Evolution of a multi-vent volcanic complex within a subsiding arc graben depression: Mount Wrightson Formation, Arizona

The nature and distribution of volcanic lithofacies in the Mount Wrightson Formation are interpreted to record the evolution of a multi-vent volcanic complex that formed within a subsiding cratonal intra-arc graben. The paucity of debris-flow deposits and the burial of near-vent facies assemblages by ignimbrites suggest that the formation was deposited in a low-relief multi-vent complex with no high-standing central edifice. The Mount Wrightson complex evolved from predominantly effusive to predominantly explosive followed by waning volcanism. Rapid intra-arc subsidence resulted in burial of vent areas by craton-derived eolian quartz arenites correlative with either the Wingate or Navajo Sandstones on the Colorado Plateau; this was particularly important as volcanism waned. -from Authors