Melas Chasma: morphology and tectonic patterns

Abstract

The central Valles Marineris is the widest part of the equatorial trough system of Mars. Melas Chasma and parts of Coprates and Candor Chasmata provide some of the clearest clues on the relationships between erosional landforms, deposits and various volcanic and tectonic features. A detailed geomorphic study of the troughs allows the identification of faults and other structures in most parts of this area, in spite of local obliteration by erosional and depositional processes. Tectonic control on erosional landforms appears mainly in the northern walls of Melas Chasma and in the edge of the inner plateau above the trough floor. Longitudinal major faults are identified only along the northern wall. However the trough may not be a simple half graben: another fault line is inferred inside Melas Chasma southern walls along the edge of a wide bench of layered deposits. A deep and relatively narrow graben linking those of Ius and Coprates Chasmata appears to be downfaulted inside a wider basin with eroded sides. Transverse or oblique faults control some outlines of these erosional landforms, whereas a few monoclines or faults restricted to the basin beds reveal compressional stresses or differential vertical movements related to the basin development.