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Quaternary sediment in the Labrador Sea was derived from many proglacial sources in Greenland and eastern Canada. Understanding the spatial and temporal changes in sediment provenance provides information on ice extent and sediment dispersal patterns. Variations in mineral composition of sediment from late Quaternary cores has been determined by a whole pattern of quantitative X-ray diffraction procedure. Mineral facies were extracted statistically by a supervised analysis of 90 samples from bedrock and ice-rafted clasts, which were then used to predict the most probable mineral facies in 1443 marine sediment samples. We used a non-parametric Classification Decision Tree (CDT) to validate that decision. Only 26% of the samples were misclassified in the CDT. The six facies identified consisted of four facies reflecting differences in the composition of Canadian and Greenland Precambrian igneous and metamorphic bedrock, a set of samples dominated by high weight percentages of calcite and dolomite (detrital carbonate (DC) and Hudson Strait Heinrich (HS-H) events), and a “shale” facies. We isolated 284 sediments from the HS-H DC facies and determined that they could be divided into four categories based on differences in their mineral proportions. These categories vary geographically, based on non-carbonate sediment supply during these events from Greenland, the Canadian Shield, the Appalachians, and the outer continental shelf. In the Holocene of the Labrador Sea, dolomite is derived from Baffin Bay and abundance of calcite is influenced by both biogenic productivity and dissolution.

Scenes of the legendary battle between Poseidon and the giant Polybotes, which occurred on the Greek island of Kos, are depicted on dozens of surviving ceramic objects. Poseidon is shown killing his opponent with his trident, while carrying a huge rock that he had ripped off the island of Kos to bury Polybotes. The legend is interpreted to represent a strong earthquake that caused a large coastal rock fall or rock avalanche. The oldest ceramics representing this disaster date from ca. 540 BCE. The disaster is interpreted to date from this time and was a major event that reverberated throughout the Greek world, triggering the imagination of its artists for several generations. Legend and ancient literary sources suggest that the event took place in southeastern Kos, near the then capital city of Astypalaia, located NW of Zini mountain. Geological studies show a large, relatively recent, rock avalanche on the steep coast on the SE side of Zini mountain. Possible tsunami sand deposits with reworked marsh foraminifera are found 7 m above sea level on NE Zini, only 1 km from the archeological site of the old city of Astypalaia and large boulders are stranded on the opposite rocky coastline up to 6 m above sea level. Noise and dust from a rock avalanche would have been terrifying for the inhabitants of Astypalaia and any tsunami would have overwashed the port at Kamari. In the absence of suitable geological dating methods, ceramics provide the best chronology for the event.

The Junggar Basin, bounded by the West Junggar along late Carboniferous strike-slip faults in the west, is a post- orogenic successor basin within the Neoproterozoic to Paleozoic Central Asian Orogenic Belt (CAOB). The Junggar Basin is a key region for understanding the Permian rifting processes since it is located in an extensional step-over zone between the Irtysh and North Tianshan strike-slip fault zones that were most active in the Permian. Based on new seismic reflection profiles, detrital petrology and zircon U-Pb ages, together with regional geological data and a refraction seismic profile, this study investigates the tectonic evolution and the geodynamic mechanics of the basin. The early Permian phase of syn-rift mechanical subsidence in the western Junggar Basin formed half grabens. Volcanic detritus is abundant, and detrital zircon U-Pb ages show sediment supply was entirely local. During the middle Permian post-rift phase with thermal subsidence, sediment supply exceeded subsidence, and there are increasingly distant sources of sediment. The Permian regional extensional stress field between major post- accretionary strike-slip fault zones triggered the reactivation of the pre-existing late Carboniferous strike-slip faults in West Junggar and produced thinning of the crust beneath the Junggar Basin, with a β crustal stretching factor of 1.74. Seismic refraction data reveals asthenospheric upwelling resulted in underplated mafic lower crust (6–10 km). The location of initial rift axis in the Junggar Basin was controlled by the juxtaposition of thin and weak crust beneath the basin and relatively strengthened thick crust in the West Junggar attributed to the cooling of A-type granites, resulting from localized strain. Similar location of post-orogenic rifting in southwestern CAOB, in areas of high heat flow following collision, suggests that Junggar Basin is an example of a more general process.

