Lower Cambrian Small Shelly Fossils of northern Sichuan and southern Shaanxi (China), and their biostratigraphic importance
Lower Cambrian Small Shelly Fossils of northern Sichuan and southern Shaanxi (China), and their biostratigraphic importance
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DOI：
10.1016/j.geobios.2003.08.001
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发表时间：
2004-03-01
期刊：
影响因子：
1.6
通讯作者：
Zhu, MY
中科院分区：
文献类型：
--
作者：
Steiner, M;Li, GX;Zhu, MY
近20年来，在扬子地台西缘（滇东、川中）浅水沉积中发现了大量下寒武统小壳化石（SSF）。然而，人们对扬子地台北方边缘SSF的时空分布知之甚少。本文报道了代表陕西西南地区的宽川铺（陕南宁强县）、沙滩、新立（均为北方南江县）和代表陕西东南-湖北西北地区的三郎铺、小湾（陕南西乡县）的SSF社团。本区下寒武统SSF地层自西向东厚度强烈减薄，地层间断增加。扬子地台北方边缘广泛分布着一个最早的寒武纪裂孔。与此同时，同生角砾岩发生在宽浅陆棚设置。可能与Rodinia分裂后冈瓦纳大陆的组装有关的构造运动可能是造成这一现象的原因。在宽川铺（宁强县）附近的剖面，梅树村阶（相当于西伯利亚的Nemakit-Daldynian至Tommotian）的层序包括约1000米。55米深的深色磷酸盐碳酸盐岩、粉砂岩和燧石。SSF组合与滇东的SSF组合相似，从上到下可划分为Anabarites trisulcatus-Protohertzina anabarica带、Watsonella yunnanensis带和Sinosachites flabelliformis-Tannuolina zhangwentangi带。在陕西西南部地区不能明确地发现三角管殖吸虫（Siphogonuchites triangularis）-亚球形副球孢菌（Paragloborilus subglobosus）带.早期报道的三沟Anabarites-Anabarica Protohertzina带内胚胎和卵的出现是值得注意的。对Olivoides/Punctatus的生活史和分类学处理进行了重新讨论。本文介绍了陕东南-鄂西北地区缺失的最早SSF组合（Anabarites trisuncatus Protohertzina anabarica带至Watsonella yunnanesis带）和Ninella tarimensis-Cambroclavus fangxianensis组合带和Rhombocorniculum cancellatum Taxon山脉带。(C)2004年，Elsevier SAS。All rights reserved.
Extensive information has been acquired on the occurrence of Lower Cambrian Small Shelly Fossils (SSF) in the shallow water sediments of the western fringe of the Yangtze Platform (eastern Yunnan and central Sichuan Provinces) during the last two decades. However, less is known on the temporal and spatial distribution of SSFs on the northern margin of the Yangtze Platform. Here we report SSF associations from Kuanchuanpu (Ningqiang County, southern Shaanxi Province), Shatan, and Xinli (both Nanjiang County, northern Sichuan Province) representing the Southwest Shaanxi region and from Sanlangpu, and Xiaowan (Xixiang County, southern Shaanxi Province) of the Southeast Shaanxi - Northwest Hubei region. The thickness of the Lower Cambrian SSF-bearing strata strongly decreases in this region from West to East and the stratigraphic hiatus increases. An earliest Cambrian hiatus is widely distributed on the northern margin of the Yangtze Platform. At the same time, a syngenetic brecciation occurred in wide shallow shelf settings. A tectonic mobilization, possibly related to the assembly of Gondwana following the breakup of Rodinia, may be responsible for this. In sections near Kuanchuanpu (Ningqiang County), the Meishucunian (equivalent to the Nemakit-Daldynian to Tommotian of Siberia) succession comprises ca. 55 m of dark phosphatic carbonates, siltstones, and cherts. The SSF associations are similar to those of East Yunnan and, in ascending order, can be discriminated into the Anabarites trisulcatus - Protohertzina anabarica Zone, the Watsonella yunnanensis Zone (previously mentioned as Heraultipegma yunnanensis Zone), and the Sinosachites flabelliformis - Tannuolina zhangwentangi Zone. The Siphogonuchites triangularis - Paragloborilus subglobosus Zone cannot be unambiguously detected in the Southwest Shaanxi region. The occurrence of embryos and eggs within the Anabarites trisulcatus - Protohertzina anabarica Zone, which has been reported earlier, is remarkable. The previously reconstructed life cycle and taxonomic treatment of Olivooides / Punctatus are re-discussed. The earliest SSF associations (Anabarites trisulcatus Protohertzina anabarica Zone to Watsonella yunnanesis Zone) are missing in the Southeast Shaanxi - Northwest Hubei region and the Ninella tarimensis - Cambroclavus fangxianensis Assemblage Zone and Rhombocorniculum cancellatum Taxon Range Zone are introduced herein. (C) 2004 Elsevier SAS. All rights reserved.