Distribution of Arenites (Fernie Sand) in the Jurassic Fernie Formation in Northeastern British Columbia, Canada

Abstract

Although a unit of quartzose sandstone in the Fernie Formation (Jurassic) of northeastern British Columbia has produced hydrocarbons, a detailed investigation of this sandstone has not yet been published. A mapping project was initiated because bounding beds have high organic content; and the presence of clean sandstone could enhance the Jurassic section's potential for unconventional development. A similar correlatable sandstone unit, which produces hydrocarbons in central and southern Alberta, is called Rock Creek Member. There it contains Middle Jurassic (Bajocian) fauna. Alberta's formational nomenclature has been largely adopted for British Columbia's Jurassic section though it might not be entirely appropriate. The age (Upper Jurassic?), stratigraphic affinity, and tectonostratigraphic significance of the rocks in northeastern British Columbia remain unclear, but we refer to them simply as Fernie Sand. Recent, limited palynological work supports a late Jurassic age for the Fernie Sand; therefore Alberta's Rock Creek Member is likely not stratigraphically equivalent and should not be used in northeastern British Columbia. As observed in core, and described in drill cuttings, the Fernie Sand consists of light greyish brown, bioturbated, glauconitic sandstone and siltstone. Despite subtle differences in grain size relative to bounding units, the Fernie Sand can be recognized on well logs by a leftward shift of the gamma-ray curve. An isopach map of relatively clean sand based on more than 700 wells and stratigraphic cross sections indicate that: 1) the Peace River arch was a paleotopographic low during Jurassic sedimentation; 2) Fernie Sand appears to define discontinuous lenses encased in finer grained rocks rather than continuous tabular bodies; 3) ovoid accumulations of Fernie Sand define a northwest-southeast oriented trend extending across the axis of the Peace River arch; and a smaller body is present near the depositional-erosional edge of the unit farther to the northwest.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016