This file is a digital line representation of measured and inferred bedrock faults in the Boulder-Weld coal field, Denver Basin, Colorado. This file was created as part of the Front Range Infrastructure Resources Project (FRIRP) of the USGS, and provides information pertaining to energy resource issues within the Colorado Front Range urban corridor in and near the Denver metro area. These data contributed to the publication titled as follows: Maps showing the extent of mining, locations of mine shafts, adits, air shafts, and bedrock faults, and thickness of overburden above abandoned coal mines in the Boulder-Weld coal field, Boulder, Weld, and Adams counties, Colorado: U.S. Geological Survey Geologic Investigations Map I-2735, 1:48000-scale.
In 1996, the U.S. Geological Survey (USGS) initiated a Front Range Infrastructure Resources Project (FRIRP) to provide relevant information to the public, land-use planners, and decision makers regarding the location and characteristics of water, mineral, and energy resources along the Front Range corridor in Colorado. Energy resource issues within the FRIRP project area include the impacts of historic coal mining, particularly in regard to the potential for subsidence over abandoned mines in recently developed areas or in areas currently being evaluated as residential, commercial, and (or) industrial building sites. In order to address this issue, the USGS and the Colorado Geological Survey (CGS) jointly undertook the development of digital datasets (coverages) based on previously published maps showing the location and distribution of abandoned underground coal mines and associated bedrock faults in the Boulder-Weld coal field north and northwest of Denver, Colorado. Mining in the coal field began in the early 1860s and continued into the 1970s with the last mine closing in 1979 because of fire. Although much of the surface expression of mine development has been removed or masked by increasing urban and residential development, subsurface features of underground mining, such as shafts and open mine rooms, are still present. Because of this, there continues to be a potential for subsidence in abandoned mine areas. //geosurvey.state.co.us.
The digital coverage of measured and inferred bedrock faults is based primarily on a previously published map showing abandoned coal mines and faults in the Boulder-Weld coal field as compiled by the consulting firm of Amuedo and Ivey for the Colorado Geological Survey in the early 1970s (see Myers and others, 1975, in reference section of metadata). In that study, the position of faults was derived in great part from historic mine maps and interpretations of Colton and Lowrie (1973). In this coverage, we have made no modifications to those previous fault interpretations. Alternative fault interpretations in the Erie and Frederick 7.5' quadrangle areas of the coal field can be found in more recent studies by Spencer (1986). Although Spencer's interpretation of faults differs in certain aspects to that of the faults represented in this coverage, we have maintained the structural interpretations of Myers and others (1975) because of the close relation between mine extent and fault locations in many instances; deviation from the original interpretations might result in inconsistencies between the mine extent and structural coverages.
publication date
These data are considered more accurate at scales of 1:48,000 or smaller.
U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center
Fault lines (arcs) were compared visually with background Tiff images of mine extent derived from photographic reproduction of mine information as depicted in Myers an others (1975).
Due to the nature and inaccuracy of the digitization process from scanned tiled images, some minor inconsistencies may exist in this file. Efforts were made to snap adjoining arcs where appropriate.
Dataset complete as representation of measured and inferred faults in the Boulder-Weld coal field based on Myers and others (1975).
map showing mined areas of the Boulder-Weld coal field
coal mine subsidence and land use in the Boulder-Weld coalfield
The digital line data representing faults were compiled from analog data plotted on a 1:24,000-scale composite base map (clear film) representing all or parts of nine USGS 7.5' topographic quadrangles within the coal field boundary. To facilitate the scanning and digitization procedures required to create the coverage, photographic reproductions were made on scale-stable mylar for each 7.5' quadrangle area within the coal field area rather than creating a single photographic reproduction of the entire composite map. Each 7.5' segment was then electronically scanned, and converted to a Tagged Image File Format (TIFF) image that could be imported into Environmental Systems Research Institute (ESRI) ArcInfo software for coverage development. The fault coverage was developed from the "on-screen" digitization of measured and inferred faults as delineated in the 7.5' quadrangle TIFF images.
Internal feature number.
ESRI
Feature geometry.
ESRI
Length of feature in meters.
ESRI
fault type
USGS
"measure" implies a greater degree of certainty for fault location and orientation based on studies of subsurface mine maps and fault expression on outcrop
USGS
imply that less information existed to support a fault location and orientation
USGS
Box 25286 Denver Federal Center
This publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Although all data and software published are used by the U.S. Geological Survey, no warranty, expressed or implied, is made by the U.S. Geological Survey as to the accuracy of the data and related materials and (or) the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials.
Faults geographic features and attribute data for the Colorado Front Range
ArcIMS Image Map Service
A web-based interactive mapping system that accesses an ArcIMS Map Service running on certmapper.cr.usgs.gov.
This product can be downloaded individually using any one of the digit form, Network_Resource_Name URLs above. Each of these URLs may provide access to various formats of the same product.
U.S. Geological Survey, Box 25046, MS 939, Denver Federal Center
For inquiries regarding this document, please include the metadata contact person's name, dataset name, and publication series and number.