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The SE Grand Banks Slope is unusual on the glaciated eastern Canadian margin in that it was remote from ice stream and glacial ice of the Laurentide Ice Sheet (LIS). It thus allows an analysis of the role of contour currents and landslides in sculpting the continental margin, processes that are largely masked where downslope proglacial sediment supply dominated. Detailed oxygen isotope, geotechnical, pXRF, and bulk sediment geochemical analyses were made on seven piston cores and were placed in context using multi-beam bathymetry and high-resolution seismic reflection profiles. Cores have a record of sedimentation back to MIS6 preserved in autochthonous sediment and slide blocks, contourites and mass-transport deposits (MTDs). Detrital‑carbonate-rich Heinrich layers (H) are present throughout the succession, but red mud layers of glacial meltwater origin from ice-streams in the SE sector of the LIS are identified only during MIS2 and late MIS3. Both layers allowed high-resolution correlation between cores. Sediments on the upper slope above H2 are condensed and the section above H1 is Five horizons with MTDs with headscarps generally up to 25 m high are recognized in the upper 50–70 m. Thick MTDs are blocky in cores and in their seismic and bathymetric expression resemble spreads, with local thin mud clast conglomerates that ran out as debris flows over the contemporaneous seabed. Geotechnical data suggest that the seabed is stable under static conditions, although there is geological evidence for fluid escape and geotechnical evidence for underconsolidation. Weak layers along which failure took place are found somewhere around H3–H4 and at or near the top of H5 and MIS6. The low plasticity and liquid limit of the H layers make these layers susceptible to failure during cyclic loading. Episodic earthquakes are the most likely cause of failure.

Twelve piston cores were used to characterize late Quaternary lithofacies, depositional processes and deglacial history along the Baffin Bay slope between Lancaster Sound and Home Bay. Core investigations show four distinct laterally correlatable lithofacies along the slope – basal and upper diamicton, laminated red brown mud, tan carbonate gravelly, sandy mud and bioturbated brown mud. Basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from Baffin Island at ~25 cal ka. The distribution and character of laminated red brown mud suggests a lateral supply to Baffin Bay slope from ice-proximal meltwater plumes and turbidity currents sourced in glacial ice from both Baffin Bay shelf and Home Bay between 41.5 cal ka to ~14.2 cal ka. An upper diamicton records a lesser, localized glacial advance that ended at about 14.2 cal ka. Tan carbonate mud events represent ice-rafted, enhanced detrital carbonate delivery to the slope between ~25 cal ka and ~11 cal ka. A gradual thinning of these events, from northern to southern Baffin Bay, corroborates a northern Baffin Bay, Lancaster Sound or Nares Strait iceberg source. Proglacial facies seaward of Home Bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice-rafted from Lancaster Sound. Baffin Bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater. As a result, axial supply from the large ice streams north of Baffin Bay (particularly Lancaster Sound) is dominant in the Baffin Bay basin and lateral supply from smaller ice streams on Baffin Island predominates on the NE Baffin Slope.

Records from cores 2011031-059 and 2011031-062 (hereafter 59 and 62) have been used to reconstruct changes in the vigor of the Labrador Current in northern Flemish Pass during the last glacial cycle. Grain size proxies for current speed, planktonic foramiferal δ18O, X-ray diffraction analysis for dolomite and calcite, and abundance of ice-rafted detritus (IRD) have been determined. An age model back to Marine Isotope Stage (MIS) 5 is based on recognition of seven Heinrich events from total dolomite and calcite, correlated to the IODP U1302/3 record, and confirmed by O-isotope stratigraphy and radiocarbon dates. A straight-line relationship between mean size of sortable silt ( SS ¯ ) and percent of sortable silt (SS%) and the lack of relationship between SS ¯ and IRD (> 500 μm) indicate well-sorted sediments in cores 59 and 62, which can be used to reconstruct the paleocurrent intensity. Intensified current vigor occurred in MIS 5, 3 and 1, so that warmer periods show faster currents, probably through the Irminger Current component of the North Atlantic subpolar gyre. Low values of δ18O, SS% and SS ¯ correspond to H events, suggesting a slowdown in the Labrador Current, followed by a rapid return to strong circulation. In some cases current vigor recovery lagged slightly after the H events. Heinrich events with larger amounts of meltwater show higher current vigor. Correlation with deep-water current vigor records in the Iceland Basin show a broad correlation on a multi-millennial scale with Labrador Current variations. As our study is on a shallow sediment drift formed by the Labrador Current, one of the surface currents of the North Atlantic sub-polar gyre, it provides new evidence for a tight connection between surface current vigor fluctuation and the vigor of the deep thermohaline circulation.

