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四川长宁位于奥陶纪华南陆块西部,临近奥陶纪康滇古陆,早及中奥陶世充足的陆源供应和局部快速沉降,在该区沉积了一套浅海相的陆源碎屑岩。长宁双河剖面早奥陶世晚期及中奥陶世地层共发现有三叶虫6科8属18种,根据共生笔石,初步建立区内大官山组(弗洛期—达瑞威尔最早期)和大沙坝组(达瑞威尔期)的三叶虫序列。除Asaphidae科的Liomegalaspides的分布几乎贯通两组的始终(filiformis-murchisoni带)外,Nileidae科的Psilocephalina和Psilocephalops分布局限于approximatus-eobifidus带;Taihungshaniidae科的Taihungshania高度分异,共有4种之多,分布于approximatus-hirundo带;Calymenidae科的Neseuretus也有4种之多,分布于hirundo-clavus带和intersitus带;Trinucleidae科的Hanchungolithus sp.分布于clavus-austrodentatus带;Leiostegiidae科的Pseudocalymene包括2种,分布于intersitus-murchisoni带,Annamitella sp.分布于murchisoni带。基于Zhou等(2011)对大官山组的三叶虫相所做研究,根据各层段三叶虫的组成、优势分子和分异度,认为approximatus-filiformis带的三叶虫属于Psilocephalina相(白云质泥岩),eobifidus-suecicus带三叶虫属于Taihungshania相(页岩、粉砂质页岩),hirundo带三叶虫属于Neseuretus相(粉砂质页岩),clavus-austrodentatus带三叶虫属于Liomegalaspides相(钙质页岩),大沙坝组(intersitus-murchisoni带)主体层段的三叶虫仍以Liomegalaspides占优,三叶虫相类型应与下伏地层(clavus-austrodentatus带)相同。长宁地区弗洛期—达瑞威尔期的岩相和生物相指示了向上逐渐加深的浅水内陆棚环境,但是即使在大坪期和达瑞威尔期的较大海侵期,水深仍应在70m以内。长宁双河的三叶虫多样性在hirundo带达到一个峰值,以Neseuretus(Calymenidae)和Hanchungolithus(Trinucleidae)为代表的Whiterock动物群在剖面中首次出现。
Located in the western part of Ordovician’s southern China block, Changning, Sichuan is near to Ordovician Kangdian ancient land, early and middle Ordovician abundant terrigenous supply and partial rapid subsidence, and a set of shallow-sea terrigenous clastic rocks was deposited in the area. There are 18 species, 8 genera, 6 families, and 18 species found in the Late Early Ordovician and Middle Ordovician strata in the Shuanghe section of Changning. Based on the symbiotic penoliths, the Dashanshan Formation (Floyd- Daruiweier The earliest) and the Dashaba Formation (Daruiweier period) trilobite sequence. The distribution of Psilocephalina and Psilocephalops in the Nileidae family is limited to the approximatus-eobifidus zone except for the Liomegalaspides in the Asaphidae family, which distributes almost always in both groups. There are 4 species of Taihungshania in the Taihungshaniidae family, There are also four species of Neseuretus in the Calymenidae family, distributed in the hirundo-clavus and intersitus belts. Hanchungolithus sp. In the Trinucleidae family is distributed in the clavus-austrodentatus belt. There are two species of Pseudocalymene in the family Leiostegiidae, distributed in intersitus -murchisoni band, Annamitella sp. distributed in murchisoni band. Based on the study by Zhou et al. (2011) on the trilobite phase in the Dashanshan Formation, the trilobite belonging to the approximatus-filiformis belonged to the Psilocephalina facies based on the composition, Dolomitic mudstone), eobifidus-suecicus with trilobite belong to the Taihungshania facies (shale, silty shale), hirundo with trilobite belong to Neseuretus facies (silty shale), clavus-austrodentatus with trilobite belong to The trilobites in the Liomegalaspides facies (calcareous shale) and intersotus murchisoni belts still dominate with Liomegalaspides and the trilobite facies should be the same type as the underlying formations (clavus-austrodentatus belts). The lithofacies and biofacies of the Floyd-Darwillian Period in the Changning area are indicative of a shallow-shelf inland environment progressively deepening, but even in the larger transgression of the Daping and Daruiweis periods, the depth should be between Within 70m. The trilobite diversity in Shuanghe of Changning reaches a peak in the hirundo zone, and the Whiterock fauna represented by Neseuretus (Calymenidae) and Hanchungolithus (Trinucleidae) first appeared in the profile.