摘要
滇东南位于奥陶纪扬子区的西南边缘,濒临古陆,水体较浅,沉积物中陆源碎屑丰富,而且因地壳升降运动幅度相对较大,导致了巨大的地层沉积厚度,仅含三叶虫地层就厚达385—2 080m,是我国奥陶纪三叶虫研究的空白地区。文中首次记述该地区下奥陶统下木都底组(下特马豆克阶)、独树柯组(上特马豆克阶)、闪片山组(特马豆克阶顶部—弗洛阶底部)、下奥陶统(弗洛阶)—中奥陶统上部(达瑞威尔阶下部)老寨组和中奥陶统顶部(达瑞威尔阶上部)—上奥陶统底部(桑比阶底部)冷水沟组的三叶虫序列,并系统描述了有关三叶虫,共计10科,15属,18种。其中特马豆克阶—达瑞威尔阶下部的三叶虫与鄂西和黔北所产最为相似,与川南及渝南一带同期分子也有关联,而达瑞威尔阶上部—桑比阶底部的分子则与黔北十字铺组动物群并无差异,代表当时滇黔隆起边缘的浅水动物群。对Mansuy(1920)描述的越南北部下奥陶统下部Dong Son组的三叶虫作了厘定,但由于有关材料保存太差、种级单元的鉴定特征模棱两可,目前暂无法得以在区内沿用。
Faunal evidence suggests that southeastern Yunnan formed part of the Ordovician Yangtze Region （Chang, 1965; Lu etal., 1976; Lai etaZ., 1982; Wang et al. , 1996; Zhou et al., 2001, 2008）. Located to the east of Mengzi and Qiubei, the north of Vietnam and the northeast of the Honghe Fault （Text-fig. 1） between 103°--106° E and 22°20′--24°20′ N, the area contains extensive exposures of thick Ordovician shallow-sea clastics and terregenous carbonates, indicating a marginal setting close with lands. The trilobite-bearing beds vary in thickness from 385 m to 2 080 m in the area, but almost no trilobites have been described before. For the first time, this paper depicts the stratigraphic succession of trilobite faunas （Text-fig. 2） from southeastern Yunnan with systematic descripion of 18 species assigned to 15 genera and 10 families from 10 horizons respective of the Early Ordovician Xiamududi Formation （early Tremadocian）, Dush- uke Formation （late Tremadocian）, Shanpianshan Formation （latest Tremadocian--earliest Floian）, the Early--Middle Ordovician Laozhai Formation （Floian--early Darriwilian）, and the Middle--Late Ordovician Lengshuigou Formation （late Darriwil- ian--earliest Sandbian）. Trilobites are mostly poorly preserved, but share a large number of species with the Tremado- cian--early Darriwilian sequence of western Hubei, northern Guizhou, southern Sichuan and southern Chongqing, except for Sthenarocalymene sp. , the genus of which being erected in the upper- most Darriwilian from the Oslo region of Norway by Siveter （1977） is recorded in the Yangtze Re- gion for the first time. Whereas, during the late Darriwilian--earliest Sandbian, trilobites dwelled in southeastern Yunnan are indistinguished from those of northern Guizhou （as described from the Shihtzupu Formation, see Zhou et al. , 1984）, and may have formed a single shallow water fauna distributed along the marginal area of the then unified Dianqian （Yunnan-Guizhou） Uplift. The Ordovician stratigraphic sequence and faunal aspects of southeastern Yunnan seem closely comparable with that of neighbouring northern Vietnam. In the latter area only the Lower Ordovician trilobites were described by Mansuy （1920） from the Dong Son Formation, including Asaphopsis jacobi, A. reedi [-as a junior synonym of jacobi, see Jell and Stait （1985）], Ogygites？ annamensis E = Asaphopsoides annamensis ; see Jell and Stait （1985）-], Isotelus stenocephalus （in au- thors＇ view, it is referable to Asaphellus）, Annarnitella asiatica, and Prosopiscus cheiruroides （in authors＇ view, it is referable to Annamitella）. However, due to the related forms being erected on the basis of poorly preserved specimens, all of them show ambiguous diagnostic characters and none of them can be employed in identifying any species of the coeval Yunnan fauna yet.
出处
《古生物学报》
CAS
CSCD
北大核心
2014年第1期33-51,共19页
Acta Palaeontologica Sinica
基金
国家自然科学基金(41221001
41290260
41172034)资助
关键词
地层纪录
奥陶纪三叶虫
滇东南
Stratigraphical record, Ordovician trilobites, southeastern Yunnan
