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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The stratigraphy of Meridiani Planum, Mars, and implications for the layered deposits' origin
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The stratigraphy of Meridiani Planum, Mars, and implications for the layered deposits' origin

机译：Meridiani Planum，火星的地层及其对分层矿床成因的启示

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摘要

Large exposures of water-altered layered deposits have recently been identified on the surface of Mars. The source materials, formation, and aqueous alteration history are presently poorly understood. The Mars Exploration Rover Opportunity has examined a tiny fraction of large-scale layered deposits in Meridiani Planum, and many questions remain about the origin and history of these widespread materials. Here we present the first detailed stratigraphic study of sulfate-bearing layers throughout the region. We used altimetry data to examine the three-dimensional disposition of twenty-two distinct stratigraphic horizons along their exposures. Our results show that most of these benchmark horizons: (1) are planar and coherent over. at least a 100-km scale, and (2) have dip azimuth and magnitudes that are similar to the underlying regional slope, which was emplaced by 3.70 Ga. Nearby ancient river valleys, that appear to have been formed by precipitation-fed surface runoff, originally were incised at similar to 3.74 Ga and then reactivated near the Noachian-Hesperian boundary (3.70 Ga). Mapping relations with these valleys suggest that the Meridiani layers formed near and after this time and without significant volumetric contributions of material excavated from the valleys. Thermal infrared data and erosional expressions imply that significant physical compositional differences exist within the stratigraphy, and these likely reflect a changing paleodepositional environment and/or chemical alteration histories. Any hypothesis for the origin of these regional-scale materials must be consistent with all these observations. We conclude that the previously stated hypotheses of aeolian deposition cemented by a fluxing groundwater table and sulfur-rich volcanic processes are both viable possibilities, while other hypotheses are not supported by these observations.
机译：最近在火星表面发现了大量水蚀层状沉积物。目前对原料，形成和含水变化的历史了解甚少。火星探测漫游者的机会已经检查了Meridiani Planum中一小部分大型分层沉积物，关于这些广泛存在的物质的起源和历史，仍然存在许多疑问。在这里，我们介绍了整个地区含硫酸盐层的首次详细地层学研究。我们使用测高仪数据来检查沿其暴露的22个不同地层的三维分布。我们的结果表明，大多数这些基准范围：（1）是平面的，并且在整个范围内是连贯的。至少100公里的规模，并且（2）的俯仰方位角和大小与下层区域坡度相似，后者被3.70 Ga所包围。附近的古老河谷似乎是由降水供给的地表径流形成的最初在类似于3.74 Ga的位置切割，然后在Noachian-Hesperian边界（3.70 Ga）附近重新激活。与这些山谷的映射关系表明，这段时间和之后形成了子午线层，并且没有从山谷中挖出的物质有明显的体积贡献。红外热数据和侵蚀表达式表明地层内部存在明显的物理组成差异，这些差异可能反映了古沉积环境和/或化学蚀变历史的变化。这些区域性材料起源的任何假设都必须与所有这些观察结果一致。我们得出的结论是，先前所说的由通量地下水位和富含硫的火山作用胶结的风沙沉积假说都是可行的可能性，而其他假说不受这些观察结果的支持。

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