Reappraisal of the Geological Setting and Hydrocarbon Potential of the Intracratonic Hudson Bay Basin, Canada: A Work in Progress

Nicolas Pinet¹, Denis Lavoie¹, Pierre Keating², and Mathieu Duchesne^1
1Geological Survey of Canada, Québec, QC, Canada.
²Geological Survey of Canada, Ottawa, ON, Canada.

The Paleozoic-Mesozoic Hudson Bay basin is a large sedimentary basin that unconformably rests over metamorphic rocks of the Canadian Shield. The basin has a nearly circular outcrop pattern with around 2/3 of its surface covered by water of the Hudson Bay. It is saucer-shaped in cross-section and is mainly filled with relatively undeformed Paleozoic sediments with up to 2.5 km of preserved thickness. Shallow water limestones, dolostones and evaporites with minor amounts of shales and silstones dominate the Upper Ordovician to Upper Devonian succession. The occurrence of Upper Paleozoic rocks is still uncertain and the presence of Cretaceous rocks over a significant portion of the basin has been proposed on the basis of fragmentary data. The current boundaries of the Quaternary marine basin mimic the limits of the Paleozoic basin, reinforcing the apparent bull’s eye geometry of the Hudson Bay basin and the hypothesis that basin’s forming mechanisms are somewhat unchanged and related to a long term lithospheric feature. However, this hypothesis may be false as the sedimentary succession recorded several episodes of deposition, some of them potentially unrelated to the presence of a restricted saucer-shaped basin.

Among the main structural features of the Hudson Bay basin is a NNW trending basin-central horst, perpendicular to the Precambrian basement suture zone. Silurian rocks exhibit onlapping relationships on the structural high, whereas Devonian rocks drape over it, indicating that the faults bounding the horst were mainly active during the Silurian. Another major structural feature is a WNW-trending fault array that forms the northern boundary of the basin. This fault array parallels the Hudson Strait, a morphologic feature that connects the Hudson Bay to the Atlantic Ocean, which may have been tectonically active during the Cretaceous or even later.

The first round of exploration (1968-1985) resulted in the drilling 5 dry offshore wells located in the central part of the Bay and few onshore wells. Reassessment of existing data and acquisition of new-targeted information are in progress. Initial results indicate that the perception in which potential source rocks are lacking and level of maturation is too low to generate hydrocarbon is in part erroneous.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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