Coastlines in eastern Canada are dominantly paraglacial, meaning that the geomorphology and morphodynamics of the coasts are largely governed by the presence of glacigenic deposits related to the Laurentide Ice Sheet. These deposits act as antecedent topography and sediment sources for these coastal systems. Chedabucto Bay (Nova Scotia, Canada) is site to uniquely preserved drowned barrier beach features, which are hypothesised to form through shoreline retreat and barrier overstepping. In this process, relative sea-level (RSL) rise forces the barrier to migrate landward, then, when the conditions allow, to be preserved in place. Due to the nature of these paraglacial beaches to organize into coarse clastic barriers, they are quite resistant to shoreline migration through wave action thus have a bias towards overstepping when compared with sandier systems. This high degree of preservation is useful for reconstructing the post-glacial sea-level history as these features are good indicators of past RSL. Here we investigate the external morphology and internal architecture of modern and drowned barrier-beach systems by using ground-penetrating radar and LiDAR, for the former, and multibeam bathymetry and seismic reflection data, for the latter, to study their differences. Offshore seismic mapping has revealed buried barrier-beach systems at ~46 metres below present-day sea level and former paleo-estuaries dated to have formed by 10.51 ka cal BP. Preliminary morphometric analysis of drowned barrier systems indicate maximum berm heights of ~5 m from toe of slope, which is comparable to those observed in the modern system. The height of the modern barrier systems varies alongshore depending on beach aspect and the dominant direction of currents and waves (drift-aligned versus swash aligned systems). Recently surveyed paraglacial barrier elevation data along northern Chedabucto Bay show a ~3 metre difference in maximum berm crest elevation between swash and drift aligned systems. With this we emphasize the need to differentiate the expected indicative range for these relict paraglacial RSL indicators based on surficial morphology and internal geometries known from modern systems. The results of this work will help inform and guide science and policy on managing shoreline retreat through overstepping and help in characterizing sediment type distribution in coastal-shallow marine paraglacial environments.

Seafloor mapping in polar regions has led to the recognition of landforms associated with subsea permafrost. Despite recent studies indicating rapid subsea permafrost degradation, information on seasonal seafloor changes remains limited. Here, we use time-lapse multibeam bathymetry (2021-2024) and bottom-water temperature data to reveal seasonal formation and degradation of small frost blisters (5 meters wide and 20 to 50 centimeters high) as ice forms within surficial sediments. These frost blisters were degraded in October 2021 at depths of ≤25 meters but were widespread in July 2023. They thawed between July and November 2023, reformed over the following winter, and were present again in August 2024. Data from moored bottom-water sensors and sediment cores indicate that the formation and degradation of frost blisters are driven by seasonal temperature changes at depth and influenced by freshened porewater in surficial sediments. This study documents previously unrecognized seasonal expansion and contraction of the seafloor driven by freeze-thaw cycles of freshened porewater.

Based on high-resolution multibeam-sonar data and low-resolution (GEBCO) bathymetry data, we classify the geomorphology of Canada’s Pacific margin within the four bioregions designated by Fisheries and Oceans Canada for management of biological resources. We designate 14 units. Nine continental shelf units are fiords, bedrock terrain, offshore banks, Haida Gwaii platform, Haida Gwaii shelf, Vancouver Island shelf, incised shelf, glacial trough, and major delta. On the continental slope, we identify the canyon zone, the accretionary wedge (off Vancouver Island), and the transform (Queen Charlotte Fault) terrain. The abyssal zone is treated as a single unit with two components: seafloor-spreading terrain, and abyssal plain with fans, seamounts, and channels. Hexactinellid sponge reefs of various morphologies are found in three of the continental shelf geomorphic units and cover up to 10% of the seafloor in the glacial trough category. Examples based on multibeam sonar imagery are used to display the chief characteristics of the 14 units, as well as the geomorphic diversity within them. Compared with Canada's east-coast glaciated passive margin, geomorphic similarities include: (1) the panoply of glacial landforms and (2) shelf terrain dissected by sub-glacial meltwater. Major differences include: (1) the presence of unique “tectonic” terrains on the Pacific continental slopes; (2) hexactinellid sponge bioherm reefs that are unique to the Pacific margin; (3) the absence of glacio-tectonic terrains on the Pacific shelves; and (4) the absence of “classic” trough-mouth fans on the Pacific margin.

