贵州独山石炭系露头层序地层学研究

On Outcrop Sequence Stratigraphy of Carboniferous in Dushan, Guizhou

通过黔南独山数条剖面的追踪、对比 ,从岩石和生物组合特征等方面分析和研究了石炭系的副层序、沉积体系域及层序关键面和层序。副层序反映了向上变浅的过程。在滨浅海沉积过程中 ,地表暴露是副层序的顶界面标志之一 ,但不足为层序界面的标志。独山地区 ,从汤粑沟组至马平组共识别出 30个层序、 171个副层序 ,其中从泥盆系Cystophrentis 石炭系Pseu douralinia间隔带中的最大海泛面至马平组Pseudoschwagerina首现之下的石炭系可识别出 2 6个层序 ,15 6个副层序。与北美大陆相对比 ,独山地区下石炭统的层序仅在相当Homceras带的德坞阶上部少一个层序 ,这与下、上石炭统之间明显的沉积间断相关 ;继承岩关期末海退的大塘期早期的第一个层序界面 ,即祥摆组第一层煤 ,可与杜内阶 /维宪阶之间的层序界面相对比。独山上石炭统的副层序大体与北美大陆上石炭统的层序大体相当 ,仅在达拉阶 /马平阶的沉积间断面之上少 1个 ,之下少 17个。石炭纪冈瓦纳冰期冰盖面积和体积的增大 ,可能反映到滨浅海沉积相的层序和副层序的缺失程度的增大。

Based on observation and correlation of several sections in the Dushan area, southern Guizhou, and having studied parasequences, sedimentary tracts and key surfaces by sedimentology and biostratigraphy, the parasequences appear from deep to shallow sedimentary courses. In shore-shallow faces as Carboniferous in the Dushan area, the exposed surfaces are a sign of the top boundary of the parasequences, but not enough to be a sequence boundary. There are 30 sequences and 171 parasequences from the Tangbangou Formation to the Maping Formation, and 26 sequences and 156 parasequences in Carboniferous, which are from the marine flooding surface in Cystophrentis-Pseudouralina interval zone in the Devonian System to the lower firstly visible Pseudoschwagerina in the Maping Formation in the Dushan area. The lower Carboniferous sequences in Dushan can correlated with that in north America, almost except less one sequence in the middle-upper part of the Dewuan Stage about Homceras zone. The first sequence boundary in the lower Datangian Age, i.e. the first coal bed in the Xiangbai Formation, which continued with the regression in later Yanguanian Age and can correlate to the sequence boundary in between Tournaisian-Visean Stages in north America. Upper carboniferous parasequences in Dushan can correlate with ones in America, except less 18 parasequences near the Dalaian-Mapingian boundary. There may be correlation between the areas and volumes of Gondwanan ice Sheet and the lacked sequences or parasequences in the Dushan area, Guizhou.