中国北方埃迪卡拉纪冰碛岩及冰川作用

中国北方从东到西绵延3000 km范围上的华北克拉通、塔里木克拉通及其中间微地块上都保存有埃迪卡拉纪冰川沉积记录，但有关它的年代学、冰川规模、古地理重建和大地构造背景等存有争论。本文基于中国北方埃迪卡拉纪冰碛岩空间分布、地层与沉积层序，沉积环境与沉积相等，结合以往国内外文献，系统分析了埃迪卡拉纪冰川上述有关问题。研究揭示，埃迪卡拉纪时期，国内外应存在年轻于(Gaskiers)580 Ma的冰期；中国北方埃迪卡拉纪冰川时限约562.5～551 Ma,堆积了冰下、冰缘和冰前沉积相(物),构成垂向上(由下至上)从冰下至冰前与海相冰碛物沉积层序，符合大陆冰川(盖)沉积响应样式；此外，国内外埃迪卡拉纪冰碛岩及冰川剥蚀地貌均十分发育；部分冰碛岩之上还可见盖帽白云岩，并呈现与成冰纪盖帽白云岩类似的沉积构造，但彼此碳同位素剖面却不尽相同；本研究推测，埃迪卡拉纪时期，原特提斯洋及周缘大陆(群)可能普遍存在至少是洲际性大陆冰盖，甚至是全球性的冰期。研究认为，埃迪卡拉纪时期的亚洲陆块群应与冈瓦纳大陆缺乏构造亲缘性的若干重要证据。本文研究结果在埃迪卡拉纪大陆及其古地理重建和大地构造背景恢复方面具有重要科学意义...

Ediacaran diamictites and glaciation in northern China

The Ediacaran glacial deposits are developed in the North China Craton, Tarim Craton and the microblocks among them, where they can extend for 3000 km from east to west. However, the chronology, scale of glaciation, paleogeographic reconstruction and tectonic setting are still controversial. Based on the spatial distribution, stratigraphy and sedimentary sequence, sedimentary environment and sedimentary facies of the Ediacaran diamictites in northern China, combined with previous literatures at home and abroad, the above issues related to Ediacaran glaciations are systematically analyzed. This paper revealed that during the Ediacaran, there should have been a glaciation of younger than 580 Ma (Gaskiers)all over the world. The age constraints of the Ediacaran glaciations in northern China were placed between 562. 5 Ma and 551 Ma, and the subglacial, periglacial, and proglacial sedimentary facies can be identified; these form the diamictite from subglacial to proglacial, followed by normal marine sedimentary sequences vertically (in ascending order), in line with the sedimentary response pattern of continental glacier (ice sheet). The Ediacaran diamictites and glacial erosional forms are widespread distributed globally, and the cap dolostones can be developed above the diamictites, exhibiting sedimentary structures similar to the Cryogenian cap dolostones, but the carbon isotope characteristics of them are not the same. This paper speculates that the Proto- Tethys Ocean and its surrounding continents may have developed continental ice sheets during the Ediacaran, but there was no affinity between the Asian blocks and the Gondwana supercontinent. The results provide geological evidences for the global paleogeographic reconstruction and tectonic setting restore of the Ediacaran period.