摘要
滇西保山地区在大地构造位置上介于怒江断裂带和澜沧江断裂带之间。段新华等(1983)发现下冈瓦纳相地层及古生物,对本区晚古生代古生物、地层和沉积相的研究为地质工作者所关注,关于上石炭统丁家寨组下部含砾层的成因解释是人们感兴趣的课题之一。王义昭(1983)、曹仁关(1986)等提出含砾层属于冰川—海洋相成因。
The pebble-bearing layer at the lower part of the Upper Carboniferous Dingjiazhai Formation in Baoshan region of Western Yunnan has been regarded as the glaciomarine deposits.The textures, structures and components of the pebble-bearing layer are restudied.The crude inverse grading and normal grading are present at the lower and upper parts of the pebble-bearing layer respectively.The elliptical and flat pebbles with better rounding which came from river and littoral area are composed of muddy siltstone, quartzite, silicolite and lithic sandstone.The predominent limestone pebbles with worse rounding are usually irregular.The features of their carbonate microfacies are very similar to those of underlying Pumenqian Formation.It provides a trustworthy clues that the limestone pebbles locally were derived from Pumenqian Formation.The convincing compression pits and striae on the surfaces of pebbles caused by glacial process have not been found.Authors consider the pebble-bearing layer to be debris flow in origin which took place at the margin of the restricted platform for lack of both deposits and fauna of deep sea environments.Trace fossils Palaeophycus, Taenidium, Dendrotichnium and Moniliform-like trace fossils in Dingjiazhai Formation are first reported.They are useful indicators in interpreting sedimentary environments.According to the palaeontological, petrological and ichnological features, six main sedim-entological facies are distinguished from the upper part of Pumenqian Formation to Dingjiazhai Formation.They are tidal flat facies, margin facies and lagoon facies which were located in the restricted platform, sand bar or shoal facies, basin facies of shallow water and open marine platform which belonged to open marine environments.Baoshan continental block was neither a part of Gondwana continent, nor a part of Europe-Asian continent and belonged to a,middle plate between them during the Late Palaeozoic Era.This conclusion is also supported by palaeontological evidences.
出处
《地层学杂志》
CSCD
北大核心
1990年第1期36-43,T002,共9页
Journal of Stratigraphy
基金
中国科学院科学基金
