Sedimentology of the Moosebar and Gates Formations (Lower Cretaceous)

Abstract

<p>The Moosebar and Gates Formations in northeastern British Columbia consist of seven major transgressive-regressive cycles. These cycles are laterally persistent and can be traced from the Foothills, eastwards into Alberta. Nonmarine sediments are thickest in the south and pinch out in a northerly direction. Shorelines were conglomeratic, within an east-west trending conglomeratic prone zone, wherever there was a local fluvial supply. Regional shorelines were oriented west northwest-east southeast. Regional paleoslope dipped northwards. During each regression, Falher coastlines prograded northwards as shoreline-attached, storm and tidally dominated strandplains. The Notikewin Member represents a progradational mesotidal barrier island system. Several of the Falher transgressive and regressive limits fall within a 30 to 40 km east-west trending zone which parallels the location and trend of the Peace River Arch. Gates cyclicity and sediment source was caused by tectonic events occurring to the west and south west, but the shoreline trends were affected by the Peace River Arch. The sediments have a multiple source rock provenance, derived from older clastic sediments, evaporites, low to medium rank metamorphics, volcanics and possibly minor amounts of plutonic igneous terrains. These source rocks are now situated both west and east of the Rocky Mountain Trench.</p>