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[Example of collonade and entablature cooling joints within a ponded lava of the Rosebank Field Upper Volcanics revealed by formation microimager log data alongside a field analogue example from the Isle of Staffa. , Abstract The Rosebank Field is located in the Faroe‐Shetland Basin and hosts hydrocarbons within siliciclastic sediments interlayered with volcanic packages of the Late Paleocene to Early Eocene aged Flett Formation. Within this study the volcanic sequences are investigated based on an integrated appraisal of available drill cuttings, sidewall cores, core and wireline logs including image log and geochemical logs from eight wells supported by 3D seismic data. The Rosebank lower (RLV), middle (RMV) and upper (RUV) volcanic sequences are inter‐layered with Colsay Member (C1–C4) fluvial to shallow marine siliciclastic intervals. A comprehensive cross‐field borehole based lithofacies interpretation is presented characterising simple, compound and ponded effusive lava flow facies along with pillow lavas, invasive lava flows, volcaniclastic sediments and complex lava–sediment interactions. Geochemical analyses of core, sidewall core, and hand‐picked cuttings spanning the field reveal separate high‐titanium (RHT) and relatively lower‐titanium (RLT) basaltic magma suites. These compositions can be identified and correlated across much of the field utilising geochemical logging data which, in combination with the geochemical analyses, reveals a two‐part stratigraphic sub‐division of each of the RLV, RMV and RUV. Geochemical logging data is also used to define a volcanic proxy (Fe/10+Ti) which utilises the elevated iron (Fe) and titanium (Ti) within all effusive and volcaniclastic basaltic lithologies to differentiate siliciclastic from volcaniclastic sediments where other logging parameters overlap. By comparing the borehole analyses with seismic data, a localised eruptive vent is interpreted within the north of the field. Finally, a cross‐field volcanic model is presented and compared with relevant global field analogues, providing a constrained spatial framework for sub‐surface modelling of inter‐volcanic sequences.]

The flank failure and collapse of Anak Krakatau on December 22nd, 2018 triggered a destructive tsunami. Whether the prior activity of the volcano led to this collapse, or it was triggered by another means, remains a challenge to understand. This study seeks to investigate the recent volcano submarine mass-landslide deposit and emplacement processes, including the seafloor morphology of the flank collapse and the landslide deposit extent. Bathymetry and sparker seismic data were used during this study. Bathymetry data collected in August, 2019 shows the run-out area and the seafloor landslide deposit morphology. Bathymetry data acquired in May, 2017, is used as the base limit of the collapse to estimate the volume of the flank collapse. Comparisons between seismic data acquired in 2017 and 2019 provide an insight into the landslide emplacement processes, the deposit sequence, and structure below the seafloor. From these results we highlight two areas of the submarine-mass landslide deposit, one proximal to Anak Krakatau island (∼1.6 km) and one distal (∼1.4 km). The resulting analysis suggests that the submarine-mass landslide deposit might be produced by a frontally compressional, faulted, landslide, triggered by the critical stability slope, and due to the recent volcanic activity. Blocky seabed features clearly lie to the southwest of Anak Krakatau, and may represent the collapse blocks of the landslide. The seismic analysis of the data acquired in August, 2019 reveals that the blocky facies extends to ∼1.62 km in the width around Anak Krakatau, and the block thicknesses vary up to 70.4 m. The marine data provides a new insight into the landslide run out and extent, together with the landslide deposit morphology and structure that are not available from satellite imagery or subaerial surveys. We conclude that the landslide run out area southwest of the recent collapse, is ∼7.02 ± 0.21 km2.