Provenance analysis provides a powerful means to understand, connect, and reconstruct source-to-sink systems and Earth surface processes, if reliable toolkits can be developed, refined, and applied. Deciphering sediment routing to the Scotian Basin, offshore eastern Canada, is marred by sedimentary recycling but is critical to understanding the evolution of the Canadian margin in response to the evolving Labrador rift. In this study, Pb isotopes in detrital K-feldspars were fingerprinted in 13 wells across the Scotian Basin to track first-cycle sand supply. Unlike previous approaches, which utilized less labile proxies such as zircon, detrital K-feldspars are unlikely to survive multiple sedimentary cycles. The Pb-isotopic data reveal a dynamic seesaw effect between hinterland sources across the Jurassic-Cretaceous boundary, reflecting the complex interplay between the northward propagation of uplift along the rising Labrador rift flank and the reactivation of fault systems in the lower drainage basin. Pb isotopes in K-feldspar record progressively increasing long-distance supply from eastern Labrador, as early as the Callovian in the central basin, alongside diminishing but persistent local sourcing from adjacent Appalachian terranes. Comparison with more resilient mineral proxies, notably zircon, appears to confirm recycling in the lower drainage basin and highlights the limitations of using a single mineral proxy in isolation. This case study serves as an example of the growing potential of multiproxy provenance toolkits not only to decipher sediment-routing corridors in paleodrainage systems, but to better define and connect the drivers, mechanisms, and spatial and temporal ranges of Earth surface processes and tectonic events.

The destruction of Ancient Helike in 373 BC as reported by ancient Greek and Roman writers is inconsistent with modern evidence on the geological context. The classical view of a strong earthquake, similar to the 1817 M = 6.6 earthquake and followed by a giant tsunami wave that permanently inundated the ruined city does not stand up to modern scrutiny. Evidence for co-seismic slip on the Helike Fault at that time and for a corresponding tsunami have already been shown to be lacking, and the archaeological evidence shows that part of the site was reoccupied within 40 years. New observations on outcrops, excavated sites, and boreholes show that at least two mudflow deposits several metres thick of slightly gravelly mud overlie 4th c. BC archaeological remains on the Katourlas fan. Upstream, landslides are common in the 4 km2river basin and could have dammed the ephemeral Katourlas River. Relics of this dam are still recognised in the riverbed as a knickpoint. Temporary damming of rivers by earthquake-triggered landslides is a common phenomenon in northern Peloponnese. The destruction of Ancient Helike appears to have been a localised non-linear cascading series of disasters, with a strong earthquake followed by a destructive mudflow generated by breaching of a landslide-dammed lake in the Katourlas basin. Historical records of flooding from the west may record another landslide dam followed by a more watery flood in the Selinous River. We propose that it was mudflows and floods from inland rather than a tsunami from the sea that contributed to the final destruction of Helike.

The 161-ka Kos Plateau Tuff (KPT) eruption deposited widespread unwelded ignimbrites, but the Dikeos and Sympetro mountains on the SE of Kos Island blocked all but the most energetic pyroclastic flows. KPT remnants north of Sympetro mountain comprise reworked tuffite containing pumice and lithic clasts that petrologically and geochemically resemble those found in KPT unit E tephra, and reworked accretionary lapilli similar to those in KPT unit F. Tuffite is found only downslope from a 375-m-high pass between the Dikeos and Sympetro mountains, which was breached at the eruption climax by pyroclastic flows that then accelerated down the 10° north slope of Sympetro. The tuffite crops out in the palaeocliffs of a prominent terrace at an elevation of 75 m, interpreted as the transgressive ravinement surface of the first interglacial marine highstand after the KPT eruption during marine isotope stage (MIS) 5e. A similar ravinement surface cuts KPT deposits in central Kos at elevations of up to 135 m and implies post-MIS 5e uplift rates of 0.7–1.0 m ka−1, confirmed by the elevation of a previously reported raised beach beneath the KPT. A Holocene raised beach on the east coast of Kos contains pumice clasts from the Yali-4 eruption at 4–3 ka. Its elevation of 2 m above sea level is consistent with the elevation of the local MIS 5e terrace. Its present erosion results from the blocking of discharge from ephemeral streams by human infrastructure. Our study provides the first integrated chronologic and neotectonic interpretation of the prominent plateau and terrace surfaces on Kos Island.

Scapolite and analcime are uncommon alteration minerals in syenite. Here we describe a syenite body in a fault zone that hosts these minerals and we elucidate the unusual chemical conditions that led to their formation. The Clarke Head syenite is part of a regional late Devonian–early Carboniferous back-arc A-type granitoid suite in the Cobequid Highlands of Nova Scotia, Canadian Appalachians. The syenite contains magmatic rutile and analcime. Magmatic K-feldspar has been largely replaced by scapolite of marialite composition, which shows a temporal transition from more Cl rich to more carbonate rich varieties. Scapolite veins cut both the syenite and associated gabbro and diorite. Analcime I occurs as a late stage interstitial magmatic mineral. Analcime II forms by alteration of albite lamellae in perthite replaced by scapolite, analcime III vugs that cross-cut scapolite and analcime IV occurs in late veins cross-cutting earlier analcime phases and scapolite. The regional A-type granite plutonism was Na- and halogen rich, with widespread late-magmatic albitization and F-related mobility of REE minerals. However, only at Clarke Head is there extreme Na- and Cl-rich metasomatism, indicated by scapolite and Cl-rich hastingsite (with >1 wt% Cl content). Cl-rich fluids were derived from regional halite evaporites at faulted basin margins. The main circulating fluids were likely of magmatic origin, based on the δ18O of both replacement and vein scapolite. As the NaCl supply was reduced, scapolite became more Ca-rich. Halogen-rich fluids also mobilized Ti and Zr, which were reprecipitated in hydrothermal rutile and zircon as the halogen activity diminished. Scapolite replacement of K-feldspar released large amounts of K+ into the circulating fluids, which converted ferromagnesian silicates in fault zones to secondary biotite.

