Regional Outcrop to Subsurface Correlation of the Montney Formation: An Evolving Understanding of Lower Mesozoic Tectono-Stratigraphic Evolution in Western Canada

Zonneveld, John-Paul; Moslow, Thomas F.

The Montney Formation comprises western Canada's most prolific unconventional hydrocarbon plays. Although restricted in grain size to siltstone and very fine-grained sandstone this unit produces from a wide variety of play types and depositional settings. Historically the Montney has been interpreted to have accumulated in a passive margin setting on the open west Pangaea coastline with sediment accumulation centered in the collapsed Peace River Embayment. Previous stratigraphic correlations have utilized subsurface datasets (well logs and core). Correlation of the Montney into the Rocky Mountain Front Ranges and Foothills utilizing detailed outcrop descriptions (including outcrop gamma spectrometry), biostratigraphy and limited chemostratigraphy has revealed a more complex basinal setting than previously postulated.

Our analyses indicate that the Montney depocentre shifted throughout the evolution of the Western Canada Sedimentary Basin region. Earliest Triassic (Early Induan) sediments of the Lower Montney are thickest in linear trend on the eastern side of the basin, and exhibit no increase in thickness into the Peace River Embayment. The Peace River Embayment became the centre of Montney deposition during the later Induan and through the Olenekian. The Montney depositional basin was bounded on the west by a subaerially exposed high, with possible openings with the Panthalassa Ocean towards the north and southwest. This high may have sourced minor amounts of sediment into the basin from the west and formed a barrier to ocean currents and wave from the west. It is interpreted to have resulted from structural movement associated with initial terrane accretion on the western margin of Pangaea. All major extra-formational and intra-formational unconformities within the Montney succession can be demonstrated to have originated through tectonic influences.

Understanding the basic architecture of the Montney depositional basin is a crucial part of developing more accurate predictive sedimentological models for this unit.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013