Submarine Canyons Research Articles

Foraminiferal insights into the complexities of the turbidity currents triggered by the 2016 Kaikoura Earthquake, New Zealand

The 2016 Mw 7.8 Kaikōura Earthquake triggered simultaneous turbidity currents down ten submarine canyons along a 200 km stretch of the continental slope, east of New Zealand. They discharged into the abyssal Hikurangi Channel which flows >1500 km northwards along the trench floor as part of the Hikurangi Subduction Margin. One hundred and thirty-six foraminiferal samples from the 2016 turbidites and pre-turbidite sediment from 25 canyon/channel cores, collected during surveys 3 days, 2.5 and 8 months after the event, were used to provide insights into the complexities of these submarine gravity flows.Transport in the turbidity currents produced no significant additional breakage of foraminiferal tests, even when transported 650 km down channel. We conclude that highly variable planktic foraminiferal fragmentation index (FI) values indicate that test breakage in turbidite samples is primarily inherited from dissolution on the seafloor at their source area, which is often anomalously high because of lowered sediment pH as a result of the breakdown of the high organic carbon flux. All turbidite and pre-turbidite faunas have strong signatures of downslope displacement (presence of shallow-water benthics, size-sorted test distributions, low percentage of planktics). This is not surprising as all cores were taken in the canyon or channel floor pathways to collect turbidite sequences, with turbidity flows estimated to have a recurrence time of ∼150 yrs. Pre-turbidite faunas can be distinguished from the 2016 turbidites' faunas by having greater percentage of planktics and lower ratios of shallow to deep benthic tests (S/D Index). 210Pb profiles show that the laminated pre-turbidite sediment accumulated slowly and the foraminiferal content indicates it is composed of reworked earlier turbidite sediment with the addition of contemporaneous deep-water benthic tests and the rain of planktic tests mixed in.There are no consistent trends in any foraminiferal faunal parameters with distance displaced in the turbidity current (10–650 km). Rather, intra-turbidite (10–75 cm thick) faunal variability in a single core is often considerable and is attributed to erosion and entrainment of deep-seafloor tests by the passage of turbulent turbidity current heads, variable source canyon depths, different source canyon provenances, and test-size sorting during transport and deposition resulting in vertical and longitudinal fractionation of the smallest tests and finest sediment.This study suggests that a single foraminiferal fauna is often, but not always, insufficient to characterise a turbidite or for use in correlation with turbidites in other cores or exposures.

Diversity, structure and spatial distribution of megabenthic communities in Cap de Creus continental shelf and submarine canyon (NW Mediterranean)

The continental shelf and submarine canyon off Cap de Creus (NW Mediterranean) were declared a Site of Community Importance (SCI) within the Natura 2000 Network in 2014. Implementing an effective management plan to preserve its biological diversity and monitor its evolution through time requires a detailed characterization of its benthic ecosystem. Based on 60 underwater video transects performed between 2007 and 2013 (before the declaration of the SCI), we thoroughly describe the composition and structure of the main megabenthic communities dwelling from the shelf down to 400 m depth inside the submarine canyon. We then mapped the spatial distribution of the benthic communities using the Random Forest algorithm, which incorporated geomorphological and oceanographic layers as predictors, as well as the intensity of the bottom-trawling fishing fleet. Although the study area has historically been exposed to commercial fishing practices, it still holds a rich benthic ecosystem with over 165 different invertebrate (morpho)species of the megafauna identified in the video footage, which form up to 9 distinct megabenthic communities. The continental shelf is home to coral gardens of the sea fan Eunicella cavolini, sea pen and soft coral assemblages, dense beds of the crinoid Leptometra phalangium, diverse sponge grounds and massive aggregations of the brittle star Ophiothrix fragilis. The submarine canyon off Cap de Creus is characterized by a cold-water coral community dominated by the scleractinian coral Madrepora oculata, found in association with several invertebrate species including oysters, brachiopods and a variety of sponge species, as well as by a community dominated by cerianthids and sea urchins, mostly in sedimentary areas. The benthic communities identified in the area were then compared with habitats/biocenoses described in reference habitat classification systems that consider circalittoral and bathyal environments of the Mediterranean. The complex environmental setting characteristic of the marine area off Cap de Creus likely produces the optimal conditions for communities dominated by suspension- and filter-feeding species to develop. The uniqueness of this ecosystem and the anthropogenic pressures that it faces should prompt the development of effective management actions to ensure the long-term conservation of the benthic fauna representative of this marine area.

