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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 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 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. [ABSTRACT FROM AUTHOR]

The 1929 Grand Banks submarine landslide on the southwestern Grand Banks of Newfoundland was triggered by a Mw 7.2 strike‐slip earthquake. It is the first studied example of a submarine mass movement known to have caused a turbidity current and tsunami. The event resulted in 28 casualties and caused severe economic damage. The St. Pierre Slope is the main source area for the sediment failure. It contains translational and probable retrogressive surficial failures (<25 m); the majority of which lie in >1,700‐m water depth. These observations contradict what might be expected for a tsunamigenic event; thus, the objective of this study is to look for other potential causal mechanisms. A comprehensive analysis of 2‐D seismic reflection data of various resolutions and multibeam bathymetry allowed mapping of new stratigraphic and structural features. Numerous, low‐angle (~17°) faults are present throughout the Quaternary section of the St. Pierre Slope that are associated with seafloor escarpments (750‐ to 2,000‐m water depth). These faults have up to 100‐m high displacement and are interpreted as part of a massive (~560 km3), complex slump. There are multiple décollements (250‐ and 400‐ to 550‐m below seafloor) within this slump and there is indication for slumping in at least two directions. Evidence suggests slumping as a result of the 1929 earthquake occurred along these faults, with ~100‐m seafloor displacement in places. The 1929 submarine landslide therefore involved two failure mechanisms: massive slumping (~500‐m thick) and consequent widespread, surficial (<25 m) sediment failure. Both failure mechanisms likely contributed to tsunami generation. Key Points: The 1929 Grand Banks tsunamigenic landslide included a massive slump and not just surficial landslides as described in earlier literatureThe slump (~500‐m thick) occurred along oblique faults (~17°) with vertical offsets of 100 m and horizontal offsets of 330 mBoth the massive slump (~560 km³) and translational surficial (upper 20 m) sediment failures likely contributed to the 1929 tsunami [ABSTRACT FROM AUTHOR]

Two-dimensional and three-dimensional multichannel seismic reflection data are utilized to examine previously unrecognized contourite depositional systems along the continental margin of Nova Scotia, Canada. Prior to this study these features were thought to be of limited extent in the study area. The new data show that contourite drifts are widespread with greatest drift development during the Late Miocene to Pliocene. Giant sediment waves form stacked, aggrading sequences of bedforms and their development is linked to pre-existing seafloor morphology. Small sediment drifts developed locally throughout the late Paleogene and Neogene, either southwest and down-current of seafloor obstacles or form channel fills. Major erosional pulses form regional seismic markers; first along the continental rise in the Early Oligocene, then along the continental slope during the Late Miocene and Pliocene. Three-dimensional seismic data show that erosion surfaces preserve along-slope amplitude anomalies, two-dimensional, low-relief sediment waves, and barchanoid bedforms. The geophysical evidence implies that a northeast-to-southwest, along-slope bottom current influenced Cenozoic depositional patterns throughout the study area. [ABSTRACT FROM AUTHOR]

The tectonic history of Amerasia Basin, Arctic Ocean, is not well known because of a paucity of data and complexities introduced by the Alpha–Mendeleev Ridge large igneous province. Makarov Basin, at the northern limit of Amerasia Basin and adjacent to Lomonosov Ridge, may provide a window into understanding the larger tectonic framework. The objective of this study is to decipher the sedimentary and tectonic history of northern Amerasia Basin by analysing the seismic stratigraphy, structure and morphology of Makarov Basin and surrounding regions (Alpha and Lomonosov ridges) of the central Arctic Ocean. The principal data sources for this study are a 400 km long multi-channel seismic line, extending from Alpha Ridge to the crest of Lomonosov Ridge via central Makarov Basin, and the Arctic bathymetric chart. The seismic record within Makarov Basin is divided into five seismic units. The first unit overlying basement hosts Late Cretaceous (minimum age) slope to base of slope sediments. Some of these sediments are interbedded with volcanic or volcanoclastic rocks with a minimum age of 89 Ma. Makarov Basin becomes isolated from proximal sources of sediments after the onset of rifting that separated Lomonosov Ridge from the Barents Shelf, which may have occurred as early as the mid-Late Cretaceous, and led to the creation of Eurasia Basin. Sediments are largely pelagic to hemipelagic as a result of this isolation. This deposition style also applies to the draped sedimentary strata on Alpha and Lomonosov ridges. The uppermost seismic units within Makarov Basin arejump-correlatedto the stratigraphic record of the ACEX drill site on top of Lomonosov Ridge to provide age control. This correlation shows that the 44.4–18.2 Ma hiatus documented in the drill core is not apparent in the basin. Inter-ridge correlations and the absence of an obvious planate surface on Alpha Ridge also suggest that sedimentation was uninterrupted on this ridge during the hiatus. Seismic data reveal a deep subbasin (~ 5 km thick) within Makarov Basin. This subbasin is immediately adjacent to Lomonosov Ridge within major bends in the general strike orientation of the ridge. The rhomboid shape of the deep subbasin, the straight and steep morphology of the Amerasian flank of Lomonosov Ridge and the presence of numerous sub-parallel ridges (e.g. Geophysicists and Marvin spurs) created by splay faulting are evidence of strike-slip (transtensional) tectonics. This interpretation supports the “rotational” model of opening of Amerasia Basin with a transform to transtensional margin at Lomonosov Ridge. As spreading continued, however, the tectonics became increasingly extensional perpendicular to Lomonosov Ridge. There is no evidence of major tectonic deformation in Makarov Basin beyond the late Paleocene. [ABSTRACT FROM AUTHOR]

