Temperate glaciation on a Snowball Earth: Glaciological and palaeogeographic insights from the Cryogenian Yuermeinak Formation of NW China
Temperate glaciation on a Snowball Earth: Glaciological and palaeogeographic insights from the Cryogenian Yuermeinak Formation of NW China
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DOI：
10.1016/j.precamres.2019.105362
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发表时间：
2019-09
影响因子：
3.8
通讯作者：
T. Vandyk;G. Wu;B. Davies;Yang Xiao;Meng Li;G. Shields;D. L. Heron
中科院分区：
文献类型：
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作者：
T. Vandyk;G. Wu;B. Davies;Yang Xiao;Meng Li;G. Shields;D. L. Heron
普遍存在的冰川作用是Cryogenian时期的标志（约1000年）。720-635 Ma），因此，了解低温期冰体的特征，行为，范围和配置是重建该时期气候和环境的基本要求。不幸的是，尽管有大量的证据表明冰川作用，有一个强烈的解释偏见盆地冰川沉积地层和对冰下地层。特别是冰下条纹表面，由于其脆弱的毫米厚度，是非常罕见的，只占全球Cryogenian露头面积的一小部分。热状况是冰川活动的最重要的控制因素之一，而冰下纹状表面是确定古代温带热状况的极少数手段之一。在这方面，我们目前的沉积学和碎屑锆石的细节，一个偶然保存的低温（马里诺）露头在阿克苏乌什地区的塔里木盆地，中国西北部。Yuermeinak组不仅保存了冰下的条纹状表面和古地形，而且还保存了薄的局部保存的冰下冰碛岩。这些都表明有冰存在。剩余的形成揭示了冰川退缩和沉积的主要是superglacially-sourced碎片在一个动态的，开放的水，冰近端的冰前环境。提出了一个古地理重建，阿克苏-乌什地区发展从深水盆地环境，没有明确的证据，冰川作用，在早期Cryogenian，山区隆起与附近接地冰川冰，在后期Cryogenian。结合本研究的碎屑锆石数据与已公布的数据，进一步提出，这种发展与一个活跃的边缘设置，无论是通过扩展的安第斯型山脉的北部的研究区域或侧翼隆起的弧后盆地。
Ubiquitous glaciation was the hallmark of the Cryogenian Period (ca. 720–635 Ma), therefore understanding the character, behaviour, extent and configuration of Cryogenian ice bodies is a fundamental requirement in reconstructing climates and environments from the period. Unfortunately, despite abundant evidence for glaciation, there is a strong preservational bias towards basinal glaciogenic sedimentary strata and against subglacial strata. In particular subglacially striated surfaces, owing to their fragile millimetre-thickness, are very rare and represent only a tiny proportion of the global Cryogenian outcrop area. Thermal regime is one of the most important controls of glacial behaviour and subglacially striated surfaces are one of the very few means of determining an ancient temperate thermal regime. In this context we present sedimentological and detrital zircon detail of a fortuitously preserved Cryogenian (Marinoan) outcrop in the Aksu-Wushi area of the Tarim Craton, NW China. The Yuermeinak Formation preserves not only a subglacially striated surface and palaeotopography but also a thin, locally preserved, subglacial tillite. Together these indicate grounded ice. The remaining formation reveals glacial retreat and deposition of predominantly supraglacially-sourced debris within a dynamic, open-water, ice-proximal proglacial environment. A palaeogeographic reconstruction is proposed in which the Aksu-Wushi area developed from a deeper-water basinal environment, without clear evidence for glaciation, during the early Cryogenian, to an area of mountainous uplift with nearby grounded glacial ice, during the latter Cryogenian. Combining detrital zircon data of this study with published data it is further proposed that this development was linked to an active margin setting, either through expansion of an Andean-type mountain range to the north of the study area or flank-uplift of a back-arc basin.