Mapping Medusae Fossae Formation Materials in the Southern Highlands of Mars
Mapping Medusae Fossae Formation Materials in the Southern Highlands of Mars
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DOI：
10.1016/j.icarus.2010.04.016
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发表时间：
2010-05
期刊：
影响因子：
3.2
通讯作者：
S. Harrison;M. Balme;A. Hagermann;J. Murray;J. Muller
中科院分区：
文献类型：
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作者：
S. Harrison;M. Balme;A. Hagermann;J. Murray;J. Muller
Medusae Fossae地层（MFF）是一个广泛的存款（2.2× 106 km 2，布拉德利，B.A.，Sakimoto，S.E.H.，Frey，H.，Zimbelman，J.R. [2002年]。J. Geophys. Res. 107，5058）的风蚀材料的广泛争论的起源，不整合覆盖在火星上的地壳二分法边界的相当大的面积。MFF显示出各种分层模式、侵蚀样式和水道状形式，并根据暴露和地层学（Scott，D.H.，Tanaka，K.L.，1986.美国地质勘探局地图I-1802-A;格里利，R.，客人，J.E.，1987.地图I-1802-B; Zimbelman，J.R.，Crown，D.，简森，D.，1996.月球。Sci.二十七.摘要#1748.）。远离三个主瓣的是MFF材料的许多异常值。这些主要是在北方低地地区报道的（Keszthelyi，L.，Jaeger，W.L.，和HiRISE团队，2008年。月球。Sci.三十九.摘要#2420。）但很少有研究探讨了在二分法边界以南的高地上MFF异常值的可能性。我们已经搜索了火星轨道器相机窄角（MOC NA）图像，以寻找该区域的异常值。我们的观测表明，在南部高地有许多MFF异常值。异常值的特征表明覆盖在下伏地形上的物质，因为它们广泛出现在倾角、陨石坑和地形低洼处。这些表面以雅丹场为代表，与MFF上部的材料具有类似的片状和不连续性质。大多数具有一致的线理方向在更广泛的区域，这与主要MFF露头中的雅丹的主导方向相匹配。此外，高程数据表明，这些新发现的异常值的最大，最小和平均海拔最接近的MFF上段。因此，我们得出结论，这些存款是MFF异常值，他们可能代表残留的上段材料。我们认为这些异常值可能有两种可能的解释：（1）MFF的侵蚀前范围比以前估计的要大得多，或者（2）主要露头的物质被侵蚀，然后向南吹到高地地区，在那里它们随后被重新加工。我们认为，该地区的地形有利于第一种选择。我们概述了一个“溢出”层饼沉积模型，在该模型中，沉积物层堆积在二分法边界上，直到它们到达高地的地形水平。然后，更多的物质（成为上层MFF物质和异常值）沉积在更广泛的区域，包括二分法边界的南部。严重的侵蚀随后去除了大部分这些物质。
The Medusae Fossae Formation (MFF) is an extensive deposit (2.2×106km2, Bradley, B.A., Sakimoto, S.E.H., Frey, H., Zimbelman, J.R. [2002]. J. Geophys. Res. 107, 5058) of wind-eroded material of widely debated origin, which unconformably overlies a considerable area of the crustal dichotomy boundary on Mars. The MFF shows a variety of layering patterns, erosional styles and channel-like forms and has been mapped into five main outcrops and three geological members according to exposure and stratigraphy (Scott, D.H., Tanaka, K.L., 1986. USGS Map I-1802-A; Greeley, R., Guest, J.E., 1987. Map I-1802-B; Zimbelman, J.R., Crown, D., Jenson, D., 1996. Lunar Planet. Sci. XXVII. Abstract #1748.). Away from the three main lobes are numerous outliers of MFF materials. These have mainly been reported in the northern lowlands regions (Keszthelyi, L., Jaeger, W.L., and HiRISE team, 2008. Lunar Planet. Sci. XXXIX. Abstract #2420.) but few studies have examined the possibility of MFF outliers on high ground south of the dichotomy boundary. We have searched Mars Orbiter Camera Narrow Angle (MOC NA) images for outliers in this region. Our observations show that there are many MFF outliers on the southern highlands. The characteristics of the outliers indicate materials which overlie the underlying terrain for they appear widely in dips, craters and topographic lows. The surfaces are typified by yardang fields and have a similar patchy and discontinuous nature to materials of the upper member of the MFF. Most have consistent lineation orientations across the wider area which match the dominant orientation of yardangs in the main MFF outcrops. Furthermore, elevation data shows that the maximum, minimum and mean elevations of these newly discovered outliers are closest to those of the upper member of the MFF. We therefore conclude that these deposits are MFF outliers and that they probably represent remnant upper member material. We suggest that there might be two possible explanations for these outliers: (1) the MFF had a much greater pre-erosional extent than previously estimated, or (2) materials from the main outcrops were eroded and then blown south to accrue in the highland areas, where they were subsequently reworked. We suggest that the topography of the region favors the first option. We outline an “overflowing” layer-cake deposition model, in which layers of sediment stacked up against the dichotomy boundary until they reached the topographic level of the highlands. Further materials (that went onto become upper-member MFF material and outliers) were then deposited across a wider area, including south of the dichotomy boundary. Severe erosion subsequently removed much of this material.