川西北晚三叠世卡尼期硅质海绵礁-鲕滩组合的沉积相分析

川西北晚三叠世卡尼期生物礁-鲕滩组合属于马鞍塘组（汉旺组），分布于现今龙门山边缘的绵竹、安县、江油辖区，是作者于1975年带领地质填图小组发现的。文中通过对研究区生物礁进行微相分析，以及与世界同类生物礁对比，认为研究区的生物礁是以六射海绵为主的硅质海绵障积作用与以蓝细菌为主形成的凝块石粘结作用共同造礁，是一种深水粘结-障积型生物礁丘，也是灰泥基质支撑的生物礁。通过微相分析，尤其与世界镶边陆架模式及缓坡模式的标准微相对比，确定了研究区生物礁群的生长基底（鲕粒滩及生屑滩）不仅是形成于缓坡，而且是形成于同斜缓坡。川西北卡尼期同斜缓坡的推论、生物礁窗模式的建立及沉积相古地理图的编制，是认识川西北晚三叠世早期大地构造格局和沉积环境的依据。

Sedimentary facies analysis of the Late Triassic Carnian siliceous sponge reef-oolite bank complex in northwestern Sichuan Province

The Late Triassic Carnian reef-oolite bank complex belongs to the Maantang(Hanwang)Formation， and is distributed along the margin of present Longmen Mountains in Mianzhu， Anxian and Jiangyou districts of northwestern Sichuan Province. It was discovered by the geologic mapping group led by the author in 1975. By microfacies analysis of reefs in this area， and comparison with similar reefs in the world， the results demonstrate that the reefs were built up owing to both baffling function of siliceous sponges mainly of hexactinellids and binding function of thrombolites formed mainly by cyanobacteria. Hence the reefs are of deep water reef mounds of binding baffling type， and of limemud matrix-supported reefs. By microfacies analysis， especially comparison with standard microfacies of rimmed shelf model and ramp model of the world， the author considers that the foundation for reef cluster growth(the oolitic bank and bioclastic bank)was formed not only on a ramp， but also on a homoclinal ramp. The inference of the Carnian homoclinal ramp in northwestern Sichuan Province， the installation of reef window model， and the compilation of sedimentary facies and palaeogeography maps serve as grounds for understanding geotectonic framework and sedimentary environments of the region.