Morpho-Structural Setting of the Ligurian Sea: The Role of Structural Heritage and Neotectonic Inversion

The review of recent bathymetric and geophysical data collected in the framework of several research and cartographic projects have allowed a detailed reconstruction of the morpho-structural setting and the (neo)tectonic evolution for both the Alpine and Apennine margins of the Ligurian Sea (Italy). The widespread occurrence of erosional processes and sediment mass movements along the steep continental slope and within the system of submarine canyons reflect the close correlation between the active tectonics and the recent morpho-dynamic evolution of the Ligurian Margin. This relation is better constrained in the western sector (Alpine) of the Ligurian Sea, where the recent uplift of the continental margin is associated to a well-developed system of inherited structures reactivated under a compressive/transpressive regime and widespread seismicity. In the eastern sector, where the seismicity is lower or absent, the mass movements are limited to few areas (e.g., the Portofino slope) coinciding with seismic clusters. Additionally, this sector is characterized by moderate and episodic fault reactivations under a compressive regime. The evidence of compressive deformation along the inherited fault systems has been revealed in some areas of the Ligurian Sea where the post-drifting extensional tectonics is interrupted by episodic tectonic inversion (at least) during the Middle–Upper Miocene and the Plio–Pleistocene until present.

Fatty acid biomarkers as indicators of organic matter origin and processes in recent turbidites: The case of the terminal lobe complex of the Congo deep-sea fan

The Congo River is connected to its submarine canyon and supplies large quantities of terrestrial organic carbon via powerful turbiditic currents down to the Congo deep-sea fan. We investigated sediment cores from the terminal lobe complex of the Congo deep-sea fan (∼750 km offshore, ∼5000 m water depth), in order to assess the value of fatty acid biomarkers as indicators of organic matter (OM) origin and processes affecting its distribution and preservation in recent turbidites. Sediments from the Congo deep-sea fan are enriched in fatty acids compared to the surrounding abyssal plains and their composition closely resembles that of sediments recovered in the Congo River. Long chain fatty acid (LCFA) biomarkers in conjunction with the branched vs isoprenoid tetraether index (BIT) show that OM mostly originates from soil erosion and continental higher plants. This material has undergone limited reprocessing during transit certainly due to tight interactions with mineral particles and rapid transfer. The presence of phytoplankton biomarkers at the entrance of the terminal lobe area highlights that inputs of fresh OM, albeit limited, can reach the lobe complex. By combining fatty acid profiles and geochemical proxies in a multivariate analysis, we highlight that OM degradation is mostly limited to the oxic layer, and that fine soil-derived particles and the coarser higher plant detritus display distinct depositional dynamics. Finally, LCFA are remarkably well preserved under anoxic conditions at different time scales, in recent turbidites deposited during the last century and those deposited several thousand years ago.

Deep-water Tectono-Stratigraphy at a Plate Boundary Constrained by Large N-Detrital Zircon and Micropaleontological Approaches: Peninsular Ranges Forearc, Baja California, Mexico

