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Home , Foreland basin, Orogeny, Sevier orogeny

The Evolution of Foreland Basins Megan Mueller Field Summer 2020 2. Review

2 Generalized History of W.

Basin & Range Extension, CRBG Pangea

Passive margin Laramide () (and Nevadaplano) Onset of FTB Building (?) Columbia/ Nuna

Begin (?) - chaotic organization - (Slide Mtn basin)

3 Pennsylvanian-Permian

• What type of margin? • transport direction? • and depositional environments? • Sediment composition?

4 Analog: Namibia

• Quadrant: aeolian dunes • Phosphoria: passive margin, epicontinental shallow sea

5 Early

• Chaotic margin • Lithology? • Depositional environment?

6 3. North American

7 North American Foreland Basin

• Major tectonic regions • Magmatic arcs, accreted • Sevier thrust belts • Sevier foreland basin system • Laramide intra-foreland uplifts & basins

DeCelles, 2004 AJS 8 North American Foreland Basin

• > 1000 km wide, 6000 km long • >100 Myr lifespan • Foreland basin system evolved in response to and processes • Late to deposition

DeCelles, 2004 AJS 9 Triassic Dinwoody Fm

PC: Marli Miller

PC: Megan Mueller 10 Triassic to Mid Jurassic

• Little topography -> open to Pacific • marine deposition • Triassic Dinwoody Fm • shallow marine shale and • Begin to set-up thrust belt • Foreland system migrates east

images by Ron Blakey, Northern Arizona University

DeCelles, 2004 AJS 11 Fuentes et al. 2011

12 PC: Maddie Hille Morrison Formation : ~158-152 Ma

PC: Megan Mueller

What is lithology and depositional environment? 13 14 Late Jurassic (155-142)

• Orogenic loading from FTB • Subsidence driven by loading • Eastward migration of • Low angle subduction or partial • Extension in SW • Obliquity of NW-SE convergence • basin?

• Morrison Fm: non-marine shale and , limestone, conglomerate, paleosols

15 DeCelles, 2004 AJS Morrison Fm Debate • Fluvial, lacustrine • Paleotopography controls thickness • Major at top

Setting and subsidence mechanism? • Foredeep • Does not thicken to W • Not flexural subsidence from FTB • Backbulge • Where is foredeep? Eroded in K. • Metamorphic grade supports thick overburden (foredeep) existed • Dynamic subsidence • Unconformity too far inboard • Slab foundering? Mezcalera or Farallon? • Wavelengths of subsidence debated

16 DeCelles, 2004 AJS PC: Maddie Hille

PC: Maddie Hille

PC: Adam Woods

What is lithology and depositional environment?

17 DeCelles, 2004 AJS Aptian

• Sevier Orogeny • East migrating • Classic flexural foreland basin • Flexural loading • Peak FTB • All 4 depozones preserved • Minimal magmatism

18 Skagit River

19 Neuquen, Argentina

Kootenai: river channels, floodplain, limestone lakes

20 Western Interior Seaway (shaded) Albian • Blackleaf Fm

PC: Adam Woods

What is lithology and depositional environment?

21 DeCelles, 2004 AJS Early to Albian • Marine transgressions & regressions • Western Interior Seaway • Kootenai Fm. and Flood Mbr.: paleosols, lacustrine , fluvial and floodplain • Chert, coarse- to fine-grained deposition, thick sed. units • Vaughn Mbr.: shallow marine deposition records transgression

22 DeCelles, 2004 AJS Coniacian (~89-85)

• Chaotic subsidence pattern further east • Dynamic subsidence dominates • Asymmetric subsidence pattern in west; symmetric in east • Demise of well-organized foreland system

23 Campanian to Eocene (83-40 Ma) • Laramide intraforeland uplifts • -involved thrusts along paleo-weaknesses • Partitioned basins • Local flexural subsidence • Eastward migration of magmatism and deformation • Interpretation:

DeCelles, 2004 AJS Dumitru 1991 24 Western Interior Seaway peak transgression ~92 Ma

Blum & Pecha, 2014

Lockshin et al. 2017 25 NA Foreland Basin Summary • Triassic – Mid-Jurassic: marine deposition, connected to Pacific Ocean • Late Jurassic: orogenic loading, dynamic subsidence from Farallon subduction • Non-marine deposition • Sevier Orogeny • Classic foreland basin system • and thrust belt building • Marine deposition from Western Interior Seaway • Coniacian (89-85) • not well-defined foredeep, dynamic subsidence dominates • ~80 Ma to Eocene: • Deformation front migrates east due to flab slab subduction • Local subsidence • Partitioned basins 26 Conclusions

• Depositional environments and sedimentary that we see in the field is evidence for all these events! • Sedimentary record preserved in foreland basins document the evolution of

• Stratigraphy is an excellent tool to reconstruct basin history and thus tectonic evolution at the regional scale • Knowledge of basin tectonic evolution helps us to better interpret long-term changes in depositional systems

Figures modified from DeCelles 2004 AJS WesternInterior Seaway (shaded)