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Case study of climatic changes in Martian fluvial systems at Xanthe Terra

机译：Xanthe Terra火星河流系统气候变化的案例研究

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摘要

An unnamed valley system was analyzed in Xanthe Terra south of Havel Vallis on Mars where three separate episodes of fluvial activity could be identified with different morphology, water source and erosional processes, inferring formation under different climatic conditions. The oldest scattered valleys (1. group) form interconnecting network and suggest areally distributed water source. Later two valley types formed from confined water source partly supported by possible subsurface water. The smaller upper reaches (2. group) with three separate segments and also a similar aged but areal washed terrain suggest contribution from shallow subsurface inflow. These valleys fed the main channel (3. group), which morphology (wide, theater shaped source, few tributaries, steep walls) is the most compatible with the subsurface sapping origin. While the first valley group formed in the Noachian, the other two, more confined groups are younger. Their crater density based age value is uncertain, and could be only 1200 million years. After these three fluvial episodes etch pitted, heavily eroded terrain formed possibly by ice sublimation driven collapse. More recently (60-200 million years ago) dunes covered the bottom of the valleys, and finally the youngest event took place when mass movements produced debris covered the valleys' slopes with sediments along their wall around 5-15 million years ago, suggesting wind activity finished earlier than the mass movements in the region. This small area represents the sequence of events probably appeared on global scale: the general cooling and drying environment of Mars. Comparing the longitudinal profiles here to other valleys in Xanthe Terra, convex shaped valley profiles are usually connected to steep terrains. The location of erosional base might play an important role in their formation that can be produced convex shapes where the erosional base descended topographically (by deep impact crater or deep outflow channel formation) as time passed by. The analysis of such nearby systems that probably witnessed similar climatic forces in the past, provides ideal possibility to identify reasons and geomorphological context of longitudinal profile shape formation for fluvial valleys in general.
机译：在火星哈维尔·瓦利斯（Havel Vallis）以南的Xanthe Terra上分析了一个未命名的山谷系统，在那里可以识别出三个不同的河流活动事件，它们具有不同的形态，水源和侵蚀过程，推断出在不同气候条件下的形成。最古老的分散山谷（1.组）形成了相互连接的网络，并建议采用面分布的水源。后来，由承压水源形成的两个山谷类型部分由可能的地下水支撑。较小的上游地区（2个组）具有三个独立的区段，并且具有相似的老化但区域被水洗的地形，表明浅层地下涌入是造成这种情况的原因。这些山谷为主要河道（3.组）提供了动力，该河道的形态（宽，剧场形震源，少量支流，陡壁）与地下裂起源最兼容。虽然第一个山谷群是在Noachian中形成的，但其他两个更受限制的群则更年轻。他们基于陨石坑密度的年龄值是不确定的，可能只有12亿年。在这三个河流事件发生蚀蚀之后，可能是由冰升华驱动的塌陷形成的严重侵蚀的地形。最近（60-2亿年前）沙丘覆盖了山谷的底部，最后最年轻的事件发生在大约5到15百万年前，大规模运动产生的碎片在山谷的山坡上沉积了沉积物，这表明风活动比该地区的群众运动更早完成。这个小区域代表着可能在全球范围内发生的事件的顺序：火星的一般冷却和干燥环境。将此处的纵剖面与Xanthe Terra中的其他山谷进行比较，通常将凸形的山谷剖面连接到陡峭的地形。侵蚀基底的位置可能在其形成过程中起重要作用，随着时间的流逝，侵蚀基底可能会形成凸形，其中侵蚀基底在地形上会下降（通过深撞击坑或深流出通道的形成）。对这些附近系统的分析可能在过去曾经历过类似的气候作用力，这为确定河谷总体纵向轮廓形状形成的原因和地貌背景提供了理想的可能性。

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  • 来源
    《Planetary and space science》 |2014年第6期|35-50|共16页
  • 作者

    Akos Kereszturi;

  • 作者单位

    Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences,Konkoly Thege M. 15-17, H-1121 Budapest, Hungary;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Mars; Water; Valley; Fluvial geomorphology;

    机译：火星;水;谷;河流地貌;

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