Three superimposed Quaternary mass transport deposits (MTD1, MTD2 and MTD3) in the Pearl River Mouth Basin of the northern South China Sea are identified using high-resolution three dimensional seismic data. This study dissects the three stacked MTDs in detail and interprets their distribution based on antecedent bathymetry and their kinematics from identified structures and sedimentological models. Each MTD is characterized by linear grooves at its base, by chaotic seismic reflections and complex internal structures, such as remnant, rafted and faulted blocks. The linear grooves and internal structures of MTDs indicate that the sediments mainly flowed from the NW to SE in the study area. Moreover, internal structures suggest that MTD2 is a spread and MTD3 is a rotational slump, both terminating upslope at a regional linear escarpment. MTD1 is interpreted as the distal part of a larger MTD. The ages of MTD1, MTD2 and MTD3, based on seismic correlation with ODP Site 1146, are 0.54 Ma, 0.79 Ma and 1.59 Ma respectively. High-amplitude seismic reflections observed below the MTDs are interpreted as coarse-grained turbidites. Headscarp locations are controlled by both the underlying structures (such as basement highs and related faults) and the distribution of weak layers that are probably gas-bearing thin turbidite silt beds. This study provides precise ages of stacked MTDs in the northern South China Sea for the first time and at least locally provides clear evidence for the flow directions and controlling factors of the stacked MTDs. Similar lower slope–rise MTDs, of local origin, may be widespread elsewhere, but would be difficult to distinguish without 3-D seismic data.

The tectonic history of a margin dictates its general shape; however, its geomorphology is generally transformed by deep-sea sedimentary processes. The objective of this study is to show the influences of turbidity currents, contour currents and sediment mass failures on the geomorphology of the deep-water northwestern Atlantic margin (NWAM) between Blake Ridge and Hudson Trough, spanning about 32° of latitude and the shelf edge to the abyssal plain. This assessment is based on new multibeam echosounder data, global bathymetric models and sub-surface geophysical information. The deep-water NWAM is divided into four broad geomorphologic classifications based on their bathymetric shape: graded, above-grade, stepped and out-of-grade. These shapes were created as a function of the balance between sediment accumulation and removal that in turn were related to sedimentary processes and slope-accommodation. This descriptive method of classifying continental margins, while being non-interpretative, is more informative than the conventional continental shelf, slope and rise classification, and better facilitates interpretation concerning dominant sedimentary processes. Areas of the margin dominated by turbidity currents and slope by-pass developed graded slopes. If sediments did not by-pass the slope due to accommodation then an above grade or stepped slope resulted. Geostrophic currents created sedimentary bodies of a variety of forms and positions along the NWAM. Detached drifts form linear, above-grade slopes along their crests from the shelf edge to the deep basin. Plastered drifts formed stepped slope profiles. Sediment mass failure has had a variety of consequences on the margin morphology; large mass-failures created out-of-grade profiles, whereas smaller mass failures tended to remain on the slope and formed above-grade profiles at trough-mouth fans, or nearly graded profiles, such as offshore Cape Fear.

The best known submarine landslides on the glaciated NW European continental margins are those at the front of cross-shelf troughs, where the alternation of rapidly deposited glycogenic and hemi pelagic material generates sedimentary overpressure. Here, we investigate landslides in two areas built of contourite drifts bounded seaward by a ridge-transform junction. Seismic and bathymetric data from the Fram Slide Complex are compared with the tectonically similar Vastness area ~120km to the south, to analyze the influence of local and regional processes on slope stability. These processes include tectonic activity, changes of climate and oceanography, gas hydrates and fluid migration systems, slope gradient, toe erosion and style of contourite deposition. Two areas within the Fram Slide Complex underwent different phases of slope failures, whereas there is no evidence at all for major slope failures in the Vastness area. The comparison cannot reveal the distinct reason for slope failure but demonstrates the strong impact of variation in the local controls on slope stability. The different failure chronologies suggest that toe erosion, which is dependent on the throw of normal faults, and the different thickness and geometry of contourite deposits can result in a critical slope morphology and exert pronounced effects on slope stability. These results highlight the limitations of regional hazard assessments and the need for multi-disciplinary investigations, as small differences in local controlling factors led to substantially different slope failure histories.

Submarine sediment failures and related mass-transport deposits (MTDs) are widespread on the eastern Canadian continental slope settings and in general, have been related to ice sheets crossing the outer shelf. The southeastern Grand Banks margin was not glaciated in the last 105 years and has a deep shelf break. As a result, the upper continental slope consists principally of sediment transported from the north by the Labrador Current. High-resolution seismic profiles and 10-m long piston cores show widespread sediment failure and MTDs in a plastered contourite drift from 500 to 1000 m water depth. This study documents the stratigraphy of the past 48,000 years and the record of sediment failure events. Heinrich layers H1 to H5 have been recognized from distinctive petrology, physical properties, and bulk geochemistry and are constrained by numerous 14C-AMS dates. The geotechnical analysis shows that the latest Quaternary sediment section is mildly underconsolidated, perhaps related to high sedimentation rates (up to 0.5 m/ka) enhanced by some leakage of deep fluids. Nevertheless, factor of safety calculations using Su/P0 and friction angles from triaxial testing suggest the slope is statically stable up to gradients of 9°. Atterberg limit measurements of silty contourite sediments indicate susceptibility to liquefaction under cyclic loading. There is evidence that apparently synchronous failure occurred over many tens of kilometres of the slope, probably as a result of rare passive margin earthquakes. These shallow water contourite deposits have a higher sand and coarse silt content, much less biogenic material, and more rapid variations in sediment and geotechnical properties than those of the deep-water equivalents, all of which make them more susceptible to sediment failure.

