西藏申扎地区的下泥盆统

申扎地区的下泥盆统出露良好、沉积连续、构造单一,生物化石丰富,门类也较为齐全。根据多门类生物化石将下泥盆统进行了划分与对比。在塔尔玛达尔东组为一套以碳酸盐岩为主的沉积地层,中间夹有少量粒级较细的碎屑岩,属于稳定陆棚浅海型沉积。根据岩性和岩相特征可以明显划分为下部和中上部,下部灰岩中产有牙形石、竹节石和头足类,并含有丰富珊瑚和腕足类化石;中上部含有较丰富的珊瑚、腕足类等底栖生物化石,并含有竹节石、牙形石和头足类等游移生物化石。该组的时代为早泥盆世,包括Lochkovian大部以及整个Pragian、Emsian期。

LOWER DEVONIAN SUCCESSlON IN THE XAlNZA AREA,Xizang

The Xainza area is so ideal for the study Lower Devonian stratigraphy and paleontology in northern Xizang because of good exposure,continuous sections,simple structure,and diverse fossils.The Lower Devonian is represented by the Daerdong Formation.In the Tarema area,the Daredong Formation is mainly composed of a set of laminate carbonate with rare fine clastic rock,and it is interpreted as stable shelf shallow sea sediment.It can be divided into the lower part and the middle-upper part according to lithologic and lithofacies characters.The limestone of lower part bears conodonts,tentaculitids,cephalopods,abundant corals,and brachipods.The middle-upper part yields abundant benthonic fossils,such as corals and brachipods,and a few pelagic fossils such as conodonts,tentaculitids,and cephalopods.According to the Early Devonian fauna in the Xainza area,the authors consider the age of the succession is likely Lochkovian,Pragian,and Emsian.