A very brief overview of the rest of the U.S. Cordillera (not California and not Cenozoic) Basil Tikoff University of Wisconsin-Madison Goal: Give an overview of US Cordillera

Dickinson, 2006

Two sources for many of the figures Animations at:

Outline Geography exercise (5 minutes) Assembly of Precambrian North America (Laurentia) The Cordillera evolution Idaho and the Canadian Cordillera A retrospective (and, perhaps, a soapbox)

Organize into groups, with no more than one person from any particular country in any group. Write the name of each state in each state (ask anyone for help)

Envelope: Parts of the Precambrian In each “geography” group, open the envelope. We’ll go through the evolution of North American by putting together a jigsaw puzzle.

Archean – grey blobs

Archean cratons (positions unconstrained; Rae and Hearne in present-day locations) > 2.0 Ga

Proterozoic accretionary belts between Archean blocks – pink zones

Front view Back view

Continued shortening across Trans Hudson orogen; closure of Great Falls Tectonic Zone and Vulcan Zone; accretion of Medicine Hat Block, and Wyoming Province Ga

Like anything that is published, it isn’t necessarly correct. In this case, it does not look like the Selway terrane exists (the area is underlain by Archean crust, determined by zircon xenocrysts in Cretaceous plutons).

Proterozoic terranes (from N to S) Yavapai (1.70 Ga accretion) Mazatzal (1.63 Ga accretion) Granite-rhyolite province (1.55 – 1.35 Ga)

Yavapai – dark green

Ga Accretion of Mojavia(?) and Yavapai Province, as a Banda Sea style assembly of arcs

DePaolo & Bennet, 1987 Hoffman, 1988

CD-ROM working group

Figure 2. Geologic cross section with data from CD-ROM Cheyenne belt seismic line. Tyson A et al. Geology 2002;30: ©2002 by Geological Society of America

Mazatzal – blue Mazatzal ( = place of the deer, or so sayeth Wikipedia) Mountains, Arizona

Ga Accretion of Mazatzal and Labradorian Provinces, as juvenile crust

Granite-rhyolite –light green St Francis Mountains, Missouri Red rock is a 1500 Ma rhyolite

Llano block

Ga Accretion of Granite- Rhyolite Province, Elzevir Block & Pinware terrane, as juvenile crust

Belt Group, from Glacier National Park Deposition estimated at ~1400 Ma

Collision! Grenville orogeny & formation of Rodinia This just wasn’t a collision – it was the assembly of a supercontinent (Rodinia) Laurentia is at the center of this collision, which means it is highly affected structurally and thermally (similar to Hercynian orogeny in Europe)

Ga Grenville orogen: Granitoids intrude juvenile belts as far west as Colorado

Simultaneous with collision, there is a major rifting event Midcontinent rift event

Ga Midcontinent Rift system: Keweenawan, Ft. Wayne rifts; Intrusion of MacKenzie and Animikie dikes

Watch animation of Rodinia assembly Questions?

Ga Rifting along western margin of Laurentia; Intrusion of Gunbarrel dikes, Deposition of Windermere Supergroup

Dickinson Inyo Mtns

Thickness of latest Proterozoic & Early Cambria strata. Contour lines (hard to see) are 2, 6, and 8 km.

Time for animation From: html Questions?

The story of the US Cordillera is one of subduction and terrane accretion to the western margin

Accreted or “suspect” terranes Dott & Prothero

When do they attach to each other, and when (and where) do they attach to the North American margin?

Tectonic map for Cambrian through Late Devonian Black material was offshore, but was being deposited

Dott & Prothero Late Mississippian

Antler orogeny Lasted ~10 m.y. Major feature: Roberts Mountain thrust During thrusting, the thrust sheets formed a highland and deposited material eastward into a well-developed foredeep No, low metamorphism Overlapped by Pennsylvanian shallow- water materials ….and, there is no/little volcanic material

Sheared and folded deep water sediments of the distal Antler marine basin thrust over and emplaced on top of the shallow water deposits of the continental margin. Robert’s Mountain thrust. Above the contact we see the Early Missisppian conglomerates and below we see a thick band of sheared rocks. From MIT website (C. Burchfiel)

Burchfiel & Royden, 1991

Ancestral Rockies Permian age Basins and uplifts in southern part of western US (they do not extend, for the most part, into the Archean Wyoming province) Results from collision of Africa on SE US …and now for the large piles of sandstone and conglomerates

Maroon Bells

Blakey, 2008Note: Large vertical exaggeration

Ancestral Rockies are interpretted by Miller et al. (1992) as a far-field effect of a continent-continent collision. The diagram shows the scale of the ongoing Himalayan collision to the Ancestral Rockies collision, emphasizing the “free” subduction boundary. Ancestral Rockies are equivalent to Baikal rift.

Watch Pangea assembly Questions?

Dickinson, 2006 Next: The Sonoman orogeny

Dott & Prothero Permian-Triassic

Sonoman orogeny Permian-Triassic Major feature: Golconda thrust A lot like the Antler orogeny: 1) Thrust sheets (Havallah sequence) were thrust on Antler orogeny and its Paleozoic overlap sequence; and 2) Little metamorphism Overlapped by Triassic shallow-water materials (Star Peak/Luning) and cut by Triassic pluton in eastern Sierra Nevada region

Triassic Development of an Andean margin offshore California, possibly with back- arc basin (Star Peak – Luning basin)

By Late Jurassic, the Sevier thrust front has developed, including a very well developed foreland basin

DeCelles, 2004 Questions?Questions?