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 stemsetc., 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.%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.
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