These nine maps depict the general ages and distribution of Quaternary geomorphic surfaces and associated alluvium of the northern Avra Valley-Desert Peak (AVDP) area, Pinal and Pima counties, southern Arizona. The area mapped includes portions of the piedmonts surrounding the Silver Bell, Picacho, and Tortolita mountains, and the basin flats between them. The southern margin of the study area is approximately 40 km northwest of downtown Tucson. The AVDP area is one of many broad valleys in the Basin and Range physiographic province of southern Arizona. The Basin and Range province in the vicinity of the study area is characterized by relatively small mountain ranges with fairly low relief separated by wide, gently sloping piedmonts and basin bottom river drainages. The major drainages flowing through study area are the Santa Cruz River, Brawley Wash, and McClellan Wash. By indicating the age and physical characteristics of surficial alluvial deposits, these maps provide a basis for evaluating the Quaternary geologic history of the area and assessing potential geologic hazards. Alluvial deposits differentiated for these maps are assigned to Quaternary and Upper Tertiary age categories primarily on the basis of the estimated age of cessation of major deposition on geomorphic surfaces associated with the deposits. Relative topographic positions of each surface, drainage patterns, surface characteristics, and degree of soil development associated with the surface are the principal criteria used to assess surface age. Six ages of surfaces are differentiated in these maps. Map units are further subdivided into piedmont and basin axis units. The characteristics of each map unit are described below. The estimated ages of the units are inferred by correlation with similar surfaces and soils dated elsewhere in the southwestern United States (Gile and others, 1981; Bull, 1991; Menges and McFadden, 1981). Generalized lithologies of exposed bedrock are also depicted on the maps. (11 pages)