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Scientific Investigations Map 2890
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Surficial geologic map of the upper Bear River and Bear Lake drainage basins, Idaho, Utah, and Wyoming

By Marith C. Reheis

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The upper Bear River drainage basin is located in the Overthrust Belt at the eastern margin of late Cenozoic basin-and-range faulting. The Bear River has its headwaters in the Uinta Mountains and flows generally north through a broad alluvial valley with few, relatively inactive faults, then jogs abruptly west into Bear Lake Valley, bounded by active faults. Surficial deposits in the Bear River Valley above the lake consist mainly of Pleistocene glacial outwash and Holocene alluvial deposits; pre-late Pleistocene terrace deposits are mainly preserved just downstream of glacial deposits in the Uinta Mountains. Extensive areas of thin pediment deposits along the valley margins attest to relative stability of this landscape. Through most of Holocene time, and at intervals in the Pleistocene, Bear River has flowed past a groundwater-fed Bear Lake; at other times, most recently in the late Pleistocene, the lake has risen and expanded to engulf the river and submerge much of the valley. Consequently, surficial deposits in Bear Lake Valley south of the modern river are dominated by lacustrine and paludal (marsh) deposits of late Pleistocene and Holocene age; from the river north, Bear River alluvium is also abundant. Older lake and marsh deposits are locally preserved along the footwall block of the East Bear Lake fault zone bounding the east side of the lake. Moraines of small valley glaciers are preserved along the Bear River Range northwest of the lake.

Version 1.0

Posted January 2006

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This geospatial database consists of ArcInfo export files and ArcView shapefiles contained in a gzipped tar archive or zip archive. Both compressed archive files contain both types of geospatial database files. Please refer to the file 2890.met for detailed metadata documentation for this geospatial database. logo