Abstract This display illustrates the geological architecture,tectonic style and geophysical expression of the northern Canadian Pacific continental margin in the vicinity of the modern triple junction between the Pacific,America and Juan de Fuca Plates. In addition to active transform and convergent tectonics, the region embraces the junctions between allochthonous, or suspect terranes. The tectonic history, distribution and suture between two of these terranes, Wrangellia and the Alexander Terrane, is partly based upon interpretations of geophysical data beneath water-covered areas and, as such, is somewhat conjectural The sources of information for the display are published and unpublished maps, reports and data files of the Geological Survey of Canada, Earth Physics Branch, Departments of Geology and of Geophysics and Astronomy, both at the University of British Columbia, and the Geological Branch of the British Columbia Ministry of Energy Mines and Petroleum Resources. Unpublished geophysical and subsurface sample information has been provided by Chevron Standard Ltd. and Shell Canada Resources Ltd.

Abstract DNAG Transect B-1. 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.

Abstract This pamphlet supplements the display sheets of Transect B2. It provides (1) descriptions of terranes on the line of Transect B2, (2) comments on gravity, magnetic and heat flow data and seismicity by R.P. Riddihough, (3) description of the seismic cross-section by R.M. Clowes, (4) bases for the compilation of Cross-section II and (5) references. The geological Strip Map and Cross-section I were taken by the contributors listed on the display sheets from both published and unpublished material and modified for this presentation. Monger was responsible for integrating the data and preparing the display sheets. He was guided through the intricacies of the geology of the eastern Cordillera by R.L. Brown, R.A. Price, P.S. Simony and J.O. Wheeler, through the Coast Plutonic Complex by G.J. Woodsworth, and through the off-shore area by C.J. Yorath. R.A. Price and P.S. Simony made the interpretation of the deep crust in the Omineca Crystalline Belt. R.L. Armstrong (principal reviewer), R.C. Speed and S. Stahl reviewed the first version of Transect B2 and made many valuable suggestions, which have modified this version, although some interpretations made herein probably are not ones that would be made by the reviewers, or even all contributors. Proterozoic and (?)Paleozoic crustal extension and rifting were responsible for creating the ancient western margin of North America (e.g. Stewart, 1976; Sears and Price, 1978). Episodes of Paleozoic(?), Mesozoic and Cenozoic crustal convergence involved not only subduction of Panthalassic/Pacific oceanic lithosphere with extensive, concomitant upper plate magmatism and intraplate, pericratonic compression, but also

Abstract DNAG Transect B-2. 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.