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We present a compilation of the western Davis Strait region offshore southeastern Baffin Island, Nunavut, Canada with new subsurface geological structural details and observations regarding past hydrocarbon occurrences from scientific and commercial exploration. This consists of seismic mapping with archival data correlated with a filtered marine Bouguer anomaly gravity compilation and magnetic data sets covering northern Saglek Basin, the western part of the Lady Franklin Basin and the Ungava Fault Zone from south of Baffin Bay. A regional seismic horizon for mapping basin architecture comes from the top of the Paleogene volcanic syn-magmatic zone, where pervasive volcanic flows and intrusions are intermingled with the sedimentary section. The seismic depth map to the top of the regional volcanic seismic horizon shows pre-rift sedimentary basins having maximum depths of approximately 4–5 km flanking the shallower Ungava Fault Zone. Correlation of Bouguer anomaly gravity and magnetic data interpretations with the seismic mapping, indicate that over some areas true crystalline basement is deeper than can be determined by reflection seismic, as the base of the syn-magmatic section is not resolvable for seismic mapping. Extensive Paleogene mafic intrusives and extrusive basalts dominate the architecture of this volcanic rifted margin as seen by the dominant high amplitude magnetic anomalies associated with many deeper structures. The over 250 km long Davis Strait Fault is recognised as the key structural element of the Ungava Fault Zone (UFZ) and valley complex. The adjoining Davis Strait High maps on seismic as a continuous structure running the length of Davis Strait plunging southwards to a Bouguer gravity high feature that terminates the western end of the extinct Eocene spreading zone south of Davis Strait. This horn shaped structural feature establishes the presence of an accommodation zone with multiple faults and localised thrust faulting as required to fit the complex mechanics for strike-slip motion that occurs along the south end of this transform fault system. The revised marine Bouguer anomaly gravity data set also defines two new, near shore grabens 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. These pre-rift basins most likely originate from the Paleozoic based on seafloor dredge and nearby shallow drill cores from previous studies. The hydrocarbon charge of a previously unexplained petroliferous shallow marine drill core that is adjacent the eastern edge of the Tariut Basin is attributed to Paleozoic source rocks that have undergone enhanced thermal maturation from sill intrusion associated with rifting. The Imaqpik Basin shows strong evidence of a hydrocarbon system from the proximity of clustered interpreted sea surface oil slicks, mapped from satellite radar images, and a local zone of anomalously high dissolved methane measured within the water column that originates from the seafloor immediately east of Cape Dyer at the northern limit of that basin. The overlying Cape Dyer flood basalt field extends from limited onshore exposures into the offshore and maps with magnetic data over an area of approximately 13,000 km2. This extrusive feature and it's implicit underlying intrusive components are likely the unconventional heat source for the anomalous enhanced thermal maturation of Paleozoic to Paleogene source rocks in these pre-rift basins that host this previously unrecognised petroleum system. • A 250 km length high angle transpressive fault, the Davis Strait Fault is recognised from gravity, magnetic and seismic data as defining the western side of the Davis Strait High. • The Ungava Fault Zone area of Davis Strait is geophysically mapped as a narrow sedimentary basin, of 2–4 km thickness, floored by widespread Paleogene volcanic rocks. • The Lady Franklin Basin is similarly mapped from the eastern side of the Davis Strait High and has a sedimentary section of at least 4 km thickness • The offshore extent of the Cape Dyer basalt field is mapped over an area of about 13,000 km2. • Two new pre Paleogene sedimentary basins, the southern Tariut and northern Imaqpik basins are of at least 4 to possibly 6 km thickness as mapped from marine Bouguer gravity and reflection seismic data. • Pervasive magmatism with wide scale sill development appears to be the primary thermal source for maturing source rocks, making this an unconventional petroleum system within this transform margin region. • The presence of radar imaged oil slick anomalies, hydrocarbon charged shallow rock cores and high amounts of dissolved water column methane near the seafloor likely all originate from this unconventional petroleum system. • Notable volcanic seismic features like SDR's and lava delta developments are seen only in the northern and southern ends of the Davis Strait transform margin. • Bouguer gravity data shows the western end of the extinct Eocene rift to have a distinct horn shape instead of the squared off edge that was previously surmised. • The transform margin consists of continental crust on both sides, with oceanic crustal pieces at either end of the fault zone. [ABSTRACT FROM AUTHOR]

