LITHOPROBE seismic reflection imaging of Rocky Mountain structures east of Canal Flats, British Columbia

Abstract

LITHROPROBE seismic reflection data, coupled with information from industry seismic data and surface geology, image the thin-skinned structures of the western Rocky Mountains from the Main Ranges to the Rocky Mountain Trench near Canal Flats, British Columbia. Reprocessing of the LITHOPROBE seismic reflection line was conducted to improve resolution of upper-crustal features. Careful application of "conventional" processing techniques significantly improved the coherence of reflections from the first 6 s. A spatial semblance filter was applied to further enhance coherent signal, and residual-statics corrections were applied by cross correlation of unstacked data with semblance-filtered pilot traces.A near-basement reflection zone arising from Middle Cambrian strata is visible on an industry reflection profile at an approximate depth of 8 km beneath the Main Ranges. A similar reflection zone is imaged on the LITHOPROBE data at a depth of 11 km bsl but is interpreted as arising from Proterozoic strata. The autochthonous crystalline basement is interpreted as being below these layers and dipping about 2 °to the west. Geometric evidence is visible for several major thrust ramps involving the basal décollement and for an intermediate-level décollement that loses displacement into folds within the Porcupine Creek Anticlinorium. Reflections related to the Gypsum fault, the Redwall thrust, and the Lussier River normal fault are also imaged.