TRANSCONTINENTAL GEOLOGIC SECTION THROUGH THE NORTH AMERICAN PLATE NEAR 36° LATITUDE: ATLANTIC OCEAN CRUST TO PACIFIC OCEAN CRUST—A TRIBUTE TO BILL MUEHLBERGER

We have produced a 4:1-exaggerated technical cross section to 150 km across North America (NA) near 36° N, and 1:1 geologic and tomographic sections to 250 km. A section for K-12, the public, and introductory geology classes is planned for comprehension of southern NA tectonics.

The E segment records crust formation over ~2 Ga and two Wilson cycles. It extends W from Atlantic Ocean crust to 99° W across the Blake Spur and East Coast magnetic anomalies, modern continental margin, Appalachians, buried Grenville front, Mississippi Embayment, and the E Mid-Continent (M-C). It also crosses the two most active seismic zones in the E U.S.: New Madrid and East Tennessee. The M-C segment records accretion of the Mid-Proterozoic Mazatzal and Yavapai arcs and late plutons, building cratonic stability despite major Ph tectonism along its southern and eastern margins. Normal-thickness crust occurs beneath the E segment, except in the southern Appalachians (~50 km).

The W segment extends E from Pacific Ocean crust across the coastal Franciscan accretionary complex, Salinia forearc microplate, San Andreas fault, Cretaceous forearc basin, Sierra Nevada Mesozoic arc, eastern California shear zone, Colorado Plateau, Rio Grande rift, Rocky Mountains, and western M-C. Plate boundary deformation here is inducing and interacting with a complex intraplate deformational field in a 1000 km-wide orogenic plateau that extends to the M-C. The scientific "punchline" for the W segment is the W NA plate is tectonically active because of interactions with flowing mantle near its base.

NA provides a superb laboratory for understanding continental plate structure and evolution. NA is profoundly segmented because of its >4 billion-year history, and was built by continental and oceanic terrane accretion to Archean nuclei. The overall theme for this and all continents involves superposition of active plate tectonic processes on a heterogeneous existing structure developed during a lengthy evolution.