贵州青岩剖面青岩阶上部牙形石的发现及其意义

在贵州青岩剖面的青岩组之上,原被认为是拉丁期的垄头组下部的层段中发现了牙形石动物群,除少量的分枝分子外,都归属于Neogondolella属,可鉴定为4个种,即Neogondolella bifurcata,N.constricta,N.mombergensis和N.navicula.建立了2个牙形石带,自下而上是Neogondolella bifurcata带和N.cinstricta带.牙形石面貌证明这段地层在时代上非常接近但尚未进入拉丁阶,属于安尼期中晚期,进一步的牙形石工作将很有可能在目前发现的牙形石层段的上部寻找到安尼阶和拉丁阶之间的界限,从而为青岩阶顶界的限定提供可靠的牙形石证据.此外,牙形石的发现还初步实现了青岩阶2大主导门类化石--牙形石和菊石在同一剖面的直接对比关系.

Discovery of the Upper Qingyanian Conodonts in the Qingyan Cross-Section of Guizhou and Its Significance

A group of conodonts were discovered in the sequence overlying the Qingyan cross-section of the Qingyan Formaiton in Guizhou,previously considered as the Lower Longtou Formation of Ladinian period.Except few ramiform elements,most elements are classified into the Genus Neogondolella,four types of which have been identified,i.e.Neogondolella bifurcata,N.constricta,N.mombergensis,and N.navicula.Two conodont zones have been established from bottom to top:Neogondolella bifurcata zone and N.constricta zone.The appearance of conodonts indicates that the strata of this period was close to but not enter the Latinian period,belonging to the mid-and late-Anisian.This will further help define the boundary between the Anisan and the Latinian and provides reliable evidence for defining the top limit of the Qianyan Formation.Additionally,the discovery of conodonts has preliminarily realized the comparison between the two main fossils of the Qianyannian-conodont and ammonites.