桂林泥盆纪碳酸盐台地礁组合的层序地层研究

Sequence stratigraphy of Devonian carbonate platform and reef complex in Guilin, Guangxi

桂林的泥盆系以发育碳酸盐台地和礁组合沉积为特征，岩相多样，地层对比和时代确定的难度较大。本文应用层序地层学原理，结合生物地层和岩石地层特征，研究桂林泥盆系露头的相结构及碳酸盐台地礁组合不同亚相的９个剖面中的不整合界面，识别出该区中、晚泥盆世地层的５个层序界面：（１）牙形刺下ｖａｒｃｕｓ亚带和中ｖａｒｃｕｓ亚带之间；（２）牙形刺ｈｅｒｍｍａｎｉ－ｃｒｉｓｔａｔｕｓ带和ｄｉｓｐａｒｉｌｉｓ带之间；（３）牙形刺下ｒｈｅｎａｎｅ亚带和上ｒｈｅｎａｎｅ亚带之间；（４）牙形刺ｅｘｐａｎｓａ带内部；（５）牙形刺ｐｒａｅｓｕｌｃａｔａ带和ｓｕｌｃａｔａ带之间。这些层序界面在岩石学上的特征为具有生物铸模溶孔的白云岩和不同规模的暴露溶蚀面。比较明显的大的海泛面有２次：（１）牙形刺ｅｎｓｅｎｓｉｓ带和ｖａｒｃｕｓ带之间；（２）牙形刺ｌｉｎｇｕｉｆｏｒｍｉｓ带和下ｔｒｉａｎｇｕｌａｒｉｓ亚带之间。

In this paper, the principles of sequence stratigraphy are applied to analyse the microfacies architecture in Devonian outcrops referred to the carbonate platform and reef complex in Guilin. Five depositional sequences have been recognized based on unconformity boundaris within nine sections representing different subfacies. Sequence boundries are defined on horizons including:(1) between lower varcut subzone and middle varcus subzone; (2) between hermmani-cristatus zone and disparilis zone;(3) between lower rhenane subzone and upper rhenane subzone;(4) within expansa zone;(5) between praesulcata zone and sulcata zone. They are commonly marked by dolomites with the well developed fossil molds and casts, and the exposure-solution surface in large- or small-scale. The distinct marine flood surfacies are dated mainly as(1)between ensensis zone and varcus zone; and(2) between linguiformis zone and lower triangularis subzone