This map of the central Sawatch Range extends from Aspen on the west to the valley of the Arkansas River on the cast and from Independence Pass on the north to Cottonwood Pass on the south. This map is centered on the Collegiate Peaks Wilderness Area, which contains some of Colorado's finest alpine scenery. Bedrock geology consists of a diverse mixture of early Proterozoic metasedimentary, metavolcanic, and plutonic rocks that are intruded by middle Proterozoic granites. Paleozoic and Mesozoic strata once covered the region but now are restricted to the far western part of the map area. Oligocene volcanism culminated in the eruption of the Grizzly Peak tuff and formation of the Grizzly Peak Caldera, which is spectacularly exposed in the north-central part of the map area.
Glacial deposits mantle many of the high cirques and valley bottoms.
Supporting text, figures, and tables summarize the geochemistry of most igneous rock units and the geochronology of the region.