New gravity observations collected over Ellesmere Island and Axel Heiberg Island have been integrated with existing Canadian and Danish data sets to produce a comprehensive regional compilation over the Innuitian Region of the Canadian and Greenland High Arctic. This compilation has provided quantitative assessment of the geometry of the plate boundary between northern Greenland and Ellesmere Island and crustal structures across the Cretaceous–Palaeogene Eurekan Orogen. A large amplitude linear gravity low—Nares Strait Gravity Low (NSGL) (<–160 mGal)—extends obliquely across Nares Strait from northern Greenland to Ellesmere Island. This feature closely correlates with the distribution of the Palaeozoic Franklinian Margin sequences and is cross-cut by the Cenozoic Eurekan Frontal Thrust (EFT), which represents the mappable western limit of the undeformed Greenland Plate associated with the Eurekan Orogen. Newly identified linear gravity features occur north of the NSGL: the Hazen Plateau Gravity High (HPGH), corresponding with the low-lying topography of the Hazen Trough and the Grantland Gravity Low (GGL), over the elevated topography of the Grantland Uplift. Gravity models for profiles crossing the NSGL, the HPGH and the GGL indicate that the long-wavelength component of the gravity anomalies is produced by systematic variations in Moho depth. Although significant Eurekan-age thrusting and thickening of low-density Palaeozoic strata is observed on Ellesmere Island, locally contributing to the mass-deficit generating the NSGL, equivalent strata on Greenland are undeformed. The NSGL is interpreted to be primarily the signature of the remnant (Early Palaeozoic) margin with the downwards flexure of the crust beneath a northwards thickening sedimentary wedge rather than purely the result of crustal thickening from the Eurekan Orogeny. Digital bathymetry and sediment thickness data were used to determine a residual ‘crustal’ gravity field, which in turn was used to calculate depth-to-Moho and crustal thicknesses. These have been interpreted in terms of crustal affinity and crustal thinning and thickening processes associated with the Late Cretaceous–Palaeogene plate tectonics of the area. Significant crustal thinning is observed beneath the Lancaster Basin, between Baffin Island and Devon Island, corresponding with 40 km of separation. This is interpreted to be a failed rift-arm of the Eocene spreading system in Baffin Bay. A Fourier-domain transfer function analysis ( Q) determined an intermediate average crustal strength (flexural rigidity of 1022 N m) over the Innuitian region. Comparisons with theoretical models, based on a simple thin elastic plate model, suggest that the crust is relatively thin (30 km) and in near-isostatic equilibrium—that is, not flexurally supporting the existing sedimentary or topographic load. A clearly defined anisotropy is identified, correlating with the direction of Eocene plate convergence, suggesting that the Eurekan collisional forces have not yet dissipated and are at least partially supporting large-scale orogenic structures. [ABSTRACT FROM AUTHOR]

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]

Ellesmere Island in Arctic Canada displays a complex geological evolution. The region was affected by two distinct orogenies, the Palaeozoic Ellesmerian orogeny (the Caledonian equivalent in Arctic Canada and Northern Greenland) and the Palaeogene Eurekan orogeny, related to the opening of Baffin Bay and the consequent convergence of the Greenland plate. The details of this complex evolution and the present-day deep structure are poorly constrained in this remote area and deep geophysical data are sparse. Receiver function analysis of seven temporary broad-band seismometers of the Ellesmere Island Lithosphere Experiment complemented by two permanent stations provides important data on the crustal velocity structure of Ellesmere Island. The crustal expression of the northernmost tectonic block of Ellesmere Island (~82°-83°N), Pearya, which was accreted during the