火星上的多相中纬度冰川：根据陨石坑计数测年得出的重叠冰川状形式的形成年代,Journal of Geophysical Research: Planets

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火星上的多相中纬度冰川：根据陨石坑计数测年得出的重叠冰川状形式的形成年代
Journal of Geophysical Research: Planets ( IF 3.9 ) Pub Date : 2019-11-20 , DOI: 10.1029/2019je006102
A. J. Hepburn _{1,

2} , F. S. L. Ng ₂ , S. J. Livingstone ₂ , T. O. Holt ₁ , B. Hubbard ₁

Affiliation

摘要重建火星的冰川历史有助于了解其自然环境和过去的气候。含有水冰的粘性流特征（VFF）的已知分布表明，其中纬度地区在亚马逊晚期（最后几亿年）期间经历了冰川作用。流到其他 VFF 上的 VFF 子群（称为叠加冰川状形式 (SGLF)）的识别表明，在此期间可能发生了多个冰川阶段。为了探索这些冰川的历史和空间范围，我们记录了全球 SGLF 的分布，并使用撞击坑计数来确定 SGLF 和它们流经的 VFF 的年代。我们的库存扩大了早期文献中报道的 SGLF 数量，包括位于中纬度地区的 320 个 SGLF。我们的年代测定显示，这些 SGLF 比它们下面的 VFF 年轻得多，这意味着空间异步冰川作用。SGLF从~65 Ma开始形成，它们的年龄集中在2-20 Ma和45-65 Ma左右的两个不同组中，而其底层VFF的年龄则广泛地跨越了最后~300 Ma。我们根据火山口测年方法的众所周知的不确定性来讨论这些结果，并推断虽然冰盖在亚马逊晚期腐烂，但高山冰川在大约 200 万年最终消亡之前至少经历了两个主要周期的增减。前。

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Polyphase Mid‐Latitude Glaciation on Mars: Chronology of the Formation of Superposed Glacier‐Like Forms from Crater‐Count Dating

AbstractReconstructing Mars's glacial history informs understanding of its physical environment and past climate. The known distribution of viscous flow features (VFFs) containing water ice suggests that its mid‐latitudes were glaciated during the Late Amazonian period (the last several hundred million years). The identification of a subgroup of VFFs—called superposed glacier like forms (SGLFs)—flowing onto other VFFs, indicates multiple glacial phases may have occurred during this time. To explore the history and spatial extent of these glaciations, we record the distribution of SGLFs globally and use impact‐crater counting to date the SGLFs and the VFFs onto which they flow. Our inventory expands the handful of SGLFs reported in earlier literature to include 320 located throughout the mid‐latitudes. Our dating reveals these SGLFs to be much younger than their underlying VFFs, which implies a spatially‐asynchronous glaciation. SGLFs have been forming since ∼65 Ma, and their ages are clustered in two distinct groups around 2–20 and 45–65 Ma, whereas the ages of their underlying VFFs span the last ∼300 Ma diffusely. We discuss these results in the light of well‐known uncertainties with the crater‐dating method and infer that while ice sheets decayed over the Late Amazonian period, alpine glaciers waxed and waned in at least two major cycles before their final demise approximately two million years ago.

更新日期：2019-11-20

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