International audience; Between 22 and 17 cal ka BP, five large meltwater events from within the Laurentian Channel Ice Stream deposited mud beds meters thick across a large area of the Laurentian Fan and adjacent continental slopes. This study determines the sources of these event beds and relates them to the glaciological evolution of the retreating Laurentian Ice Stream. We analyzed major element and magnetic mineral contents of these event beds and compare them with a new collection of 80 source reference samples from the Gulf of St. Lawrence area. Element ratios suggest a steady compositional change from older to younger outburst event beds, while element-specific offsets from reference sample compositions indicate grain-size and mineral/element partitioning during suspension transport. Their magnetic properties place event beds on the source mixing trend of four reference samples groups, which represent two magnetite-rich sources (Canadian Shield and/or Southern Newfoundland) and two hematite-rich sources (Appalachian red beds). Using a deterministic linear source mixing model based on IRM 100mT , HIRM and Ca%, we find that the earlier two outburst events had higher contributions from granitic and calcareous sources than the later three events. Combining materials, timing and scenarios of the outburst events with ice-sheet retreat and ice-stream dynamics, we argue that the subglacial sediment depocenter of the earlier two event beds was located in the lower Laurentian Channel while that of the later three events was upstream from Cabot Strait.

Siliceous (chert) concretions are a prominent component of Cretaceous limestones in the Ionian zone of western Greece. This study investigates the diagenetic evolution of such cherts from two localities: largely undeformed strata on Kastos Island and highly faulted strata at Araxos. In both areas, lower Cretaceous limestones contain abundant small chert nodules, whereas in the upper Cretaceous nodules are larger but less abundant. Seventy seven powdered samples, from 67 representative field samples, were analyzed by X-ray Powder diffraction (XRPD). The analyzed samples came from both nodular and siliceous beds and showed that quartz is the dominant mineral, with rare to common residual calcite. The presence of moganite and opal-A minerals suggests that quartz recrystallized from original amorphous silica. A few samples from Araxos contain traces of halite and anhydrite. The variability in the calcite content and the presence/absence of halite and anhydrite in the different studied areas are related with the different tectonic activity in these areas, with more intense tectonic activity in NW Peloponnesus than in Kastos Island. Size of nodules is related to variation in primary porosity of the host rocks. Finally, the presence of dolomite was related with the pre-existing underlying dolomites of Early Cretaceous age in Ionian basin, whereas the presence of maghemite is due to the presence of iron minerals in water solutions.

The detrital mineralogy of Upper Jurassic to Lower Cretaceous sandstones from the Continental Offshore Stratigraphic Test G-2 well in the Georges Bank Basin was studied to better understand the varying supply of clastic sediment to the basin. Heavy minerals separated from cuttings were identified by chemical analyses, zircons were dated, and Raman spectroscopy was applied to identify titania polymorphs (rutile, anatase, and brookite). Upper Jurassic (Oxfordian) sands contain tourmaline, fluorapatite, Mn-almandine and grossular garnets (derived from the central Maine and coastal Maine belts), and pumice and trachytes reworked from volcanics in the Long Island platform. Zircon geochronology (300–450 and 550–700 Ma) supports sources from peri-Gondwanan Appalachian terranes. Lower Cretaceous heavy minerals show that Oxfordian supply was diluted to 30%, mostly by additional ilmenite, zircon, tourmaline, and staurolite, probably by components from central and northern Maine and New Brunswick. Rutile and anatase from metapelites are more common than in the Oxfordian, where mafic igneous sources predominate. Lower Cretaceous zircons include a few Mesoproterozoic grains that might be reworked from middle Paleozoic sedimentary rocks in the Gander terrane of northern Maine and New Brunswick, although subhedral grains together with rare chromite may indicate minor or intermittent supply from the Sable River draining Labrador. Heavy minerals provided important provenance information not available from zircon geochronology alone. Progressive enlargement of the catchment area resulted from an increasingly humid climate in the latest Jurassic and active mostly northeast-trending faults in the Early Cretaceous. This resulted in greater supply of petrographically more-mature sand to the basin.