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]

Abstract: It is the intent of this paper to explore a significant extent of an entire passive continental margin for hydrate occurrence to understand hydrate modes of occurrence, preferred geologic settings and estimate potential volumes of methane. The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated stability zone calculations, but little physical evidence has been offered. An extensive set of 2-D and 3-D, single and multi-channel seismic reflection data comprising in excess of 140,000 line-km was analyzed. Bottom simulating reflections (BSR) were unequivocally identified at seven sites, ranging between 250 and 445 m below the seafloor and in water depths of 620–2850 m. The combined area of the BSRs is 9311 km2, which comprises a small proportion of the entire theoretical stability zone along the Canadian Atlantic margin (∼715,165 km2). The BSR within at least six of these sites lies in a sedimentary drift deposit or sediment wave field, indicating the likelihood of grain sorting and potential porosity and permeability (reservoir) development. Although there are a variety of conditions required to generate and recognize a BSR, one might assume that these sites offer the most potential for highest hydrate concentration and exploitation. Total hydrate in formation at the sites of recognized BSR’s is estimated at 17 to 190 × 109 m3 or 0.28 to 3.12 × 1013 m3 of methane gas at STP. Although it has been shown that hydrate can exist without a BSR, the results from this regional study argue that conservative estimates of the global reserve of hydrate along continental margins are necessary. [Copyright &y& Elsevier]

Canada has the longest coastline and largest continental margin of any nation in the World. As a result, it is more likely than other nations to experience marine geohazards such as submarine landslides and consequent tsunamis. Coastal landslides represent a specific threat because of their possible proximity to societal infrastructure and high tsunami potential; they occur without warning and with little time lag between failure and tsunami impact. Continental margin landslides are common in the geologic record but rare on human timescales. Some ancient submarine landslides are massive but more recent events indicate that even relatively small slides on continental margins can generate devastating tsunamis. Tsunami impact can occur hundreds of km away from the source event, and with less than 2 hours warning. Identification of high-potential submarine landslide regions, combined with an understanding of landslide and tsunami processes and sophisticated tsunami propagation models, are required to identify areas at high risk of impact. [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]

Eastern Juan de Fuca Strait of southwestern British Columbia/northwestern Washington State is near the western and southern terminus of Late Wisconsinan glaciation in North America. Seismic-reflection profiles, bathymetric data, sediment core data and 41 new radiocarbon dates provide insight into the history of ice retreat and sea-level change in the eastern portion of the strait. The retreating ice margin appears to have passed through the area between 14,460±200 and 13,595±145 14C yr. Glacial marine sediments date between 12,889±50 and 11,110±50 14C yr BP. Wave-eroded unconformities, drowned prograded deposits and a partially isolated low-stand basin are evidence attributed to low-stand sea levels following deglaciation and five new control points on the local eustatic sea level curve are assigned based on radiocarbon dating of these features. Sea-level change was rapid: from +75 m immediately after deglaciation to possibly -60.4 m at 9920±60 14C yr BP. After this time, gradual sea level transgression took place. Relative sea level reached its approximate present position by 5470±115 14C yr BP. Since then, relative sea level has remained constant suggesting eustatic rise is balanced by crustal uplift. [Copyright &y& Elsevier]

Investigates Late Quaternary sediment, sediment mass flow processes and slope stability on the Scotian Slope in Canada. Evidence of erosion, rotational slumping and internal deformation at the near surface sediment; Observation that mass failure deposits form a part of the sedimentary column in this bathymetrically smooth region.