Hemipelagic sediment on the upper continental slope is commonly transported from the adjacent continental shelf, but along-slope transport of sediment by thermohaline currents may be an important source of sediment. One such case is Flemish Cap, a promontory of the eastern Canadian continental shelf protected from direct continental sediment supply by the deep-water Flemish Pass. Pleistocene sediment drifts around Flemish Cap accumulated glacially derived sediment from the north, transported by the Labrador Current. This study determines the changing sources and controls on the accumulation of bioturbated hemipelagic sediment through the Holocene. From a set of >150 box cores in water depths of 600–1200 m, some 30 push cores, up to 55 cm long, were studied in detail for stratigraphic variation in grain size, bulk geochemistry (XRF) and detrital petrology (granule petrology and qXRD). Criteria were developed to identify trawling disturbance. Two Holocene stratigraphic units, A) almost lacking ice-rafted detritus and B) with some coarse IRD and higher detrital carbonate, correlate with similar units farther north on the Labrador Shelf and Slope. Sedimentation rates based on 26 radiocarbon dates were ~ 0.02–0.03 m/ka over much of the region below the 800 m isobath, locally reaching 0.1 m/ka in some sediment drifts, but as low as 0.01 m/ka on southeastern Flemish Cap. Where sedimentation rate was >0.03 m/ka, the record of flow vigor from the sortable silt proxy since 6 ka shows three different zones of Labrador Current flow with different timing of changes in flow vigor. The mid to early Holocene record shows that the meltwater-driven inner Labrador Current extended across the entire study area. Where sedimentation rates are lower, periods of sediment bypassing are inferred and the sortable silt record varies little. Correlation with external drivers is hampered by century-scale core resolution and sparse dating control. The distinctive abundance of dolomite rock flour in hemipelagic sediments around Flemish Cap indicates important supply from Baffin Bay icebergs during the entire Holocene, diluted prior to 6 ka by sediment from Hudson Strait and some Labrador ice streams. Baffin Bay icebergs melt preferentially in the southern Labrador Sea, dropping their load, with the fine grained component transported to the south by the Labrador Current. Similar partitioning of coarse- from fine-grained components of IRD may take place on other high-latitude outer continental margins.

The stacking pattern of shoreline progradational sequences in subsiding basins have been used as a chronologic tool in the Mediterranean region. Most previous studies have used a few key seismic lines seaward of deltas, where the record is complicated by deltaic distributary switching. Southeastern Saronikos Gulf, in the western Aegean Sea at the northwestern end of the South Aegean Arc, lacks large river input of sediment. The ENE-WSW and NW-SE trending neotectonic Aegina and Methana basins lie between the tectonically active Gulf of Corinth and the relatively stable Cyclades plateau. New high-resolution seismic profiles from southeastern Saronikos Gulf have been interpreted according to the principles of seismic and sequence stratigraphy. Alpine basement and marine Pliocene sediments have been recognized in the surrounding basin margins and more than 300 m and 150 m of unconsolidated sediments have been mapped in Aegina and Methana basin respectively. Progradational clinoforms that toplap against transgressive surfaces, have been traced along strike, leading to the establishment of a robust chronostratigraphic framework further controlled by sedimentation rates as extracted from cores. Southeastern Saronikos Gulf poses an outstanding example of development of progradational wedges formed within a microtidal, wave dominated regime of low sedimentation rates, between 2.8 cm/ka and 3.2 cm/ka, within the framework of low subsiding basins with rates between 0.03 and 0.31 m/ka. In this environment, more than 180 well preserved shoreline progradational units, with attributes similar to the ones reported from the Aegean and Eastern Mediterranean seas, have been mapped and correlated to sea level lowstands back to 866 ka. Deeper Mid-Pleistocene progradational units are also recognized, tentatively back to 1.4 Ma. Subsidence rate shows a dramatic decrease in the last 1 Ma and significant numbers of faults became inactive during the last 130 ka. In Early-Middle Quaternary, Methana basin was an isolated lake and extended terrestrial areas were shaped in the Poros-Agios Georgios plateau during sea level lowstands. Aegina basin was continuously connected to the Aegean through the Agios Georgios fault valley. This study demonstrates the robustness of chronology based on stacked shoreline progradational sequences and its applicability to determining rates of tectonic subsidence.

Submarine canyons are the principal conduit for turbidity currents transporting sediment to the deep sea. This study examines the interplay between ice-margin conditions and the style of turbidity currents during deglaciation from 19 to 11 ka. We investigated 7 cores from Halibut Canyon, located seaward of a small ice stream draining the Newfoundland Ice Dome. Cores were X-radiographed for sedimentary structures, sediment provenance was assessed from X-ray fluorescence geochemistry, and age was determined by AMS C-14 dating. High resolution seismic profiles and cores show three phases of canyon evolution: (1) Canyon erosion by plunging hyperpycnal meltwater from shelf-edge ice at maximum ice extent. (2) During deglaciation, active deposition of an inner levee by turbidity currents, adjacent to an erosional talweg system, recorded in cores from the Younger Dryas (12 ka) to before H1 (16.5 ka). (3) Passive canyon fill during the Holocene by the alongslope Labrador Current, with only minor down-canyon sediment supply. In the active canyon depositional phase, turbidity currents were of variable size, reaching thicknesses >390 m at 40 km down canyon. Numbers of sand beds and mean grain size decrease down canyon, which is inferred to result from rapid entrainment of ambient seawater on the steep gradient and a downflow thinning of the lower part of the current with fine sand in suspension. Silt becomes increasingly segregated from muds downcanyon as a result of floc break-up and re-formation. The processes inferred from Halibut Canyon are representative of other canyons on formerly glaciated margins.

The continental slope of the Canadian Beaufort Sea presents an exceptional opportunity to study the relationship between the fluid venting and the formation of mass-transport deposits. The continental shelf was emergent and partially ice-free during the last glaciation and is underlain by widespread permafrost. Water-column backscatter has shown the locations of more than 40 active gas vents along seaward margin of the subsea permafrost at the shelf break and upper slope. New multibeam bathymetry and subbottom profiler data show shallow potentially late Holocene failures and mass-transport deposits on the upper slope. Upslope from a prominent headscarp, undulating seabed with apparent growth faults overlies an acoustically incoherent to stratified horizon at 50 m sub-bottom interpreted as a decollement surface over which progressive creep has occurred. Similar creep is present in places on the upper slope and in places seems to have evolved into small translational slides, involving more compacted sediment buried > 25 m, or into muddy debris flows where sediments buried

Throughout the last glacial period, massive volumes of icebergs were discharged periodically through Hudson Strait during so-called Heinrich (H) events. These icebergs transported sediments that were subsequently deposited in distinct layers across the North Atlantic as they melted. The objective of this research was to measure and describe sedimentation associated with a meltwater plume discharged during the H1 ice-rafting event at about 17 ka by examining sediment texture. The H1 layer was sampled in 11 piston cores that cover about 4000 km of the slope between Hudson Strait and the Gulf of Maine. Disaggregated inorganic grain size (DIGS) distributions were determined using a Coulter Counter. Additionally, the CaCO 3 content and the > 63 μm fraction were measured and DIGS distributions were sorted using entropy analysis. Entropy analysis proved to be a useful tool for distinguishing between sediment delivery mechanisms. Textural interpretation of sediment dynamics during the H1 event was broadly consistent with facies interpretations. H1 layer sediments were mainly delivered by plume and ice-rafting, with some samples showing higher-energy sorting. In general, plume deposition was dominant within 1000 km of Hudson Strait, and distal sediments were mainly delivered by ice-rafting. Entropy analysis of DIGS distributions provides a robust means of understanding fine fraction (

The origin of a large field of sand ridges offshore from the north Jiangsu coast in the South Yellow Sea has been investigated on the basis of bathymetry, seabed samples, high-resolution seismic profiles and 31 to 71 m deep boreholes. Sediment composition including heavy minerals and clay minerals sampled from surface sediments shows that most of the sand was derived from the Changjiang (Yangtze) River, but in the northern part of the field particularly the clay came from the Huanghe (Yellow) River. Seismic profiles show late Pleistocene distributary channels of the ancient Changjiang River underlying much of the southern part of the sand ridge field. The Holocene transgression cut a widespread ravinement surface reworking abundant late Pleistocene sandy sediment. The available sand was reworked by tidal currents into large ridges. The location of the ridges is strongly influenced by relict channels in the southern part of the field and by tidal currents in the northern, and especially the northeastern part of the field, resulting in a radiating ridge pattern. These ridges provide an example of the evolution of a large scale geomorphic feature resulting from river–sea interaction, in which climatic and sea level changes played an important role.

Flemish Pass is a small, perched slope basin seaward of the Grand Banks on the eastern Canadian continental margin. Glacial ice crossed the Grand Banks to reach the upper continental slope during some Mid to Late Quaternary glaciations but terminated on the middle shelf, 200 km distant, at the last glacial maximum. This study investigates the effect of ice extent on slope sedimentation processes. Sediment in Flemish Pass comprises muds of hemipelagic and proglacial plume origin, minor thin-bedded turbidite sands, and thick-bedded mass-transport deposits (MTDs). A regional stratigraphy, based on 500 km of high-resolution seismic profiles and 60 piston cores up to 11 m long, was dated using 30 radiocarbon dates, the presence of Ash Zone II and oxygen isotope stratigraphy. This provided stratigraphic control for till tongues in water depths

The origin of acoustically transparent fan deposits overlying glacial till and ice-proximal sediments on the southern margin of the Norwegian Channel has been studied using high-resolution seismic-reflection profiles and multibeam bathymetry. The first deposits overlying glacigenic sediments are a series of stacked, acoustically transparent submarine fans. The lack of glaciomarine sediments below and between individual fans indicates that deposition was rapid and immediately followed the break up of the Late Weichselian ice cover. The fans are overlain by stratified glaciomarine sediments and Holocene mud. Because of the uniformity of this drape, the upper surface of the fan deposits is mimicked at the present seafloor, and the bathymetric images clearly show the spatial relationship of the fans to bedrock ridges and the presence of braided channel-levee systems on the surface of the youngest fans. The acoustically transparent character of the fan deposits indicates that they comprise silt and clay, and their lobate form and lack of internal stratification indicates that they were deposited by debris flows. The channel-levee morphology indicates deposition from more watery hyperconcentrated fluid flows. The fan sediments were either derived from 1) erosion of Mid Weichselian lake deposits in southern Skagerrak or 2) from Late glacial ice-margin lake deposits, ponded against the Norwegian Channel ice stream, which collapsed catastrophically when the lateral support was removed as the ice disintegrated. Fans composed almost exclusively of fine-grained sediment need not, therefore, rule out an origin in a deglacial setting relatively close to the former margins of glaciers and ice sheets.

The Gulf of Amvrakikos is one of several E–W grabens developed in the Middle Quaternary almost orthogonal to the tectonic grain of the external Hellenides in western Greece and is critically located at the termination of the Kefallinia transform fault linking the Hellenic subduction zone to the Adriatic-Dinaride collision lineament. The tectonic evolution of the Gulf and the response of sedimentation have been investigated based on 3.5 kHz and sparker profiles. The Holocene stratigraphy results from rising eustatic sea-level breaching the tectonic sill north of Preveza and inundating the braid plain of the Arachthos river, which then prograded across the northern Gulf following the formation of the maximum flooding surface. Older major transgressive surfaces are recognised in sparker profiles. Interpretation of these transgressions in terms of eustatic sea-level changes allows a chronology to be established and estimates to be made of neotectonic rates of subsidence. Two sets of neotectonic faults are present: reactivated NNE-trending mid-Tertiary thrusts of the Ionian zone and more active E–W trending faults. The sedimentary succession in the Gulf of Amvrakikos is the result of a complex interplay between eustatic sea level changes, the neotectonic creation of accommodation, and autocyclic delta distributary switching. The details of this process are resolved for the Holocene and the general sedimentation pattern established back to marine isotope stage (MIS) 8 (245–300 ka). In general, MIS 8 shows greater evidence of terrestrial deposition, compared with MIS 6 (130–190 ka) and especially MIS 2–4 (10–80 ka), when there was lacustrine deposition and some marine incursions at intermediate eustatic sea levels. This implies that regional subsidence has been taking place at least since MIS 8. In addition, changing sediment supply plays a role in overall sediment architecture, but is only well resolved for the Holocene, with higher rates of fluvial supply recognised in the mid Holocene.

The Late Cenozoic evolution of the upper Laurentian Fan, offshore eastern Canada, was studied by integrating single and multi-channel airgun seismic surveys collected over the past three decades. The upper Laurentian Fan has a complex history, strongly influenced by the growth and decay of continental ice sheets since at least the Middle Pleistocene. Four regional stratigraphic horizons (O, Q, B, and A, in order of increasing sub-bottom depth) were correlated throughout the single channel airgun data set and have been identified in low-resolution, multi-channel data. An additional deeper horizon, L, only identified in the multi-channel data, marks the Pliocene onset of Laurentian Fan development. Correlation of the seismic markers, in conjunction with seismic facies analysis, provided the basis for dividing the evolution of the fan into five major phases: i) initial development of a single, progradational leveed channel; ii) erosional over-deepening of this channel associated with the onset of glaciation; iii) major re-organization of the fan system coinciding with the glacial excavation of Laurentian Channel on the continental shelf; iv) further re-organization of the fan associated with ice streams flowing through Halibut Channel; and v) predominantly aggradational growth of the fan and a progressive westward shift of the upper fan depocentre. A chronology for the fan was determined indirectly using sparse biostratigraphic data from seafloor outcrops, extrapolation of sediment accumulation rates, and correlation to the global oxygen isotope curve. It shows that the regional reflectors O–A correspond to marine isotope stages 4, 6, 12 and (?) 22. Average sediment accumulation rates show a gradual increase through time consistent with the generally progradational character of the fan. Comparison of Laurentian Fan with the Northwestern Atlantic Mid-Ocean Channel in the Labrador Sea, both glacially-fed submarine channel–levee systems, suggests that Eastern Valley of Laurentian Fan is analogous to the submarine braidplain in the Labrador Sea. Ice-margin flow separation, similar to that inferred at the head of NAMOC, resulted in coarse-grained bedload flowing down Eastern Valley as hyperpycnal inflows, whereas Western Valley and the canyons of the East Scotian Slope were fed principally by finer-grained sediment from meltwater plumes. The turbidity currents associated with these plume deposits were initiated either by remobilization of this material due to upper slope failures or through hyperpycnal flows created by double diffusive sedimentation. The stratigraphic evolution of Laurentian Fan records a wealth of glaciogenic and paleoclimatic information that would be further revealed by the collection of long cores (e.g., Integrated Ocean Drilling Program boreholes).

The distribution and stratigraphy of volcanic rocks around the island of Milos has been interpreted from seismic reflection profiles. A consistent seismic stratigraphy can be recognised in the major basins, which contain mostly hemipelagic to low-energy gravitative sedimentation interrupted only locally by mass-transport deposits, despite the proximity to volcanic islands. Volcanic rocks have a distinctive rather incoherent acoustic signature and in places overlie stratified marine sediment. Their age is inferred from position relative to the Messinian seismic marker and by correlation with volcanic episodes dated on land. Volcanic rocks underlie an area five times larger than the present outcrops of volcanic rocks on Milos and adjacent islands. The main phase of volcanism was of late Pliocene age. It locally overlies folded lower Pliocene strata. In places the volcanic rocks have been planed off by Quaternary coastal erosion surfaces and have subsequently subsided, at rates of 0.2–0.35 mm/yr. Basin margins appear to have been generally stable, probably as a consequence of the relatively shallow water depths. Volcano flank failure deposits do not appear to be a major component of the sedimentary architecture.

The sedimentary and tectonic Quaternary evolution of the South Aegean arc has been interpreted from 8000 line-km of sparker seismic reflection profiles. The older parts of basins formed by E–W-trending faults and accumulated hemipelagic sediment. Younger active faulting trends NNW in the western part of the arc and ENE in the eastern arc. The ENE-trending faults record sinistral strike-slip motion broadly parallel to the convergence direction of the Aegean–Anatolian and African plates. The north–south faults in the western arc are similar to those on land in the south Peloponnese. Chronology is estimated from sedimentation rates in cores and from stacked progradational units on basin margins controlled by eustatic changes in sea level. The younger fault pattern developed at 0.6–0.8 Ma in the western and central arc, but progressively younger in the southeastern part of the arc. The older basin fill with E–W faults is of early Quaternary and Pliocene age. An older regional unconformity corresponds to an early Pleistocene unconformity in the Cretan basin. Particularly in the area east of Santorini, faulting has resulted in startling changes in palaeogeography, such that some areas were late Pliocene basins, positive features during the Pleistocene and then subsided 600 m in the last 0.2 Ma. Such rapid basin inversion resulted in uplift of stratified hemipelagic muds, which were deformed by creep or failure, so that debris flow deposits accumulated in valleys and ponded basins. These fundamental tectonic changes in the past two million years indicate that much of the deformation resulting from the interaction of the Eurasian, African and Anatolian–Aegean plates is taken up at the southern margin of the Aegean microplate, probably because subduction of the African plate has slowed as a result of collision of continental crust. Regional fault patterns are a consequence of spatially varying effects of subduction roll-back.

Large-scale sediment waves, composed of gravels and sands, have been studied using deep-water sidescan systems. New data are presented from submarine channels off the Canary Islands and from canyon mouths off Portugal. Data from other areas are briefly reviewed, including a re-interpretation of data from Laurentian Fan, in order to summarise the varied morphology and setting of these bedforms. Coarse-grained sediment waves are found in the proximal, dominantly bypassing areas of deep-water turbidite systems, within canyons, channels and channel-lobe transition zones. Wave heights are in the region of 1-10 m, and wavelengths are up to several hundred metres. The distribution of waves, and sparse sedimentological evidence from modern and ancient sediment wave fields, suggests that initial transport and deposition of coarse sediment occurs within a high-density turbidity current, and not as a non-Newtonian debris flow. In some cases the development of pronounced wave asymmetry, and evidence of wave disruption and reworking, suggests that the wave morphology is at least partially controlled by a later phase of low-density turbidity flow. Grain size also appears to exert some control on wave morphology, for example, gravel-rich waves have a greater height for the same wavelength than sand-rich waves. Coarse-grained sediment waves are often difficult to recognise on the seafloor because of reworking or burial by younger turbidity currents, and are equally difficult to recognise in outcrop because of their large size

The Gulf of Corinth in central Greece has a maximum depth of about 900 m and is separated from the open sea by the Rion Strait, with a sill depth of 62 m marked by an extensive submarine terrace. During eustatic sea-level lowstands, the Gulf of Corinth was a lake. Under lacustrine conditions, stratified sediments accumulated in the deep-water basins and turbid underflows from rivers eroded the basin slopes. As the sea level rose, marine waters flooded the Gulf and deltas prograded across the shelves. In shallow-water areas, two key reflectors termed Z and X are terrace surfaces, commonly erosional, which mark the base of the overlying deltaic sequences. In deep-water basins, Z and X mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites; reflectors Y and W mark the base of these stratified intervals and overlie acoustically transparent sections similar to the Holocene section. The last lacustrine conditions in the Gulf (Z to Y) were during isotopic stage 2 and terminated about 12 000 yr ago. Age estimates based on sedimentation rates suggest that the X to W interval corresponds to the stage 4 lowstand of sea level. In the western Gulf of Corinth, shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised. This seismic stratigraphy permits a detailed interpretation of the history of the Gulf of Corinth in the past hundred thousand years. It also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate.

A seabed 2-m-long cone penetrometer and coring system (Geotechnical Module) has been used at 17 stations in four transects on the Scotian Slope to characterise in situ shear strength and induced pore pressure on several different types of late Pleistocene and early Holocene failure. Study sites were selected using the SAR high-resolution deep-towed acoustic system equipped with a digital 160–190 kHz sidescan sonar and a 3.5 kHz subbottom profiler. Several distinctive types of “geotechnical signature” were recognised from plots of cone resistance and induced pore pressure with depth in the sediment. Normally consolidated sediments show a progressive increase in cone resistance with depth (to about 75 kPa at 2 m subbottom). Holocene surficial muds show spectacular apparent overconsolidation, reaching a peak of 250 kPa at about 50 cm subbottom and then decreasing down to 1.5 m. This overconsolidation is associated with Zoophycos burrows. Late Pleistocene sediments exhumed by bedding plane slides show strong true overconsolidation consistent with the original depth of burial inferred from high-resolution seismic stratigraphy. Debris flows show only a slight shear stress gradient with depth (40–45 kPa over 0.5–1 m subbottom) with under-consolidation due to remoulding of sediment.

Detailed single-channel airgun and 3.5 kHz profiles from the northeastern Mediterranean Sea show that the continental shelf is formed by superimposed deltaic successions (depositional sequences), separated by major erosional unconformities. Each depositional sequence is composed of a sigmoid prograding package overlain by an oblique prograding package, representing respectively delta progradation during high and low sea levels of interglacial and subsequent glacial stages. During the glacio-eustatic lowstands of sea level, deltas prograded seaward. The present-day shelf break denotes the topset to foreset transition at maximum progradation during the last glacial period. During post-glacial transgressions, the deltas initially lost their dynamic equilibrium with the environment and rapidly retreated landward. leading to the deposition of a thin veneer of sediments originating from reworking of formerly coastal sediments. At the highstand position the deltas were re-established in the ancestral Adana Bay and foreset progradation started. Chronology suggests that the Cilicia and Iskenderun Basins are subsiding at rates of 0.38 m 1000 yr-1 and 0.33 m 1000 yr-1. respectively. Seismic reflection profiling shows that delta architecture in the Adana. Cilicia and Iskenderun Basins is mainly controlled by glacio-eustatic sea-level fluctuations and continuous basin subsidence.

Seismic reflection profiles have been used to map the Messinian erosion surface and associated basin-margin deposits on the continental margin off Nice. A palaeovalley extends seaward from the incised Var palaeovalley mapped on land. The lower part of this valley is filled by an acoustically incoherent unit with a flat top and steep slope into the basin: this unit is interpreted as a coarse-grained deltaic deposit that accumulated synchronously with the upper Messinian evaporites in a ponded lake basin. Two submersible dives on strategic outcrops supported the interpretation of the seismic profiles. We examined and sampled outcrops of probably early Tertiary sandstones underlying the Messinian erosion surface and of a fining-up, predominantly conglomeratic sequence that fills Messinian channels on the continental slope and probably overlies the deltaic deposits. These conglomerates pass up into Early Pliocene marls and have turbidite sedimentary structures. These are prodeltaic deposits formed during the transgression at the end of the Messinian. Based on seismic facies mapping, sampling and submersible observations, a palaeogeographic reconstruction of the area is proposed. A basal erosion surface, including the Var palaeovalley, represents extreme dessication of the western Mediterranean and was followed by accumulation of the main Messinian salt. Following this, a lake was ponded in the Ligurian Basin, with accumulation of evaporites and shales. A Gilbert-type delta prograded into the basin from the Var palaeovalley. Relative sea (lake)-level lowering is estimated to be about 1200 m at this time. There has been little faulting on the margin since the Early Pliocene transgression, but there is estimated to have been about 800 m of flexural subsidence due to both thermal subsidence and water loading.

The Gulf of Patras is an actively subsiding late Cenozoic graben in western Greece that receives deltaic sediment from the large Acheloos and Evinos rivers. The late Quaternary sedimentation history of the gulf is interpreted from 3.5 kHz profiles, numerous short cores, and airgun seismic profiles. A widespread unconformity represents the isotopic stage 2 marine lowstand, when the gulf was subaerially exposed. Subsequent deltaic progradation and associated coastal transgression was greatest during the 13-10.5 ka slowdown in sea-level rise and the period of stable sea level since the mid-Holocene. Switching of delta distributaries can be related to the known evolution of the subaerial parts of the deltas. The stage 2 unconformity provides a datum for quantitative determination of rates of subsidence. The central graben is subsiding at rates of 3–5 mm/yr; rates in the northern part of the gulf average 1–2 mm/yr. This is consistent with a listric faulting model for the origin of the modern Patras graben.

