论上扬子区上奥陶统大渡河组

发布时间：2018-05-29 21:38

本文选题：生物地层 + 笔石　；参考：《地层学杂志》2017年02期

【摘要】：在滇东北永善莲峰新发现的万和剖面,奥陶系-志留系交界地层发育良好、地层连续,化石丰富,含有笔石、腕足类、三叶虫、牙形类、几丁类和疑源类化石,包括了大渡河组、产Hirnantia动物群的观音桥层和龙马溪组。此处大渡河组可分为上、下两段,下段为灰岩与钙质泥页岩互层,上段为钙质泥岩夹灰岩。笔石自下而上可识别为Dicellograptus complexus带、Paraorthograptus pacificus带(下亚带、Tangyagraptus typicus亚带和Diceratograptus mirus亚带)以及Metabolograptus extraordinarius带,为凯迪晚期至赫南特早期。几丁类尚未在上段发现,下段属于Eisenackitina ripae带。上段底部(即Tangyagraptus typicus亚带底)产腕足类Kassinellasp.,Leptellinasp.,Paromalomenasp.等,属于深水BA5(底栖组合),在华南同期地层中未见及。观音桥层产典型的Hirnantia动物群,属于BA3,为标准的浅凉水组合。依据万和及相邻地区的资料,厘定了大渡河组。大渡河组分布于扬子台地西部(滇东北—川西南),与扬子台地内部广布的五峰组和扬子台地西南缘的铁足菲克组(大部分)、西缘的大箐组(上部)属同期异相。从产BA5腕足类的大渡河组上段底部,到产BA3赫南特贝动物群的观音桥层,再到龙马溪组下部黑色页岩,是奥陶纪末大灭绝第一幕和第二幕全球气候快速变冷和转暖、海平面迅速地先降后升在扬子海盆的充分反映。
[Abstract]:In the newly discovered Wanhe section of Yongshan Lianfeng in northeastern Yunnan, the Ordovician Silurian boundary strata developed well, the strata were continuous and rich in fossils, and contained graptolith, brachiopods, trilobites, odontoids, tetracyclines and suspected origin fossils. It includes the Daduhe formation, the Guanyinqiao layer and the Longmaxi formation of the Hirnantia fauna. Here the Daduhe formation can be divided into upper and lower sections, the lower part is interbedded between limestone and calcareous shale, and the upper member is calcareous mudstone intercalation. From the bottom to the top, graptolites can be identified as the Dicellograptus complexus belt, Paraorthograptus pacificus belt (lower subzone Tangyagraptus typicus and Diceratograptus mirus subzone) and Metabolograptus extraordinarius zone, which is from late Keti to early Hernant. Class D has not been found in the upper segment, the lower segment belongs to the Eisenackitina ripae zone. The bottom of the upper segment (that is, the bottom of Tangyagraptus typicus subzone) produces the brachiopod Kassinellasp.Leptellinasp.Paromalomenia. It belongs to the deep water BA5 (benthic assemblage), which is not found in the synchronic strata of South China. Guanyinqiao layer is a typical Hirnantia fauna, belonging to BA 3, which is a standard shallow cool water combination. Based on the data of Wanhe and its adjacent areas, the Daduhe formation was determined. The Daduhe formation is distributed in the western part of the Yangtze platform (northeast Yunnan and southwest Sichuan) and belongs to the same phase as the Wufeng formation, which is widely distributed in the interior of the Yangtze platform, and the Tiefike formation, which is located in the southwest margin of the Yangtze platform, and the upper part of the Daqing formation in the western margin. From the bottom of the upper member of the Daduhe formation of the BA5 brachiopod, to the Guanyinqiao layer of the BA3 Hernantebe fauna, and to the black shale in the lower part of the Longmaxi formation, it is the first act and the second act of the great extinction of the late Ordovician that rapidly cooled and warmed the global climate. Sea level rapidly falls first and then rises in the Yangtze basin fully reflected.
【作者单位】：现代古生物学和地层学国家重点实验室中国科学院南京地质古生物研究所;北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室(北京大学);
【基金】：国家自然科学基金(No.41521061;41530103;41290260)资助 IGCP591(The Early to Middle Paleozoic Revolution)项目成果之一
【分类号】：P534.42

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