Abstract A 1500-km transect from offshore southern California to central New Mexico portrays the transition from oceanic crust to stable North American craton (Figure 1). Three sheets of maps and sections cover segments of offshore and onshore southern California, southwestern Arizona adjacent to the international border, as well as southeastern Arizona and central New Mexico. The western edge of the offshore segment is Long. 122°W and the corridor lies between Lat. 33°N and Lat. 34°N. A northward extension, which continues to Lat. 35°N, includes the western Tranverse Ranges. After crossing the Peninsular Ranges, the corridor bends sharply toward the international border to pass through southeastern California and southwestern Arizona to Long. 111°W near Tucson, where the transect bends northeastward and terminates near Socorro, New Mexico at Long. 106°W between Lat. 33°30′N and 34°30′N. The east-west cross section generally is about halfway between the boundaries of the transect. A north-south section approximately along Long. 119°30′W, crosses the western Transverse Ranges and adjacent northern Channel Islands. A brief tectonic history of the continental margin of the southwestern United States is presented using the concept of tectonostratigraphic terranes. This history is supported by the Appendix, in which the stratigraphy of each terrane is described. Geologic relations depicted deeper than a few kilometers are inferential and somewhat subjective. Nevertheless, this summarization of contemporary tectonic interpretations is expected to stimulate interest and further research in this region. The following text embellishes the Chronology of Terrane Assembly diagram and Tectonostratigraphic Columns shown on sheet 1.

Abstract DNAG Transect C-3. Part of GSA’s DNAG Continent-Ocean Transect Series, this transect contains all or most of the following: free-air gravity and magnetic anomaly profiles, heat flow measurements, geologic cross section with no vertical exaggeration, multi-channel seismic reflection profiles, tectonic kindred cross section with vertical exaggeration, geologic map, stratigraphic diagram, and an index map. All transects are on a scale of 1:500,000.