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ABSTRACT: GLORIA Mosaic of the Western United States Exclusive Economic Zone

H. A. Karl

A reconnaissance-scale survey was conducted of the western conterminous U.S. Exclusive Economic Zone (EEZ) using the GLORIA digital long-range side-scan sonar system as part of the U.S. Geological Survey EEZ-SCAN program. The side-scan images obtained during the survey have been processed and compiled into one large, complete mosaic. The area surveyed covers more than 750,000 km2 and extends from the U.S.-Mexican to the U.S.-Canadian borders and seaward to the 200 nautical mile boundary of the EEZ.

Many of the major tectonic and sedimentologic features of the offshore are well known from numerous earlier cruises. However, the GLORIA mosaic depicts the midocean ridges, transform faults, seamount provinces, and sediment fans that dominate this region in their entirety with more detail than has been possible in the past. For example, the western terminations of Murray, Pioneer, and Mendocino fracture zones have been documented and the entire morphology of the Blanco fracture zone and its geometric relationship with the Juan de Fuca and Gorda ridges is clearly seen. Also, the imagery has led to a better understanding of the interrelationship between tectonic and sedimentologic processes. For instance, uplift and slope accretion caused by plate convergence has forced Cascadia Channel to migrate basinward and erode a series of descending terraces. In addition to clearly defining known features, the GLORIA survey has revealed previously unmapped features that include more than 100 new seamounts and two new submarine fans.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990