陕西省镇安县任和沟碳质大化石的发现及镇旬地区构造演化

Carbonaceous Megafossils from Renhegou, Zhenan, Shaanxi Province and Tectonic Evolution in Zhenan-Xunyang District

碳质大化石为广布于世界各地和我国秦岭南北的晚前寒武纪特征化石。笔者在陕西省镇安县原志留系地层中首次发现其球形、似球形类的Chuaria,包括Chuaria circularis Walcott和Shouhsienia shouhsienensis Xing两个属种;同时在化石产层中测得183Ma的Rb—Sr同位素年龄。这些成果表明镇旬地区可能存在由晚前寒武纪地层构成的滑脱片体或早古生代微陆块。其深入研究对前寒武纪生物和地层、秦岭古生代构造演化以及秦岭区测都有重要意义。

The carbonaceous megafossils from Renhegou, Zhenan County, Shaanxi Province contain 2 species, namely: Chuaria circularis Walcott and shouhsienia shouhsienensis Xing. It is first reported from QinLing, orogenic belt. According to the extensive distribution of carbonaceous megafossils in Precambrian strata in China and other countries, the strata distribuitng in Zhenan—Xunyang, in which fossils was found, must belong to Precambrian instead of Silurian, which means Zhenan-Xunyang district was a small continental block in early Paleozoic.