Abstract Characterized by an active margin to the west, passive margins to the east and north, and numerous fjords and estuaries, the seafloor of Canada is prone to subaqueous landslides. The Geological Survey of Canada (GSC) facilitates government response in times of crisis by providing timely and concise information to Canadians, and informs the strategies to address natural hazards. Thus, the GSC is conducting a national assessment of the subaqueous landslide hazard. This paper reviews dozens of major subaqueous mass movement deposits with an emphasis on recent publications and summarizes the attempt to produce a national database. The types range from ephemeral turbidity current deposits to very large deposits (>100 km 3 ). To date, 1266 deposits are identified with many more expected as mapping progresses. This work is important as it will feed into the larger national tsunami strategy, and is a step forward for the national government to manage the risk. Canada is among the first countries to enter its entire database using the consistent morphometric characterization recommended by members of the UNESCO IGCP-640 (S4SLIDE) Community.

ABSTRACT Defining temporal and spatial distribution of shortening is critical to reconstruct past plate motions and to examine mechanical coupling processes at convergent plate boundaries. Understanding the collisional evolution of the British Mountains and Beaufort-MacKenzie basin in the northern Alaska–Yukon region is key for the geodynamics of the Arctic region. With the aim to resolve the exhumation history of this region, we present the first zircon fission-track and (U-Th)/He analyses on apatite and zircon from the Neruokpuk Formation (ca. 720–485 Ma), which forms the orogenic basement of the British Mountains. Zircon fission-track ages show partial resetting, indicating the Proterozoic basement did not reside at temperatures above 240 °C. Thermal modeling of zircon and apatite (U-Th)/He data indicates that our samples reached this maximum temperature at ca. 100 Ma. The onset of the Brookian collision is indicated by exhumation from ca. 80 Ma. A total exhumation of 7–8.5 km since the Late Cretaceous is inferred. Apatite (U-Th)/He ages of ca. 50 Ma show that exhumation was less than 2.5 km since the early Eocene. We infer from a comparison with the temporal evolution of exhumation from adjacent orogenic domains that shortening progressively shifted northward from the British Mountains to the Barn Mountains and offshore in the Beaufort Sea during the Paleocene. Along-strike variations in the architecture of the rifted margin of Arctic Alaska is suggested to have exerted a strong control on the structural styles and observed exhumation patterns.

Abstract This paper synthesizes the framework and geological evolution of the Arctic Alaska–Chukotka microplate (AACM), from its origin as part of the continental platform fringing Baltica and Laurentia to its southward motion during the formation of the Amerasia Basin (Arctic Ocean) and its progressive modification as part of the dynamic northern palaeo-Pacific margin. A synthesis of the available data refines the crustal identity, limits and history of the AACM and, together with regional geological constraints, provides a tectonic framework to aid in its pre-Cretaceous restoration. Recently published seismic reflection data and interpretations, integrated with regional geological constraints, provide the basis for a new crustal transect (the Circum-Arctic Lithosphere Evolution (‘CALE’) Transect C) linking the Amerasia Basin and the Pacific margin along two paths that span 5100 km from the Lomonosov Ridge (near the North Pole), across the Amerasia Basin, Chukchi Sea and Bering Sea, and ending at the subducting Pacific plate margin in the Aleutian Islands. We propose a new plate tectonic model in which the AACM originated as part of a re-entrant in the palaeo-Pacific margin and moved to its present position during slab-related magmatism and the southward retreat of palaeo-Pacific subduction, largely coeval with the rifting and formation of the Amerasia Basin in its wake. Supplementary material: Supplementary material Plate 1 (herein referred to as Sup. Pl. 1) comprises Plate 1 and its included figures, which are an integral part of this paper. Plate 1 contains regional reflection-seismic-based cross sections and supporting material that collectively constitute CALE Transects C1 and C2 and form an important part of our contribution. Plate 1 is referred to in the text as Sup. Pl. 1, Transects C1 and C2 as Plate 1A and 1B, and plate figures as fig. P1.1, fig. P1.2, etc.). Supplementary material 2 contains previously unpublished geochronologic data on detrital zircon suites and igneous rocks. Supplementary material are available at https://doi.org/10.6084/m9.figshare.c.3826813

Abstract The Dinkum graben system beneath the central to eastern Beaufort shelf of Arctic Alaska comprises a complex of grabens and horsts that records multiple phases of extension and contraction spanning the Mississippian through Early Cretaceous (Neocomian). The graben system extends from about 150°W eastward for more than 200 km, approximately parallel to the Alaska Beaufort Sea coast. The eastern extent of the graben system (east of about 145.5°W) is masked by deep burial beneath Cenozoic strata and by complex Cenozoic structures. The graben system developed above regional basement that includes the pre-Mississippian Franklinian sequence, interpreted as Late Proterozoic-Devonian strata deformed and metamorphosed during the Ellesmerian orogeny. Franklinian rocks display in seismic data a range of variably dipping structural and metamorphic fabrics described in a companion abstract (Connors and Houseknecht). Previously published interpretations of the Din-kum graben suggest two phases of extension related to rift opening of the Amerasia basin, a Jurassic phase characterized by generally south-dipping normal faults and an Early Cretaceous phase characterized by generally north-dipping normal faults. However, our interpretation of 2D seismic data, tied to well control near the coast and potential fields data across the Beaufort shelf, documents a geologic history commencing with Mississippian extension accommodated by both north- and south-dipping normal faults detached along the variably dipping basement fabrics. Growth strata indicate that pulses of extension in the graben system occurred during the Mississippian, Late Triassic–Early Jurassic, and Neocomian. Further, certain faults accommodate Mid-Late Jurassic growth strata that grade from positive to negative growth along strike, suggesting inversion of older structures, perhaps by stresses oblique to older fault planes. This polyphase deformational history is reflected in a complex graben system that accommodates Mississippian-Neocomian strata at least 5 km thick in places. The newly recognized presence of pre-Jurassic strata in the Dinkum graben system has significant implications regarding petroleum systems. Upper Triassic growth strata likely include oil-prone source rocks in the Shublik Formation, corroborated along the southern margin of the graben by oil accumulations ( e.g. , Northstar) with implausible migration pathways from sources to the south, and by chemistry that suggests a Triassic source rock containing more detrital components and less carbonate than typical Shublik of the North Slope. Considering the timing of extensional pulses discussed above, the presence of Lower Jurassic and Neocomian source rocks also is likely. Although all these source rocks likely are thermally overmature in deeper parts of the graben, shallower parts of the graben, horsts within the graben, and southern and northern margins of the graben may be in the oil window, and may have been charged from the graben.