Source‐to‐sink studies and numerical modelling software are increasingly used to better understand sedimentary basins, and to predict sediment distributions. However, predictive modelling remains problematic in basins dominated by salt tectonics. The Lower Cretaceous delta system of the Scotian Basin is well suited for source‐to‐sink studies and provides an opportunity to apply this approach to a region experiencing active salt tectonism. This study uses forward stratigraphic modelling software and statistical analysis software to produce predictive stratigraphic models of the central Scotian Basin, test their sensitivity to different input parameters, assess proposed provenance pathways, and determine the distribution of sand and factors that control sedimentation in the basin. Models have been calibrated against reference wells and seismic surfaces, and implement a multidisciplinary approach to define simulation parameters. Simulation results show that previously proposed provenance pathways for the Early Cretaceous can be used to generate predictive stratigraphic models, which simulate the overall sediment distribution for the central Scotian Basin. Modelling confirms that the shaly nature of the Naskapi Member is the result of tectonic diversion of the Sable and Banquereau rivers and suggests additional episodic diversion during the deposition of the Cree Member. Sand is dominantly trapped on the shelf in all units, with transport into the basin along salt corridors and as a result of turbidity current flows occurring in the Upper Missisauga Formation and Cree Member. This led to sand accumulation in minibasins with a large deposit seawards of the Tantallon M‐41 well. Sand also appears to bypass the basin via salt corridors which lead to the down‐slope edge of the study area. Sensitivity analysis suggests that the grain size of source sediments to the system is the controlling factor of sand distribution. The methodology applied to this basin has applications to other regions complicated by salt tectonics, and where sediment distribution and transport from source‐to‐sink remain unclear.

Chert concretions in thick limestone successions preserve a more complete paragenetic sequence of diagenetic minerals than their host limestone and interbedded shale. The goal of this study was to test the possible presence of a high-temperature mineralising system in the Ionian basin of western Greece. Upper Cretaceous chert nodules were sampled at Araxos, where rocks are highly faulted and uplifted by salt diapirism, and on Kastos Island, on the flanks of a regional anticline. Chert concretions have microporosity produced by recrystallisation of opal to quartz and fractures produced in the brittle chert during basin inversion. Diagenetic mineral textures were interpreted from backscattered electron images, and minerals were identified from their chemistry. Diagenetic minerals in pores and veins include sedimentary apatite (francolite), dolomite, Fe-chlorite, Fe oxide-hydroxide mixtures, sphalerite, barite and calcite. Sphalerite is restricted to Araxos, suggesting that inferred basinal fluids were hotter and more saline than at Kastos. At Araxos, the Fe oxide-hydroxide also includes minor Cu, Zn, and Ni. Whether the transported metals were derived from sub-salt clastic rocks and basement, or from enriched Mesozoic black shales, is unclear. The effectiveness of this novel approach to understanding fluid flow history in thick limestone successions is validated.

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.

The early Miocene Sigri Pyroclastic Formation in western Lesbos Island hosts the famous petrified forest of silicified tree fossils, protected as a UNESCO Geopark. The formation consists primarily of flow tuffs, mud flow deposits and stream conglomerate. Hydrothermal veins rich in silica, iron, and manganese are preferentially developed in major fault zones and along paleosols. The purpose of this study is to understand the nature of the hydrothermal system and its relationship to the preservation of tree fossils. Samples were collected from fresh and altered pyroclastic rocks, hydrothermal veins and petrified wood. Rock mineralogy and chemistry were investigated using a petrographic microscope, scanning electron microscope, electron microprobe, Laser Raman spectroscopy, and X-ray powder diffraction. Early devitrification of volcanic glass in tuffs formed opaline silica and locally resulted in smectite. At the same time, fossil trees were partly replaced by amorphous silica. Epithermal alteration and hydrothermal veins include (1) adularia + silica + kaolinite; (2) jarosite + hematite + amorphous silica; and (3) “Fe-oxide” and/or “Mn-oxide” + amorphous silica. The MnSi mixture and Mn-oxides comprise structurally amorphous romanechite with some more crystalline grains of todorokite, ramsdellite and/or nsutite. The mixtures of Fe-oxides and silica are also largely amorphous and include α-cristobalite. Such mixtures replace parts of the petrified wood including cell walls. The various colors observed from the petrified wood are principally related to the abundance of iron and organic matter. Faulting and complex hydrothermal alteration was related to the emplacement of laccoliths and dykes around 18 Ma, 1–3 Ma after deposition of the Sigri Pyroclastic Formation. The observed types of low temperature epithermal alteration are compared with that produced by different circulating waters in the modern Taupo volcanic zone of New Zealand. Hydrothermal deposition of Fe-oxides and silica played an important role in the preservation of the petrified forest.

