滇东奥陶纪三叶虫序列  

FAUNAL SUCCESSION OF ORDOVICIAN TRILOBITES IN EASTERN YUNNAN

作　　者：罗惠麟 周志毅[2] 胡世学 詹冬琴 卢玉喜 

机构地区：[1]云南省地质科学研究院,昆明650051 [2]中国科学院南京地质古生物研究所,南京210008

出　　处：《古生物学报》2014年第2期146-171,共26页Acta Palaeontologica Sinica

基　　金：国家自然科学基金(41221001;41290260;41172034)联合资助

摘　　要：滇东属于奥陶纪扬子地层区西缘的重要组成部分,本文系统描述该地区奥陶系8个层位的三叶虫,共计10科17属18种(其中包括1个新属种,即Daketia spinata gen.and sp.nov.),初步建立区内的三叶虫动物群地层序列,据此可靠确定有关地层的时代,包括:汤池组(特马豆克晚期—弗洛最早期)、红石崖组(弗洛早期—达瑞威尔最早期)、下巧家组(大坪期—达瑞威尔中期)、上巧家组(达瑞威尔晚期—桑比早期)。典型的红石崖组发育于滇东南部的昆明和宜良一带,其上部为含二叶石砂岩,假整合于泥盆纪石英砂岩之下,但是这部分层段在武定-寻甸一线以北地区并未见及,却沉积了一套砂岩、页岩、泥灰岩和白云质灰岩(即下巧家组);按区内地层发育的时空分布来判断,Zhou等(2011)提出的下巧家组和红石崖组上部应系同期异相沉积的观点得到证实。各地层单元的三叶虫动物群分异度低且均为扬子陆块浅水区的常见地方性分子(包括原来记录于越南北部的Vietnamia douvillei(Mansuy)),指示浅内陆棚环境。Eighteen Ordovician （late Tremadocian-early Sandbian） trilobite species, including one new form, Daketia spinata, belonging to 17 genera and 10 families are described from eight horizons of eastern Yunnan, an area that may have formed part of western marginal area of the Yangtze Block. The trilobite succession established herein affords reliable evidence for the age determination of each of trilobite-bearing stratigraphic units： the Tangchi Formation （ late Tremadocian-earliest Floian）, Hongshiya Formation （ early Floianearliest Darriwilian）, Xiaqiaojia Formation （early Dapingian-middle Darriwilian） and Shangqiaojia Formation （ late Darriwilian-early Sandbian ） （Text-fig. 2）. The Hongshiya Formation is typically developed in the south of eastern Yunnan round Kunming and Yiliang （Text-fig. 1）, with Cruziana sandstone in the upper, which is in turn disconformably covered by the overlying Devonian quartzose sandstone. The upper sandstone is however absent across a large area, north of Wuding- Xundian, where a set of sandstone, shale, muddy limestone and dolomitic limestone （the Xiaqiaojia Formation） was deposited instead. Judging from the regional stratigraphie context, we follow Zhou et al. （2011） in considering both the Xiaqiaojia Formation and the upper part of the Hongshiya Formation as heteropic deposits. Trilobite assemblages are all of low diversity in composition and nearly all the species are endemic to the shallow sites of the Yangtze Region, including a newly recorded Vietnamese Vietnarnia douvillei （Mansuy） ,indicating inner-shelf environments. There are two highly endemic asaphid trilo- bites in our collection. One is Fenghuangchengia, established by Luo （1979） from the basal part of the Xiaqiaojia Formation （early Dapingian） at Daketi of Luquan and Gengdi of Ludian, with F. binodosa Luo as its type species, which is rede- scribed in the present paper. The genus is closely comparable with the coeval form Eoisotelus Wang, 1938 recorded from North China.

关 键 词：三叶虫 序列 奥陶纪 滇东 

分 类 号：Q915[天文地球—古生物学与地层学]