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Ferricrete, manganocrete, and bog iron occurrences with selected sedge bogs and active iron bogs and springs in the upper Animas River watershed, San Juan County, Colorado

Miscellaneous Field Studies Map 2406

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Abstract

During 1996 to 2000, the Bureau of Land Management, National Park Service, Environmental Protection Agency, United States Department of Agriculture (USDA) Forest Service, and the U.S. Geological Survey (USGS) developed a coordinated strategy to (1) study the environmental effects of historical mining on Federal lands, and (2) remediate contaminated sites that have the greatest impact on water quality and ecosystem health. This dataset provides information that contributes to these overall objectives and is part of the USGS Abandoned Mine Lands Initiative. Data presented here represent ferricrete occurrences and selected iron bogs and springs in the upper Animas River watershed in San Juan County near Silverton, Colorado. Ferricretes (stratified iron and manganese oxyhydroxide-cemented sedimentary deposits) are one indicator of the geochemical baseline conditions as well as the effect that weathering of mineralized rocks had on water quality in the Animas River watershed prior to mining. Logs and wood fragments preserved in several ferricretes in the upper Animas River watershed, collected primarily along streams, yield radiocarbon ages of modern to 9,580 years B.P. (P.L. Verplanck, D.B. Yager, and S.E. Church, work in progress). The presence of ferricrete deposits along the current stream courses indicates that climate and physiography of the Animas River watershed have been relatively constant throughout the Holocene and that weathering processes have been ongoing for thousands of years prior to historical mining activities. Thus, by knowing where ferricrete is preserved in the watershed today, land-management agencies have an indication of (1) where metal precipitation from weathering of altered rocks has occurred in the past, and (2) where this process is ongoing and may confound remediation efforts. These data are included as two coverages-a ferricrete coverage and a bogs and springs coverage. The coverages are included in ArcInfo shapefile and ArcInfo interchange file format.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Ferricrete, manganocrete, and bog iron occurrences with selected sedge bogs and active iron bogs and springs in the upper Animas River watershed, San Juan County, Colorado
Series title:
Miscellaneous Field Studies Map
Series number:
2406
Edition:
Version 1.0
Year Published:
2003
Language:
ENGLISH
Description:
map; Sheet 54 by 42 inches (in color). Accompanied by 10 page text
Scale:
24000