The distribution of sedimentary systems on Earth’s surface is intimately linked to tectonics, therefore, at plate boundaries the stratigraphic archive can unlock the timing and style of tectonism and relative plate motions. Using large-n detrital zircon and micropaleontological analyses, tied to field mapping and data collection, we unravel the timing of strike-slip motion and its influence on the development of a Cretaceous submarine canyon on a long-lived oblique-convergent margin. Structural analysis demonstrates that the canyon bedrock, composed of fluvial rocks (La Bocana Roja Fm., of maximum depositional age (MDA): 93.6±1.1 Ma), underwent both syn- and post-depositional contractional and extensional deformation during the Cenomanian-Turonian in response to dextral strike-slip movement. Relative sea-level rise associated with basin subsidence and hinterland uplift was coincident with incision and fill of a submarine canyon system (Punta Baja Fm., MDA 87.1±1.5 Ma to 84.9±2.0 Ma), which exploited structural lineaments in the bedrock. The canyon was filled by sediment derived from an uplifted magmatic arc during the Coniacian to Santonian, most likely shed from erosional topography associated with plutonic intrusions to the NE. Structural data suggest that oblique dextral strike-slip motion on the Pacific margin controlled the development and location of submarine erosion, and had ended by the earliest Santonian, significantly earlier than previously estimated. Basinward tilting led to uplift, followed by transgression and wave ravinement of the canyon fill, which was then overlain by a shallow-marine to fluvial system. Thus, the canyon was cut, filled, buried, uplifted and rotated basinward, planed off through wave ravinement, and onlapped by shallow-marine to fluvial sediments within an 8 Myr period. Our findings, in part, reconcile contrasting basin evolution models for the Late Mesozoic Pacific margin.

Foraminiferal evidence for the provenance and flow history of turbidity currents triggered by the 2016 Kaikōura Earthquake, New Zealand

ABSTRACT The 2016 Mw 7.8 Kaikōura Earthquake triggered simultaneous turbidity currents down ten submarine canyons along a 200 km stretch of the continental slope, east of New Zealand. Some discharged into the Hikurangi Channel which flows >1500 km northwards along the abyssal trench floor. To better understand provenance continuity in deep-sea sedimentary records, foraminiferal samples from the 2016 turbidites from 17 canyon and channel cores were used to investigate the source histories of these submarine gravity flows. Cluster analyses suggest the canyon provenances for most 2016 turbidite faunas should be determinable using a combination of the relative abundance of key benthic genera, planktic foraminiferal index (dissolution), absolute test abundance and planktic % of the foraminiferal faunas. Two ordinations (PCA, PCO) based on these parameters were used to infer provenance and flow history. One hundred kilometres down the Hikurangi Channel, faunas in the 2016 turbidite confirm a Kaikōura Canyon source. Further downstream, 200–500 km north of the confluence with Campbell, Cook and Opouawe canyons, faunas indicate that the 2016 turbidite in the northern Hikurangi Channel is a composite deposit, from an initial Opouawe-Cook canyon-sourced turbidity current over-ridden and partly mixed with, a Kaikōura Canyon-sourced flow that arrived sometime later.

Example of Coastline Changes from the Last Glacier Maximum to the Present: Çanakkale Strait

Climate change emerges as an important problem for the earth today. Although the negative effects of this problem are not directly reflected in the time we live in, it is revealed by the scientists working on the subject that it will be observed in human life for decades-centuries and will be observed in detail on the earth for thousands of tens of thousands of years later. This predicted climate change can be considered a normal situation when considering the time that has passed from the formation of the earth to the present, approximately 4.5 billion years (except that the difference between the reasons for climate changes in the past geological times and the predicted climate change is the human effect). The effects of Quaternary climate change can be observed on the earth both on a global scale and on a regional scale. As an example of global climate change, the continuous change of sea level can be given, and the best indicators of this change are geological/geomorphological structures such as marine terraces or submarine canyons observed on the coasts on the regional scale. On the local scale, stalactites and stalagmites observed in caves, lake sediments, deep sea sediments, glacial cores are among the best examples of climate change. In this study, the land-sea boundary (coastal line) changes of the coasts of the Çanakkale Strait, which is the southern branch of the Turkish Straits System, have been investigated, considering the sea level changes that show the climate change best in the last 25 thousand years. In this context, the coastal changes of the Çanakkale Strait coasts from the Late Pleistocene to the present are modeled using geographic information systems programs, by using different global and regional sea level change charts showing climate changes. The most striking of these new maps is the one from 20 thousand years ago. At this time, it is known that the global sea level is 120 meters lower than today and the deepest point of the Çanakkale Strait is around -113 meters today. Therefore, it is not possible to mention a Mediterranean-Black Sea waterway connection through the Çanakkale Strait at these times.

