Abstract We present new data on the Vichigasta Carboniferous paleovalley, a glacial trough crucial to understand the type of glaciation that affected western Gondwana during the Late Paleozoic Ice Age (LPIA). The filling of this paleovalley starts soon after the mid-Carboniferous glacial peak. Stage I represents pro-glacial lacustrine deposits with outwash, glacially rafted dropstones, mass transport deposits (MTDs) and turbidites of the trunk and a lateral tributary valley. Base-level drop created the scenario for Stage II outwash deltas and sandur deposits, with westward flow. Stage III represents a flooding at the base of the Bashkirian, characterized by typical transgressive dark shales and distal turbidites. Stage IV represents a highstand prograding turbidite wedge. We worked in a detailed terrain analysis, surveyed the scarce sedimentary record left and recovered a rich palynoflora from mudstones of Stage 3. The almost complete erosion of the fill allowed us to analyze the shape of this paleovalley and compare it to Olta and Malanzan ones. Vichigasta and Malanzan paleovalleys show similar size, a clear U-shape and regular and homogeneous width downslope, a requisite for bypass glacial paleovalleys carved in a subcrop of homogeneous composition (basement), which allow us to interpret them as outlet valleys. Olta paleovalley ranks as tributary as its capacity is only one-third of the others. We also identified a basement high over the Vichigasta valley floor that suggests the presence of a potential drumlin supporting our interpretation as a bypass glacial valley. This post-glacial flooding event is widely observed at other glacial valleys as the Olta-Malanzan herein analyzed and others like Las Lajas and Quebrada Grande. The new data from Vichigasta paleovalley reinforce the hypothesis of a large ice-sheet located to the east of the craton.

中文翻译：

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Vichigasta 冰川古河谷：阿根廷中部石炭纪中期大型大陆冰盖的古地貌和沉积学证据

摘要 我们提供了 Vichigasta 石炭纪古河谷的新数据，这是一个冰川槽，对于了解晚古生代冰河时代 (LPIA) 影响冈瓦纳西部的冰川类型至关重要。在石炭纪中期冰川高峰之后不久，这个古山谷的填充就开始了。阶段 I 代表具有外冲、冰川漂流的落石、物质输送沉积物 (MTD) 和干流和侧向支流河谷的浊积岩的前冰川湖沉积物。基准面下降创造了第二阶段外冲三角洲和桑杜尔沉积物向西流动的情景。第三阶段代表巴什基尔盆地底部的洪水，其特征是典型的海侵深色页岩和远端浊积岩。第四阶段代表高位进积浊积楔。我们进行了详细的地形分析，调查留下的稀有沉积记录，从第 3 阶段的泥岩中恢复了丰富的孢粉植物群。填充物的几乎完全侵蚀使我们能够分析这个古山谷的形状，并将其与奥尔塔和马兰赞的古山谷进行比较。Vichigasta 和 Malanzan 古河谷大小相似，呈明显的 U 形，下坡宽度规则且均匀，这是绕过冰川古河谷的必要条件，这些古河谷雕刻在均质成分（基底）的亚作物中，这使我们能够将它们解释为出口山谷。奥尔塔古河谷作为支流，其容量仅为其他河谷的三分之一。我们还确定了 Vichigasta 谷底高处的地下室，这表明存在潜在的鼓声，支持我们将其解释为旁路冰川谷。这种冰川后洪水事件在其他冰川山谷中被广泛观察到，如本文所分析的 Olta-Malanzan 以及其他如 Las Lajas 和 Quebrada Grande。来自 Vichigasta 古河谷的新数据加强了位于克拉通以东的大型冰盖的假设。