Movement of sediment along shallow continental shelves is a natural process with wide-ranging environmental and economic implications, making it of high importance to marine spatial planning efforts in the offshore. Development of marine renewable energy, for instance, requires detailed understanding of the morphodynamics of mobile bedforms to select foundation types and ensure safe installation of infrastructure in shallow shelf environments. This study evaluates geomorphology and sediment mobility of Dogfish Bank (< 20 mbsl) in the Hecate Strait offshore British Columbia, Canada, using hydroacoustic and airborne bathymetric data combined with seismic profiles and grain-size information. These data reveal current-swept features ranging from sediment-depleted lag to sediment-abundant sand ridges and dunes, with sand ribbons and furrows in-between. Seismic reflection data show up to 15 m of surficial sand concentrated beneath north-aligned sand ridges that dominate the bathymetry of northwest Hecate Strait. Sand ribbons (typically understood sediment-limited features in shallow marine environments) are notably maintained over seabed with comparable sand thickness to adjacent dunes (i.e. sediment-abundant features), suggesting local spatial variability in hydrodynamics and sediment characteristics (principally grain size) influence expression of mobile bedforms. Repeat mapping between 2008 and 2019 shows dunes and ribbons both migrate northwards, with largest seafloor changes along northeast-facing lee sides of dunes, matching closely with published models of sediment mobility which suggest northward bedform migration is largely driven by storms. Median total migration distance is 164 m (northward) for dunes (time-averaged rate of 14.9 m/year). Sand ribbons show less migration (median northward distance of 73 m) and migrate in a depth-dependent manner. Because sand ribbons are typically flow-parallel features, their lateral migration likely results from varying current directions and flow acceleration over shallower seabed. Sand ribbon migration should therefore a consideration in studies examining seabed change, particularly when they are formed over unconsolidated sediment.

The distribution and state of subsea permafrost is largely unknown. Present maps, which rely heavily on model results, suggest that subsea permafrost is confined to the Beaufort, Siberian and Laptev seas. Here we show that discontinuous subsea permafrost exists along the Labrador coast (56 degrees N) under the influence of the Labrador Coastal Current. High-resolution bathymetric data reveal the presence of subsea thermokarst environments on the coastal seabed of Nain, Nunatsiavut, where an ice-rich sediment sample was recovered in July 2022 at a water depth of 27 m. Porewater analysis indicates that ground ice can persist in the sediments due to freshened submarine groundwater seepage that freezes at higher temperatures (0 degrees C) than seawater (-1.8 degrees C). The formation and preservation of subsea permafrost landforms is due to cold waters of the Labrador Coastal Current entering the coastal areas and remaining less than 0 degrees C for most of the year. Therefore, evidence of subsea permafrost landforms in coastal Labrador and the distribution of cold bottom water in the Northern Hemisphere suggests that subsea permafrost is likely to be preserved elsewhere in subarctic regions, especially where freshened submarine groundwater seepage elevates the freezing temperature. This highlights the potential underestimation of subsea permafrost in the world's coastal oceans. Observations from the Labrador Coast indicate the presence of subsea permafrost landforms outside of the Arctic, suggesting a potential underestimation of subsea permafrost in the world's oceans.

The accelerating Arctic cryosphere decline severely impacts the land on which northern communities live through the presence of coastal and marine geohazards and coastal erosion, which further places the cultural heritage of coastal archaeological sites at risks. Sea ice decline also compromises the formation of polynyas, with unknown consequences for the regional ecosystems. From the 10th to the 18th of July 2022, a scientific cruise onboard the research vessel William-Kennedy allowed the collection of a suite of samples and data from the marine coastal environment of Nain, Nunatsiavut. In total, 42 surface sediment samples, 29 sediment cores, 41 conductivity-temperature-depth (CTD) profiles, 13 water samples, 24 phytoplankton nets and 13 zooplankton nets were collected. The cruise allowed the deployment of 2 moorings equipped with sediment traps in Nain Bay and within deeper offshore waters. Triangulation showed that the 2 moorings were correctly placed near their target locations. Drop camera transects were deployed in Webb Bay and at the easternmost tip of Paulmp;gt;'s Island to image the seabed and study benthic habitats. Finally, acoustic sub-bottom profiling along the entire study area allowed a high-resolution characterization of the stratigraphy of the seafloor, helped identifying locations for sediment sampling and inferring geological information about the depositional environments. The material and data collected during the research cruise will be key to 1) evaluating the productivity and dynamics of small recurring polynyas (i.e., rattles) on diverse timescales, 2) assessing marine and coastal geohazards (e.g., landslides) in relation to the deglacial history of Nain, 3) investigate the seabed geomorphology in Webb Bay and linkages with permafrost and sea-level changes and 3) conducting benthic habitat characterization. Co-led by the University of New Brunswick (UNB) and Natural Resources Canada (NRCan), this cruise was done in collaboration with the Government of Nunatsiavut, Université du Québec à Montréal, Université Laval, Dalhousie University and Memorial University, and was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and NRCan.

