因地区而异。最上层的二叠纪石灰岩偶尔含有丰富的海绵，并显示鸟瞰结构。放射虫丰富，特别是在大隆组硅质岩中。少

Environmental change and process of mass extinction of Paleozoic organisms in Yangtze Block during Late Paleozoec to Early Mesozoec timeThe main purpose of this project was to study the environmental changes and the processes of mass extinction of Paleozoic or, anisms at the end Permian. Emphasis was placed to clarify the vertical distributions of such mega- and microfossils as corals, radiolarians, conodonts and fusulinids through continuous straligraphc successions of the Permian to Triassic in the Yangize Block. In addition, we aimed to reconstruct the sedimentary environments across the Permian-Triassic boundary.The studied areas were west Guizhou and central to west Guangxi both on the Yangize Block. Following twelve sections (1-7 in Guizhou and 8-12 in Guangxi) were studied.1. Chouzushan (17km north of Anshun), G-H-I, 20m ; 2. Maoshachin (34km south of Ziyun), D-G-I, 400m ; 3. Saiwa (18km south of Ziyun), P3, 1100m ; 4. Taizucho (Guiyang), E-G-H-I, 240m ; 5. Duraying (Guiyang), C … More -E-G-I-J, 40m+ ; 6. Dwansha (85km south of Guiyang), D-G-I-K, 220m ; 7. Nashui (40km southwest of Luodian), D3-T1 ; 8. Tungtienyien (20km south of Liuzhou), A-B, 40m+ ; 9. Niumuping (10km northeast of Liuzhou), F-H, 200m+ ; 10. Linalang (20km east-northeast of Pingguo), D3-T1, 450m+ ; 11. Tsiping (20km northwest of Pingguo), A-C-F-K, 70m+ ; 12. Guofualungchiu (20km west of Pingguo), P-T1, 50m+(A) Chibsia Formation [P21] ; (B) Kufebg Fm. : (C) Maokou Fm. [P2, 2] ; (D) Wujiaping Fm. : (E) Lungtan Fm. : (F) Hoshan Fm. [P31] ; (G) Changxing Fm. : (H) Talung Fm. [P32] ; (I) Tayeh Fm. : (J) Yehlang Fm. : (K) Luolou Fm. [T11]In each section, litho- and biostratigraphic studies and systematic sampling of fossils and sedimentary rocks were carried out.1. LithofaciesThe Upper Permian is divided into three lithofacies ; carbonate, clastic and reworked-carbonate, and clastic and siliceous facies, which are equivalent to platform, slope and basin sediments, respectively. The uppermost Permian is conformably overlain by the Lower Triassic clastic rocks.2. Sedimentary faciesThe Lungtan Formation reveals coarsening-upward sequences of a deltaic origin as well as occasional occurrences of tidal flat deposits. The calcareous turbidite facies locally shows cyclic sedimentation demonstrated stacked thinning-upward sequences. Clastic facies of the Lower Triassic is interpreted as the shallow marine deposits as revealed by common presence of hummocky cross-stratification.3. BiofaciesRugose corals are common in the Middle Permian, but are sparse in the Upper Permian (Wujiaping and Changxin, Formations). Corals are facies-dependent and are variable in taxonomic composition from area to area. The uppermost Permian limestones occasionally contain abundant sponges and show bird's-eye structure. Radiolarians are abundant, especially in the Talung Formation of siliceous rocks. Less