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浙江常山黄泥塘剖面在1996-1997年被国际奥陶系分会和国际地质科学联合会(IUGS)确立为全球中奥陶统达瑞威尔阶(Dariwillian)层型剖面。从该剖面守国组Azygograptus suecicus-Exigraptus clavus笔石带 至Undulograptus sinicus笔石亚带下部的页岩及灰岩中获得丰富的,保存不很好的疑源类化石。它们包含26个形态属,41个已知种和12个未定名种。该宁国组疑源类组合极少有环冈瓦纳古陆的‘冷水’类型。根据疑源类类型在地层柱的首次出现,可划分两个与Azygograptus suecicus和Undulograptus austrodentatus笔石带相吻合的疑源类生物地层单元。结合中国南方在奥陶纪的古地理位置加以讨论,当前疑源类组合表明,中奥陶世环冈瓦纳古陆的‘冷水’洋流至下扬子区已很微弱。
Zhejiang Changshan Huangniatang section was established by the International Ordovician Branch and the International Geological Consortium (IUGS) as the global middle-Ordovician Dariwillian profile in 1996-1997. From this shale shoal group, the Azygograptus suecicus-Exigraptus clavus penne belt to the lower part of the Undulograptus sinicus penicilli shale and limestone is rich and well-preserved fossil of doubtful origin. They contain 26 morphological, 41 known and 12 unidentified species. The Ningguo Formation has very few “cold water” types of Huanghuanwalan paleosol. Based on the first appearance of the suspected source type in the stratum, two suspected biostratigraphic units can be divided into two zones consistent with Azygograptus suecicus and Undulograptus austrodentatus peninslids. Combined with the discussion on the paleogeographic location of Ordovician in southern China, the current combination of provenances shows that the cold current of the Central Ordovician Central Gondwana is very weak to the Lower Yangtze region.