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The Fort Morgan 7.5' quadrangle is located on the semiarid plains of northeastern Colorado, along the South Platte River corridor where the river has incised into Upper Cretaceous Pierre Shale. The Pierre Shale is largely covered by surficial deposits that formed from alluvial, eolian, and hillslope processes operating in concert with environmental changes from the late Pliocene to the present. The South Platte River, originating high in the Colorado Rocky Mountains, has played a major role in shaping surficial geology in the map area, which is several tens of kilometers downstream from where headwater tributaries join the river. Recurrent glaciation (and deglaciation) of basin headwaters has affected river discharge...
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This 1:50,000-scale geologic map represents a compilation of the most recent geologic studies of the upper Arkansas River valley, between Leadville and Salida, Colorado. The valley is structurally controlled by an extensional fault system that forms part of the prominent northern Rio Grande rift, an intra-continental region of crustal extension. This work also incorporates new detailed geologic mapping of poorly understood areas within the map area and reinterprets previously studied areas, aided by lidar data that covers 59 percent of the map area. The mapped region extends into the Proterozoic metamorphic and intrusive rocks in the Sawatch Range west of the valley and the Mosquito Range to the east. Paleozoic...
Categories: Data; Tags: 207Pb/206Pb zircon age, 40Ar/39Ar age, Arkansas River, Balltown, Balltown placer gold mining areas, All tags...


    map background search result map search result map Data release for the geologic map of the upper Arkansas River valley region, north-central Colorado Data release for the geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado Data release for the geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado Data release for the geologic map of the upper Arkansas River valley region, north-central Colorado