Sedimentology and stratigraphy of the Lower Triassic Montney Formation, Peace River Basin, subsurface of northwestern Alberta

The Lower Triassic Montney Formation in the Cindy Graben area of the Peace River Basin forms a westward thickening wedge of coastal plain, shoreface, offshore marine, turbidite and tempestite deposits. The Montney succession was divided into nineteen regionally correlatable parasequence sets, which were grouped into three 3rd order sequences. The first consists of transgressive and highstand systems tracts of Griesbachian to Dienerian age based on conodont biostratigraphy. The second sequence is Smithian in age and includes lowstand, transgressive and highstand systems tracts, respectively. The Dienerian and Smithian strata are separated by a sequence boundary, the result of a major structural inversion and a global eustatic sea-level fall. This tectonic event created upwarped “barrier islands” and downwarped “estuarine valleys”, which affected sedimentation patterns during the earliest Smithian lowstand and subsequent transgression. The mid-Montney lowstand turbidites were characterized as a shoreface-fed turbidite ramp with multiple sediment sources. They were initiated and localized as a result of paleotopography created by the Early Smithian structural inversion. The uppermost sequence was not biostratigraphically dated within the study area, but is most likely Spathian in age on the basis of regional correlations. It consists of shelf margin and transgressive system tracts. The Montney is a primary hydrocarbon exploration target and the reservoir potential was evaluated.