DEEP SEISMIC PROFILES FOR CRUSTAL ARCHITECTURE: AN EXAMPLE FROM THE BEAUFORT SEA CONTINENTAL MARGIN, ARCTIC CANADA

The Mackenzie Delta formed at the junction of the Arctic passive margin and the Canadian-Alaskan Cordillera after the Early Cretaceous opening of the Beaufort Sea (Canada Basin). The crustal architecture of this complex continental margin is revealed by a 15,000 km multiclient 2D regional reconnaisance seismic reflection survey utilizing wide-aperture acquisition geometry, 18 second recording, and advanced processing techniques to yield 40 km deep PSDM (Pre-Stack Depth Migrated) profiles. The new seismic data from the Beaufort-Mackenzie Basin distinguish continental, transitional and oceanic crust, and the superposed extensional, compressional and strike-slip structures of the thick Meso-Cenozoic sedimentary prism derived from the Mackenzie River. The western basin is distinguished by the Beaufort Foldbelt, a sub-shelf marine compressional foldbelt linked to the Tertiary deformation of the flanking Cordillera, and characterized by large-amplitude folds rarely seen in passive margins of the world. Detachment in deep mobile Cretaceous shales in response to 12 km of sediment loading controlled the deformation style and eastward terminus of the foldbelt. Therefore, the foldbelt segment of the margin comprises an unusual hybrid basin: both passive margin and foreland. The foldbelt itself mostly obscures the seismic imaging of the sub-detachment transitional crust and continent ocean boundary, but to the north, in deep water beyond the frontal folds, the continuation of the Early Cretaceous Canada Basin spreading center may be recognized. East of the foldbelt, a typical hanging-wall passive margin structure is observed extending north to Amundsen Gulf where Moho reflections are obtained and further constrained by gravity data. Our tectonic interpretations enable novel refinement of models for development of the Canada Basin and margins, and demonstrate the investigative powers of advanced industry seismic technology for deep crustal studies.