Offshore wind farms typically host tens to hundreds of turbines that are individually sited on foundations or anchored if floating. These are connected by inter-farm cables which feed into one or more marine-based substations, further feeding one or more shore-connected high-voltage cables - all infrastructure that requires knowledge of water depth, metocean conditions, and seabed/subsurface geology. With this industry set to establish itself on the continental shelf of Atlantic Canada, knowledge of the geological conditions from the seabed to tens of metres below will be essential for farm layout and foundation design. Thus, geoscience questions addressing regional geomorphology, Pleistocene glacial retreat and sea-level change, the characteristics of key individual stratigraphic layers, and the magnitude and patterns of sediment mobility are important. In Atlantic Canada, ongoing efforts to address these questions are using legacy data, but new data is required to further our understanding of the shallower portions of the shelf. Examples include: what is the distribution of buried tunnel valleys under offshore banks, and might their complex facies infill affect foundation conditions? How and where would the organic sediments, left by a coastal suite of landforms drowned during transgression, affect foundation or landfalling cable stability? How active is salt diapirism, and could it be considered a geohazard? Are demonstrated sediment mass failures also a risk? What is the current understanding of sediment mobility in shallow waters, and how does that affect infrastructure armouring/depth of burial? What is the variability of the geotechnical properties of our offshore sediments? What is the foundation suitability of offshore Tertiary semi-consolidated bedrock? To conclude, the initial scope of a developing regional foundation suitability model will be presented for the Eastern Scotian Shelf.

Microfossils represent an important part of studying past depositional environments and determining ages for the strata they are found within. The key to ascribing paleoenvironmental interpretations to the sediments in which a microfossil is found is accurate identification of the microfossil. A number of techniques can be used to identify microfossils, including ones that use key features, morphologies, and characteristics from imagery acquired using a scanning electron microscope. A low-cost, efficient alternative method is digital photography of optical microscope images. This technical note presents a method for acquiring photos of microfossils and two methods for compiling them into high-resolution images using focus stacking. The process is described in four main steps: image acquisition, exportation, focus stacking, and annotation.

Impacts from a changing climate, in particular sea-level rise, will be most acutely felt on small oceanic islands. A common configuration of mid-latitude islands is the sandy barrier island. Sable Island, Nova Scotia, Canada is a vegetated sand island near the shelf edge, 160 km from the nearest point of land, that is morphologically similar to a barrier island. This study uses 60 years of airphoto records to analyse changes in coastline position through digitized shore and vegetation (foredune proxy) lines. Rates of coastal movement are analysed to model the future (2039) coastal configuration. The analyses suggest that the majority of the coastline on Sable Island is in retreat, with net retreat on the south side of the island only partially offset by modest net advance on the north side. The different morphologies of the beach–dune systems of South Beach and North Beach, driven by incident wind and waves, yield these different coastline responses. Projected loss of 10 ha by 2039 of the climax heath vegetative community to shoreline retreat suggests a trend toward island instability due to coastline migration. Island-wide data set trends show support for two different but complementary hypotheses about whole-island evolution: (1) the island is mobile via bank migration driving southern coastline changes and experiencing sediment transport toward the east, or (2) the island is generally immobile and losing subaerial sediments (and thus shrinking) likely due to ongoing (and accelerating) sea-level rise.

ABSTRACTDeltas are at the transition between fluvial and marine sedimentary environments where sediment density flows are often triggered during high river discharge events, forming submarine channels and sediment waves. On wave‐influenced deltas, longshore currents are particularly efficient at transporting sediment alongshore, reducing the likelihood of sediment density flows from occurring at river mouths. This study describes four deltaic sedimentary systems at different stages of their evolution on a formerly glaciated continental inner shelf of eastern Canada in order to better understand the distribution of sediment density flows on wave‐influenced deltas. Three types of settings are recognized as being prone to sediment density flows: (i) in the early stages of wave‐influence and on large deltas, converging longshore currents can lead to offshelf sediment transport; (ii) on wave‐influenced to wave‐dominated deltas, a sandy spit can re‐route the river mouth and sediment density flows form where the spit intersects the delta lip; (iii) in advanced stages of wave‐dominated deltas and during their demise, rocky headlands are exposed and can intersect the slope, where off‐shelf sediment transport occurs. These types of sediment density flows were all characterized by debris flows or surge‐type turbidity currents which have limited offshore run‐out. More rarely, hyperpycnal flows form at the river mouths, especially where the river incises glaciomarine clays prone to landsliding in the river, which increases fine‐grained fluvial suspended sediment concentration. Overall, these results highlight the predominance of fluvial‐dominated deltas during a phase of relative sea‐level fall combined with high sediment supply. However, as soon as sediment supply diminishes, wave action remobilizes sediment alongshore modifying the distribution and types of sediment density flows occurring on wave‐influenced deltas.

