古地理学报2009，Vol.11Issue(5)：503-512,10.
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
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
摘要
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 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.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Key words
Guangxi/ Caiziyan/ Middle-Upper Devonian/ lithofacies/ biofacies/ sea-level change/ dolostone/mid-Givetian分类
天文与地球科学引用本文复制引用
李华,马学平,韦龙明..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[J].古地理学报,2009,11(5):503-512,10.基金项目
国家自然科学基金项目(编号: 40472009, 40872007, 40830211)和国家重点基础研究发展规划项目(编号:2006CB806400)联合资助 （编号: 40472009, 40872007, 40830211）
