Eastern Section Meeting

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Possible Tectonic Influence on Upper Ordovician Stratigraphy and Source Rock Distribution in the Southern Hudson Platform, Northern Ontario


The Ontario Geological Survey (OGS) has been working on the Hudson Platform Project with the geological surveys of Canada and Manitoba. The project involved reassessment of existing data (e.g. offshore and onshore wells, seismic surveys) and acquisition of new data (e.g. biostratigraphy, apatite fission track, Rock EvalTM6). Results indicate that the Hudson Bay Basin (HBB) has oil potential. The Platform in northern Ontario includes the southern margin of the HBB, Cape Henrietta Maria Arch (CHMA), and Moose River Basin (MRB). The present day basin configuration probably developed in the Devonian. The Paleozoic succession consists of Upper Ordovician (Edenian) to Upper Devonian (Famennian) shallow marine carbonates, evaporites and shales. The Aquitaine Sogepet et al. Pen No. 1 well is an important reference section in the southern HBB. Recent mineral exploration drilling in the northern MRB provides abundant new data. Correlation of Ordovician and Silurian stratigraphy from Pen No. 1 well into the MRB has been assisted by new bio- and chemo-stratigraphic data. The Upper Ordovician transgression extended into the northern MRB and is represented by Maysvillian bioturbated subtidal carbonates overly thin basal siliciclastics. Near the CMHA these are overlain by organic-rich lime mudstones of the Maysvillian to Richmondian Boas River Formation that represent either maximum transgression or the onset of regression. The latter is suggested by: 1) sparse restricted faunal assemblage; 2) the overlying restricted evaporite-bearing dolomudstone unit (Surprise Creek Fm); and 3) roughly equivalent strata in the MRB, consisting of restricted marine dolomudstones with thin organic-rich seams (up to 15% TOC). Data are very sparse in the southern HBB, so this organic facies may be more widespread than current data indicate. Overlying the regressive Surprise Creek Formation in the HBB are subtidal bio-wackestones of the Caution Creek and Chasm Creek formations. These units are mostly absent in the MRB, either not deposited or cut by an overlying unconformity. The overlying Red Head Rapids (RHR) Formation is characterized by evaporite cycles in the HBB and poorly developed cycles which include terrestrial(?) red beds in the MRB. New stratigraphic evidence suggests that part of the Red Head Rapids is Hirnantian. Missing sub-RHR strata in the MRB suggests either differential subsidence across the CMHA or differential uplift of the MRB area prior to RHR time.