1. Regional geology and tectonic history of Wyoming Geological Field Techniques Course

2. Wyoming geologic history See the summary chart in your guidebook Begin to place events in proper context

3. Regional physiography Wyoming straddles the Great Plains and Rocky Mountains

4. Regional tectonic provinces Central craton surrounded by orogenic belts NuNA = nucleus of North America

5. Basement rocks Subdivided by age and tectonic affinity

6. 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

7. Cambrian paleogeography Maps from Dr. Ron Blakey’s web site http://jan.ucc.nau.edu/~rcb7/globaltext.html

8. Early Paleozoic stratigraphy Reflects passive margin and shallow continental sea deposition Sandstones, shales and carbonates Global sea level changes exert dominant control

9. 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

10. Permian paleogeography Ancestral Rockies related to continent-continent collision Assembly of Pangaea Only minor deformation in Wyoming Major transition in depositional environments begins

11. Permian – Jurassic is tectonically quiet Little deformation in Wyoming Sonoma and Nevadan orogenies to west Major fall in global sea level

12. Early Cretaceous paleogeography Accretion of exotic terranes Creation of Andean style subduction margin The Sevier orogeny

13. Sevier – Laramide stratigraphy

14. Sevier orogeny Creation of continental magmatic arc Extensive thin-skinned deformation Foreland basin deposition

15. Sevier deformation front Great Valley Foreland fold and thrust belt

16. Sevier orogeny deformation style Thin-skinned Sedimentary “cover” detached from basement

17. Idaho – Wyoming thrust belt Cross sectional view westeast

18. Tectonic configuration – Late Sevier

19. Foreland basin of the Sevier orogeny Western Interior Basin

20. Formation of foreland basins Thickening and loading of crust causes flexure Creates accommodation space to capture debris eroded from mountains

21. Cretaceous foreland basin Sediment sources and crustal loading patterns revealed by stratigraphic thickness and facies variations

22. Late Cretaceous paleogeography Two major tectonic changes Shut down of magmatic arc Change in deformation location and style Laramide orogeny

23. Tectonic configuration - onset Laramide

24. Laramide basement uplifts A distinctly different structural style In a very different place

25. Colorado plateau Laramide uplifts Capitol Reef National Park After Billingsley, Huntoon and Breed (1987)

26. Black Hills Laramide uplift

27. Laramide sedimentary basins Basement uplifts subdivide the Sevier foreland basin into many smaller basins Intermontaine basins

28. Geometry of Laramide basins Asymmetric Basin axes close to uplift margins Facies and thickness changes indicate uplifts were sediment sources

29. Regional structure of Wyoming

31. Detailed structure of basement arches Flexing of crustal rocks creates many smaller scale basement-involved folds Erslev et al. (2001)

32. Why the change in structural style? Change in plate convergence Direction Rate Younger, hotter, more buoyant crust begins to subduct more rapidly

33. Sevier to Laramide transition Related to change in subduction angle

34. Consequences of shallow subduction Causes reactivation of old crustal weaknesses Laramide uplifts resulted from inversion of Proterozoic extensional faults Marshak et al. (2000)

35. Cenozoic tectonics 30 Ma20 Ma10 MaPresent

36. Magmatic shift Laramide magmatic gap closes and migrates southward

37. Miocene paleogeography

38. Basin and Range extension

40. Basin and Range faulting Alternating mountain ranges and basins Horst and graben systems

41. Basin and Range faulting

42. Basin and Range faulting in Wyoming Teton National Park

43. Cenozoic volcanism Columbia River flood basalts Yellowstone hot spot