Geologists continue to debate the merits of alternative interpretations of the geological history, from 270 to 150 Ma, of the western US. In one interpretation, most elements of the western US are assumed to have been derived tectonically from North America. In the second tectonic interpretation ("or"), in which some exotic elements are considered to have originated far from North America (accreted terranes).
Roll-over the dated links for preview images of maps of the time periods, or visit the website for links to major periods. Click here to follow continental and offshore alternative sequences.
Playlist: Geology of the Grand Canyon (not my videos): link.
[links: all maps in sequence: 1.7 Ga, 1.1 Ga, 650 Ma, 510 Ma, 470 Ma, 470 Ma w, 430 Ma, 430 Ma w, 370 Ma, 370 Ma w, 340 Ma, 340 Ma w, 310 Ma, 310 Ma w, 280-270 Ma, 280-270 Ma w, or 270 Ma w, 250 Ma, 250 Ma w, or 250 Ma w, 240 Ma, 240 Ma w, 215 Ma, 215 Ma w, 200 Ma, or 200 Ma w, 170 Ma, or 170 Ma, 150 Ma, or 158 Ma, or 155 Ma, or 150 Ma, 145 Ma, 130 Ma, 90 Ma, 75 Ma, 65 Ma, 50 Ma, 35 Ma, 20 Ma, 10 Ma ; geological age of rocks by State: Arizonia, California, Colorado, New Mexico; Nevada; Utah (adjacent Idaho, Kansas, Nebraska, Oregon, Texas, Wyoming), boundaries; webpages: Geological History of the western US: Paleogeology of the southwestern US; Precambrian, Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian, Triassic, Jurassic, Cretaceous, Tertiary]