The Old Fort Point Formation, an Organic-Rich Deep-Water Deposit in the Neoproterozoic Windermere Supergroup, Western Canada

Mark Smith
University of Ottawa, Department of Earth Sciences
Ottawa, Ontario, Canada
mark.smith@science.uottawa.ca

The Old Fort Point Formation (OFP) is a fine-grained mixed clastic + carbonate succession in the Windermere Supergroup and is exposed over 35,000 km² in the southern Canadian Cordillera. Earlier workers generally dismissed it as a local succession of uncertain importance and as a consequence its lithologic characteristics and lithostratigraphic significance have been largely unexplored. Recently, however, it has been proposed that the OFP may represent an important regional stratigraphic marker that coincided with a major glaciogenic eustatic sea-level rise.

Stratigraphically-upward the deep-marine OFP consists of a TST, an organic-rich condensed section capped by a highstand deposit with the organic-rich horizon representing a potentially significant hydrocarbon source rock. Exposures of the OFP, which range from 100 – 250 m thick and represent deposition on different parts of a basin slope to floor transect, outcrop at a number of previously determined locations. Complete vertical sections of the OFP will elucidate the vertical and lateral changes that occur in the sedimentology, stratigraphy and chemistry in this formation across the basin. The stratigraphic distinctiveness and regional extent of the OFP also makes it an excellent example for reconstructing a slope to basin-floor transect by applying the principles of sequence stratigraphy to a deep-water succession.

The OFP in the southern Canadian Cordillera presents a unique opportunity to study deep-water, locally organic-rich strata. In addition, the OFP offers the chance to examine a more complete and representative record of the sedimentological, stratigraphic and paleo-oceanographic changes during the Neoproterozoic when compared to other slope-setting studies.