Geologic map of the MTM-15147 quadrangle, Mangala Valles region of Mars

The map area is in the Mangala-Memnonia region (fig. 1), which contains remarkably diverse geologic features and terrain types. Studies of the Mariner 9 images revealed the wide range of ages of the major rock units in this region; age assignments were based on the density of impact craters preserved on the various surfaces (Mutch and others, 1976, p. 56-60; Scott and Carr, 1978; Mutch and Morris, 1979). The region includes ancient cratered highlands, more sparsely cratered smooth plains, young volcanic plains, and the Mangala Valles channel system. The sinuosity of the streamlined landforms within the Mangala Valles, combined with braided channels evident throughout the lower reaches of the valley system, were recognized as indicators that he Mangala area was subject to substantial erosion by a flowing fluid, most likely water (Milton, 1973; Baker and Milton, 1974; Sharp and Malin, 1975). Recent global mapping based on the Viking Orbiter images (Scott and Tanaka, 1986) has refined the relative ages of many rock units on Mars, but it has modified only slightly the basic interpretations of features in the Mangala-Memnonia region.