Ash Flows and Related Volcanic Rocks Associated with the Creede Caldera, San Juan Mountains, Colorado

A complex pile of Tertiary volcanic rocks in the central San Juan Mountains, Colo., consists of welded ash-flow tuffs, lava flows, and breccias from several sources. A more limited sequence within this assemblage originated in or bordering the Creede caldera and is the subject of this report. The Creede caldera sequence consists of five major ash-flow formations, locally interlayered lava flows, a succeeding lava-flow formation, and the volcanic-clastic Creede Formation.