Geochemical and Nd isotopic evidence for sedimentary-source changes in theDevonian miogeocline of the southern Canadian Cordillera

Sedimentological evidence indicates that elastic sediments of the Western C anada Sedimentary Basin were derived predominantly from the north and east, an exception being the westerly sourced Sassenach Formation in the Upper D evonian, A comparison of geochemical and Sm-Nd isotopic data of the Sassena ch Formation and the underlying Perdrix and Mount Hawk Formations, which ha ve easterly sources, support a change in sedimentary provenance, The Frasni an Perdrix and Mount Hawk Formations have initial epsilon(Nd) values of -7 to -8.5. This range of values is higher than that of the underlying Precamb rian basement and reflects a mixture of older and younger crustal detritus (Late Proterozoic to Devonian) eroded and transported from orogens in the A rctic. The overlying Famennian Sassenach Formation yields lower initial eps ilon(Nd) values that decrease from as high as -8.5 at the base to about -11 near the top,The lower epsilon(Nd) values of the Sassenach Formation imply that the western crustal source of the Sassenach sediments was, on average , older than the eastern crustal sources of the underlying formations. This older western source appears to be related to uplift and reworking of olde r miogeosynclinal sediments in the west as a result of compression related to the Antler orogeny.