The currently favored hypothesis for Late Paleozoic Ice Age glaciations is that multiple ice centers were distributed across Gondwana and that these ice centers grew and shank asynchronously. Recent work has suggested that the Transantarctic Basin has glaciogenic deposits and erosional features from two different ice centers, one centered on the Antarctic Craton and another located over Marie Byrd Land. To work towards an understanding of LPIA glaciation that can be tied to global trends, these successions must be understood on a local level before they can be correlated to basinal, regional, or global patterns. This study evaluates the sedimentology, stratigraphy, and flow directions of the glaciogenic, Asselian–Sakmarian (Early Permian) Pagoda Formation from four localities in the Shackleton Glacier region of the Transantarctic Basin to characterize Late Paleozoic Ice Age glaciation in a South Polar, basin-marginal setting. These analyses show that the massive, sandy, clast-poor diamictites of the Pagoda Fm were deposited in a basin-marginal subaqueous setting through a variety of glaciogenic and glacially influenced mechanisms in a depositional environment with depths below normal wave base. Current-transported sands and stratified diamictites that occur at the top of the Pagoda Fm were deposited as part of grounding-line fan systems. Up to at least 100 m of topographic relief on the erosional surface underlying the Pagoda Fm strongly influenced the thickness and transport directions in the Pagoda Fm. Uniform subglacial striae orientations across 100 m of paleotopographic relief suggest that the glacier was significantly thick to “overtop” the paleotopography in the Shackleton Glacier region. This pattern suggests that the glacier was likely not alpine, but rather an ice cap or ice sheet. The greater part of the Pagoda Fm in the Shackleton Glacier region was deposited during a single retreat phase. This retreat phase is represented by a single glacial depositional sequence that is characteristic of a glacier with a temperate or mild subpolar thermal regime and significant meltwater discharge. The position of the glacier margin likely experienced minor fluctuations (readvances) during this retreat. Though the sediment in the Shackleton Glacier region was deposited during a single glacier retreat phase, evidence from this study does not preclude earlier or later glacier advance–retreat cycles preserved elsewhere in the basin. Ice flow directions indicate that the glacier responsible for this sedimentation was likely flowing off of an upland on the side of the Transantarctic Basin closer to the Panthalassan–Gondwanide margin (Marie Byrd Land), which supports the hypothesis that two different ice centers contributed glaciogenic sediments to the Transantarctic Basin. Together, these observations and interpretations provide a detailed local description of Asselian–Sakmarian glaciation in a South Polar setting that can be used to understand larger-scale patterns of regional and global climate change during the Late Paleozoic Ice Age.

中文翻译：

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早二叠世南极冰川岩相分析：南极沙克尔顿冰川区宝塔组

目前对晚古生代冰河时代冰川作用的支持假设是，多个冰心分布在冈瓦纳大陆，并且这些冰心的生长和收缩是异步的。最近的工作表明，跨南极盆地有来自两个不同冰中心的冰川沉积物和侵蚀特征，一个以南极克拉通为中心，另一个位于玛丽伯德地上方。为了努力了解与全球趋势相关的 LPIA 冰川作用，必须在当地层面了解这些演替，然后才能将它们与盆地、区域或全球模式相关联。这项研究评估了冰川成因的沉积学、地层和流动方向，来自横贯南极盆地沙克尔顿冰川地区四个地点的 Asselian-Sakmarian（早二叠世）宝塔组，以表征南极盆地边缘环境中晚古生代冰河时代的冰川作用。这些分析表明，在深度低于正常波基的沉积环境中，宝塔组的块状、砂质、贫碎屑混叠岩沉积在盆地边缘水下环境中，通过各种冰川形成和冰川影响机制。出现在宝塔组顶部的电流输送砂和分层混叠岩沉积为接地线风扇系统的一部分。宝塔组下方侵蚀表面上至少 100 m 的地形起伏强烈影响了宝塔组的厚度和运移方向。跨越 100 m 古地形起伏的统一冰下条纹方向表明冰川明显厚到“超过”沙克尔顿冰川地区的古地形。这种模式表明冰川可能不是高山，而是冰盖或冰盖。沙克尔顿冰川地区宝塔组的大部分是在一次退缩阶段沉积的。这一退缩阶段以单一冰川沉积序列为代表，其特征是具有温带或温和的亚极地热状况和大量融水排放的冰川。在这次撤退过程中，冰川边缘的位置可能经历了轻微的波动（重新上升）。虽然沙克尔顿冰川地区的沉积物是在单一冰川退缩阶段沉积的，这项研究的证据并不排除在盆地其他地方保存的较早或较晚的冰川进退循环。冰流方向表明，造成这种沉积的冰川很可能从跨南极盆地一侧的高地流出，靠近 Panthalassan-Gondwanide 边缘（玛丽伯德地），这支持了两个不同的冰中心贡献了冰川沉积物的假设到跨南极盆地。总之，这些观察和解释提供了对南极环境中阿瑟利-萨克马冰川的详细局部描述，可用于了解晚古生代冰河时代区域和全球气候变化的更大规模模式。冰流方向表明，造成这种沉积的冰川很可能是从跨南极盆地一侧的高地流出的，靠近 Panthalassan-Gondwanide 边缘（玛丽伯德地），这支持了两个不同的冰中心贡献了冰川沉积物的假设到跨南极盆地。总之，这些观察和解释提供了对南极环境中阿瑟利-萨克马冰川的详细局部描述，可用于了解晚古生代冰河时代区域和全球气候变化的更大规模模式。冰流方向表明，造成这种沉积的冰川很可能是从跨南极盆地一侧的高地流出的，靠近 Panthalassan-Gondwanide 边缘（玛丽伯德地），这支持了两个不同的冰中心贡献了冰川沉积物的假设到跨南极盆地。总之，这些观察和解释提供了对南极环境中阿瑟利-萨克马冰川的详细局部描述，可用于了解晚古生代冰河时代区域和全球气候变化的更大规模模式。这支持了两个不同的冰中心为跨南极盆地贡献了冰川沉积物的假设。总之，这些观察和解释提供了对南极环境中阿瑟利-萨克马冰川的详细局部描述，可用于了解晚古生代冰河时代区域和全球气候变化的更大规模模式。这支持了两个不同的冰中心为跨南极盆地贡献了冰川沉积物的假设。总之，这些观察和解释提供了对南极环境中阿瑟利-萨克马冰川的详细局部描述，可用于了解晚古生代冰河时代区域和全球气候变化的更大规模模式。