川东北地区上二叠统长兴组生物礁组成及成礁模式

The organic reefs and their reef-forming model for the Upper Permian Changxing Formation in northeastern Sichuan

川东北地区在地表露头上目前发现的长兴组生物礁以盘龙洞、通江铁厂河和羊鼓洞生物礁为代表。野外和室内综合研究表明:盘龙洞生物礁发育完好,生长有大量骨架岩,而羊鼓洞生物礁骨架岩几乎不发育,以障积岩为主夹少量粘结岩;盘龙洞骨架间充填物为生物碎屑和砂屑为主,泥晶灰泥很少,而羊鼓洞以生物碎屑和方解石灰泥为主;盘龙洞生物礁普遍发生了白云岩化,而羊鼓洞白云岩化极其微弱。通过盘龙洞与羊鼓洞生物礁对比研究,认为两者非同时形成,羊鼓洞生物礁早于盘龙洞,生物礁有由台地向盆地迁移趋势,其成礁模式为台地边缘礁滩组合型缓坡模式。

The present paper gives a detailed description of the organic reefal outcrops represented by the (Panlongdong), Tiechanghe and Yanggudong organic reefs in northeastern Sichuan. The Panlongdong organic reefs are generally subjected to dolomitization and composed of extensive framestone, which is filled by organic (remains) and sandy fragments, with minor micritic mud, whereas the Yanggudong organic reefs are dominated by bafflestone with a small amount of bindstone, which consists of organic remains and calcitic mud, and are slightly dolomitized. The comparative study shows that the Panlongdong and Yanggudong organic reefs are not (contemporaneous); the latter is earlier than the former in age. On the whole, the organic reefs in the study area (exhibit) a trend of transition from a platform to a basin, and a ramp model of platform margin reefs-bank type.