甘肃靖远石炭系研究新进展

<正> 甘肃靖远磁窑的石炭系出露完整,富含生物化石,李星学等(1974)作了较详细研究,奠定了本区石炭系层序的基础,首次建立了西北地区属于纳缪尔期的地层单元——靖远组。此后,不少地层和古生物工作者在对靖远磁窑石炭系作过调查,高联达对下石炭统作过孢粉研究(1980),王志浩、王成源(1983),史美良、赵治信(1985)对该区石炭系部分层

New advance in the study of Carboniferous rocks of Jingyuan, eastern Gansu

Since the study by Lee et al. (1974) of the Carboniferous biostratigraphy of Jingyuan District, E. Gansu, the Tsingyuan Formation with rich characteristic Namurian biotas has been known widespread in NW China, especially well represented at the SE edge of the northern Mt. Qilian.In the Yushuliang-Hongtuwa-Dashuigou section located at the Ciyao Coal Mine of Jingyuan, the Carboniferous strata attain a thickness of about 624 m of alternations of marine and non-marine rocks. On the basis of recent biostratigraphic and lithostratigraphic studies, the Carboniferous in Jingyuan area is composed of, and redivided into, descendingly the Yanghukou Fm. (Early Westphalian), the Hongtuwa Fm. (Late Namurian A-Earliest Westphalian), the Tsingyuan Fm. (Early Namurian A), the Chouniukou Fm. (Visean) and the Qianheishan Fm. (Tournasian).Within this stratigraphic sequence of marine and non-marine facies the completeness of the lithps-tratigraphic record showing no perceptible break and the abundance of palaeontologic materials are ideal for the designation of a boundary stratotype for :.he Upper and Lower Carboniferous of China.The boundary for this stratotype is proposed at the contact between the Hongtuwa and Tsingyuan Fms., mainly because the significant conodont species Declinognathodus noduliferui was the first occurrence to be associated with Neognathodus symmciricus at the lowest limestone of the Hongtuwa Em., and because the marine intercalations in the upper part of the Tsingyuan Fm. yield typical goniatites Eumorphoceras bisulcatum, E. kansuense, along with conodonts like Gnathodus bilincatus bollandensis, all indicating an E2 stage of the longstanding goniatitic zone-sequence for the Carboniferous of Europe.The Tsingyuanian represents a period of continuous deposition ranging from the flint limestone-bearing Chouniukou Formation (Late Visean) below and the Hongtuwa Formation containing conodont limestone of Zone H above, characterized predominantly by such faunas as ammonoids Eumorphoceras-Cra-venoceras and conodont Gnathodus bilineatus bollandensis, and plants Eleutherophyllum waldenburgense, Sphenophyllum lenerrimum and by many of Westphalian floras like a variety of Linopteris, along with sporo-pollen assemblage zones TA and VR, all serving as the distinguishable marks for its biota (zone), i.e. Early Namurian E, with the Tsingyuan Formation as its lithostratigraphical unit. Lithostratigraphically, the Carboniferous of Jingyuan area is laid mainly in a paralic platform with local basins separated by barriers through margin facies to terrestrial swamps, which places it between continental and open-sea areas of deposition.