TRANSCONTINENTAL GEOLOGIC CROSS SECTION

This AGI (American Geological Institute) project will produce an annotated geological cross section across the continent that can be used for K-12, the general public, introductory college geology classes and professionals to give them a greater understanding of the complex sequence of tectonic events that have produced our continent. This visual representation will have an oblique map view as well as the cross section at a 4:1 vertical exaggeration and a 1:2M horizontal scale that will portray the geology to depths of 250 km. Although no single cross section can show all of the events that resulted in the present continent, this line along the 37th parallel crosses most of the significant tectonic features of the United States.

The eastern segment starts in Atlantic Ocean crust and extends west across the southern Appalachians and the Grenville Front; recording two complete Wilson cycles. The mid-Continent segment records accretion of the Mid-Proterozoic Mazatzal and Yavapai arcs and late plutons, and illustrates the stability of the craton (once its was ‘cratonized) despite major Phanerozoic tectonic events along its southern margin. The southern Rocky Mountains-Rio Grande rift-Colorado Plateau segment displays a crust of cratonized Proterozoic accretionary belts followed by several Phanerozoic orogenic events (Ancestral Rockies, Laramide, and Rio Grande rift orogenies) that broke it into large rigid segments. The western segment crosses the currently active zone of the continent with Basin and Range extension in the eastern part, Mesozoic arc and accretionary prisms now being transposed by San Andreas transform plate margin structures that continues offshore to the continental contact with the Pacific Ocean crust..

This section also provides a first cut based on current knowledge of lithospheric and upper mantle structure, and opportunities for refinement as the Earthscope Project moveable array visits the belt traversed by the section.