Gravity and aeromagnetic constraints on the structure of the Woods Mountains volcanic center, southeastern California

The Woods Mountain volcanic center is a well-exposed, mildly alkaline volca nic center that formed during the Miocene in southeastern California. Detai led geologic mapping and geochemical studies have distinguished three major volcanic phases: precaldera, caldera forming, and postcaldera. Geologic ma pping indicates that caldera formation occurred incrementally during erupti ons of three large ignimbrites and continued into a period of voluminous in tracaldera lava-flow eruptions. Rhyolitic ignimbrites and lava flows within the caldera are associated with large amplitude, circular gravity, and mag netic minima that are among the most prominent gravity and magnetic anomali es in southeastern California. Analysis of a Bouguer gravity anomaly map, r educed-to-the-pole magnetic intensity map, and three-dimensional gravity an d magnetic models indicates that there is a single, funnel- to bowl-shaped caldera approximately 4 km thick and approximately 10 km wide at the surfac e. This model is consistent with other siliceous, pyroclastic-filled calder as on continental crust, except that most siliceous volcanic centers associ ated with more than one eruption are characterized by more than one caldera .