广西菜子岩剖面中上泥盆统界线附近沉积相与海平面变化*——兼论华南吉维期中期的海退及时间

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。

Sedimentary facies and sea-level change across the Middle-Upper Devonian boundary at Caiziyan section,Guangxi:The mid-Givetian regression and its timing in South China

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 phas...