Provenance of Upper Devonian-Lower Carboniferous miogeoclinal strata, southeastern Canadian Cordillera: Link between tectonics and sedimentation

Upper Devonian-Lower Mississippian siliciclastic miogeoclinal strata in the southern Canadian Rocky Mountains provide a partial record of the geograph ic and tectonic setting of the Paleozoic western margin. Although these mar ine strata (Exshaw and lower Banff formations) contain extensive shale and mudstone, and some quartzofeldspathic sandstone and siltstone, as well as v olcanic ash layers, the provenance of these elastic units has, thus far, re mained poorly or incompletely understood. The integration of sandstone petr ofacies analysis with neodymium isotopic and trace-element (rare earth elem ent, Th, and Sc) analyses of mudrock facies was undertaken in this study to constrain better the sedimentary provenance. Coarse siltstones and sandstones in the Exshaw and Banff formations are chi efly subfeldspathic and feldspathic (quartzose-arkosic) arenites, with a co mplex sedimentary history involving derivation, at least in part, from an u plifted plutonic and volcanic source, such as possible western "Antler" oro genic highlands. The presence of monocrystalline quartz (inclusionless and with unit extinction) and sanidine in Exshaw sandstones at some sections su ggests at least a partial acidic volcanic or shallow intrusive source compo nent. The Exshaw and Banff petrofacies reflect the possible combined effect s of regional tectonic complexity (different and/or mixed source terranes), sediment transport and recycling, complex sediment dispersal paths, and we athering and diagenesis, Mudrock elemental and isotope geochemistry also su pport a provenance involving potentially multiple sources (mixed provenance ), Chondrite-normalized REE distribution patterns and La-Th-Sc ratios for E xshaw and Banff mudrocks resemble patterns for sediments derived from old c ontinental crust (e.g., passive margins, etc.) as well as some are settings . Nd isotopic compositions of the Exshaw and Banff formations do not suppor t a specific provenance, but they are consistent with addition of material younger than Archean in age.