Geologic observations of the Martian highland boundary in the Mamers Valles region

A geologic map of the Ismenius Lacus (MC-5) Southwestern subquadrangle of Mars is described, using the 1:2,000,000 photomosaic as a base. The mapping, and a limited study of the surrounding areas, was done to determine the nature and origin of fretted terrain, fretted channels, and the northern highland scarp. Some highlights resulting from the mapping and accompanying topical investigations are included.