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在湖北省建始县北部细沙坝剖面志留系最上部发现腕足动物及几丁类化石。腕足动物组合以华美瓦尔达贝(Valdaria lauta)为典型分子,属于秀山动物群第二组合带;同时根据几丁类的组合带延限,综合分析确定其时代为特列奇中期,相当于秀山组上段的中部。鉴于与典型纱帽组在岩性、时代的明显差别,鄂西地区的来凤、咸丰、鹤峰、宣恩、恩施、建始、巴东等地的这套以往称作纱帽组的地层改称为秀山组为宜。建始细沙坝与桐梓韩家店、石阡雷家屯、秀山溶溪、宣恩高罗、宜昌大中坝等五地志留系对比说明,上扬子区各地志留系兰多维列统的顶界是参差不齐的,其中秀山的相关地层顶界最高,桐梓和宜昌的最低。上述情况反映当时海域沉积受广西运动的直接影响,导致地壳上升,从而海水退尽,岩层差异剥蚀强烈,此系华夏古陆向西北方向显著扩张的结果。
The brachiopods and chimpanzees were found in the uppermost part of the Silurian in the Xisha Sag, northern Jianshi County, Hubei Province. Brachiopods combined with Valdaria lauta as the typical molecule belonged to the second group of Xiushan fauna. At the same time, according to the combination of the two species, Middle of the upper section of the group. In view of the obvious difference with the typical yarn-cap group in lithology and age, the strata formerly called the yarn cap group in Laifeng, Xianfeng, Hefeng, Xuan’en, Enshi, Jianshi, Badong in Western Hubei are renamed as Xiushan Group is appropriate. The beginning of the fine sand dam and Tongzi Han shop, stone path Lei Jiatun, Xiushan melting Creek, Xuan Goulou, Yichang Dazhong and other five places Silurian comparison shows that the uplift of the Silurian Lan Duo Weilei system Top is uneven, of which Xiushan the highest stratigraphic top strata, Tongzi and Yichang lowest. The above situation shows that the sediments in the sea were directly affected by the Guangxi movement at that time, leading to the rise of the crust, thus the seawater was depleted and the denudation of the strata was strongly denuded. This was the significant expansion of the Huaxia paleosol to the northwest.