Longest sediment flows yet measured show how major rivers connect efficiently to deep sea

Here we show how major rivers can efficiently connect to the deep-sea, by analysing the longest runout sediment flows (of any type) yet measured in action on Earth. These seafloor turbidity currents originated from the Congo River-mouth, with one flow travelling >1,130 km whilst accelerating from 5.2 to 8.0 m/s. In one year, these turbidity currents eroded 1,338-2,675 [>535-1,070] Mt of sediment from one submarine canyon, equivalent to 19–37 [>7–15] % of annual suspended sediment flux from present-day rivers. It was known earthquakes trigger canyon-flushing flows. We show river-floods also generate canyon-flushing flows, primed by rapid sediment-accumulation at the river-mouth, and sometimes triggered by spring tides weeks to months post-flood. It is demonstrated that strongly erosional turbidity currents self-accelerate, thereby travelling much further, validating a long-proposed theory. These observations explain highly-efficient organic carbon transfer, and have important implications for hazards to seabed cables, or deep-sea impacts of terrestrial climate change.

Trench floor depositional response to glacio-eustatic changes over the last 45 ka, northern Hikurangi subduction margin, New Zealand

ABSTRACT Glacio-eustatic cycles lead to changes in sedimentation on all types of continental margins. There is, however, a paucity of sedimentation rate data over eustatic sea-level cycles in active subduction zones. During International Ocean Discovery Program Expedition 375, coring of the upper ∼110 m of the northern Hikurangi Trough Site U1520 recovered a turbidite-dominated succession deposited during the last ∼45 kyrs (Marine Isotope Stages (MIS) 1–3). We present an age model integrating radiocarbon dates, tephrochronology, and δ18O stratigraphy, to evaluate the bed recurrence interval (RI) and sediment accumulation rate (SAR). Our analyses indicate mean bed RI varies from ∼322 yrs in MIS1, ∼49 yrs in MIS2, and ∼231 yrs in MIS3. Large (6-fold) and abrupt variations in SAR are recorded across MIS transitions, with rates of up to ∼10 m/kyr occurring during the Last Glacial Maximum (LGM), and <1 m/kyr during MIS1 and 3. The pronounced variability in SAR, with extremely high rates during the LGM, even for a subduction zone, are the result of changes in regional sediment supply associated with climate-driven changes in terrestrial catchment erosion, and critical thresholds of eustatic sea-level change altering the degree of sediment bypassing the continental shelf and slope via submarine canyon systems.

The return of the Iváň Canyon, a large Neogene canyon in the Alpine-Carpathian Foredeep

The submarine Iváň Canyon oriented parallel along the front of the Western Carpathian fold and thrust belt and the foreland of the Bohemian Massif has been studied on numerous 2D seismic sections and available borehole cores. The canyon can be followed over the distance of more than 75 km indented within the sedimentary infill of the Alpine-Carpathian Foredeep from Lower Austria into the Czech Republic. Seismic data reveal up to 600 m depth of the canyon and its width of 2.5–6 km. The canyon is characterized by a low sinuosity planform architecture with an axial main channel and several tributary channels of varying dimensions. Six seismic facies were identified, separated by three erosional surfaces, which led to recognition of seven evolutional stages of the canyon.Facies analysis, clast composition and heavy mineral spectra indicate derivation from a siliciclastic source area, cannibalization of an older basin infill and an important role of sustained low-density turbidity currents in transport and deposition. The strontium isotope stratigraphy data supported by microbiostratigraphy and by foraminiferal δ18O and δ13C isotope analysis confirmed, that the depositional history of the canyon infill lasted from the upper Burdigalian/Langhian boundary up to the lower Serravalian, with the dominance of Langhian deposits in its infill.The formation and depositional history of the canyon is explained by the complicated structural and depositional history of the Alpine-Carpathian Foreland basin during the lower/middle Miocene transition and middle Miocene (Langhian) with a dominant role of tectonic subsidence and basin re-configuration accompanied by eustatic sea-level fluctuations. The Iváň Canyon as axial channel developed in the elongate foreland basin reveals several differences if compared to typical ancient submarine canyons in the passive margin settings.

