摘要： 湘中—湘南地区位于扬子陆块与华夏陆块之间的过渡区域。根据研究区寒武系沉积特征,识别出4种沉积相类型:碳酸盐陆棚亚相、深水盆地相、碎屑陆棚亚相及混积陆棚亚相。纽芬兰世—第二世早期(梅树村期—沧浪铺期),深水盆地分布范围广,占据了湘中及湘南大部分地区,湘东南发育碎屑陆棚沉积。第二世中晚期(龙王庙期),相对海平面下降,深水盆地范围略有减小,研究区西北部碳酸盐沉积逐渐占主导,碎屑陆棚面积变化不大。第三世(毛庄期—崮山期),海平面持续下降,碳酸盐陆棚及碎屑陆棚由两侧向中间推进,深水盆地面积急剧减小;湘西北一带发育混积陆棚亚相,沉积物以碳酸盐沉积为主混有陆源碎屑。芙蓉世(长山期—凤山期),碳酸盐陆棚范围迅速增大,深水盆地面积继续锐减,碎屑陆棚与碳酸盐陆棚毗邻发育,湘南区发育混积陆棚亚相。总之,寒武纪扬子陆块与华夏陆块间沉积相带连续完整,存在碳酸盐岩与碎屑岩混积的过渡沉积物,推测两者处于同一浅海海域,为由北西、南东向中部变深的沉积格局。

关键词: 混积陆棚, 岩相古地理, 寒武系, 湘中—湘南地区

Abstract: Based on the sedimentary characteristics of the Cambrian,the carbonate shelf subfacies,clastic shelf subfacies,mixed shelf subfacies,and deep-water basin facies onto the shelf had been distinguished in the central and southern Hunan Province,which located in the intermediate zone between Yangtze Block and Cathaysia Block.During the Terreneuvian to Early Epoch 2(Meishucun Age-Canglangpu Age),the deep-water basin facies was nearly dominated in the study area,and the clastic shelf subfacies just distributed in the southeastern Hunan Province.In the Late Epoch 2(Longwangmiao Age),due to the relative sea level declining and the scope of the deep-water basin decreasing,the carbonate sediments had gradually been the main deposition of the northwestern study area;meanwhile the scope of the clastic shelf subfacies had kept unchanged.In the Epoch 3(Maozhuang Age-Gushan Age),the carbonate shelf subfacies and clastic shelf subfacies gradually occupied the central Hunan Province from both sides of deep-water basin facies,whose range decreased sharply,and the mixed shelf subfacies with the mixed sediment of carbonates and clasolites developed in the northwestern study area.Till the Furongian(Changshan Age-Fengshan Age),the carbonate shelf subfacies increased tempestuously as the carbonate aggradation,while the deep-water basin facies still kept decreasing.The clastic shelf subfacies developed adjacently to carbonate shelf subfacies,and the mixed shelf subfacies appeared in the southern Hunan Province.In a word,the mixed sediments existed between Yangtze Block and Cathaysia Block,and the sedimentary facies were continuous and integrates.It indicated that Yangtze Block and Cathaysia Block maybe had been in the same neritic area,and its depositional pattern was characterized by water depth that became deeper gradually from the northwest and southeast to the middle in the Cambrian.

Key words: mixed shelf, lithofacies palaeogeography, Cambrian, central and southern Hunan Province

中图分类号: 

• P531A