Stratigraphic nomenclature of the Miocene Superstition Volcanic Field, central Arizona

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).Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu