A new desktop synthesis of archival seismic, gravity and magnetic data in the western Davis Strait region offshore southeastern Baffin Island, Nunavut, Canada by Jauer, Oakey and Li (2019) yields new subsurface insights on the complex subsurface geology of the region. The marine geology of Davis Strait has been studied over the past 50 years along with significant petroleum exploration work, albeit largely on the Greenland side. Early geological studies show the link between the volcanic rocks on both sides of the strait, this was an important clue to the eventual understanding of how the underlying tectonic plates for both North America and Greenland have moved over the past 65 million years as shown by Oakey and Chalmers (2012). Their use of gravity and magnetic measurements from ships and satellites were crucial tools in their reconstruction of the tectonic history along with some seismic imaging. The new study uses significantly more seismic data and a re-filtered version of the gravity data using the higher resolution Bouguer anomaly gravity method.
Volcanic rifted margins like Davis Strait are dominated by basalt flows seen at surface or near seafloor and intrusions of similar volcanic rock into pre-existing sedimentary basins. The extensive Paleogene age volcanics present in Davis Strait dominate the geology, seen as the many high amplitude magnetic anomalies often tied to deeper structures mapped as gravity or seismic highs. At Cape Dyer, the flood basalt field extends from limited onshore exposures into the offshore and maps with the magnetic data over an area of approximately 13,000 km2. The over 250 km long, seismically imaged thrust fault along the Ungava Fault Zone is mapped as the key structural element of the Davis Strait complex with sedimentary basins on either side. The revised Bouguer anomaly gravity data set reveals two new, near shore sedimentary basins east of Cumberland Sound, the southern Tariut Basin and the northern Imaqpik Basin, each extending over 100 km in length, with sediment thicknesses of at least 4 km as interpreted from the seismic data.
The hydrocarbon charge of a previously unexplained petroleum bearing shallow drill core (GSC Petro core on map) adjacent to the eastern edge of the Tariut Basin is now linked to Paleozoic age source rocks, known from offshore dredging and onshore diamond exploration drilling. These rocks have undergone enhanced thermal maturation from the many sill intrusions associated with rifting that are recognised on the seismic data. Both the Tariuk and Imaqpik basins show strong evidence of an active hydrocarbon system from the proximity of clusters of sea surface oil slick features, seen from satellite radar images. A local zone of anomalously high dissolved methane is measured in the water column, originating from the seafloor immediately east of Cape Dyer close to the oil slick features shown at the northern limit of the Imaqpik Basin (Punshon et al., 2014). Methane can be generated biologically, e.g., swamp gas, but this data shows the gas originating from the seafloor.
Petroleum that is associated with the occurrence of volcanic rocks is a newer concept, but is now proven in several areas of the world with similar geological settings to the Davis Strait (Jerram, 2015). The collation of remote sensing, gravity, magnetic and seismic data with geological samples gathered by the drill and dredge shows that petroleum deposits exist in the region. Whether these deposits prove to be of economic value will require new data and additional study.
This work was a product of the Geo-mapping for Energy and Minerals (GEM-2) by Natural Resources Canada.
Jauer, C.D., Oakey, G.N., Li, Q. (2019) Western Davis Strait, a volcanic transform margin with petroliferous features. Marine and Petroleum Geology, vol 107, pp. 59-80
Jerram, D.A. (2015) Hot rocks and oil: Are volcanic margins the new frontier? Elsevier R & D solutions
Oakey, G.N. & Chalmers, J.A. (2012) A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Starit and Nares Strait regions between Canada and Greenland. Journal of Geophysical research, vol. 117, B10401
Punshon, S., Azetsu-Scot, K., Lee, C.M. (2014) On the distribution of dissolved methane in Davis Strait, North Atlantic. Marine Chemistry, vol 161, pp. 20-25