Plate Tectonics

Detailed analysis of the geology of western North America in relation to the motion of plates in the eastern Pacific Ocean show four iterations of a basic subduction cycle:

1. Rapid subduction (>10 cm/year) and arc compression for approximately 30 m.y. best exposed today by porphyry copper deposits.
2. Formation of granitic batholiths over a few million years in a trans-tensional regime topped by major silicic volcanic provinces.
3. Pulling apart of the subducted plate, relieving trench normal compression, opening of the Basin and Range.
4. Onset of major strike-slip motion.

Explained in detail in the following papers:

Ward, P. L., 1991, On plate tectonics and the geologic evolution of southwestern North America: Jour. Geophys. Res., 96, p. 12479-12496.                                                   Click here to download    PDF

Ward, P. L., 1995, Subduction cycles under western North America during the Mesozoic and Cenozoic Eras: Geol. Soc. Special Paper 299, p. 1-45.                                       Click here to download    PDF