西秦岭造山带早白垩世大陆裂谷存在的依据 ——青海同仁地区麦秀山群新建的意义

青海省唯一的一套早白垩世陆相火山岩地层分布在青海省黄南州同仁县—泽库县之间的麦秀山一带，位于西秦 岭地层区泽库地层分区。根据剖面研究和区域地层对比，将这套地层新命名为早白垩世麦秀山群（K1M），下部的紫 红—灰紫色中基性火山岩夹砂砾岩新建为多禾茂组（K1d），为一套典型的陆相裂隙式喷发的碱性玄武岩+陆相红层沉 积建造，上部的紫红色砂砾岩组合延用万秀组（K1w），为一套冲积扇相陆相红层的类磨拉石建造，二者之间为明显 的整合接触关系。根据麦秀山群与上下地层之间的角度不整合接触关系，以及多禾茂组火山岩中的同位素年龄和万秀 组的昆虫、叶肢介、植物化石，可确定麦秀山群的形成时代为早白垩世。麦秀山群沿近南北向张裂带分布，是在早白 垩世陆内环境下产生并在陆内环境下消亡的陆内裂谷相沉积，它的形成标志着西秦岭地区在早白垩世进入区域性伸展 阶段。

The evidence for the existence of Early Cretaceous continental rift in West Qinling orogenic belt: the significance of the newly built Maixiushan Group in Tongren area of Qinghai Province

The only Early Cretaceous continental volcanic strata in Qinghai Province are distributed in Maixiushan area between Tongren County and Zeku County in Huangnan Prefecture of Qinghai Province and lie in Zeku subunit of West Qinling stratigraphic unit. Based on profile study and regional stratigraphic correlation,the authors newly named this suite of strata Early Cretaceous Maixiushan Group(K1M).The purplish red-grayish purple intermediate-basic volcanic rocks intercalated with sandy conglomerate in its lower...