CENOZOIC PALEOTECTONICS AND PALEOGEOGRAPHY OF THE SOUTHWEST MARGIN OF NORTH AMERICA

During the Cenozoic, the dynamic Southwest margin of North America evolved from a subduction margin to a transform margin. This alteration was accompanied by region-wide extension. As a result, the paleogeography of the region experienced dramatic transformation as sedimentary basins and volcanic fields were warped, dismembered, and uplifted. To illustrate these complicated events, a series of 14 paleotectonic maps were created between 50 Ma and present; from these maps, paleogeographic maps were constructed.

The data for the 14 time slices was gleaned from published sequential restorations that display tectonic blocks and elements, volcanic areas, and shorelines of sedimentary basins. Additional data showing paleo drainages, patterns of uplift and subsidence, and ancient sedimentary environments were also integrated into the maps. The region of emphasis is from coastal California eastward into the Basin and Range – the Colorado Plateau is fixed with respect to the dynamic terrain to the west. Several individual time slices are emphasized to show the methodology in map construction and accentuate the impressive changes through the Cenozoic.

The maps display a synthesis of vast amounts of data obtained over a broad, complicated region of North American geology. The sequential time slices illustrate the complex geologic history of the region as individual basins, blocks, and terranes can be followed throughout the Cenozoic.