TECTONIC SIGNIFICANCE OF GRAVITY AND MAGNETIC VARIATIONS ALONG THE LITHOPROBE SOUTHERN CANADIAN CORDILLERA TRANSECT

Correlation of potential field data to regional geological features wi thin the Lithoprobe southern Canadian Cordillera transect corridor all ows characterization of anomaly patterns according to their likely sou rces. Long-wavelength Bouguer gravity anomalies are attributed to isos tatic effects of topography, which in most areas is compensated. Two n otable exceptions occur: in the Foreland belt a large positive isostat ic anomaly is likely due to mechanical support of topography formed as Cordilleran thrust sheets were emplaced over the thick craton, and on the west coast, isostatic anomalies are related to active subduction. Long-wavelength magnetic anomalies in the Foreland belt are associate d with cratonal basement beneath the thrust sheets, and these can be f ollowed westward to near the Omineca belt. A prominent positive magnet ic anomaly along the western Coast belt is probably associated with ma fic rocks generated during subduction. Elsewhere, relatively short wav elength gravity and magnetic anomalies correlate well with either plut ons (both gravity and magnetic), volcanics (primarily magnetics), or f aults (magnetics) within the region of accreted terranes.