Chapter 70 The Elatina glaciation (late Cryogenian), South Australia

Deposits of the late Cryogenian Elatina glaciation constitute the Yerelina Subgroup in the Adelaide Geosyncline region, South
Australia. They have a maximum thickness of c. 1500 m, cover 200 000 km2, and include the following facies: basal boulder diamictite with penetrative glaciotectonites affecting preglacial beds;
widespread massive and stratified diamictites containing faceted and striated clasts, some derived from nearby emergent diapiric
islands and others of extrabasinal provenance; laminated siltstone and mudstone with dropstones; tidalites and widespread
glaciofluvial, deltaic to marine-shelf sandstones; a regolith of frost-shattered quartzite breccia up to 20 m thick that contains
primary sand wedges 3+ m deep and other large-scale periglacial forms; and an aeolian sand sheet covering 25 000 km2 and containing primary sand wedges near its base. These deposits mark a spectrum of settings ranging from permafrost regolith
and periglacial aeolian on the cratonic platform (Stuart Shelf) in the present west, through glaciofluvial, marginal-marine
and inner marine-shelf in the central parts of the Adelaide Geosyncline, to outer marine-shelf in sub-basins in the present
SE and north.
The Elatina glaciation has not been dated directly, and only maximum and minimum age limits of c. 640 and 580 Ma, respectively, are indicated. Palaeomagnetic data for red beds from the Elatina Formation (Fm.) and associated
strata indicate deposition of the Yerelina Subgroup within 10° of the palaeoequator. The Yerelina Subgroup is unconformably
to disconformably overlain by the dolomitic Nuccaleena Fm., which in most places is the lowest unit of the Wilpena Group and
marks Early Ediacaran marine transgression.

晚冰河时代的 Elatina 冰川沉积构成了澳大利亚南部的阿德莱德地槽区的 Yerelina 亚组。其最大厚度约为 1500 米，覆盖面积达 200,000 平方公里，包括以下岩性：基底的巨砾状冰碛岩，其侵入性冰川构造影响前冰川地层；广泛分布的致密和层状冰碛岩，包含具有棱角和条纹的碎屑，其中部分源自附近的隆起地幔侵入岛，其余则为来自盆地外的物质；层状粉砂岩和泥岩，含有坠落石；潮汐岩和广泛分布的冰川河流相、三角洲至近海架的砂岩；厚度达 20 米的冻融破碎石英岩角砾岩风化壳，其中包含深度达 3+ 米的原始沙楔和其他大规模的近冰川形态；以及覆盖面积达 25,000 平方公里的风成沙丘，其底部附近含有原始沙楔。这些沉积物标志着从现今西部克拉通平台（斯图尔特架）上的永久冻土风化壳和近冰川风成沉积，经过阿德莱德地槽中部地区的冰川河流相、边缘海洋相和内海架，直至现今东南部和北部的海底架的一系列环境。Elatina 冰川作用尚未直接定年，仅指示了约 640 百万年至 580 百万年之间的最大和最小年龄限制。来自 Elatina 组（Fm.）及其相关地层的红层古地磁数据表明，Yerelina 亚组的沉积位置距离古赤道纬度不超过 10°。Yerelina 亚组不整合或断续不整合地覆盖在白云岩质的 Nuccaleena 组之上，在大多数地方，该组是 Wilpena 组的最低单元，标志着早埃迪卡拉纪的海侵。” }