The Superstition volcanic field is defined as all area within the outcrop belt of the Apache Leap Tuff. This definition follows that of Sheridan (1978) who defined the Superstition - Superior field as the area within the areal extent of the Apache Leap Tuff and the Superstition Tuff. Before Sheridan (1978) coined the term Superstition – Superior volcanic field, the field was referred to as the Superior volcanic field (e.g. Ransome, 1903; Sheridan et al., 1969). Since it has become apparent that the Apache Leap Tuff and Superstition Tuff are part of the same major regional ash-flow tuff sheet (Ferguson et al., 1998; McIntosh and Ferguson, 1999), and because it is clear that volcanoes in the Superstition Mountains were the source of most of the region's Mid-Tertiary volcanic rocks, shortening the name to the Superstition volcanic field seems appropriate. Our work shows that only one regional ash-flow tuff is present (the 18.58 + 0.03 Ma Apache Leap Tuff), and that this tuff was probably derived from only one major source cauldron (the Superstition Cauldron). The Apache Leap Tuff occurs in the middle of a relatively simple sequence of lava and sedimentary units that span the interval of time 20.5 – 16.0 Ma. Previously, 4 major ash-flow tuff units and at least 4 major source cauldrons had been identified, along with a complex sequence of interbedded lava, non-welded tuff, and sedimentary units that spanned a much longer (27-14 Ma) interval of time (Stuckless and Sheridan, 1971).