The continental rise southeast of the Grand Banks of Newfoundland was surveyed many times during the last 8 years, especially during the search area for the wreck of the Titanic . High-resolution sidescan sonar images (systeme acoustique remorque, SAR) have shown an area characterised by complex surficial morphology, referred to as in “instability corridor”. New seismic reflection profiling has shown that the instability corridor is more extensive than was previously believed and that it is the expression of the distal part of a large sediment slide. It consists of upslopedipping imbricated sediment blocks which are tens of metres thick and many kilometres in length. Downslope from the slide is an acoustically incoherent unit interpreted as comprising debris flow deposits which could represent the final phase of evolution of the slide. The slide is blanketed by 5–10 m of younger sediment. The upper part of this blanket has been recovered by coring and consists of foram ooze, thin sandy turbidites and muddy beds with mudstone clasts. Radiocarbon dating and foram assemblages show that the upper metre of the core is late Holocene in age, with about eight resedimented beds forming in the last 4000 years. These recent turbidity currents cut erosional furrows and refresh the pre-existing steps of the slide. Three phases characterise the evolution of the instability corridor: (1) the major event involving a giant slide of bedded sediments up to 100 m thick, with a source probably on the steep continental slope of the Grand Banks 100 km to the north, (2) a draping of normal continental margin terrigenous sediments, and (3) erosion by one or a series of high-density turbidity currents. The giant slide created an instability corridor within which a number of channeled and non-channeled events took place during the late Holocene.

Detailed 3.5-kHz seismic-reflection profiling and coring have shown that the continental shelf break and slope off Izmir Bay, Turkey, are formed by prograding deltaic silty mud sequences. The muds contain shallow brackish-water benthic and cold-water planktonic foraminifera. They were deposited when sea level was about 110 m below its present position, during the last Pleistocene glaciation. Slumping took place on the prodelta slope, leaving rotational slump scars and imbricate slump blocks downslope. Delta-top truncation took place in shallow water by erosive coastline retreat after distributary abandonment. There has been little or no sedimentation since that time: outer Izmir Bay is thus floored by relict sands. Following rapid post-glacial transgression, the Gediz delta was reestablished in Izmir Bay. Archaeological evidence shows it has prograded during the last 3000 yrs. At least six shifts in the position of the Gediz mouth are distinguished during this time, and abandoned delta-top channels can be correlated with submarine delta-lobe sequences.

Air-gun and 3.5-kHz seismic profiles from the eastern Aegean Sea off Turkey show that the continental shelf of outer Izmir and Candarli bays is formed by several superimposed deltaic sequences. During times of lowered sea level associated with late Quaternary glaciations, deltas prograded seaward more than 60 km from their present positions. Foreset progradation ceased with the rise of sea level in interglacial and post-glacial times and deltas were reestablished far inland in drowned river valleys. These major transgressions resulted in unconformities within the superimposed prograded delta sequences. The most recent three unconformities are correlated with the beginning of oxygen isotope stages 5, 3 and 1, and provide chronostratigraphic markers for a detailed analysis of sedimentation patterns in the late Quaternary. The coastal shelf and basins are subsiding at an average rate of about 1 m per 1000 years. This tectonic subsidence manifests itself as widespread normal block faulting which can be related to the pre-Miocene structural framework of the region.

A small area of the Scotian Slope has been investigated in detail as a type example of a high-latitude continental slope adjacent to a major ice outlet. The geologic framework has been defined by airgun seismic profiles, which show that Late Tertiary shales have irregular dips, but overlie undisturbed strata. These shales form a zone of diapirs at around 1200 m water depth, which have ponded the prograding Quaternary sediments upslope. High-resolution sparker profiles, SeaMARC I mid-range sidescan imagery, and piston cores have been used to investigate the Late Quaternary sedimentary sequence. A prominent gullied horizon about 40 m subbottom, that is overlain by acoustically unstratified sediments (?sands), is correlated with the occurrence of an early Middle Wisconsinan grounded icesheet at the top of the continental slope. It is overlain by a thick sequence of proglacial muds and a thin veneer of Holocene sediments. Much of the Late Wisconsinan sequence has been dissected by a series of closely spaced gullies. Both sidescan and subbottom profiler data show that slumping is common in the Late Wisconsinan sequence, as a result of high sedimentation rates and local gully erosion. Piston cores provide evidence for debris flows and turbidity currents. Depositional sediment mounds in the diapir zone have accumulated sediment at three times the regional sedimentation rate, suggesting that large amounts of fine sediment reached the slope in suspension, and that much of the proglacial sediment by-passed the continental slope.