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TitleThe 3D geophysical investigation of a Middle Cretaceous to Paleocene regional décollement in the Cordillera of northern Canada and Alaska
AuthorHayward, NORCID logo
SourceAME Roundup 2019; 2019 p. 1
Alt SeriesNatural Resources Canada, Contribution Series 20190396
PublisherAssociation for Mineral Exploration
MeetingAME Roundup 2019; Vancouver, BC; CA; January 28-31, 2019
NTS84D; 84E; 84L; 84M; 85D; 85E; 85K; 85L; 85M; 85N; 86C; 86D; 86E; 86F; 86K; 86L; 94; 95; 96; 104E; 104F; 104G; 104H; 104I; 104J; 104K; 104L; 104M; 104N; 104O; 104P; 105; 106; 114; 115; 116; 117A; 117B
AreaMackenzie Mountains; Rocky Mountains; Ogilvie Mountains; Wernecke Mountains; Alaska; Canada; United States of America
Lat/Long WENS-156.0000 -116.0000 68.0000 56.0000
Subjectstectonics; geophysics; structural geology; Science and Technology; Nature and Environment; Paleogene; Paleocene; tectonic history; tectonic evolution; decollement; displacement; intrusions; emplacement; geophysical interpretations; gravity interpretations; crustal structure; models; bedrock geology; structural features; faults; Canadian Cordillera; Tintina Fault; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous
ProgramGEM2: Geo-mapping for Energy and Minerals Western Cordillera, Devonian and Permian structural architecture
Released2019 01 28
AbstractA new approach to the 3D inversion and interpretation of gravity data is applied to the crustal architecture of the northern Cordillera of Canada and Alaska. The technique models the distribution and depth extent of rocks with systematic density contrasts, such as sedimentary or intrusive rocks. In the northern Cordillera, the geometry of low-density zones, primarily associated with middle to Late Cretaceous granitic intrusions, and Neoproterozoic and Cretaceous sedimentary rocks, is defined. Variation in the depth extent of these zones delimits a surface, interpreted herein as a regional décollement syntectonic with, or postdating, middle Cretaceous intrusions, but predating and displaced ~430 km by the Eocene-aged Tintina fault. The décollement trends N35°E and shallows from a depth of ~15-20 km beneath Selwyn basin to ~11 km beneath the Mackenzie Mountains. Here surface faults echo the décollement geometry, linked to fold and thrust belt development between the middle Cretaceous and Paleocene. The décollement continues southward for an unknown distance into northern British Columbia, but the Liard line represents a structural discontinuity between the fold and thrust belts of the Mackenzie Mountains and northern Rocky Mountains. The décollement's northwestern extent is broadly defined by surface faults in the northern Ogilvie Mountains. However, prior to Tintina fault displacement, the décollement was likely connected to a fold and thrust belt and related décollement in east-central Alaska. Estimates of post-middle Cretaceous exhumation suggest regional tectonic modification of the décollement, possibly including the presently active detachment inferred for the weak lower crust.

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