Simulations of the erosion, transport of fine-grafted sediment, such as that of Greenberg & Amos and the Hydraulics Research Station, have illustrated a general lack of reliable field data. Consequently, some standard equations and constants used in modellilng the sedimentation character of fine-grained cohesive sediment from the Bay of Fundy. Initial results showed that the resistance of erosion of intertidal fine-grained sediment is controlled largely by the degree of subaerial exposure and the consequently dehydration and compaction. The sediment shear strength was high (4 kPa), but generally decreased seawards across the intertidal zone. The resistance of intertidal mud to erosion can be 80 times greater than sub-tidal counterparts. The rate of sediment erosion varied as a complex function of the applied bottom shear stress. At stresses immediately above the critical, the erosion rate decreased asymptotically with time. At higher excess stresses, the erosion rate was linear with respect to time. Thus sediment erosion cannot be represented by a single coefficient. The Krone method of computing sedimentation rates of suspended material was shown, by comparisons with direct measurement, to over-predict by 29%. All variables used in his method were measured in the evaluation with the exception of the critical deposition stress (τ[SUBd]). The closest comparisons were obtained when τ[SUBd] was assigned a value of 0.1 N m[SUP-2] following Creutzberg & Postma. The in situ still-water particle setting rate (V[SUB0]) was constant with respect to time (2.1 × 10[SUP-3] m s[SUP-1]). However, the settling tube measures of settling rate, compared to in situ results, under-predicted particle settling by an order of magnitude (2·7 × 10[SUP-4] m s[SUP-1]). The reason for this discrepancy is not apparent from our results. [ABSTRACT FROM AUTHOR]

The eastern Canadian continental margin is a typical glaciated passive margin where historic earthquakes have triggered submarine landslides. This study compares seismological estimates of earthquake recurrence with the geological record over the past 85 k.y. offshore of Newfoundland to assess the reliability of the geologic record. Heinrich layers in cores provide chronology at ~3-5 k.y. resolution in high-resolution seismic-reflection profiles across headscarps and mass-transport deposits. Landslide-generated turbidites on the basin floor have distinctive petrology, sedimentology, and distribution, with ~1 k.y. chronologic resolution. Large slope failures occurred synchronously over margin lengths of 50-300 km. Since 85 ka, four failures have affected a >150-km-long sector of the slope and 18 failures were large enough to be recognized in seismic-reflection profiles and/or cores. The widespread failures were earthquake triggered; other mechanisms for triggering laterally extensive synchronous failure do not apply. A frequency-magnitude plot of length of failed slope was calibrated by the published relationship that an order-of-magnitude increase in failed slope length corresponds to two orders of magnitude of earthquake energy, together with the published estimate of Mw = 8.0 for the largest earthquake on the Canadian eastern continental margin. Mean recurrence interval of M = 7 earthquakes at any point on the margin is estimated at 25-30 k.y. from both seismological models and the sediment failure record. On such a margin with modest sedimentation rates (~0.3 m/k.y.) and low seismicity, sediment failures provide a robust estimator of past seismicity. [ABSTRACT FROM AUTHOR]

This study examines the velocity structure of Makarov Basin and the adjacent Alpha Ridge to determine the tectonic origins of these features and link them to the larger Amerasia Basin. Seismic data from sonobuoys distributed along a 650 km-long line extending from Alpha Ridge and across Makarov Basin to the Lomonosov Ridge were analyzed for this purpose. Forward modelling of traveltimes, supported by coincident multi-channel seismic reflection and shipborne gravity data, were used to determine the P-wave velocity structure along the line. The sedimentary cover averages 0.5 km-thick on Alpha Ridge and 1.9 km-thick in Makarov Basin, but reaches up to 5 km-thick at the base of Lomonosov Ridge. Velocities in the sedimentary section range from 1.6 to 4.3 km s − 1 . As suggested by relatively high velocities, interbedded volcaniclastic or volcanic rock may occur in the deep sedimentary section. The shallow basement of Alpha Ridge (3.3 to 3.6 km s − 1 ) is characterized by semi-continuous high amplitude reflections and is interpreted as volcanic rock possibly intercalated with sedimentary rock. Velocities do not vary significantly in the upper and mid-crustal layers between Alpha Ridge and Makarov Basin. Total crustal thickness decreases from 27 km beneath Alpha Ridge to 5 km-thick in Makarov Basin then thickens to > 20 km over a short distance as part of Lomonosov Ridge. The crustal structure of Alpha Ridge is consistent with previous studies suggesting that the Alpha-Mendeleev ridge complex is part of a large igneous province (LIP) with thick igneous crust. The lack of change in crustal velocities between Alpha Ridge and Makarov Basin suggests that the basin, at least partly, either formed during or was influenced by LIP-related magmatism. The rapid transition of crustal thicknesses from Makarov Basin to Lomonosov Ridge supports the interpretation that this section of the ridge is a transform margin. [ABSTRACT FROM AUTHOR]

