Geologic map of the MTM-15147 quadrangle, Mangala Valles region of Mars
The map area is in the Mangala - M e mnonia 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 wer e based on the density of impact craters preserved on the various surfaces ( Mutch and others, 1976, p. 56-60; Scott and Carr , 1978; Mut c h 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 l an dforms within the Man g ala 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 slightl y the basic interpretations of features in the Mangala- Memnonia region.