One of the fastest growing areas of Arizona is the eastern part of the PhoenixBasin near the communities of Chandler, Gilbert, Mesa, and Apache Junction. Much ofthis development has occurred on the piedmont near the base of the mountains where littleof the surficial geology has ever been mapped. Because this area of the Phoenix Basin willcontinue to grow in the future, there is a need to understand the nature and distribution ofsurficial deposits. Surficial geologic mapping provides a spatial data base for assessingpotential geologic hazards (pearthree, 1991), for defining important groundwater rechargezones, and for analyzing the physical characteristics of surface deposits for excavationpurposes. Such mapping is also valuable to earth scientists who are interested in definingthe links between landscape evolution and climate change (Bull, 1991).This report presents the results of surficial geologic mapping in the eastern marginsof the Phoenix Basin including the Superstition Mountain piedmont and Queen Creekalluvial fan (Figure 1). The region mapped is contained within the Florence Junction,Florence NE, Goldfield, Magma, and Superstition Mountains SW quadrangles (1:24,000),and part of the Weavers Needle quadrangle (1:24,000). This area contains a variety oflandscape elements including steep mountain slopes, pediments, and alluvial fans.Included within this report is a discussion of the origins of pediments and an analysis ofstreamflow processes on the Queen Creek fan. ( 33 pages; 6 map sheets, map scale 1:24,000)