Search

Canada ratified the United Nations Convention on the Law of the Sea (UNCLOS) in 2003. With that ratification is an obligation to submit data and information to the U.N. pertaining to the limits of the country's extended continental shelf (ECS); the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of Canadian scientists, managers, and legal experts that included representation from three Federal Departments (Natural Resources Canada, Fisheries and Oceans Canada, and Global Affairs Canada) with additional support from other departments, spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada's seaward most maritime limit. The submission has the potential to provide Canada with 2.4 million km (2) 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 and in particular 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 to substantiate Canada's outermost maritime limits. 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 doing so, the paper demonstrates the geologic complexity of Canada's margins as illustrated in scientific publications that have resulted from these new data collections, while at the same time presenting new scientific evidence and interpretations. This collection of data and information provides a wealth of new knowledge in Canada's offshore regions. The massive data compilation in the Atlantic led to conception of continental margins, in a source-to-sink scenario, as having an equilibrium base level or graded form, comparable to river systems. Departures from this shape relate to the interplay of sedimentary processes and in particular to those processes that do not fit the source-to-sink paradigm. For example, a significant part of the Atlantic margin is shown to be heavily influenced by along-slope geostrophic currents that generated massive contourite drift deposits. These deposits reflect lateral transport of sediment that had a significant impact on the morphology of the margin. The role of mass transport processes in shaping continental margins is also highlighted, and in particular the collapses of entire segments of the margin were observed. The prominent role mass failure processes play in delivering sediment to the adjacent abyssal plain is also critical in the ECS context. These observations challenge the entrenched notion of a continental margin comprising a shelf, slope, and rise and in particular the concept of the "continental rise". Prior to 2006, regions of the Arctic Ocean seaward of the Canadian landmass had fewer than 5000 km of seismic reflection data. The massive efforts of Arctic coastal States to map their margins for ECS purposes have led to a leap in technological advances to acquire data in ice-covered seas and have led to a wealth of new geoscientific knowledge. Perhaps foremost amongst this knowledge is demonstration that Canada Basin is indeed a fully developed ocean basin, albeit significantly infilled with sediment. Based on this knowledge and identification of related structures, new realistic tectonic scenarios for opening of the Amerasia Basin are proposed that include a significant component of transform or strike-slip motions. With seismic velocity and rock sample information, the continental nature of Alpha and Mendeleev ridges has been substantiated. Even bathymetric data were lacking in the Arctic and new editions of seafloor maps now support grids of 500 m spacing; although some regions remain sparse. Once thought to be relatively stagnant, sedimentary processes such as found in many ocean basins were discovered in the Arctic Ocean. Evidence of geostrophic currents, sediment mass failures, and deep-sea turbidity current channels were found to be ubiquitous, even in the deepest parts of the Arctic's basins. Key words: United Nations Convention on the Law of the Sea, extended continental shelf, continental margin, Atlantic Ocean, Arctic Ocean, 1. Introduction It is a common adage that we know more about the Moon and Mars than we do about the oceans on Earth. As an example, according to the [...]

Turbidity currents are fundamental marine sedimentary processes that deliver sediments from continental margins to deep ocean basins. They develop and maintain deep-sea channels that act as principal conduits for this sediment delivery. While turbidity current channels are frequently considered as analogous to river channel systems, there are distinct differences in the mechanisms that govern their formation. This is particularly true at high-latitudes, where glacial margin processes and Coriolis effects have direct consequences on the characteristics of channel-forming turbidity currents. Understanding the latitudinal controls that influence the structure of these channels is thus a key objective of this study. The geomorphology of the glacial-fed NP-28 Channel in the Amundsen Basin of the Arctic Ocean, the highest-latitude deep-sea channel on Earth, is assessed. Compilation of available bathymetry shows that the channel follows a low-gradient, low-sinuosity path roughly paralleling the base of Lomonosov Ridge. The channel has a broad cross-section comparable to other glacially-fed and tributary-fed deep-ocean channel systems. High-resolution subbottom profiles reveal intrachannel terraces and an incised channel thalweg that were likely formed through erosion by traction-dominated currents; stratified levees and sediment waves were likely deposited by overbank flows. Coriolis deflection of channel-filling currents is evident from consistent levee asymmetry along the entire channel path. Within the channel, the channel floor geometry suggests local dominance of both Coriolis and centrifugal forces at the base of the channel; the latter in particular where the channel is deflected by external bedrock. Overall, channel morphology is largely consistent with existing models of Coriolis force effects on turbidity currents at high latitudes. This influence of Coriolis force, in addition to the presumed glacial style of the sediment input and bedrock interaction with the channel path, are considered the major factors that affected channel morphology. [Display omitted] • Geomorphology of the highest-latitude submarine channel on Earth is presented. • Asymmetric levees are consistent with strong influence of Coriolis force of suspended currents. • Channel floor geometries are consistent with centrifugal and Coriolis-dominated basal currents. • Coriolis force, bedrock control and presumed glacial source are factors in channel geomorphology. [ABSTRACT FROM AUTHOR]

• Subbottom profiler data in Canada Basin, Arctic Ocean, reveal contourites. • Contourites are within mixed systems of turbidity and contour current origin. • Contourites suggest cyclonic movement of Arctic Ocean Bottom Current (AOBC). • Higher sediment flux and more vigorous AOBC were likely during past glacial epochs. Canada Basin Abyssal Plain (CBAP) of the Arctic Ocean is incredibly flat and featureless at first appearance. Sediments of the basin have been interpreted to be turbidites interbedded with hemipelagic sediments. It is hypothesised, however, that deep-ocean geostrophic currents are active here as they are in most ocean basins. Compilations of modern bathymetry and subbottom profiler data are used to assess the possibility of ocean currents and their influence on sediment distribution within Canada Basin. Off of the Alaska-Beaufort margin, eastwardly deflected levees and fans in 3000 to 3800 m water depth along with oblique sediment waves on top of these features suggest a mixed system of turbidity currents influenced by cyclonic flowing geostrophic currents. These features probably formed during glaciations and lower sea level stands when the adjacent Chukchi Shelf was subaerial. Sediment delivery to the margin was likely more pronounced than today, and bottom current activity was presumably intensified. A large (100 km-wide) plastered drift and smaller bedforms were revealed by subbottom profile data along the Canadian Arctic Archipelago margin, in 3000 to 3850 m water depth. It is presumed that these deposits were formed as plumes of sediment, input through glacial outwash or outwash via the Mackenzie River. These plumes were then affected by deep contour-following currents to produce contourites. Large (up to 30 km wavelength) migrating bedforms within northern CBAP are believed to have resulted from turbidity current plumes sourced from the Mackenzie Fan that were additionally influenced by contour current reworking as part of returning cyclonic flow of deep geostrophic currents. There is little to no age control to groundtruth the stratigraphy observed in seismic profiles, but it seems likely, given their near-surface appearance, that sediment input and bottom current intensity was heavily influenced by climatic conditions related to past glaciations and associated relative sea level changes. [ABSTRACT FROM AUTHOR]