Early Carnian conodont fauna at Yongyue, Zhenfeng area and its implication for Ladinian-Carnian subdivision in Guizhou, South China
Early Carnian conodont fauna at Yongyue, Zhenfeng area and its implication for Ladinian-Carnian subdivision in Guizhou, South China
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贞丰地区永岳早期卡尼期牙形刺动物群及其对贵州拉丁期-卡尼期细分的意义
DOI：
10.1016/j.palaeo.2017.02.011
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Wignall P. B.
中科院分区：
文献类型：
--
作者：
Zhang Z T;Sun Y D;Lai X. L.;Joachimski M. M.;Wignall P. B.
贵州地区拉丁期和卡尼期地层的划分一直是一个争论激烈的问题，因为缺乏可确定时代的动物群。本文对黔西永越剖面杨柳井组、竹竿坡组和瓦窑组的牙形石进行了详细的生物地层学研究。牙形刺仅在竹竿坡组和瓦窑组中多产。共鉴定出3属20种，其中包括2个新种--华南四头虫Quadralellawanensisn. sp.和四节藻Quadralella yongyueensisn.它们代表了卡尼早期相当特有的动物群。建立了四个牙形石带。从上到下依次为Paragondolella foliata、Quadralella polygnathiformis、Quadralella atadpole和Quadralellaaff. praelindae带，因此，研究区竹杆坡组的时代一般为卡尼早期（Julian 1），瓦窑组的时代可能从Julian 2延续到卡尼晚期（Tuvalian亚期）。由于缺乏菊石Daxatina canadensis和牙形刺，Ladinian-Carnian界线（LCB）无法精确界定。然而，LCB不可能低于杨柳井-竹竿坡组接触面。Julian 1-Julian 2（卡尼期早期）亚期界线以Julian 2菊石型Austrotrachycerasex gr.A的出现为界。austriacumand的消失也证明了上覆瓦窑组中大部分短距离Julian 1牙形刺的消失。
The subdivision of Ladinian and Carnian strata in Guizhou, South China has been a matter of intense debate because of the paucity of age-diagnostic faunas. Here we have carried out a detailed conodont biostratigraphic investigation on the Yangliujing, Zhuganpo and Wayao formations in the Yongyue section of western Guizhou Province. Conodonts are only prolific in the Zhuganpo and Wayao formations. Three genera and twenty species are identified, including two new speciesQuadralella wanlanensisn. sp. andQuadralella yongyueensisn. sp. They represent a rather endemic fauna of early Carnian age. Four conodont zones are established. They are, in the ascending order, theParagondolella foliata,Quadralella polygnathiformis,Quadralellatadpole, andQuadralellaaff.praelindaezones.Thus in the study area, the Zhuganpo Formation is generally of early Carnian (Julian 1) age whilst the Wayao Formation probably extends from the Julian 2 into the late Carnian (Tuvalian substage). The Ladinian–Carnian boundary (LCB) cannot be precisely defined due to the absence of the ammonoidDaxatina canadensisand the paucity of conodonts. However, the LCB is unlikely lower than the Yangliujing–Zhuganpo formation contact. The Julian 1–Julian 2 (early Carnian) substages boundary is defined in the uppermost Zhuganpo Formation by the occurrence of basal Julian 2 ammonoidAustrotrachycerasex gr.A. austriacumand is also evidenced by the disappearance of most short-range Julian 1 conodonts in the overlying Wayao Formation.