Hughes et al. (1977) hypothesized of a pan-Arctic Ice Sheet that behaved as a single dynamic system during the Last Glacial Maximum. Moreover, the authors suggested a nearly grounded ice shelf in Davis Strait implying that little or no exchange between Baffin Island and the Labrador Sea. Here we present data at 1-cm (

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.

The Kos-Nisyros-Yali volcanic region is one of the centers in the South Aegean Volcanic Arc to exhibit Holocene volcanic activity, with poorly dated thin tephra layers on Yali associated with Neolithic artifacts. This paper helps to resolve the age and character of early to mid - Holocene volcanism in the South Aegean Sea. It presents the lithostratigraphic record of seven newly recovered cores from this region at the SE termination of the South Aegean Volcanic Arc. The cores were scanned for magnetic susceptibility, split, logged and sampled at one centimeter resolution for carbonate content. Selected intervals were analyzed for grain size, organic carbon content, and feldspar content by XRD, in order to identify lithostratigraphic levels with enhanced volcanic minerals. Subsequently, textural and electron microprobe analyses of volcanic glass shards and pumice fragments were carried out on 20 samples. Chronology was inferred from the upper and lower limits of the S1 sapropel and from five AMS 14C dates on foraminifera. In several cores in the S1 interval, mixed volcanic glass types that compositionally correlate with the Nisyros Lower and Upper Pumice, Yali pumices and KPT suggest that the volcanic glass is reworked from previous deposits and transported by turbidity currents. Cores from deep water northeast and northwest of Yali have a single population of tephra at two or more horizons within S1 that geochemically resembles Holocene Yali–4 pumice on land. These beds likely represent air-fall ash that was dispersed at least 10 km from Yali, with ages of 8 and 10 ka. Moreover we report two or more tephra layers within S1 from the Kalymnos Basin that are not reworked and geochemically resemble Santorini tephra. This study thus confirms the occurrence of small early Holocene eruptions at Yali and provides possible evidence for early Holocene eruptions at Santorini.

A Mw 7.2 earthquake centred beneath the upper Laurentian Fan of the SW Newfoundland continental slope triggered a damaging turbidity current and tsunami on 18 November 1929. The turbidity current broke telecommunication cables, and the tsunami killed 28 people and caused major infrastructure damage along the south coast of Newfoundland. Both events are believed to have been derived from sediment mass failure as a result of the earthquake. This study aims to identify the volume and kinematics of the 1929 slope failure in order to understand the geohazard potential of this style of sediment failure. Ultra-high-resolution seismic reflection and multibeam swath bathymetry data are used to determine: (1) the dimension of the failure area; (2) the thickness and volume of failed sediment; (3) fault patterns and displacements; and (4) styles of sediment failure. The total failure area at St Pierre Slope is estimated to be 5200 km2, recognized by escarpments, debris fields and eroded zones on the seafloor. Escarpments are typically 20–100 m high, suggesting failed sediment consisted of this uppermost portion of the sediment column. Landslide deposits consist mostly of debris flows with evidence of translational, retrogressive sliding in deeper water (>1700 m) and evidence of instantaneous sediment failure along fault scarps in shallower water (730–1300 m). Two failure mechanisms therefore seem to be involved in the 1929 submarine landslide: faulting and translation. The main surficial sediment failure concentrated along the deep-water escarpments consisted of widely distributed, translational, retrogressive failure that liquefied to become a debris flow and rapidly evolved into a massive channelized turbidity current. Although most of the surficial failures occurred at these deeper head scarps, their deep-water location and retrogressive nature make them an unlikely main contributor to the tsunami generation. The localized fault scarps in shallower water are a more likely candidate for the generation of the tsunami, but further research is needed in order to address the characteristics of these fault scarps.

The Naskapi Member of the Logan Canyon Formation, a 150 m thick shale-dominated unit, lies in between sand-dominated units of Upper Missisauga Formation below and the Cree Member above. The great decrease in sediment supply has been suggested as due to tectonic and (or) eustatic sea-level changes. Wireline logs and recent biostratigraphy of 30 wells from the Scotian Shelf and Georges Bank, mudstone geochemistry from the Naskapi and Cree Members, and modal composition and chemical variation of detrital heavy minerals in sandstones were examined to better understand the deposition of the Naskapi Member and its regional implications. Minor sandy intervals at the base of the Naskapi Member were correlated based on gamma and sonic log signatures from the type section in the Cree E-35 well to progressively more distant wells, on the assumption that the sands represent periods of lowered eustatic sea level. Correlation was confirmed by the distribution of highstand black shales in washed cuttings and biostratigraphic markers identified in some wells. The geochemistry of mudstones from the Naskapi Member resembles mudstones sourced from the Meguma Terrane, except for a higher abundance of elements likely reworked in smaller amounts from the Upper Missisauga Formation. Based on the correlation and geochemistry of mudstones and detrital minerals, we suggest the diversion of Sable River through the Gulf of St. Lawrence to either the Orphan Basin or towards western Canada was responsible for the decrease of sediment supply in the Scotian Basin during the deposition of the Naskapi Member shales.

