广西桂林泥盆纪礁组合中的地层问题  

Stratigraphic boundaries on Devonian carbonate platform and reef complexes in Guilin, Guangxi

作　　者：沈建伟[1] 俞昌民[1] 

机构地区：[1]中国科学院南京地质古生物研究所,南京210008

出　　处：《地层学杂志》1996年第1期1-8,共8页Journal of Stratigraphy

摘　　要：广西桂林的泥盆系包含艾菲尔期(包括少部分吉维期)的碎屑岩和吉维期至法门期的碳酸盐岩。以碳酸盐沉积发育期的5个实测剖面为基础,并结合牙形刺生物地层和不同沉积单元的微相研究探讨碳酸盐台地礁组合沉积的地层问题。根据牙形刺Icriodus和Polygnathus的组合特征提出广布于桂东北的信都组的顶界约相当于varcus带的底界;根据礁前斜坡相和台内浅水相沉积中的牙形刺、四射珊瑚及腕足类的组合特征,认为台内浅水相区的中、上泥盆统的界线应置于桂林组下段内;根据额头村D/C界线层的牙形刺、珊瑚和碳酸盐微相序列的研究,认为Cystophrentis四射珊瑚带属泥盆纪,CP间隔带属石炭纪。In the Guilin area, the boundary between the lithostratigraphic units of the Xindu Fm. and the Tangjiawan Fm. has been generally considered as the boundary between Eifelian and Givetian, although this has not been proved by any sufficient data. The first finding of the conodonts in this work from the basal part of Tangjiawan Fm. in Shahe of Guilin, representing restricted platform subfacies, suggests that the boundary between Xindu Fm. and Tangjiawan Fm. is approximately corresponding to the base varcus zone. In Wuguishan section of Guilin, the Givetian and Frasnian deposits assigned to the hemipelagic facies yield corals, brachiopods and conodonts. According to the range of this faunal association in the section, it seems that after the extinction of Stringocephalus there exists an interval filled by the existence of rugosa assemblage, i. e. the Spinophyllum-Kwangxiastraea Assemblage and can be dated as the disparilis Zone. Inferring from this, the boundary between Middle and Upper Devonian in the interior platform subfacies is not corresponding to the boundary between Tangjiawan Fm. and Kueilin Fm., and may be within the lower part of the Kueilin Fm.. The D/C boundary beds in Etoucun, south of Guilin, representing the shallow water carbonate platform deposits is characterized by yielding benthic fauna including foraminifers, stromatoporoids, corals, algae etc.. No conodont has been reported and the D/C Boundary has been drawn mainly on the basis of data on foraminfers (Wang, 1987). In this work, the first findings of conodonts including Polygnathus, Pseudopolygnathus, Bispathodus, Spathognathus, Euprioniodina, HindeoUa and Branmella from the section reveal that the D/C Boundary can be drawn at the base of Bed 84 in the Etoucun section. According to the conodont data, the coral assemblage zone, namely, the Cystophrentis Zone which has been traditionally considered as the basal coral assemblage zone of Lower Carboniferous should be referred to the Uppermost Devonian, and the so called CP interval Barren Zone whic

关 键 词：泥盆纪 礁组合 桂林 广西 生物地层 

分 类 号：Q911.644[天文地球—古生物学与地层学]