Ellesmerian orogeny, is similar to that at the southernmost part, which is part of the Precambrian Laurentian (North America- Greenland) craton. Both segments have thick crystalline crust (~35-36 km) and comparable velocity-depth profiles. In contrast, crustal thickness in central Ellesmere Island decreases from ~24-30 km in the Eurekan fold and thrust belt (~79.7°-80.6°N) to ~16-20 km in the Hazen Stable Block (HSB; ~80.6°-81.4°N) and is covered by a thick succession of metasediments. A deep crustal root (~48 km) at ~79.6°N is interpreted as cratonic crust flexed beneath the Eurekan fold and thrust belt. The Carboniferous to Palaeogene sedimentary succession of the Sverdrup Basin is inferred to be up to 1-4 km thick, comparable to geologically-based estimates, near the western margin of the HSB. [ABSTRACT FROM AUTHOR]

We calculate the anomalous basement topography for the North Atlantic Ocean from 30° to 70°N latitude and from 0° to 70°W longitude at a resolution of roughly 6×6 km, using grids of total sediment thickness and observed and predicted sea-floor bathymetry to correct for the effects of isostatic sediment loading and lithospheric age. Plotting this residual topography for various plate reconstructions during opening of the North Atlantic, we delineate consistent patterns of basement highs related to variations in hotspot-related volcanism. In addition to Iceland and the Azores, we recognize three centers of excess volcanism at the mid-Atlantic ridge: the Milne Seamounts and Azores-Biscay Rise (∼75–40 Ma), the Southeast Newfoundland Ridge and Madeira-Tore Rise (∼130–110 Ma), and the East and West Thulean Rises (∼60–50 Ma). The duration of volcanic activity ranges from 8 to 10 m.y. (Thulean Rises) to 60 m.y. (Iceland) and thus it appears that both long- and short-lived hotspots coexist, even in relatively close proximity. In contrast, during the period 110–60 Ma we observe little excess volcanism during either continental breakup or seafloor spreading.We estimate isostatic crustal thickness from the anomalous basement depths, after first removing dynamic effects created by mantle flow. Maximum thicknesses of volcanic features, from 30 km beneath the Greenland–Iceland–Faeroe ridge to ∼15 km beneath the Azores-Biscay Rise, are broadly consistent with seismic data and predictions of decompression melting. Widths of volcanic features indicate that thickening primarily occurs within 100–200 km of hotspots except along continental margins that rifted at the time of the hotspot activity (i.e. East Greenland and the Hatton-Rockall Bank). We observe conjugate structures south of Greenland and Edoras Bank, where excess volcanism appears to have extended beyond the margin proper and into oceanic crust. Similar conjugate features appear in the Labrador Sea south of Davis Strait. Finally, we identify anomalous oceanic regions adjacent to some continental margins, where unusually low values of predicted crustal thickness suggest either additional variations in plate properties or non-isostatic effects within the mantle. [Copyright &y& Elsevier]

An improved compilation of magnetic and gravity data has been interpreted in conjunction with seismic reflection profiles to provide new information about the complex structure of the northeastern Gulf of St. Lawrence, Atlantic Canada. This region was affected by plate divergence and convergence events during the Grenville and Appalachian orogenies and the opening of the Iapetus Ocean. The Anticosti Basin, which developed as a foreland basin over the margin of Laurentia, is filled with a thick succession of Cambrian to Silurian sedimentary strata. Most of the interpreted magnetic and gravity anomalies have sources within the basement rocks, which is interpreted as Grenville crust beneath much of the study area. A V-shaped zone of lower amplitude gravity and magnetic anomalies in the center of the region is associated with a slight thickening of Cambrian to Middle Ordovician sedimentary rocks over a downthrown block of anorthositic Grenville crust, with a locally lower density and magnetization. Extensional faults bordering the zone presently display 130–250 m of downthrow at basement depths, increasing to the southeast, but show no disruption of strata younger than Middle Ordovician. A magnetic low 200 km to the northeast is of similar geophysical character and is associated with a similar geological structure. Numerous NE-trending normal faults associated with segmentation of the Grenville basement are manifested in the magnetic and seismic data. Related anomaly sources are also present within the overlying Ordovician calcareous and