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GEOREF RECORD

Steeply dipping heaving bedrock, Colorado; Part 1, Heave features and physical geological framework

Abstract

Differentially heaving bedrock has caused severe damage near the Denver metropolitan area. This paper describes heave-feature morphologies, the underlying bedrock framework, and their inter-relationship. The heave features are linear to curvilinear and may attain heights of 0.7 m (2.4 ft), widths of 58 m (190 ft), and lengths of 1,067 m (3,500 ft). They are nearly symmetrical to highly asymmetrical in cross section, with width-to-height ratios of 45:1 to 400:1, and most are oriented parallel with the mountain front. The bedrock consists of Mesozoic sedimentary formations having dip angles of 30 degrees to vertical to overturned. Mixed claystone-siltstone bedding sequences up to 36-m (118-ft) thick are common in the heave-prone areas, and interbeds of bentonite, limestone, or sandstone may be present. Highly fractured zones of weathered to variably weathered claystone extend to depths of 19.5 to 22.3 m (64 to 73 ft). Fracture spacings are 0.1 to 0.2 m (0.3 to 0.7 ft) in the weathered and variably weathered bedrock and up to 0.75 m (2.5 ft) in the underlying, unweathered bedrock. Curvilinear shear planes in the weathered claystone show thrust or reverse offsets up to 1.2 m (3.9 ft). Three associations between heave-feature morphologies and the geological framework are recognized: (1) Linear, symmetrical to asymmetrical heaves are associated with primary bedding composition changes. (2) Linear, highly asymmetrical heaves are associated with shear planes along bedding. (3) Curvilinear, highly asymmetrical heaves are associated with bedding-oblique shear planes.


ISSN: 1078-7275
EISSN: 1558-9161
Coden: ENGEA9
Serial Title: Environmental & Engineering Geoscience
Serial Volume: 13
Serial Issue: 4
Title: Steeply dipping heaving bedrock, Colorado; Part 1, Heave features and physical geological framework
Affiliation: Colorado Geological Survey, Denver, CO, United States
Pages: 289-308
Published: 200711
Text Language: English
Publisher: Association of Engineering Geologists and the Geological Society of America, College Station, TX, United States
References: 52
Accession Number: 2008-028642
Categories: Engineering geologySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: http://eeg.geoscienceworld.org/cgi/reprint/13/4/289
Illustration Description: illus. incl. strat. col., sects., sketch map
N39°40'00" - N39°47'60", W105°04'60" - W104°49'60"
Secondary Affiliation: Colorado School of Mines, Department of Geology and Geological Engineering, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Association of Engineering Geologists and the Geological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200809
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