Giant deep submarine depressions: A combined dissolution-mechanical process along carbonate margins

AbstractSubmarine depressions are common features on the eastern Bahamian seafloor but the genesis of the deepest ones (&amp;gt;4000 m in water depth) is not well understood. We conducted a morphometric analysis and compared them to a worldwide database of rounded depressions, whatever their genesis is. The deep Bahamian depressions are large elongated structures, among the largest on Earth, with a width greater than 1000 m and a depth sometimes greater than 200 m. They extend at the toe of the Blake Bahama Escarpment (BBE), one of the tallest escarpments on Earth. Some of them align parallel to the BBE. Other depressions align along large submarine canyon axes. When aligned along canyon axes, the depressions closest to the canyon head are flanked by a topographic high interpreted as a slope-break deposit, i.e., sediment deposited after flow expansion following a hydraulic jump. Turbidity currents in the carbonate canyon system are not permanent processes, but are rather triggered during sea-level highstands when the carbonate platform is flooded. In addition, some depressions are not located in canyon axes. Consequently, the size and location of the depressions are not likely explained by a simple plunge pool mechanical erosion. Rather, our data suggest that all depressions could be initiated by giant karstic dissolution structures (dolines or sinkholes). Under interpretation, those located in canyon axes are sporadically refreshed by carbonate-laden turbidity currents. The height of the outsized chutes marking the crossing of the BBE by the canyon mouth generates a hydraulic jump allowing sediment deposition toward the bottom of the depression. Large depressions observed at this location in the Bahamas were the result of an initial dissolution phase related to retreat of the BBE and the more recent sediment-laden flow activity. The depressions orientated along canyon axes facilitated the regressive erosion that formed the canyons. At present, the depressions located at canyon mouths act as regular plunge pools.

Diurnal Coastal Trapped Waves and Associated Deep‐Ocean Mixing Near the Head of Suruga Trough

AbstractCoastal submarine canyons are expected to be sites of enhanced turbulent mixing which create productive fishing areas in coastal waters. Recent studies suggested the potential role of diurnal coastal trapped waves (CTWs) in inducing significant turbulent mixing in coastal submarine canyons poleward of 30° where the diurnal tide becomes subinertial. Nevertheless, the detailed physical processes responsible for the generation and dissipation of CTWs in such submarine canyons have hardly been investigated so far. In the present study, to investigate the turbulent mixing processes associated with diurnal CTWs in submarine canyons, we carry out high‐resolution (Δx, Δy = 1/240°) non‐hydrostatic three‐dimensional numerical experiments focusing on Suruga Bay located at the north end of Suruga Trough, Japan. The numerical experiments show that diurnal (subinertial) tidal currents over the Izu Ridge generate CTWs which propagate cyclonically along the coast of Suruga Bay. In the middle of Suruga Bay, bottom‐intensified flow due to the diurnal CTWs interacts with rough seafloor topography to excite upward propagating internal lee waves, which create mixing hotspots extending high above the seafloor. The resulting diurnal (subinertial) tidal energy dissipation in Suruga Bay is found to be much larger than that associated with semidiurnal (superinertial) internal tides. Furthermore, it is found that baroclinic energy flux based on a simple barotropic‐baroclinic decomposition severely underestimates the wave energy flux in areas with high CTW activity. These results strongly indicate that the existence of CTWs might be a key factor to clarify the dissipation/mixing processes in submarine canyons.