Intra-continental shear zones developed during continental collision may experience prolonged magmatism and mineralization. The Cobequid Shear Zone formed part of a NE–SW-trending, orogen-parallel shear system in the late Devonian–early Carboniferous, where syn-tectonic granite-gabbro plutons and volcanic rocks 4 km thick were progressively deformed. In late Carboniferous to Permian, Alleghanian collision of Africa with Laurentia formed the E–W trending Minas Fault Zone, reactivating parts of the Cobequid Shear Zone. The 50 Ma history of hydrothermal mineralization following pluton emplacement is difficult to resolve from field relationships of veins, but SEM study of thin sections provides clear detail on the sequence of mineralization. The general paragenesis is: albite ± quartz ± chlorite ± monazite → biotite → calcite, allanite, pyrite → Fe-carbonates, Fe-oxides, minor sulfides, calcite and synchysite. Chronology was determined from literature reports and new U-Pb LA-ICPMS dating of monazite and allanite in veins. Vein mineralization was closely linked to magmatic events. Vein emplacement occurred preferentially during fault movement recognised from basin-margin inversion, as a result of fractures opening in the damage zone of master faults. The sequence of mineralization, from ca. 355 Ma riebeckite and albite veins to ca. 327 (−305?) Ma siderite-magnetite and sulfide mineralization, resembles Precambrian iron-oxide–copper–gold (IOCG) systems in the literature. The abundant magmatic Na, halogens and CO2 in veins and some magmatic bodies, characteristic of IOCG systems, were derived from the deeply subducted Rheic Ocean slab with little terrigenous sediment. Regional extension of the Magdalen Basin caused asthenospheric upwelling and melting of the previously metasomatized sub-continental lithospheric mantle. Crustal scale strike-slip faulting facilitated the rise of magmas, resulting in high heat flow driving an active hydrothermal system.

Eastern Canadian margin sediments bear testimony to several catastrophic deglacial meltwater discharges from the retreating Laurentide Ice Sheet. The reddish-brown plumite layers deposited on the levees of the Laurentian Fan valleys have been recognized as indications of multiple outburst floods between Heinrich events 2 and 1. Five event layers have been consistently recorded in three new gravity cores retrieved on the SW Grand Banks slope and comply with the previously published Laurentian Fan core MD95-2029. The apparently huge extent of these outburst plumes around the Laurentian Fan as well as their causes and consequences are investigated in this study using physical properties, rock magnetic and grain-size analyses, together with seismoacoustic profiling. We provide the first detailed 14C ages of the outburst event sequence and discuss their recurrence intervals in the context of regional ice retreat. Compared to the hemipelagic interlayers, event layers have overall uniform and systematic changes of rock-magnetic properties. Hematite contents increase over time and proximally while magnetite grain sizes fine upwards and spatially away from the fan. Based on the sediment composition and load, we argue that these plumites were formed by recurrent erosion of glacial mud deposits in the Laurentian Channel by meltwater outbursts. Three alternative glaciological scenarios are evaluated: in each case, the provenance of the transported sediment is not an indicator of the precise source of the meltwater.

The Laurentian Fan is one of the largest submarine fans on the western margin of the North Atlantic. Recently acquired high-resolution multibeam bathymetric data (60 m horizontal resolution) reveal a major mass transport deposit (MTD) on the Western Levee of Western Valley (WLWV), covering >14 000 km2 in water depths from 3900 m to >5000 m. Typical submarine landslide features are observed such as headscarps that in places reach the crest of the levee, crown cracks, extensional ridges, blocky debris and flow lineations. Multiple headwalls are observed on 3.5 kHz sub-bottom profiles indicating that the landslide retrogressed upslope. While the upper parts of the MTD consist of intact blocks that were displaced downslope as ridges and troughs, the lower parts exhibit a ~30 m thick incoherent to transparent acoustic facies typical of debris flows. Landslide geomorphology thus suggests that it was generated as a retrogressive spread and that slide blocks disintegrated downslope to become a blocky landslide with a surficial debris flow. The blocky landslide/debris flow extends downslope ~90 km and partially fills a submarine channel. The superposition of the MTD filling the channel and its location at the top of the stratigraphic succession in the levee suggests that it is late Quaternary in age, possibly Holocene. Deeper seismic reflection data also show that this is a rare event during the Quaternary; it is the largest MTD observed in the upper ~375 m of the levee succession and among the largest and deepest in the Western North Atlantic.

