晚古生代右江盆地层序格架中的生物礁

Late Paleozoic reefs from sequence framework in Youjiang basin

通过对右江盆地泥盆纪、二叠纪生物礁的时空分布和成因类型的研究,结合层序地层研究的成果,将其划分为低位礁、陆棚边缘礁、海侵礁、高位礁。低水位礁仅发育于台盆背景,以加积丘礁或点礁为特色,常与混屑浊积岩、硅灰岩、硅泥岩共生。陆棚边缘礁发育于台盆和斜坡背景,与低水位礁相比,具有礁体大、数量多的特点。由于海平面的向陆超覆而形成的海侵型台盆礁、斜坡礁、台缘礁、台内礁组合,具加积 退积型堆积序列,礁顶发育硬底、生物挠动面、海底溶蚀面、淹没面、水下中止面等,礁盖包括硅岩、火山碎屑浊积岩、放射虫岩、骨针岩、深水退积相、生物密集层、浮游相灰岩、含锰磷酸盐灰泥岩等,生长方式主要是追补式和中止式,以宝塔礁、链状礁、点礁为主。高水位礁以进积礁、加积礁和混积礁组合为特征,广泛发育于台内、台缘、斜坡、台盆等环境,具向上变浅序列,礁顶发育暴露面、岩溶面、冲刷侵蚀面、钙化壳、白云岩帽等,礁盖主要有残积相、开阔台地相、浊积相、丘滩相等,规模大、分布广,以堤礁、环礁、马蹄形礁为主。

By studying the genetic types and space-time distribution of the Devonian and Permian reefs in the Youjiang basin, then combined with sequence stratigraphy study results, the reefs are divided into LST reef, SMT reef, TST reef and HST reef. LST reef characterized by aggradational bioherm or patch reef is generally associated with mixed clastic turbidite, siliceous limestone and mudstones reef. The shelf margin reef is larger in size and relatively more in amount compared to LST reef and develops within interplatform basin and slope because of a better hydrodynamic environment during SMT. During transgression, the interplatform basin bioherm-reef complex continuously or discontinuously retrogrades towards basin margin and slope and then internal platform, and finally brings about transgresssive bioherm-reef complex overlapping from basin to platform, including interplatform-basin reef, slope reef, platform edge reef and internal platform reef with reefal top characterized by hard ground, bioturbate texture, submerged corrosion surface, submerged surface, submerged giving up surface. The reef cover includes silicalite, volcanic clastic turbidite, euabyssite, specularite, deepwater retrograde facies, biology dense layer, and pelagic limestone, phosphate lime mud cotained Mn et al. Its growth modes are catching-up and giving-up. The reef kinds are tower reef, catenarian reef and point reef. HST reef characterized by aggradational bioherm, transgresssive bioherm and mix reef develops abroad interplatform, platform margin, slope and basin among platforms environments, with shallowing upward sequence. Its reef top includes exposure surfaces, karst surfaces, scour surfaces, calcified crust, dolomite cover et al. Its reef cover consists of eluvial facies, open platform, turbidite, biology dune or bar. The main kinds are barrier reef, atoll, and horseshoe atoll.