Cadomin Conglomerate of Western Alberta -- A Result of Early Cretaceous Uplift of the Main Ranges

摘要: ABSTRACT A petrographic and sedimentologic study of the Lower Cretaceous Cadomin Conglomerate was made at nine localities. The is about 11 m in thickness, consists primarily chert quartzite pebbles, quartz sandstone. Approximately 5 per cent pebbles are fossiliferous. Foraminifera silicified fossiliferous clasts Carboniferous age. cherts were probably derived from upper Paleozoic formations only, orthoquartzites Cambrian Gog Group. few shale siltstone Triassic Jurassic strata. sheet-like areal distribution, well-rounded good sorting, clay-free matrix, poor stratification but pebble alignment relative uniformity composition along strike conglomerate favour a pediment deposit overlain by an alluvial-plain or distal alluvial-fan environment for area studied central Foothills. represents different depositional environments various Coarse, thick deposits depicting proximal alluvial fans grade eastward other areas into plains. distinct lithologies, especially carbonates, orthoquartzite clasts, indicate sedimentary source exposing wide variety stratigraphic levels ranging Mesozoic to Cambrian. most probable sources thrust sheets within near eastern part Main Ranges Rocky Mountains. estimated on basis sizes transport mechanism have been maximum 60 80 km minimum 10 32 west present westerly outcrops Omineca geanticline Mountain Trench can be ruled out as lack metamorphic volcanic sizes, rate thickening clastic wedge, known ages structures (Main Early earlier). In addition, palinspastic structural reconstructions suggest that more than 95 wedge may erosion western Front Ranges.