摘要： 广西菜子岩剖面处于台地边缘地带，含有底栖生物及浮游生物化石。综合岩相、生物相等资料，按牙形石带时限讨论了该地区吉维期—弗拉斯期早期主要的海平面变化历史。吉维期早期(相当于东岗岭组)经历了持续的海侵，大致下varcus带末期可能出现短暂的海退；“谷闭组”下部岩性复杂，海平面波动强烈，其中较大规模的包括了发生于上varcus带的海退(即吉维期中期海退)及下hermanni-cristatus带初期的海侵。吉维期晚期地层含有丰富的床板珊瑚以及其他礁体生物碎屑，产层孔虫、海百合等，意味着这个时期研究区可能处于礁前的上斜坡部位。“谷闭组”上部（牙形石falsiovalis带至transitans带下部）的岩性为中—薄层与厚层的灰岩互层，以正常的底栖生物为主，反映了由原来的礁前到滩前的变化，但水体深度在中—晚泥盆世界线前后可能总体相似。融县组(底部)以浅灰、灰白色的中—薄层至厚层—块状灰岩为特征，其沉积始于牙形石transitans带中部，证据表明此时海水可能变深。菜子岩剖面的白云岩位于上varcus带的下部，主要为细—中晶结构，见有灰岩残余以及正常海相生物碎屑。横向上与其他剖面对比表明，广西地区上varcus带可能出现了区域性的海退事件。

关键词: 广西, 菜子岩, 中上泥盆统, 岩相, 生物相, 海平面变化, 白云岩, 吉维期中期

Abstract: The Caiziyan section was located in a platform margin zone， with relatively abundant benthic and common-rare pelagic fossils， which may be regarded as a quite suitable reference section for stratigraphic correlation and division. On the basis of lithofacies and biofacies characteristics， sea-level change history is reconstructed for the interval from the Givetian to the Early Frasnian times. The Early Givetian Donggangling Formation of the study area may represent deposits under a persistent transgressive phase， probably with a slight sea-level fall at the end of the Lower varcus Zone. The lower part of the “Gubi” Formation is complex in lithology， probably resulting from extensive sea-level changes， including a significant transgressive event at the initial period of the Lower hermanni-cristatus Zone and the long-recognized mid-Givetian regression， whose timing has been precisely determined to be the Upper varcus Zone for the first time. The Late Givetian deposits host abundant tabulate corals and reef-associated bioclasts， including stromatoporoids， crinoid stems etc.， implying that the study area was probably located on the upper slope in front of a reef complex. The upper part of the “Gubi” Formation(conodont falsiovalis to lower transitans zones)is characterized by alternating medium-thin and thick bedded limestones(mainly with bioclasts of level-bottom organisms)， which indicates a change from fore-reef to fore-shoal environments， probably with little overall sea-level change across the Middle-Upper Devonian boundary. The Rongxian Formation(basal part)is characterized by grayish to gray-white thin-bedded to massive limestones， which may represent a significant sea-level rise in the Middle transitans Zone in South China. The finely-medium crystalline dolostone layer at Caiziyan is within the Upper varcus Zone， with normal marine fossils including corals and conodonts. The proposed interpretation for this dolostone layer is that a substantial sea-level fall event happened in the Upper varcus Zone in the Guangxi area， based on temporal and spatial correlation of the dolomitized layers and evidence of sea-level fall in other sections.

Key words: Guangxi, Caiziyan, Middle-Upper Devonian, lithofacies, biofacies, sea-level change, dolostone, mid-Givetian

中图分类号: 

• P512.2