Tectonosynthems and New Tectonic Map of North America

W. R. Muehlberger, P. R. Tauvers

Major episodes in the evolution of the North American continent can be characterized by unconformity-bounded stratigraphic units (synthems) comprised of various tectonically related rocks. These subdivisions (referred to as tectonosynthems) embrace the "classical" orogenies locally defined around the North American craton. The Tectonic Map of North America (TECNA), the AAPG Foundation's contribution to the DNAG project, uses unconformity-bounded map units in order to most effectively illustrate the relationship between tectonics and regional sedimentation, plutonism, and metamorphism. "Orogenies" are not correlated, and only their bounding unconformities (which may well be diachronous surfaces) are used. This approach eliminates the need to export local orogeny names and ates but posits testable, objective criteria for craton-wide synthesis. The tectonosynthems of North America can be directly correlated with changes in overall plate motions through time. Oceanic crust is colored according to the age of the tectonosynthem extant during its formation. Color (tectonosynthem) boundaries in oceanic crust are usually coincident with a major change in spreading direction or rate. In continental areas, these boundaries indicate significant changes in tectonic regime over widespread areas. Lithotectonic units (e.g., volcanic arc, accretionary prism, continental shelf) within individual tectonosynthems are illustrated using patterns.

In addition to the standard Precambrian subdivisions, the TECNA map shows 10 tectonosynthems spanning the late Precambrian to the Holocene. Major episodes involve (a) the breakup of the late Proterozoic supercontinent, (b) early Paleozoic arc-continent interactions, (c) North America--Gondwana collision in the late Paleozoic, (d) initiation of subduction on the Pacific margin and rifting on the Atlantic margin in the Mesozoic, (3) flat-slab subduction and foreland deformation in the earliest Tertiary, and (f) Eocene ignimbrites, middle Tertiary extension, and late Cenozoic strike-slip tectonics in the Cordillera.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.