clastic rocks that were deposited during extension associated with the onset of the Taconian orogeny. Other anomalies are associated with faulting and folding of shallower strata, and seismic data indicate that some of the NE-trending faults were reactivated as thrusts towards the close of the Taconian orogeny in the Late Ordovician. The geophysical data show no evidence of significant deformation north of the western margin of Newfoundland that would be associated with later compressive events of the Acadian orogeny.Une compilation améliorée de données magnétiques et gravimétriques, interprétées conjointement avec des profils de sismique réflexion, a fourni de nouvelles informations sur la structure complexe du nord-est du Golfe du Saint-Laurent, dans le Canada atlantique. Cette région a été touchée par des événements de divergence et de convergence des plaques au cours de l'orogène du Grenville et celui des Appalaches et durant l'ouverture de l'océan Iapetus. Le bassin d'Anticosti qui s'est développé en tant qu'un bassin d'avant pays sur la limite de la Laurentia est rempli d'une épaisse séquence de strates sédimentaires datant du Cambrien au Silurien. La plupart des anomalies magnétiques et gravimétriques ont leur source dans le socle; ce dernier est interprété comme une croûte grenvillienne sous une grande partie de la région à l'étude. Au centre de la région, une zone en forme de « V » d'anomalies magnétiques et gravimétriques à faible amplitude est associée à un léger épaississement des roches sédimentaires (Cambrien à Ordovicien moyen) au-dessus d'un bloc de croûte anorthositique (Grenville) à rejet vers le bas, ce bloc ayant localement une densité et une magnétisation plus faibles. Des failles d'extension en bordure de la zone montrent présentement 130–250 m de rejet vers le bas, à des profondeurs du socle et augmentant vers le sud-est, mais on ne voit aucune perturbation des strates plus jeunes que l'Ordovicien moyen. Un creux magnétique à 200 km vers le nord-est possède des caractéristiques géophysiques semblables et il est associé à une structure géologique similaire. De nombreuses failles normales à tendance NE associées à la segmentation du socle grenvillien ressortent des données magnétiques et séismiques. Des sources d'anomalies connexes sont aussi présentes dans les roches calcareuses et clastiques sus-jacentes (Ordovicien) qui ont été déposées durant l'extension associée à l'amorce de l'orogène taconien. D'autres anomalies sont associées avec la formation de failles et de plis de strates à moindre profondeur. Les données séismiques indiquent que quelques failles NE ont été réactivées en tant que failles de chevauchement vers la fin de l'orogène taconien à l'Ordovicien tardif. Les données géophysiques ne montrent aucune évidence de déformation significative au nord de la bordure ouest de Terre-Neuve qui pourrait être associée à des événements postérieurs de compression durant l'orogène acadien.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The northeastern Canadian Arctic margin is bordered to the north by Alpha Ridge, a dominantly magmatic complex within the Amerasia Basin of the Arctic Ocean, which forms part of the High Arctic Large Igneous Province (HALIP). The characteristics of the gravity and magnetic anomaly fields change notably along the Arctic margin, with two main segments recognised. Aeromagnetic and gravity data in the transition zone between these contrasting domains of the Canadian Arctic margin are analysed here in detail. Results obtained using a variety of edge enhancement (derivative) methods highlight several magnetic domains and a major offshore sedimentary basin as well as some known and a number of previously unknown tectonic and magmatic elements. A magmatic intrusion distribution map derived from the edge enhanced magnetic anomaly maps reveals that magmatic rocks are much more widespread in the relatively shallow subsurface than implied by surface geological mapping. Magmatic intrusions (mainly dykes) and other geological structures have NW–SE, NE–SW and N–S major trends. Broad gravity and pseudogravity lows across most of the Sverdrup Basin region are due to thick, less dense sedimentary succession and low magnetised crust. Magnetic and pseudogravity highs observed over Alpha Ridge indicate high crustal magnetisation associated with the occurrence of extensive and voluminous crustal magmatic bodies. Absence of these volcanic and intrusive rocks in the imaged sedimentary basin beneath the northeast Canadian Arctic margin region suggests that the basin probably formed after the cessation of HALIP magmatism. [ABSTRACT FROM AUTHOR]