BOTTOM CURRENT DERIVED BIOCLASTIC HORIZONS IN THE LOWER TRIASSIC MONTNEY FORMATION OF BRITISH COLUMBIA, CANADA

The depositional origin of the “Claraia Zone” in the Lower Triassic Montney formation, British Columbia and Alberta, Canada, has been mistakenly interpreted as an offshore turbidite fan. Analysis of core has revealed that this unit is a bioclastic interval that shows lithological characteristics inconsistent with this interpretation. The “Claraia Zone” has been delineated and mapped using core data sets and wire line log characteristics. Core were logged and facies identified based on lithological characteristics of the units. Sedimentological and taphonomic evidence indicate that the “Claraia Zone” consists of proximal offshore deposits modified by bottom water currents. Bioclasts in this unit are fragmentary and made up of bivalve shells that are thicker than those found outside of this interval in the same area and were likely transported from outside the system. Interbedded bedforms reflecting suspension and traction deposition in the rippled to laminated heterolithic very fine-grained sandstone to fine siltstone facies (SL2) are comparable with recent deposits in the Gulf of Mexico by which are influenced by the wind driven Loop Current. A similar current likely resulted in the genesis of the “Claraia Zone”, which has been expressed separately as SL2 and a laminated bioclastic siltstone. This unit is interpreted as a contourites succession based on the shape of the deposit and its sedimentological characteristics, particularly the identification of the traction structures from SL2 Identification of these deposits as bottom current-driven contourites provides new information on circulation in the Peace River Embayment during the Early Triassic.