Triggers in science communication: “The Nazaré Wave: A trigger for learning”

Meeting current coastal and ocean sustainability challenges requires wiser governance. Scientists, as knowledge generators, have the responsibility to contribute to a more informed society, which in turn will be able to support better decisions. However, inspiring the audience and assuring their receptivity to often complex scientific message is not a trivial task, particularly when the importance of the topic is not part of people's everyday life. This is the case of shelf-incised submarine canyons, which usually go unnoticed as they are “hidden” by the sea. This work aims to highlight how the use of an adequate communication trigger was effective in capturing the attention of a non-scientific audience to canyon and shelf processes. The study is supported by an outreach project: “The Nazaré Wave: a trigger for learning”. The Nazaré Wave is the highest wave ever surfed that became a very popular subject capturing extraordinary media coverage. Results show that selecting the adequate communication trigger effectively boosts scientific knowledge transfer and raised the predisposition conditions for the audience to be receptive to non-trivial ocean-related scientific topics. “The Nazaré Wave: a trigger for learning” revealed to be a highly successful initiative and similar strategies may be adopted in other projects aiming at increasing coastal and ocean literacy. The relevance of findings and outcomes of this study are especially relevant at the time marking the onset of the United Nations Decade of Ocean Science for Sustainable Development, which acknowledges ocean literacy as a key pillar of global development.

The roles and seismic expressions of turbidites and mass transport deposits using stratigraphic forward modeling and seismic forward modeling

• Mass transport is more efficient than turbidity current in forming submarine canyons . • Turbidites are inside the river-fed systems as jigsaw puzzle geometries vertically. • MTDs are not constrained by river-fed systems and tend to occur in the bottom. • MTDs have chaotic or transparent seismic facies with irregular, massive thick shapes. • Turbidites have high amplitude seismic facies with sheet, mound or channel shapes. Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions. The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multi-process and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability. Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelf-incised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.

How do tectonics influence the initiation and evolution of submarine canyons? A case study from the Otway Basin, SE Australia

The architecture of canyon-fills can provide a valuable record of the link between tectonics, sedimentation and depositional processes in submarine settings. We investigated the role of plate tectonics in the initiation and evolution of submarine canyons. We demonstrate that events at the plate tectonic scale (i.e. continental break-up and shortening) have a first-order influence on the initiation and development of submarine canyons. The Late Cretaceous ( c. 65 Ma) separation of Australia and Antarctica initially resulted in extensional fault systems, which then formed a steep stair-shaped palaeoseabed. Subsequently, the Late Miocene ( c. 5 Ma) collision of Australia and Eurasia resulted in substantial uplift and exhumation on the SE Australian continental margin. These tectonic events led to elevated seismicity, which ultimately gave rise to gravity-driven processes (i.e. turbidity currents and mass wasting processes) and formed the base of the canyon. The inherited stair-shaped topography then facilitated further gravity-driven processes that established a mature sediment conduit extending from the shallow marine shelf to the abyssal plain. We suggest that the stratigraphic architecture of canyons can be used as an archive to record tectonic movements. Moreover, the factors that precondition and trigger gravity-driven processes can induce canyon initiation and facilitate canyon development. Supplementary material: A PDF file containing all the clean, uninterpreted seismic sections is available at https://doi.org/10.6084/m9.figshare.c.5937760

Depositional Controls on Detrital Zircon Provenance: An Example From Upper Cretaceous Strata, Southern Patagonia