Interpretations of the Late Cretaceous to Quaternary geological history of the North American Basin rely on a seismic and lithostratigraphic framework developed predominantly from data along the northeastern United States margin. Prior to this study, attempts to extend this framework northward to the Nova Scotia margin were hindered by correlation issues across seamounts, limitations in data coverage, and significant complications caused by widespread canyon erosion and shallow salt structures. These challenges are overcome using modern seismic reflection data along the southwestern Nova Scotia margin, in the Shelburne sub-basin, where Upper Cretaceous through Quaternary sequences manifest four distinct phases in the interplay between down-slope and along-slope depositional and erosional processes. The first phase, spanning the Late Cretaceous to Late Eocene, is characterized by widespread periods of gully erosion interspersed with periods of pelagic and hemipelagic, carbonate-rich sedimentation. Extensive failure of upper slope regions related to the Montagnais meteorite impact also occurred during this time. The second phase, spanning the Oligocene to Late Miocene, is dominated by widespread erosion, deposition by gravity flow processes, and sediment re-working by bottom currents. Marked erosion and/or non-deposition along the mid-to lower slope is attributed both to down-slope and along-slope processes. The third phase, spanning the Late Miocene to Late Pliocene, is dominated by bottom current deposition including stacked sequences of giant sediment waves and large contourite drifts along the slope. The final phase, from the Late Pliocene to present, exhibits a return to predominance of down-slope gravity flows with deposition focused below the upper slope. This four phase history of depositional and erosional processes is similar to that documented south of the study area along the U.S. margin. [ABSTRACT FROM AUTHOR]

Mass transport deposits, up to 3·9 m thick, have been identified from piston cores collected from canyon floors and inter-canyon ridges on the central Scotian Slope. These deposits are characterized by four distinct mass-transport facies – folded mud, dipping stratified mud, various types of mud-clast conglomerate, and diamicton. Commonly, the folded and stratified mud facies are overlain by mud-clast conglomerate, followed by diamicton and then by turbidity current deposits of well-sorted sand. Stratified and folded mud facies were sourced from canyon walls. Overconsolidation in clasts in some mud-clast conglomerates indicates that the source sediment was buried 12–33 m, much deeper than the present cored depth, implying a source in canyon heads and canyon walls. The known stratigraphic framework for the region and new radiocarbon dating suggests that there were four or five episodes of sediment failure within the past 17 ka, most of which are found in more than one canyon system. The most likely mechanism for triggering occasional, synchronous failures in separate canyons is seismic ground shaking. The facies sequence is interpreted as resulting from local slides being overlain by mud-clast conglomerate deposits derived from failures farther upslope and finally by coarser-grained deposits resulting from retrogressive failure re-mobilizing upper slope sediments to form debrisflows and turbidity currents. [ABSTRACT FROM AUTHOR]

Abstract: Five sites located on a bathymetric transect of the distal Demerara Rise were studied by ODP Leg 207. Albian sediments of essentially terrigenous nature (clay, siltstone, sandstone) are the oldest drilled stratigraphic levels and form apparently the top of the synrift sequence. They are overlain by Cenomanian to Santonian finely laminated black shales, rich in organic matter of marine origin, which accumulated on a thermally subsiding ramp. Early Campanian hiatuses are thought to be the result of final disjunction of Demerara Rise (South America) from Africa and the onset of deep water communication between the two Atlantic basins (south and central). The overlying Uppermost Cretaceous–Oligocene chalk includes rich and diversified calcareous plankton assemblages, as well as two radiolarian-rich intervals (Late Campanian and Middle Eocene). A complex erosional surface developed during the Late Oligocene–Early Miocene. Sedimentation was impeded since then on the intermediate and deep sites of Demerara Rise, possibly due to the action of deep submarine currents. To cite this article: T. Danelian et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]