Canada’s maritime frontier: the science legacy of Canada’s extended continental shelf mapping for UNCLOS

Abstract

Canada ratified the United Nations Convention on the Law of the Sea in 2003. With that ratification came an obligation to submit data and information to the United Nations pertaining to the limits of the country’s extended continental shelf; the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of scientists spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada’s outermost maritime limits. The submission has the potential to provide Canada with 2.4 million km2 of additional submarine landmass in the Atlantic and the Arctic oceans over which Canada exercises sovereign rights for the purpose of exploring and exploiting its natural resources. Specific information such as the tectonic framework of the continental margin, the geomorphology of the margin, sedimentation on the continental slope, the geologic nature of adjoined ridges, rises, and plateaux, and sediment thickness within adjacent basins are examples of fundamental pieces of geoscientific information needed. This paper highlights a number of segments of Canada’s continental margins to showcase this scientific evidence and how it is applied in the UNCLOS context. In so doing, the paper demonstrates the immensity of new knowledge gained of Canada’s offshore lands.

Rift to Post‐Rift Tectonostratigraphy of the Sverdrup Basin in Relation to Onset of the High Arctic Large Igneous Province (HALIP) in the Early Cretaceous, Arctic Canada

“…The crustal model presented by Oakey and Saltus (2016) for the Alpha Ridge shows that the continental crust was extended and thinned less than the surrounding areas and was subsequently underplated by mafic magmas, intruded by magma, and overlain by submarine flood basalts (Figure 3). Seismic data from southern Alpha Ridge indicate that sediment in the surrounding basins onlap the Alpha Ridge (Mosher et al., 2023), consistent with it being a remnant bathymetric high. The proposition that extension and crustal thinning surrounding the Alpha Ridge preceded HALIP (as in Grantz et al., 2011) appears supported by seismic data that show volcanic rocks onlapping the southern rifted margin of the Lomonosov Ridge and interfingering with the sedimentary fill of the Amerasia Basin (Kristoffersen et al., 2023).…”

“…Beneath the Alpha Ridge, the base of the moho is at 20–30 km depth, with shallower zones of ∼15 km around the edge where the sedimentary cover is thicker and so the basement crust is even thinner than 15 km (Mosher et al., 2023; Schiffer et al., 2018). Maps of crustal and lithospheric thickness show a remarkable coincidence below the center of the Alpha Ridge, where the moho is deepest (∼30 km) and yet the lithosphere‐asthenosphere boundary is shallowest (∼50 km) (Schiffer et al., 2018).…”

“…The High Arctic Magnetic High Domain overprints the underlying crust in the northern Amerasia Basin, and to the south in the Canada Basin, it was a multi-kilometer thick accumulation of sediment that hindered investigations into the type of the crust in the basin, in terms of the presence of oceanic crust and the extent of the continent-ocean transition (COT) (see discussion Grantz et al, 1990). New geophysical data from the greater Amerasia Basin (e.g., Døssing et al, 2013;Gaina et al, 2011;Mosher et al, 2023;Zhang et al, 2019) have led to more refined interpretations of the spreading center, oceanic crust and associated seafloor spreading magnetic anomalies, and the extent of transitional lithosphere of the COT (Chian et al, 2016;Gaina et al, 2014;Mosher et al, 2023;Zhang et al, 2019); which in turn have sparked new kinematic models for the divergent plate motion that formed the basin (e.g., Døssing et al, 2020;Hutchinson et al, 2017;Shephard et al, 2013). Jakobsson et al (2012).…”

Seismic data and ancient zircons discovered on the Mendeleev Rise, Arctic Ocean, indicate continental crust

“…The entire area of the Alpha-Mendeleev Rise and most of the associated, flanking, deep-water basins are covered by, and likely intruded with, HALIP magmas, some of them comprising seaward-dipping reflectors (SDRs). The age of HALIP magmatism is ~130-80 Ma with a peak in magmatic activity between 125 and 100 Ma 4,6,12,18 .…”

“…There is now strong evidence that the Amerasia Basin is largely floored by continental crust and to be of Early Cretaceous age [2][3][4][5][6]11,12 . The Alpha-Mendeleev Rise is thought to have formed from continental crust that underwent significant stretching and was heavily magmatized by large amounts of basaltic material 1,2,6,10,[12][13][14] . As a result, the crust of the Rise is considered to comprise a mixture of continental and basaltic material 15 .…”