滇西亲冈瓦纳相生物群特征及地层时代的重新厘定

BIOTA FEATURES OF THE GONDWANA AFFINITY FACIES AND REVIEW OF THEIR STRATIGRAPHIC AGES IN THE WESTERN YUNNAN

滇西保山地区丁家寨组及其上覆卧牛寺组,前人根据其中(虫筳)类化石定为上石炭统(马平阶),沿用至今。笔者在该区多门类化石中,见到不同时代的化石混积在一起,包括异地再沉积的早石炭世腕足类Syringothyris,石炭纪的(虫筳)类、珊瑚等。原地埋藏的腕足类有Steriochia litostyla等,并保存有完好的壳刺。厘定后的时代为Sakmarian晚期至Artinskian,它可与西藏的冈瓦纳相地层及生物群进行对比。 滇西腾冲地区空树河组及其上覆的岩子坡组,前人因其含(虫筳)Triticites,Quasifusulina等也定为上石炭统。实际上,空树河组中、上部的多门类化石(包括腕足类、苔藓虫、单体珊瑚和微古植物等),与丁家寨组相似,具有强烈的二叠纪面貌,与冈瓦纳相更为接近。厘定空树河组时代为Sakmarian—Chihsian,它与西藏的相应地层可以很好地进行对比。

The most marked Gondwana facies developed during the Permian Asselian to Artin- skian. There are strata of the same age with the Gondwana affinity biota in the western Yunnan. The Dingjiazhai Formation and its overlying Woniusi Formation in the Baoshan region were referred to as Upper Carboniferous(the Maping Stage ) by predecessors. The authors have found fusulinids. corals, brachiopods and bryozoans from the strata, where fossils of different ages were redeposited and mixed together, including reworked Lower Carboniferous brachiopods Iike Syringothyris, Carboniferous fusulinids, Corals and au- tochthonous brachiopods like Steriochia litostyla which was in good preservation, with well preserved spines. The age of the strata is, therefore, revised as Late Sakmarian to Artin- skian. The fossils and strata mentioned above can be correlated with those of the Tibetan Gondwana facies. The Kongshube Formation and the succeeding Yanzipo Formation in the Tengchong . region were referred to as Upper Carboniferous by former workers, according to fusulinlds such as Triticites and QuaSifusulina. In fact, the fossils (brachlopods. bryozoans, single corals and microflora ) found from the middle and upper parts of the Kongshuhe Formation are quite similar to those of the Dingjiazhai Formation with strong Permian features and close to the Gondwana facies. Thus, the Kongshuhe Formation is revised as belonging to ' Sakrnarian to Chihs1an in age and it can be correlated with equivalent strata in Tibet.