Data release for the geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado

Dates

Publication Date: 2018-06-07
Time Period: 2018

Citation

Berry, M.E., Taylor, E.M., Slate, J.L., Paces, J.B., Hanson, P.R., and Brandt, T.R., 2018, Data release for the geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado: U.S. Geological Survey data release, https://doi.org/10.5066/F7QC02PQ.

Summary

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 and sediment supply [...]

Summary

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 and sediment supply far downstream, influencing deposition of alluvium and river incision in the Fort Morgan quadrangle. Distribution and characteristics of the alluvial deposits indicate that during the Pleistocene the course of the river within the map area shifted progressively southward as it incised, and by late middle Pleistocene the river was south of its present position, cutting and filling a deep paleochannel near the south edge of the quadrangle. The river shifted back to the north during the late Pleistocene. Kiowa and Bijou Creeks are unglaciated tributaries originating in the Colorado Piedmont east of the Front Range that also have played a major role in shaping surficial geology of the map area. Periodically during the late Pleistocene, major flood events on these tributaries deposited large volumes of sediment at and near their confluences, forming a broad, low-gradient fan composed of sidestream alluvium that could have occasionally dammed the river for short periods of time. Wildcat Creek, also originating on the Colorado Piedmont, and the small drainage of Cris Lee Draw dissect the map area north of the river. Eolian sand deposits of the Sterling (north of river) and Fort Morgan (south of river) dune fields cover much of the quadrangle and record past episodes of sand mobilization during times of prolonged drought. With the onset of irrigation and damming during historical times, the South Platte River has changed from a broad, shallow, and sandy braided river with highly variable seasonal discharge to a much narrower, deeper river with braided-meandering transition morphology and more uniform discharge.

Contacts

Point of Contact :: Margaret E Berry, U.S. Geological Survey
Originator :: Margaret E Berry, Emily M Taylor, Janet L Slate, James B Paces, Paul R Hanson, Theodore R Brandt
Metadata Contact :: Theodore R Brandt, U.S. Geological Survey
Publisher :: U.S. Geological Survey
Distributor :: U.S. Geological Survey - ScienceBase
SDC Data Owner :: Geosciences and Environmental Change Science Center
USGS Mission Area :: Core Science Systems

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SIM3408.xml Original FGDC Metadata	View	34.52 KB	application/fgdc+xml
SIM3408.met “metadata text/plain”		39.05 KB	text/plain
SIM3408GIS.zip		2.11 MB	application/zip
SIM3408.gdb.zip		12.03 MB	application/zip
ftmobasr.tif		80.98 MB	image/geotiff
ftmobasr.tfw		89 Bytes	text/plain

Related External Resources

Type: Related Primary Publication

Geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado	https://doi.org/10.3133/sim3408

Type: Web Link

Data release of OSL, 14C, and U-series age data supporting geologic mapping along the South Platte River corridor in northeastern Colorado	https://doi.org/10.5066/F7QN65M3

Purpose

To provide a geologic map database showing the distribution of fluvial, eolian, and hillslope deposits along the South Platte River corridor in the Fort Morgan, Colorado area, to better understand past geomorphic system response to environmental change and the geologic framework of South Platte River corridor ecosystems.

Data release for the geologic map of the Fort Morgan 7.5' quadrangle, Morgan County, Colorado

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