A widespread volcanic field covered most of the Southern Rocky Mountains in middle Tertiary time, 40 to 25 m.y. ago (approximately Oligocene time). This field covered an erosion surface that beveled structures formed during the Laramide orogeny in Late Cretaceous and early Tertiary time. The source

Upper Cenozoic terrestrial basin-fill sedimentary and basic volcanic rocks are common in the 20,700 km2 Basalt area, which includes parts of the Gore, Sawatch, and southern Park Ranges, Elk Mountains, Grand Mesa, and White River Plateau. Principally on the basis of whole-rock K-Ar ages from basalt f

Miocene-Pliocene history is recorded in south-central Colorado by sediments deposited in subsiding basins bounded by fault-block mountains and by faulted sedimentary and volcanic deposits lying on a channeled late Eocene erosion surface of regional extent. The San Luis Valley and upper Arkansas Vall

This chapter contains sections titled: Introduction Background Geometric and Kinematic Analysis of the Black Canyon Region The Dubois and Cochetopa Successions The Black Canyon and Dubois Succession Contact The Cebolla Creek Quartzite Conglomerate The Proterrozoic Rocks of the Uncompahgre Plateau U-

The central Colorado landscape bears a strong imprint of post-Laramide (late Eocene to Quaternary) tectonics, volcanism, climate change, and drainage rearrangement. This field trip will examine the post-Laramide evolution of central Colorado, traversing the Front Range, from the Colorado Piedmont on

The Paradox Basin is an asymmetric foreland basin, developed along the southwestern flank of the Uncompahgre uplift in southeast Utah and southwest Colorado, USA. This large basin (265km by 190km) developed during the middle Pennsylvanian-Permian ancestral Rocky Mountain orogenic event. Salt structu

This field trip guidebook chapter outlines the glacial history of the upper Arkansas River valley, Colorado, and builds on a previous GSA field trip to the same area in 2010. The following will be presented: (1) new cosmogenic 10Be exposure ages of moraine boulders from the Pinedale and Bull Lake gl

The Early and Middle Proterozoic rocks in the Needle Mountains include three distinct rock sequences (1) multiply deformed bimodal metavolcanic rocks, related sedimentary rocks, and plutonio units, all metamorphosed to medium grade; (2) multiply deformed clastic sedimentary rocks metamorphosed to lo

Irrigation water from a southeastern Colorado county has been sold to distant municipalities. The county's junior water right delivered limited and uncertain water supplies which were used on relatively poor soils. The ability of water markets to allocate water to the highest-valued use was addresse

The Collaborative Forest Landscape Restoration Program (CFLRP) created the conditions for translating the idea of collaborative adaptive management (CAM) into practice. In theory, CAM engages stakeholders to collectively ‘learn by doing’ through a continuous cycle of goal-setting, implementing, moni

Geomorphic changes in reconfigured reaches of three Colorado rivers in response to floods in 2005 provide a benchmark for "restoration" assessment. Sediment-entrainment potential is expressed as the ratio of the shear stress from the 2 yr, 5 yr, 10 yr, and 2005 floods to the critical shear stress fo

The theme of the 2004 GSA Annual Meeting and Exposition, "Geoscience in a Changing World," covers both new and traditional areas of the earth sciences. The Front Range of the Rocky Mountains and the High Plains preserve an outstanding record of geological processes from Precambrian through Quaternar

The Southern Rocky Mountain volcanic fi eld contains widespread andesite and dacitic lavas erupted from central volcanoes; associated with these are ~26 regional ignimbrites (each 150–5000 km3) emplaced from 37 to 23 Ma, source calderas as much as 75 km across, and subvolcanic plutons. Exposed pluto

Abstract The Black Canyon in southwestern Colorado is easily reached by passenger car from U.S. 50 (Fig. 1). Turn north 8 mi (13 km) east of Montrose, Colorado, to reach Black Canyon of the Gunnison National Monument in the most impressive part of the canyon. The National Monument boundary is 5 mi (

which, following Aldenderfer (2006), we define as locations at elevations greater than 2,500 meters above sea level (e.g.,