The Quaternary history of the Atlantic Canadian inner shelf shares some similarities with the North Sea and northern United States of America (US) Atlantic coast, with the influence of large-scale glaciation and subsequent sea level transgression being the main drivers of seafloor morphology, sedimentology, and uppermost stratigraphy. The geology of the inner shelf, generally confined to 100 m water depth for this study, is an important constraint on the development of offshore renewables, in particular wind energy. Offshore wind has seen rapid growth, particularly in Europe and Asia, where the industry has now experienced decades of production. In the US, one small-scale production farm and many hundreds of MW are in the production pipeline. In contrast, offshore wind in Canada, despite onshore installed wind capacity that ranks highly globally, lacks any operating turbines and there are no plans for development in the wind resource-rich Atlantic Canadian region. In this study, the geological constraints on offshore wind in Atlantic Canada are explored. Generally, the available offshore wind resource is high, and thus the main geophysical constraint on the development of offshore wind energy converters is the inner shelf geology. Several sites with available high-resolution geophysical data are selected for in-depth analysis and comparison with production and planned offshore wind farm sites found elsewhere. In general, a lack of sufficiently thick Quaternary sedimentation—necessary for the most common bottom-fixed foundations for wind turbines—will make developing offshore wind in Atlantic Canada challenging when compared with North Sea and US Atlantic Coast locations. A few locations may be suitable geologically, such as Sable Island Bank in Nova Scotia (thick package of sands), Northumberland Strait between Prince Edward Island and Nova Scotia (shallow firm seabed and sandbanks), Baie des Chaleurs in New Brunswick/Québec (thick, low relief fine sediments), and St. George's Bay, Newfoundland (shallow, postglacially modified moraine).

After retreat of the Cordilleran Ice Sheet ( CIS ) and subsequent glacio‐isostatic adjustment of the central coast of British Columbia ( BC ), Canada, a complex coastline emerged as relative sea level rapidly reached equilibrium and maintained stability over the end of the Late Pleistocene and Holocene. This study provides a late Quaternary reconstruction of the landscape evolution of a geographically distinct location on the central BC coast, northwest Calvert Island, which experienced a re‐advance of the CIS near the end of the Late Pleistocene and minimal subsequent relative sea‐level change. Geomorphological observations from Li DAR imagery, sedimentological and palaeoecological evidence from exposures, cores and shovel pits, and a robust luminescence and 14 C‐based chronology spanning the last 15 000 years are used to reconstruct the landscape of northwest Calvert Island following CIS retreat. A single‐aliquot regenerative dose protocol that was developed specifically for luminescence dating of the sediments on Calvert Island was utilized in this study. Localized proglacial sedimentation was linked to the glacial re‐advance experienced at the end of the Late Pleistocene. Extensive coastal reconfiguration (e.g. rapid shoreline progradation of >1 m a −1 ) occurred in the absence of extensive RSL change, which was the main driver of coastal change elsewhere along the BC coast. Changes in climate, small magnitude changes in RSL , and fire all probably played a role in isolated aeolian landform development and stabilization in the study area. An important contribution of this study is the documentation of the multi‐disciplinary approach for reconstructing palaeogeography, using multiple geochronological methods, micro‐ and macro‐sedimentology, the palaeoecology inferred from both macro and microfossils (e.g. diatoms and foraminifers), stratigraphy, field mapping and remote sensing. In addition, these findings inform our understanding of the drivers of coastal sedimentary processes, particularly in the temperate coastal rainforest region of BC , and the role that fire may play in those processes. Coastal palaeogeography studies in the region will become increasingly important as discoveries of Late Pleistocene human habitation along the coastal migration route continue to be documented.

Several methods exist that use sediment properties to characterize depositional setting and related mechanisms of transport, including analysis of grain-size distributions, sediment petrology, micromorphology, and grain structure. Techniques that rely on electron or optical microscopy produce results with varying degrees of success and applicability. Here, a new method is presented and used to differentiate between littoral and eolian sands that were extracted from recently formed landforms, as well as landforms that are from mid to late Holocene in age. The method utilizes a standard optical microscope with a mounted digital camera, paired with freely available software (ImageJ) to characterize grain shape parameters. The method was tested on nearly 6000 sand grains from samples with varied transport histories, and it was found that grain solidity was the most distinguishable characteristic between eolian and littoral samples, differentiating them 86% of the time for calibration samples. The method was used to correctly identify the mechanism of transport for 76% of the samples. Patterns in the results indicated that this method could be extended to link potential sediment sources to various depositional basins, and future work includes testing the method in areas with a different mineralogy and/or landscape history.