Geology of the Valles Marineris: First analysis of imaging from the Viking 1 Orbiter Primary Mission
Geology of the Valles Marineris: First analysis of imaging from the Viking 1 Orbiter Primary Mission
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水手谷的地质：对 Viking 1 轨道飞行器主要任务成像的首次分析
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
H. Masursky
中科院分区：
文献类型：
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作者：
K. Blasius;J. Cutts;J. Guest;H. Masursky
水手谷是一个巨大的峡谷系统，横跨火星赤道周长的四分之一以上，其地貌表现出独特的火星伸展构造和各种侵蚀和沉积过程的后果。这里报道的是新的见解的峡谷系统的演变和可能的证据周期性气候变化的赤道地区。构造控制似乎是对峡谷形成和演化的根本影响，但构造作用的类型或强度似乎是区域性变化的。在西部和中部峡谷地区，细长的坑链，地堑，和实际的槽都被推断为显着的南北和二次东西地壳伸展的表现。有人提出，这一地区的水手谷是由大量的离散细长块体，已转移垂直和倾斜的关系。取决于这种调整的几何形状，表层作为一个连贯的块体下沉或塌陷形成一系列凹坑。在东部的峡谷和混乱的地形，构造似乎遵循不同的模式，因为地壳层分裂成大片的等分块，似乎反映了地壳伸展量较少。峡谷中不同的壁特征和不同的滑坡形态表明，物质已从槽壁转移到地板上，导致其扩大。峡谷内小撞击坑的缺乏表明，这一过程跨越了火星历史的很大一部分，甚至可能直到今天。小的，明确界定的陡坎削减侵蚀功能的许多峡谷壁，这表明峡谷扩大的驱动力继续下降。这一结论得到了缺乏证据的外生过程中挖掘的支持。许多海槽被分割成封闭的盆地，排除了碎屑的横向运输，除了风成的紧缩，这方面的证据很少。在至少两个互不相连的峡谷的底部，已经发现了大量有规律的分层沉积物。沉积速率或条件的周期性变化是隐含的。各种层状和非层状峡谷内部物质以及沙丘场之间的地层关系要求，自形成以来，某些峡谷内发生了大量沉积和再侵蚀。水手谷伸展构造的普遍影响使我们怀疑，是否需要用地面冰的腐烂或火山活动来解释东部峡谷或混乱地形的崩塌。我们没有发现有说服力的证据，前河流事件槽系统适当的，大多数侵蚀功能可以占质量浪费。然而，有人认为，周期性的气候变化在峡谷中分层物质的发展中发挥了作用，就像它显然控制了极地地区沉积物的分层一样。在塔尔西斯-叙利亚隆起东侧的水手谷（Valles Marineris），长期的构造活动可能与西侧的长期火山作用和构造作用有关。这种关系所暗示的火星内部深处的长期动态过程也可能是与上升相关的大重力异常的原因。
The Valles Marineris, an enormous canyon system spanning more than one quarter of the equatorial girth of Mars, exhibits in its landforms the consequences of uniquely Martian extensional tectonics and a variety of erosional and depositional processes. Reported here are new insights into the evolution of the canyon system and possible evidence for cyclical climate change from the equatorial region. Tectonic control appears to be the fundamental influence on canyon form and evolution, but the style or intensity of tectonism appears to be regionally variable. In the region of the west and central canyons, chains of elongate pits, graben, and the actual troughs are all inferred to be manifestations of pronounced north-south and secondary east-west crustal extension. It is proposed that this region of the Valles Marineris is made up of a large number of discrete elongate blocks which have shifted vertically and tilted in relation to one another. Depending on the geometry of this adjustment the surface layer subsides as a coherent block or collapses to form a chain of pits. In the eastern canyons and chaotic terrain the tectonics appear to follow a different pattern, as the crustal layer breaks up into large patches of equant blocks, seemingly reflecting a lesser amount of crustal extension. Diverse wall features and varied landslide morphologies in the canyons indicate that material has been transported from the walls of the troughs to the floors, contributing to their widening. The paucity of small impact craters inside the canyons suggests that this process spans a large part of Martian history, perhaps even up to the present day. Small, sharply defined scarps cut erosional features on many canyon walls, suggesting that the driving force for canyon enlargement continues to be downfaulting. This conclusion is supported by the absence of evidence for excavation by exogenic process. Many troughs are segmented into closed basins, precluding lateral transport of debris except by aeolian deflation, for which there is little evidence. Substantial accumulations of regularly layered sediments have been recognized on the floors of at least two unconnected canyons. Cyclical variations in sedimentation rates or conditions are implied. The stratigraphic relationships among various layered and unlayered canyon interior materials as well as dune fields require that substantial deposition and reerosion have taken place within some canyons since their formation. The pervasive influence of extensional tectonics in the Valles Marineris leads us to doubt that the decay of ground ice or volcanism needs to be invoked to explain collapse in the eastern canyons or chaotic terrain. We find no persuasive evidence for former fluvial episodes in the trough system proper, where most erosional features can be accounted for by mass wasting. There are suggestions, however, that cyclical climate change has played a role in the development of layered materials in the canyons in the same way that it has apparently controlled layering of deposits in the polar regions. Prolonged tectonic activity in the Valles Marineris, on the east flank of the Tharsis-Syria Rise, may correlate with prolonged volcanism and tectonism in evidence on the west flank. The long-lived dynamic process in the deep Martian interior suggested by this relationship may also be responsible for large gravity anomalies associated with the rise.