贵州省盘县地区羊圈-楚皮凹剖面中三叠统关岭组上段牙形石生物地层

Conodont Biostratigraphy of the Upper Member of the Guanling Formation in Yangjuan-Chupiwa Section,Guizhou Province,South China

选择贵州省盘县地区新民乡羊圈村附近羊圈-楚皮凹剖面中三叠统关岭组上段至杨柳井组下部地层进行牙形石生物地层再研究,补充描述牙形石Neogondolella constricta cornuta,Neogondolella constricta longa,Neogondolella constricta balkanica,Neogondolella alpina alpina,Neogondolella cf.Neogondolella acuta,Paragondolella excelsa和Paragondolella torna?sis等物种,丰富了该段地层牙形石多样性组成,并重新划分牙形石带,进行区内和区外对比。结果表明:1)羊圈-楚皮凹剖面关岭组上段至杨柳井组下部可划分5个牙形石带,自下而上为Nicoraella germanica带(未见底界)、Nicoraella kockeli带、Neogondolella bifurcata带、Neogondolella constricta带和Neogondolella constricta cornuta带(未见顶界);2)该段地层牙形石序列区内可与贵州省青岩剖面垄头组上部(台缘斜坡)、关刀(2)剖面关刀岩楔(盆地边缘相)同名化石带对比,区外与西特提斯生物区菊石binodosus带、trinodosus带、reitizi带内的牙形石面貌组成相似;3)进一步证明该段地层时代为中三叠世安尼期Pelsonian亚期至Illyrian亚期中晚期,但未进入拉丁期。

The conodonts biostratigraphy from the Upper Member of the Guanling Formation to the basal Yangliujing Formation in Yangjuan-Chupiwa Section was re-analysed and the conodont Neogondolella constricta cornuta, Neogondolella constricta longa, Neogondolella constricta balkanica, Neogondolella alpina alpina, Neogondolella cf. Neogondolella acuta, Paragondolella excelsa, Paragondolella tornasis were described. Based on the stratigraphical distribution and morphological variations of these conodonts, five conodont zones were re-established and the relevant biostratigraphic comparisons were made. The results reveal that： 1） From the Upper Member of the Guanling Formation to the basal Yangliujing Formation, five conodont zones can be investigated. In ascending stratigraphical order, they are Nicoraella germanica Zone （the bottom undefined）, Nicoraella kockeli Zone, Neogondolella bifurcata Zone, Neogondolella constricta Zone, and Neogondolella constricta cornuta Zone （the top undefined）; 2） These conodont zones are comparable to the same-named conodont zones of the Upper Longtou Formation at Qingyan Section （platform-margin slope） and of the Guandao wedge at Guandao （2） Section （basin-margin facies） in Guizhou Province, and these conodonts are also present in the ammonoid binodosus Zone, trinodosus Zone, and reitizi Zone in the West Tethys; 3） It further proves that the studied strata can be considered as the Pelsonian-Illyrian substages of the Anisian stage （Middle Triassic）, not going into the Ladinian of the Middle Triassic.