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Into the Heartland of Laramide Tectonics

Posted on the 19 June 2014 by Hollis

Into the Heartland of Laramide Tectonics

My destination ... where on (Google) Earth??? (click on image for better view)

I leave soon for the “Heartland of Laramide Tectonics” of Lillegraven and Snoke (1996).  They were referring to the creation of the Rocky Mountains -- the Laramide Orogeny.

Into the Heartland of Laramide Tectonics

Laramide uplifts and basins were created roughly 75 to 40 million years ago during the Laramide Orogeny.  Modified from Snoke 1993 (from Hamilton 1988).

Precisely when Laramide deformation started and stopped is still being debated.  The cause is even more controversial, for it’s very odd to have a major mountain-building event so far from a plate boundary (west coast of North America).  In contrast, there is general agreement about the style of deformation, which is distinctive and consistent.

Into the Heartland of Laramide Tectonics

Laramide-style deformation: "very deep basin where range thrust up & over ... typ. Rky Mtn structure involving craton"  Class notes,  Regional Geomorphology, Dr. B. Mears, Jr., Univ. Wyoming, 1984.

“... the Rocky Mountain foreland was fractured by deep-rooted reverse and thrust faults that uplifted broad blocks of Precambrian basement rocks, separated by deep basins.”  Rock beds were folded to produce as much as 45,000 ft of displacement between a range and the adjacent basin -- “staggering structural relief” (Snoke 1993).

This will be a short trip, posts should be up soon.  I'll tweet photos from the Heartland if reception allows.

Into the Heartland of Laramide Tectonics

Field gear in the digital age.

Literature Cited
Lillegraven, JA and Snoke, AW.  1996.  A new look at the Laramide orogeny [...].  WY State Geological Survey Public Information Circular No. 36.Snoke, AW  1993.  Geologic history of Wyoming within the tectonic framework of the North American Cordillera, in Snoke, AW, Steidtmann, JR, and Roberts, SM, eds.  Geology of Wyoming.  WY State Geological Survey Memoir 5:  2-56.

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