摘要
详细研究了广西凭祥剖面下-中二叠统界线(即Guadalupian统底界)附近的牙形石动物群,发现了M.idahoensis lam-berti-J.nankingens insankingensis演化系列和M.idahoensis.idahoensis-J.nankingensis gracilis演化系列混生现象。前者与温水型牙形石分子M.siciliensis,M.rustagensis和Sweetgnot hsuusbasymmetricus共生,后者与凉水型牙形石分子M.pro-longata和M.phosphoriensis共生。两个演化系列中温水型牙形石分子J.nankingensis nankingensis和凉水型牙形石分子J.nankingensi sgracilis首现在同一层位,从而准确地将Guadalupian统底界面标定在剖面中的第9-18层之底。在Guadalupian统底界附近的一套硅质灰岩标本中同时鉴别出混生的牙形石动物群,这说明在早-中二叠世转换期,来自高纬度区的凉水洋流上涌事件曾经发生并侵入到处于亚热带的扬子板块之中。
The mixed conodont faunas containing both the transitional morphocline from M. idahoenszs lamberti to J. nankingensis nankingensis and the morphoeline from M. ida. idahoensis to J. nan. gracilis were recovered from the base-Guadalupian boundary interval at Pingxiang section, southwestern Guangxi, South China. The former transitional morphocline coexists with typical warm-water conodont taxa such as M. siciliensis, M. rustagensis and Sweetgnothus subasymmetricus , while the latter morphocline coexists with M. prolongata and M. phosphoriensis which belong to cool-water conodont taxa. The base-Guadalupian series boundary is consistently indicated at the base of bed 9-18 by the first occurrence of J. nan. nankingensis and J. nan. gracilis within both transitional morphoclines. Recognition of mixed faunas in the same set of chert samples of base-Guadalupian boundary interval suggests that the upwelling of cool temperature currents had impact on the subtropical Yangtse Block during earliest Guadalupian.
出处
《地质科技情报》
CAS
CSCD
北大核心
2008年第5期47-53,共7页
Geological Science and Technology Information
基金
国家自然科学基金项目"华南陆内硅质岩模式及对二叠纪硅质岩事件的响应"(40572068)