Understanding how depositional environments within a sedimentary system redistribute and sequester sediment is critical for interpreting basin-scale provenance trends. However, sedimentary source-to-sink models commonly examine temporal changes and do not consider how variation in sedimentation processes across a dispersal pathway may result in contrasting provenance signatures. In this paper, we demonstrate a down-paleoslope shift in detrital zircon provenance signatures correlated with shallow-marine lithofacies patterns from the Upper Cretaceous La Anita Formation and underlying continental slope lithofacies of the Alta Vista Formation (Magallanes-Austral Basin, southern Patagonia). New stratigraphic, sedimentologic, and lithofacies analysis results from the La Anita Formation suggest an upward shoaling succession, from a 1) storm-influenced shoreface, 2) fluvially dominated, wave-influenced delta, and a 3) high-energy, gravelly foreshore. Stratigraphic sections are paired with U-Pb detrital zircon sandstone samples (N = 20; n = 5,219), which provide both maximum depositional ages and provenance characteristics. While all samples contain abundant zircon derived from the Andean volcanic arc (ca. 145–75 Ma), the amount from both Jurassic distal volcanic massifs (ca. 188–162 Ma) and recycled orogenic sources exhumed during the advance of the Cretaceous fold-and-thrust belt (&amp;gt;200 Ma; 157–142 Ma) vary with changes in depositional environment. We argue that down-paleoslope, systematic enriching of local fold-and-thrust belt material within the La Anita Formation is reflective of progressive mixing of grains transported via shallow-marine processes, while distally enriched fluvio-deltaic transported zircons were sourced from large, regional catchments. This suggests that competition between transport processes across a shallow and marginal marine sequence of rocks affects the resulting provenance signatures recorded within a single stratigraphic succession. These data also detail the degree of sediment pathway connectivity between shallow-marine sources and deep-marine sinks. Detrital zircon results from muddy continental slope facies of the Alta Vista Formation are made up entirely locally derived material, while zircon results from deep-water, sand-rich channel facies of the Formation are indistinguishable from coeval fluvio-deltaic zircon signatures. This implies that continental shelf-to-slope connectivity in a sediment dispersal system, via submarine canyons or shelf-edge delta progradation, is necessary for detrital zircon distributions from the shallow-marine realm to propagate into the deeper marine.

Tectonostratigraphic evolution of the Sohar Basin, exploration concepts and emerging plays offshore on the UAE's east coast

The Sohar Basin, located offshore the East Coast of the Arabian Peninsula, is an area that has seldom been the focus of international oil companies. While all commercial discoveries in the UAE and Oman have been made to the west and south of the Oman Mountains, the Sohar Basin is underexplored and remains prospective. This lack of activity is primarily because the Thamama reservoir, which has yielded huge success to the west of the Oman Mountains is likely not present within the Sohar Basin. However, potential traps, reservoirs, and source rocks are present within the Tertiary succession. The Sohar Basin formed in the late Cretaceous after the obduction of the Semail Ophiolite onto the Arabian Plate. Following a period of tectonic quiescence, which lasted until the Early Eocene, the gravitational collapse occurred along the eastern edge of the present-day Oman Mountains.Interpretation of both 2D and 3D seismic reveals that the subsurface is comprised of three tectonostratigraphic units, defined as pre-, syn-, and post-tectonic packages. North-South trending thrust faults generate distinct mini-basins within the pre- and syn-tectonic sequences. The post-tectonic sequence is defined by the development of prograding systems in a tectonically quiescent margin formed in the Lower Miocene and which persists to the present day. Deep-water depositional systems dominate the undrilled far-east and south of the basin where the presence of submarine canyon systems and associated basin floor fans is supported by 3D seismic data. In recent times, the Sohar Basin has been subject to extensional faulting likely driven by sediment load caused by a prograding delta system.The results of this work reveal that multiple untested play types exist within the Sohar Basin, which are comprised of both structural and stratigraphic elements. This paper integrates both a structural and sequence stratigraphic interpretation to provide insights into the tectonostratigraphic evolution of the Sohar Basin. Consequently, the fundamentals of play fairway mapping have been employed to unlock the hydrocarbon prospectivity offshore the UAE's East Coast.

Morphosedimentary characterization of the Capbreton submarine canyon system, Bay of Biscay (Cantabrian Sea)

Various studies have been carried out to the declaration of new marine protected areas for their importance for habitats, according to the Natura 2000 Network. One of these sites is a sector of the Capbreton Submarine Canyon System, located in front of the Basque Country coast, in the Bay of Biscay (North Atlantic). During the Intemares_CapBreton 0619 and 0620 surveys; bathymetric, backscatter, high-resolution parametric data and samples of sediments, rocks and benthic communities from the seabed were acquired. The study was completed by recording video transects with the underwater vehicle ROTV Politolana from the IEO. The processing and analysis of the geophysical information has allowed obtaining a detailed bathymetry grid of 10 × 10 m, from which the first morphosedimentary characterization of the system of tributary canyons to the E-W trending main canyon and its interfluves has been made. One of the main features of this canyon system is the presence of a large pockmark field on adjacent platforms between canyons, located between 500 and 1000 m water depth. Within this field, pockmarks are shown as circular to elliptical depressions, most likely related to gas rich-fluid emissions to the subsurface.

