Regional geology and tectonic history of Wyoming Geological Field Techniques Course.
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Transcript of Regional geology and tectonic history of Wyoming Geological Field Techniques Course.
![Page 1: Regional geology and tectonic history of Wyoming Geological Field Techniques Course.](https://reader035.fdocuments.us/reader035/viewer/2022062322/56649d305503460f94a08c57/html5/thumbnails/1.jpg)
Regional geology and tectonic history of Wyoming
Geological Field Techniques Course
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Wyoming geologic history
See the summary chart in your guidebook Begin to place events
in proper context
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Regional physiography
Wyoming straddles the Great Plains and Rocky Mountains
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Regional tectonic provinces
Central craton surrounded by orogenic belts NuNA = nucleus of
North America
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Basement rocks
Subdivided by age and tectonic affinity
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Tectonic history of the U.S. Cordillera
Seven major periods of tectonism Antler (Mississippian) Ancestral Rockies (Mississippian – Permian) Sonoma (Permian) Nevadan (Jurassic) Sevier (Cretaceous) Laramide (Late Cretaceous - Eocene) Cenozoic tectonics (continuing today!)
Basin and Range extension San Andreas fault Volcanism
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Cambrian paleogeography
Maps from Dr. Ron Blakey’s web sitehttp://jan.ucc.nau.edu/~rcb7/globaltext.html
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Early Paleozoic stratigraphy
Reflects passive margin and shallow continental sea deposition Sandstones, shales and carbonates Global sea level changes exert dominant control
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Uplifts of the Ancestral Rockies
Mississippian – Permian Earliest motion on
some classic Rocky Mountain ranges
Colorado Front Range Uncompaghre
New Mexico Sangre de Cristo
West and North Texas
Marathon Llano
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Permian paleogeography
Ancestral Rockies related to continent-continent collision Assembly of Pangaea Only minor deformation in Wyoming Major transition in depositional environments
begins
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Permian – Jurassic is tectonically quiet
Little deformation in Wyoming Sonoma and Nevadan orogenies to west
Major fall in global sea level
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Early Cretaceous paleogeography
Accretion of exotic terranes Creation of Andean style subduction margin
The Sevier orogeny
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Sevier – Laramide stratigraphy
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Sevier orogeny
Creation of continental magmatic arc Extensive thin-skinned deformation Foreland basin deposition
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Sevier deformation front
Great Valley
Foreland fold and thrust belt
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Sevier orogeny deformation style
Thin-skinned Sedimentary
“cover” detached from basement
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Idaho – Wyoming thrust belt
Cross sectional view
westwest easteast
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Tectonic configuration – Late Sevier
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Foreland basin of the Sevier orogeny
Western Interior Basin
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Formation of foreland basins
Thickening and loading of crust causes flexure Creates accommodation space to capture debris
eroded from mountains
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Cretaceous foreland basin
Sediment sources and crustal loading patterns revealed by stratigraphic thickness and facies variations
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Late Cretaceous paleogeography
Two major tectonic changes Shut down of magmatic arc Change in deformation location and style
Laramide orogeny
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Tectonic configuration - onset Laramide
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Laramide basement uplifts
A distinctly different structural style In a very different place
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Colorado plateau Laramide uplifts
Capitol Reef National Park
After Billingsley, Huntoon and Breed (1987)
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Black Hills Laramide uplift
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Laramide sedimentary basins
Basement uplifts subdivide the Sevier foreland basin into many smaller basins Intermontaine
basins
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Geometry of Laramide basins
Asymmetric Basin axes close
to uplift margins Facies and
thickness changes indicate uplifts were sediment sources
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Regional structure of Wyoming
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Regional structure of Wyoming
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Detailed structure of basement arches
Flexing of crustal rocks creates many smaller scale basement-involved folds
Erslev et al. (2001)
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Why the change in structural style?
Change in plate convergence Direction Rate
Younger, hotter, more buoyant crust begins to subduct more rapidly
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Sevier to Laramide transition
Related to change in subduction angle
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Consequences of shallow subduction
Causes reactivation of old crustal weaknesses Laramide uplifts resulted from inversion of
Proterozoic extensional faults
Marshak et al. (2000)
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Cenozoic tectonics30 Ma 20 Ma 10 Ma Present
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Magmatic shift
Laramide magmatic gap closes and migrates southward
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Miocene paleogeography
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Basin and Range extension
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Basin and Range extension
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Basin and Range faulting
Alternating mountain ranges and basins Horst and graben
systems
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Basin and Range faulting
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Basin and Range faulting in Wyoming
Teton National Park
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Cenozoic volcanism
Columbia River flood basalts Yellowstone hot spot