摘要
本文记述了黔北桐梓红花园山王庙剖面下奥陶统的胞石,计有4属、7种及1未定属种;讨论了胞石的层位与笔石带的关系,与世界同期地层作了对比,指出了Conochitina symmetrica和Desmochitina bulla的重要地层意义。
Gao (1980) was the first to publish information about early OrdovicianChitinozoa from China. He noted a diverse fauna from the Arenigian HongshiyanFormation in Wuding and Luquan,Yunnan.This fauna is a mixture betweenBaltoscandian and North African elements and yields such species as Cyathochitina calix, Cyathochitina? clepsydra, Eremochitina baculata, Lagenochitina esthonica (Grahn'spersonal observations, 1983). The chitinozoan assemblage is indicative of an EarlyArenigian age. The oldest known chitinozoans from China were reported fromyellow-green shales in the topmost part of the Fenxiang Formation (Upper Trem-adoc) in Yichang, Hubei (Hou & Wang, 1982; Geng, 1984). In the present study,a perspicuous investigation is made on Upper Tremadocian(Adelograptus-ClonograptusZone) and Arenigian chitinozoans from the Honghuayuan section in northernGuizhou. Zhen (1985)described a chitinozoan fauna from the upper part of theMeitan Formation in an adjacent section of this section. The Honghuayuan sectionis situated at Shanwangmiao about 8 km southeast of Tongzi(Fig.1). This sectionwas described by Zhang et al. (1962), and his lithology and stratigraphy arefollowed here. Lithology and stratigraphical ranges of the chitinozoan speciesare given in figure 2. The chitinozoan fauna from the Honghuayuan section consists of eight species(Fig. 2), of which two, Conochitina symmetrica and Desmochitina cf. bulla, areexcellent index fossils. Upper Arenigian specimens of Eisenackitina was previouslydescribed from Bohemia (Paris & Mergl, 1984), but otherwise are Eisenackitinospecies hitherto not known for certain from Tremadocian or Arenigian strataelsewhere. The Eisenackitina tongziensis specimens in the Honghuayuan sectionmight have a biostratigraphical value. The specimens herein referred to as Cono-chitina cf. ventriosa have a morphology similar to Conochitina (Fustichitina) ven-triosa Achab, known from Upper Tremadocian and Arenigian strata in Quebec,Canada. Huwever, only a few specimens in a bad state of preservation wereencountered in the Hunghuayuan Formation. The state of preservation is ingeneral bad, and this has prevented a satisfactory identification of the remainingfour species. Conochitina symmetrica has been described from the Adelograptus-Clonograptus and Tetragraptus approximatus zones, which is in agreement with itsoccurrence in the Honghuayuan section. Geng (1984) reported it as Conochitinasp. 1 and probable C. sp. 2 from lowermost Arenigian at Huanghuachang, Yichang,Hubei. Dcsmochitina bulla is a characteristic upper Arenigian species previouslyunreported from China, and the occurrence of similar specimens in the middlepart of the Meitan Formation suggests a late Arenigian age for this part of theformation. All together, the chitinozoan fauna confirms a late Tremadocian--Arenigian age for the investigated sequence.
出处
《微体古生物学报》
CSCD
北大核心
1990年第3期219-229,共11页
Acta Micropalaeontologica Sinica
