Landslide deposits are common in basin fill of tectonically active areas, including the Basin and Range province of western North America. However, interpreting and reconstructing ancient landsliding events from these deposits is challenging, but can be aided by detailed field analysis. Remnants of the Blue Diamond landslide breccia are exposed capping hills and ridges in the foothills of the eastern Spring Mountains near Blue Diamond, Nevada, USA. Uncertainties surrounding the origin and emplacement of the ancestral Blue Diamond landslide have emerged based on the disparate distribution of landslide outcrops. Therefore, in this study we used detailed sedimentological data and observations to interpret a two-phase emplacement history for the Blue Diamond landslide.Sedimentological observations are consistent with Blue Diamond landslide breccia emplacement as a rock avalanche. The presence of clastic dikes and flame structures and negligible incorporation of bedrock substrate material suggest that runout occurred over a saturated substrate. Flow transformation into a debris avalanche is ruled out because clast-count data show that debris entrainment was not sufficient to act as the sole mechanism behind the excessive mobility experienced by the Blue Diamond landslide. Instead, we propose that the excessive mobility was driven by flow entrainment of large Aztec Sandstone boulders and interaction with a saturated runout path substrate that caused a reduced basal frictional resistance, enabling initial emplacement onto Blue Diamond Hill. We therefore suggest that the Blue Diamond landslide was derived from a source area about 8.5 km northwest of the Blue Diamond townsite and flowed into the Blue Diamond Hill site where it was emplaced onto Moenkopi Formation atop the hill during the Miocene. Due to loading by this new overburden, incompetent gypsum horizons failed in the upper Kaibab Formation stratigraphically below the Moenkopi Formation. These failed gypsum horizons then served as a compound landslide rupture surface, transporting the overlying Moenkopi Formation and landslide breccia. This secondary emplacement likely ceased by late Miocene to Pliocene time.

中文翻译：

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美国内华达州南部蓝钻滑坡角砾岩的起源和位置

滑坡沉积在构造活动区域的盆地填充中很常见，包括北美西部的盆地和山脉省。然而，从这些沉积物中解释和重建古代滑坡事件具有挑战性，但可以通过详细的现场分析来帮助。Blue Diamond 滑坡角砾岩的残余物暴露在美国内华达州 Blue Diamond 附近的 Spring Mountains 东部山脚下的山丘和山脊上。基于滑坡露头的不同分布，出现了围绕祖先蓝钻滑坡的起源和位置的不确定性。因此，在这项研究中，我们使用详细的沉积学数据和观察来解释蓝钻滑坡的两阶段就位历史。沉积学观察结果与蓝钻滑坡角砾岩侵位为岩崩相一致。碎屑岩堤和火焰结构的存在以及基岩基质材料的可忽略不计的结合表明，跳动发生在饱和基质上。由于碎屑计数数据显示，碎屑夹带不足以作为蓝钻石滑坡经历的过度流动性背后的唯一机制，因此排除了流动转变为碎屑雪崩的可能性。相反，我们提出过度流动是由大型阿兹台克砂岩巨石的流动夹带驱动的，以及与饱和的跳动路径基板的相互作用，导致基础摩擦阻力降低，从而能够在 Blue Diamond Hill 上进行初始就位。因此，我们认为 Blue Diamond 滑坡起源于 Blue Diamond 城镇遗址西北约 8.5 公里的源区，并流入 Blue Diamond Hill 遗址，在那里它在中新世期间被安置在山顶的 Moenkopi 组上。由于这种新的覆盖层的加载，在地层上位于 Moenkopi 组下方的 Kaibab 组上部，不合格的石膏层位失效。这些失败的石膏层随后成为复合滑坡破裂面，输送上覆的 Moenkopi 组和滑坡角砾岩。这种次生就位可能在晚中新世至上新世时期停止。在 Moenkopi 组下方地层上的 Kaibab 组上部，不合格的石膏层位失败。这些失败的石膏层随后成为复合滑坡破裂面，输送上覆的 Moenkopi 组和滑坡角砾岩。这种次生就位可能在晚中新世至上新世时期停止。在 Moenkopi 组下方地层上的 Kaibab 组上部，不合格的石膏层位失败。这些失败的石膏层随后成为复合滑坡破裂面，输送上覆的 Moenkopi 组和滑坡角砾岩。这种次生就位可能在晚中新世至上新世时期停止。