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.

Major intra-continental shear zones developed during the later stages of continental collision in a back-arc setting are sites of prolonged magmatism. Mantle metasomatism results from both melting of subducted sediments and oceanic crust. In the Cobequid Fault Zone of the northern Appalachians, back-arc A-type granites and gabbros dated ca. 360 Ma are locally intruded by lamprophyric dykes dated ca. 335 Ma. All the lamprophyres are kersantites with biotite and albite, lesser ilmenite, titanite and fluorapatite, and minor magmatic calcite, allanite, pyrite, magnetite, quartz and K-feldspar in some samples. The lamprophyres show enrichment in Rb, Ba, K, Th and REE and classify as calc-alkaline lamprophyre on the basis of biotite and whole rock chemistry. Pb isotopes lie on a mixing line between normal mantle-derived gabbro and OIB magma. Nd isotopes range from 1.3–3.5 eNdt, a little lower than in local gabbro. Most lamprophyres have δ18O = 3.8–4.4‰. Country rock is cut by pyrite-(Mg)-chlorite veins with euhedral allanite crystals that resemble the lamprophyres mineralogically, with the Mg-chlorite representing chloritized glass. Early Carboniferous unenriched mafic dykes and minor volcanic rocks are widespread along the major active strike-slip fault zones. The lamprophyres are geographically restricted to within 10 km of a small granitoid pluton with some sodic amphibole and widespread albitization. This was displaced by early Carboniferous strike-slip faulting from its original position close to the large Wentworth Pluton, the site of mantle-derived sodic amphibole granite, a major late gabbro pluton, and a volcanic carapace several kilometres thick, previously demonstrated to be the site of mantle upwelling and metasomatism. The age of the lamprophyres implies that enriched source material in upper lithospheric mantle or lower crust was displaced 50 km by crustal scale strike-slip faulting after enrichment by the mantle upwelling before lamprophyre emplacement. This indicates a multi-stage process to emplace lamprophyric magma.

Frontier basins are difficult to model with forward stratigraphic modeling software, due to the limited amount of geological information available from sparse wells and limited seismic coverage. Five different simulations with varying amounts of geological information are compared to a geologically constrained reference case model using all available data for the Shelburne sub-basin, in order to understand the relative importance of various geologically constrained parameters to modeling frontier basins. The modeling has been performed with DionisosFlow™, a 4D multilithology diffusion-based deterministic forward stratigraphic modeling software. All five less constrained models resemble the major features of the reference case model, with a similar distribution of sand on the shelf and localized progradation of sand across a delta into deep-water. In detail, there are significant deviations in sedimentation patterns. Not all geologically constrained parameters are equally important to modeling; the most influential parameters are paleobathymetry and sediment thickness defined by seismic surfaces. In this case study, the model could not be calibrated unless three sediment input points were chosen, as demonstrated independently from detrital petrology studies. Predefining certain modeling parameters generally reduces computational time. Unconstrained models offer a first overview of the probable architecture of the basin, and are a useful tool which can reduce the overall computation time of the modeling process and give insight into sedimentation patterns.

The Labrador Current (LC) provides freshwater from the Arctic to the North Atlantic, modulating the Atlantic Meridional Overturning Circulation (AMOC), and therefore affecting the broader North Atlantic climate. The Holocene alongflow variability of the LC vigor, and the associated forcing mechanisms, are poorly understood due to the limited data near the southern limit of the LC. Here we present a new 9.4 ka record of distal LC vigor over the Scotian Shelf using the sortable-silt proxy, which allows for the first time an assessment of the alongflow changes in Holocene LC vigor and hence its forcing mechanisms. LC speed on the Scotian Shelf decreased slightly from 9.4 to 8.0 ka, during which the 8.1 ka meltwater event had a strong influence. The LC progressively intensified from 8.0 to 5.0 ka, weakened between 5.0 and 1.8 ka and gradually intensified from 1.8 to 0.5 ka. Our synthesis reveals that the Holocene flow history of the LC appears geographically variable due to the interaction of the inner and outer LC. The mean size of the sortable silt data on the Scotian Shelf involve inner or outer LC signals in different periods of the Holocene. The LC vigor on the Scotian Shelf between 9.4–8.0 ka and 1.8–0.5 ka represent the outer LC, which is consistent with the stronger West Greenland Current and increased influx of Atlantic-sourced water to the outer LC. We find a broad agreement between inner LC vigor and AMOC-related sea surface temperature (SST) of the subpolar North Atlantic and the North Atlantic Oscillation (NAO), which suggests that a strong (weak) inner LC is generally associated with regional warm (cold) climate and negative (positive) NAO. The outer LC vigor is dominated by the NAO during the Holocene and partly controlled by freshwater supply between 10.0 and 5.0 ka. We also demonstrate the negative/positive link between the inner/outer LC vigor and the NAO on a millennium time scale. This study improves our understanding of LC variability and sensitivity to anthropogenic warming, and suggest that inner (outer) LC vigor may experience not only a decreasing (increasing) trend in a future warmer climate, with additional effects resulting from enhanced melting of the Greenland ice sheet.