Benthic organisms in marine ecosystems modify the environment on different spatial and temporal scales. These modifications, many of which are initially at a microscale, are likely to have large scale effects on benthic seascapes. This is especially so if the species are ecosystem engineers. Most species of infaunal and epifaunal invertebrates and macrophytes contribute at a geophysical or geochemical level. Microorganisms also play a key but currently neglected role. In the intertidal and immediately sublittoral zone, algae and seagrasses, and mussels in mussel beds have received considerable attention. A substantial fossil record also exists. Mathematical modelling of these systems is still in its infancy, although several sophisticated mathematical tools have been applied. The effects of bioturbation and of microorganisms have been less studied, and little is known about the activities of benthic organisms in the deep sea. This paper addresses all these effects, and places them in the context of large scale benthic seascapes and of the extensive literature on species defined as ecosystem engineers in the sea.

Abstract An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry of the La Jolla Canyon especially with respect to the pre-canyon host sediments. The floor of the axial channel is covered with unconsolidated sand similar to the sand on the shelf near the canyon head, lacks outcrops of the pre-canyon host strata, has an almost constant slope of 1.0° and is covered with trains of crescent shaped bedforms. The presence of modern plant material entombed within these sands confirms that the axial channel is presently active. The sand on the canyon floor liquefied during vibracore collection and flowed downslope, illustrating that the sediment filling the channel can easily fail even on this gentle slope. Data from the canyon walls help constrain the age of the canyon and extent of incision. Horizontal beds of moderately cohesive fine-grained sediments exposed on the steep canyon walls are consistently less than 1.232 million years old. The lateral continuity of seismic reflectors in minisparker profiles indicate that pre-canyon host strata extend uninterrupted from outside the canyon underneath some terraces within the canyon. Evidence of abandoned channels and point bar-like deposits are noticeably absent on the inside bend of channel meanders and in the subsurface of the terraces. While vibracores from the surface of terraces contain thin (

Abstract The exact location and depth of the deepest places in each of the world's oceans is surprisingly unresolved or at best ambiguous. Out of date, erroneous, misleading, or non-existent data on these locations have propagated uncorrected through online sources and the scientific literature. For clarification, this study reviews and assesses the best resolution bathymetric datasets currently available from public repositories. The deepest place in each ocean are the Molloy Hole in the Fram Strait (Arctic Ocean; 5669 m, 79.137° N/2.817° E), the trench axis of the Puerto Rico Trench (Atlantic Ocean; 8408 m 19.613° N/67.847° W), an unnamed deep in the Java Trench (Indian Ocean; 7290 m, 11.20° S/118.47° E), Challenger Deep in the Mariana Trench (Pacific Ocean; 10,925 m, 11.332° N/142.202° E) and an unnamed deep in the South Sandwich Trench (Southern Ocean; 7385 m, 60.33° S/25.28° W). However, discussed are caveats to these locations that range from the published coordinates for a number of named deeps that require correction, some deeps that should fall into abeyance, deeps that are currently unnamed and the problems surrounding variable and low-resolution bathymetric data. Recommendations on the above and the nomenclature and definition of deeps as undersea features are provided.

A new swath bathymetry compilation of the Gulf of Cadiz Area and SW Iberia is presented. The new map is the result of a collaborative research performed after year 2000 by teams from 7 European countries and 14 research institutions. This new dataset allow for the first time to present and to discuss the missing link in the plate boundary between Eurasia and Africa in the Central Atlantic. A set of almost linear and sub parallel dextral strike-slip faults, the SWIM Faults (SWIM is the acronym of the ESF EuroMargins project “Earthquake and Tsunami hazards of active faults at the South West Iberian Margin: deep structure, high-resolution imaging and paleoseismic signature”) was mapped using a the new swath bathymetry compilation available in the area. The SWIM Faults form a narrow band of deformation over a length of 600 km coincident with a small circle centred on the pole of rotation of Africa with respect to Eurasia, This narrow band of deformation connects the Gloria Fault to the Rif-Tell Fault Zone, two segments of the plate boundary between Africa and Eurasia. In addition, the SWIM faults cuts across the Gulf of Cadiz, in the Atlantic Ocean, where the 1755 Great Lisbon earthquake, M~8.5-8.7, and tsunami were generated, providing a new insights on its source location.

