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GEOREF RECORD

Syntectonic sedimentation in the Proterozoic upper Belt Supergroup, northwestern Montana

David L. Kidder
Syntectonic sedimentation in the Proterozoic upper Belt Supergroup, northwestern Montana
Geology (Boulder) (July 1988) 16 (7): 658-661

Abstract

Deepening environments in the Proterozoic Libby Formation record a tectonically induced style of sedimentation distinctly different from that of older Belt rocks. Facies associations and sedimentary structures indicate that deposition in the lower Libby Formation occurred above fair-weather wave base. Thick, widespread hummocky cross-stratified quartzite in the upper Libby Formation lacks the association of shallow-water features present in the lower Libby Formation, suggesting that upper Libby deposition occurred below fair-weather wave base and above storm wave base. Independent evidence for tectonism during deposition of the Belt Supergroup exists but is plagued by poor age control. The angular unconformity that occurs between Libby-equivalent rocks and the overlying Windermere Supergroup indicates tectonic activity between deposition of the Belt-Purcell and Windermere Supergroups. The interpreted subsidence or rise in basin water level combined with newly uplifted source areas as recorded in the upper Libby Formation and Garnet Range Formation could have been an early manifestation of movements that produced this unconformity.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 16
Serial Issue: 7
Title: Syntectonic sedimentation in the Proterozoic upper Belt Supergroup, northwestern Montana
Author(s): Kidder, David L.
Affiliation: Univ. Calif., Dep. Geol., Davis, CA, United States
Pages: 658-661
Published: 198807
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 41
Accession Number: 1988-048336
Categories: Sedimentary petrologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
N47°34'60" - N49°00'00", W115°01'00" - W112°52'00"
N47°52'60" - N49°00'00", W116°02'60" - W114°37'00"
N46°40'00" - N47°31'60", W115°45'00" - W114°25'00"
N46°34'60" - N47°34'60", W114°45'00" - W113°15'00"
N32°00'00" - N65°00'00", W155°00'00" - W103°00'00"
N47°10'00" - N48°19'60", W116°04'60" - W114°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1988
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