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Exhumation of the North American Cordillera revealed by multi-dating of Upper Jurassic-Upper Cretaceous foreland basin deposits

Clayton S. Painter, Barbara Carrapa, Peter G. DeCelles, George E. Gehrels and Stuart N. Thomson
Exhumation of the North American Cordillera revealed by multi-dating of Upper Jurassic-Upper Cretaceous foreland basin deposits
Geological Society of America Bulletin (June 2014) 126 (11-12): 1439-1464

Abstract

New low-temperature thermochronology and geochronology data from Upper Jurassic-Upper Cretaceous strata from the North American Cordilleran foreland basin in Utah, Colorado, Wyoming, and South Dakota document rapid exhumation rates of the adjacent Cordilleran orogenic belt to the west. Both zircon (U-Th-[Sm])/He (zircon He) and apatite fission track (AFT) thermochronology were applied to proximal and distal synorogenic deposits in order to identify a thermochronometer suitable to record source exhumation during the North America Cordilleran orogeny. AFT lag times from Upper Jurassic-Upper Cretaceous deposits are 0-5 m.y. and indicate a relatively steady-state to slightly increasing exhumation rate between 118 Ma and 66 Ma. These lag-time measurements are consistent with active shortening and rapid exhumation rates of approximately 0.9->1 km/m.y. of the North American Cordillera throughout the Cretaceous. Double dating of the detrital AFT samples was performed on apatites with young AFT cooling ages, in order to test whether or not the young cooling ages represent a signal related to exhumation rather than volcanic activity. Maximum depositional ages using detrital zircon U-Pb geochronology match existing ages on basin stratigraphy. This study indicates that AFT is the most effective thermochronometer to resolve source exhumation from Lower to Upper Cretaceous foreland stratigraphy in the central Cordilleran foreland, and indicates that source material was exhumed from 4 to 5 km depths but was never buried more than a few kilometers (<4 km) since Cretaceous time. Zircon He dates indicate that the orogenic hinterland could not have been exhumed from depths >8-9 km. Double dating of apatites (with AFT and U-Pb) shows that volcanic contamination is a significant issue that can, however, be addressed by double dating.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 126
Serial Issue: 11-12
Title: Exhumation of the North American Cordillera revealed by multi-dating of Upper Jurassic-Upper Cretaceous foreland basin deposits
Affiliation: University of Arizona, Department of Geosciences, Tucson, AZ, United States
Pages: 1439-1464
Published: 20140602
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 159
Accession Number: 2014-048927
Categories: Structural geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2014223
Illustration Description: illus. incl. 6 tables, geol. sketch map
N37°00'00" - N41°00'00", W109°00'00" - W102°00'00"
N42°30'00" - N45°55'00", W104°04'60" - W96°27'00"
N37°00'00" - N42°00'00", W114°04'60" - W109°04'60"
N41°00'00" - N45°00'00", W111°04'60" - W104°04'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201427
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