Todarodes sagittatus (N=1131) were opportunistically sampled from commercial and research trawling in Irish and Scottish waters between 1993 and 1998. The results suggest that the species is common in deep waters (>200 m) to the west of Ireland and Scotland, particularly in late summer and autumn. The size of squid caught was related to depth, with larger squid caught deeper, and is indicative of an ontogenetic, bathymetric migration. Females were more common (sex ratio 1·00:0·46), and attained a larger maximum size (520 mm mantle length (ML)) than males (426 mm ML). Mature females (360–520 mm ML) were caught in deep water (>500 m), between March and November, with a large catch of mature females taken off the west coast of Ireland in August 1996. Mature males (300–426 mm) were found from August to November. Potential fecundity was estimated to range from 205,000–523,500 eggs female−1. Putative daily increments in statoliths indicated a life cycle of slightly over a year, with rapid growth of approximately 1·8 mm d−1 during subadult and adult life. Fish were the most important prey of T. sagittatus and 17 fish prey taxa were identified, of which pelagic species were the most important.

High-resolution bathymetric data from the New Jersey and Californian continental margins show a marked depression running along parts of the base of the continental slope. Detailed analysis reveals that the depressions are a series of discrete ‘plunge pools’ with associated downslope topographic ramparts. We have used new bathymetric data to create our own data base (of over 150 examples) and systematically analyse plunge pool morphology and location. Previous observations of plunge pools have been sparse. Plunge pools are up to 1100 m wide and 75 m deep, with a mean diameter of 400 m and a mean depth of 21 m. Plunge pools only occur where there are sharp decreases in slope of more than 4°, and are well developed where changes in slope exceed 15°. We propose plunge pools can be created by two mechanisms. Firstly, they may be due to reduced bed shear stress downstream of hydraulic jumps in submarine sediment-laden density flows that causes the deposition of bedload and the creation of a sediment bar. This bar then defines the downslope margin of a pool. Secondly, the impact of high-momentum sediment-laden density flows can excavate a depression, as has been observed for subaerial snow avalanches. Sediment deposited downslope of these impact pools is very poorly sorted, and partly derived from erosion within the pool. Both mechanisms influence whether turbidity currents are generated from high-density sediment-laden density flows, influence whether depositional flows are channelised, and have implications for base-of-slope facies models.

Surface-ship and submarine pendulum gravity measurements have been compiled in a new free air gravity anomaly map of the central Pacific Ocean in the region of Hawaii. The main features of the map are large amplitude positive anomalies (up to +700 mGal) over the Hawaiian ridge, large amplitude negative anomalies (up to −136 mGal) flanking the ridge, and a broad belt (>250 km) of positive anomalies (+25 to +50 mGal) bordering the negative anomalies. The map has been used to construct 1°×1°, 5°×5°, and 10°×10° free air anomaly averages. The main feature of the 5°×5° average map is a long-wavelength (∼2200 km) positive anomaly (up to +15 mGal) over the southeastern end of the Hawaiian ridge. A long-wavelength positive anomaly is also seen on the 10°×10° average map, which agrees well with the Gem 6 satellite-derived solution to harmonic degree 16. Computations suggest that crustal structure of the Hawaiian ridge is unlikely to contribute significantly to these long-wavelength positive anomalies. The positive anomalies correlate closely with the Hawaiian swell upon which the Hawaiian ridge is superimposed. The regression lines representing 1°×1° and 5°×5° averages of gravity against topography slope at 21 mGal/km and 22 mGal/km, respectively. These slopes are smaller than those over other regions where the lithosphere is warped for large distances, suggesting that if the swell is warped, it must be compensated. The form which the compensation takes is uncertain, but it may be related to some pattern of flow beneath the lithosphere which maintains both the swell and the associated long-wavelength gravity anomalies.