A new octocoral species of Swiftia (Holaxonia, Plexauridae) from the upper bathyal off Mauritania (NE Atlantic).

Three species of the genus Swiftia are known for the NE Atlantic Ocean and Mediterranean Sea. Remotely-operated vehicle (ROV) surveys and sampling on board RV Maria S. Merian during cruise MSM 16/3 'PHAETON' in 2010 provided footage and specimens of octocorals off Mauritania. Micro-computed tomography (micro-CT) reveals, for the first time in taxonomy of octocorals, the three-dimensional arrangement of the sclerites in a polyp. Swiftiaphaeton sp. nov. is described for the continental slope off Mauritania. This azooxanthellate octocoral is distinctive from NE Atlantic and Mediterranean congenerics by the dark red colour of the colonies (including the polyps), the presence of a layer of rod sclerites on top of the polyp mounds, and different sizes of polyps and sclerites. Using micro-CT has allowed the observation and imaging of a layer of sclerites that is distinct from other species of the same genus. ROV images revealed live records of S.phaeton sp. nov. in submarine canyons and on cold-water coral mounds in the upper-bathyal off Mauritania (396-639 m depth), mainly attached to dead coral, coral rubble, or rocks. The new species represents an extension of the genus distribution to the tropical latitudes (17°07'N and 20°14'N) of the NE Atlantic Ocean.

A Cycle of Wind-Driven Canyon Upwelling and Downwelling at Wilmington Canyon and the Evolution of Canyon-Upwelled Dense Water on the MAB Shelf

Submarine canyons provide a conduit for shelf-slope exchange via topographically induced processes such as upwelling and downwelling. These processes in the Wilmington Canyon, located along the shelf-break of the Mid-Atlantic Bight (MAB), have not been previously studied, and the associated hydrographic variability inside the canyon and on the adjacent shelf are largely unknown. Observations from an underwater glider deployed in Wilmington Canyon (February 27 - March 8, 2016), along with wind and satellite altimetry data, showed evidence for a wind-driven canyon upwelling event followed by a subsequent downwelling event. Next, a numerical model of the MAB was developed to more fully represent these two events. Modeled results showed that under upwelling-favorable winds during February 25 - March 3, sea level increased seaward, shelf currents flowed northeastward, and canyon upwelling developed. Then under downwelling-favorable winds during March 4-7, sea level increased landward, shelf currents flowed southwestward, and canyon downwelling developed. Modeling experiments showed that canyon upwelling and downwelling were sub-tidal processes driven by winds and pressure gradients (associated with SSH gradients), and they would occur with or without tidal forcing. During the upwelling period, slope water originating from 150-215 m depths within the canyon (75 m below the canyon rim), was advected onto the shelf, forming a cold and dense canyon-upwelled slope-originated overflow water at the bottom of the outer shelf (75-150 m isobaths). The dense overflow current flowed was directed northeastward and expanded in the cross-shelf direction. It was 5-20 km wide and 10-30 m thick. The estimated volume of the plume overflow water exceeded 6×109 m3 at peak. The density front at the shoreward side of the dense overflow water caused a subsurface baroclinic frontal jet, which flowed northeastward and along-shelf with maximum speed exceeding 0.5 m/s. In the ensuing downwelling event, a portion of the previously upwelled dense water was advected back to the canyon, and then flowed down-slope in the upper canyon in ~0.3 m/s bottom-intensified currents. Dynamical investigation of the overflow current showed that its evolution was governed by unbalanced horizontal pressure gradient force in the cross-shelf direction and that the current was geostrophic.