The provenance of detrital quartz is a useful predictor in frontier basin sandstone reservoirs of the availability of coarse-grained quartz grains of plutonic or high grade metamorphic origin. The standard approach is to use scanning electron microscope (SEM) panchromatic cathodoluminescence (CL) imagery and observations from an optical petrographic microscope. We describe a work flow, modified from previous literature proposals, to determine quartz provenance in detrital grains using optical petrographic microscopy and CL properties from both a hot-cathode cathodoluminescence microscope attachment (HCMA) and panchromatic SEM-CL. HCMA analysis permits better discrimination of different types of metamorphic quartz. This method is applied to a Middle Jurassic to Lower Cretaceous section in the Bandol-1 wildcat well, located in the Laurentian sub-basin south of Newfoundland. Two types of high-grade metamorphic quartz are distinguished, one with low luminescence as described in previous literature and one with medium blue CL colour and a moderate colour shift that is also known from granulite in the hinterland. Three phases of detrital supply are identified, suggesting progressive unroofing of higher grade metamorphic sources through the middle Jurassic and major input of plutonic quartz in the early Cretaceous.

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.

Latest Devonian (∼365–358 Ma) A-type granites in the Cobequid Highlands host complex sequences of rare-earth element (REE) and other hydrothermal minerals. The West Moose River pluton is the only pluton truncated and brittly deformed by the mid-Carboniferous (∼327 Ma) strike-slip Minas Fault Zone during the Alleghanian orogeny. Fractures in the granite provide a record of several deformational and hydrothermal events with distinct mineral assemblages. Early sodic alteration produced albitization of feldspar, and riebeckite and tourmaline veins. The δ18O of albite and albitized granite (5‰–6‰) is similar to other regional granites, suggesting a mantle source of albitizing fluids. Nearby halite deposits are younger and thus not a source of Na. Early chlorite veins were followed by potassic alteration and hydrothermal biotite, and by diabase and lamprophyre dyke emplacement. Euhedral magnetite occupies new cross-cutting fractures and vugs, correlated with regional iron oxide – carbonate – sulphide mineralization following initiation of the Minas Fault Zone. This change in stress field resulted in widespread fracturing of the granite, greatly increasing its permeability. Magnetite is postdated by titania minerals with hydrothermal REE minerals in dissolution voids. The spatial variation in REE mineral types indicates variable availability of F, Cl, and CO2 in mineralizing fluids derived from groundwater. REE mineralization is rare in veins in country rock, demonstrating local plutonic sources of REEs. The emplacement of REE minerals was complex in time and space and was a consequence of pervasive microfracturing of the granite.

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.

Small appinite plutons ca. 610 Ma outcrop in the peri-Gondwanan Avalon terrane of northern Nova Scotia, with different structural levels exposed. Field mapping shows that the Jeffers Brook pluton is a laccolith emplaced along an upper crustal thrust zone, likely in a dilational jog in a regional dextral strike-slip system. The oldest rocks are probably mafic sills, which heated the area facilitating emplacement of intermediate magmas. Cross-cutting relationships show that both mafic and intermediate magmas were supplied throughout the history of pluton emplacement. The modal composition, mineral chemistry, and bulk chemistry of gabbro, diorite, tonalite, granodiorite, and granite have been studied in the main plutonic phases, dykes, and sills, and mafic microgranular enclaves. As with the type appinites in the Scottish Caledonides, the pluton shows evidence of high water content: the dominance of hornblende, locally within pegmatitic texture; vesicles and irregular felsic patches in enclaves; and late aplite dykes. Analyzed mafic microgranular enclaves are geochemically similar to larger diorite bodies in the pluton. Tonalite–granodiorite is distinct from the diorite in trace-element geochemistry and radiogenic isotopes. Elsewhere to the east, similar rocks of the same age form vertically sheeted complexes in major shear zones; hornblende chemistry shows that they were emplaced at a deeper upper crustal level. This implies that little of the observed geochemical variability in the Jeffers Brook pluton was developed within the pluton. The general requirements to form appinites are proposed to be small magma volumes of subduction-related magmas that reach the upper crust because of continual heating by mafic magmas moving through strike-slip fault pathways and trapping of aqueous fluids rather than venting through volcanic activity.