Abstract Gale crater is a large impact crater with a ca 5 km thick sequence of stratified rocks in it, expressed today as a central eroded mound (i.e., Aeolis Mons informally named Mt. Sharp). A goal of the current Mars Science Laboratory mission in Gale crater is to investigate the processes that deposited, lithified, and eroded this fill. The Light-Toned Yardang Unit (LTYu) unit, the subject of the present research, is one of the geological units of Mt Sharp. Our specific purpose here is to refine and interpret the imaging documentation of the morphologic and stratal components of the LTYu, at large outcrop scale. In combination with established orbital images, we use the Remote Micro-Imager (RMI) of ChemCam, a remote sensing instrument currently operated onboard Curiosity rover, which provides several types of context imaging. RMI capabilities now include “Long Distance” acquisitions of targets several kilometers away. In these new acquisitions, substantial differences are visible in LTYu yardang attitudes from lowest to uppermost elevations allowing tentative subdivision of the LTYu into subunits. Bedding geometries in the lower LTYu are consistent with eolian dune foresets which collectively prograde towards an average N134° direction. Based on stratal architectures, the LTYu is viewed as an amalgamated stack of at least two, and possibly four, ancient erg systems bounded by large deflationary “supersurfaces”. Observations point to a multistory generation of yardangs interpreted to have been successively buried during the stratigraphic building of Mt Sharp. We conclude that the successive sequences of eolian deposition-erosion recorded by the LTYu have been generated by cyclic changes from semi-arid to arid conditions, coupled in climatic cycles, including wind regime change. The regional unconformity that tops the Lower mound formation of Mt Sharp, and the subsequent emplacement of the LTYu, collectively express a clear tendency toward sustained arid environments for this region of Mars around the Early – Late Hesperian transition. Given the large time scale involved (i.e., a few tens of million years as a minimum), we consider it likely that the local evidence for increased aridity in the Mt Sharp stratigraphy is a manifestation of climate change affecting the whole planet.

中文翻译：

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火星盖尔陨石坑夏普山浅色调雅丹形成单元的沉积和侵蚀

摘要 Gale 陨石坑是一个大型撞击坑，其中有约 5 公里厚的层状岩石序列，今天表示为中央侵蚀土丘（即，非正式命名为 Mt. Sharp 的 Aeolis Mons）。当前火星科学实验室在盖尔陨石坑执行任务的目标是调查沉积、岩化和侵蚀这种填充物的过程。本研究的对象浅色调雅丹单元（LTYu）单元是夏普山的地质单元之一。我们在这里的具体目的是在大的露头尺度上改进和解释 LTYu 的形态和地层成分的成像文件。结合已建立的轨道图像，我们使用 ChemCam 的远程微成像仪 (RMI)，这是一种目前在好奇号火星车上运行的遥感仪器，可提供多种类型的背景成像。RMI 功能现在包括对几公里外目标的“远距离”获取。在这些新的收购中，从最低海拔到最高海拔的 LTYu yardang 态度明显不同，允许将 LTYu 暂时细分为亚单位。LTYu 下部的层理几何形状与共同向平均 N134°方向前进的风成沙丘预报一致。基于地层结构，LTYu 被视为至少两个，也可能是四个古老的 erg 系统的合并堆栈，这些系统以大型通缩“超表面”为边界。观察表明，在夏普山地层建造过程中，被解释为连续掩埋了多层雅丹。我们得出的结论是，LTYu 记录的连续风积沉积-侵蚀序列是由从半干旱到干旱条件的循环变化产生的，加上气候循环，包括风况变化。夏普山下丘形成顶部的区域不整合面，以及随后的 LTYu 就位，共同表达了火星这一地区在早-晚 Hesperian 过渡期间持续干旱环境的明显趋势。鉴于所涉及的时间尺度很大（即最少几千万年），我们认为夏普山地层干旱增加的当地证据很可能是气候变化影响整个地球的表现。夏普山下丘形成顶部的区域不整合面，以及随后的 LTYu 就位，共同表达了火星这一地区在早-晚 Hesperian 过渡期间持续干旱环境的明显趋势。鉴于所涉及的时间尺度很大（即最少几千万年），我们认为夏普山地层干旱增加的当地证据很可能是气候变化影响整个地球的表现。夏普山下丘形成顶部的区域不整合面，以及随后的 LTYu 就位，共同表达了火星这一地区在早-晚 Hesperian 过渡期间持续干旱环境的明显趋势。鉴于所涉及的时间尺度很大（即最少几千万年），我们认为夏普山地层干旱增加的当地证据很可能是气候变化影响整个地球的表现。