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首页> 外文期刊>Planetary and space science >Formation of coarse sediment lags in ice-sediment mixtures: A geomorphic signature of sublimation on regolith surfaces
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Formation of coarse sediment lags in ice-sediment mixtures: A geomorphic signature of sublimation on regolith surfaces

机译:冰沙混合物中粗大沉积物滞后的形成:re石表面升华的地貌标志

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摘要

In many high-latitude locations on Mars, boulder sized clasts are present at the ground surface atop finer-grained sediments. These areas are concentrated in the latitude dependent mantle (LDM), an ice-rich surface unit that is globally distributed polewards of similar to 30 degrees latitude. Here, we test the hypothesis that sublimation of buried ice can drive grain size sorting in elastic deposits. We conducted pilot laboratory experiments to determine how buried and interstitial dry ice (CO2) sublimation modifies the grain size distribution in overlying and intermingled lithic sediments. We found that sublimation can sort grains into horizons with distinct grain size distributions by allowing fines to winnow into space freed by sublimation of underlying ice. On sloped surfaces, this mechanism enables lateral sorting by concentrating large grains on the surface and allowing them to slide or roll downslope. We infer that sublimation-driven sorting may affect the surface grain size distribution of solar system objects for which solid-vapor phase transitions dominate (e.g., modern Mars, comet 67P/Churyumov-Gerasimenko, asteroids, etc.).
机译:在火星上许多高纬度地区,较细颗粒沉积物顶部的地面上都存在巨石大小的碎屑。这些区域集中在纬度相关地幔(LDM)中,这是一种富含冰的地表单元,在全球范围内向纬度分布,类似于30度纬度。在这里,我们测试了一种假设,即地下冰的升华可以驱动弹性沉积物中的颗粒大小排序。我们进行了试点实验室实验,以确定掩埋和间隙干冰(CO2)的升华如何改变上覆和混杂的岩性沉积物中的粒度分布。我们发现,升华可以通过将细粉吹入下层冰升华而释放的空间中,从而将晶粒分类为具有不同晶粒尺寸分布的地层。在倾斜的表面上,此机制可以通过将大颗粒集中在表面上并使它们滑动或向下倾斜来实现横向分类。我们推断升华驱动的分类可能会影响以固态蒸气相变为主的太阳系物体的表面晶粒尺寸分布(例如现代火星,彗星67P / Churyumov-Gerasimenko,小行星等)。

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