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Abstract Carbonate sedimentary successions that developed on isolated oceanic islands typically comprise a series of unconformity-bounded packages of strata that reflect eustatic sea level changes superimposed on local tectonic movements. Resolving the subsidence and/or uplift of these islands, which are often assumed to have simple tectonic histories, is challenging because the tectonic movements are commonly of similar magnitudes to the eustatic oscillations. The uncertainty associated with each of the components involved in the construction of subsidence diagrams (e.g., age constraints, decompaction, eustatic sea level curves, paleobathymetry), therefore, introduces significant error margins when assessing the tectonic histories of isolated carbonate platforms. By using two end-member subsidence diagrams for the Paleogene to Neogene successions on Grand Cayman and Cayman Brac, it can be shown that their subsidence rates were heterogeneous over time and that the evolution of these islands vary significantly even though they are situated in the same basin. Although these islands, located 150 km apart, were subject to uniform changes in eustatic sea level, they have different stratigraphic architectures owing to their independent tectonic histories. From the Oligocene to the late Pliocene, the tectonic histories of Grand Cayman and Cayman Brac were analogous, and they subsided at a rate of 5.6 to 9.9 m/Myr. From the late Pliocene to ~400 ka, however, northeast Cayman Brac was uplifted by 165 m and tilted with a rotational axis offshore from the southwest end of the island, whereas Grand Cayman was uplifted by ~10 m with no rotational component. The results of this study challenge the assumption that isolated carbonate platforms have simple tectonic histories, while exploring and highlighting the common problems that are encountered with the construction of subsidence diagrams.

AbstractDownstream passage of Lake Sturgeon Acipenser fulvescens through hydroelectric facilities is known to occur but is poorly understood. Acoustic telemetry was used to investigate downstream‐passage routes, survival, and fine‐scale movements at the Slave Falls Generating Station, located on the Winnipeg River, Manitoba. Downstream‐passage rates were estimated at 2.9% (range = 0.0–4.4%) per year for Slave Falls Reservoir adults and 21.1% (range = 19.3–22.9%) per year for subadults tagged in the lowermost section of the reservoir. No juvenile passage was observed. Lake Sturgeon movements immediately upstream of the Slave Falls Generating Station main sluiceway gates were related to bathymetric features. Fish that approached via deepwater habitat tended to abandon their downstream trajectory movements before or upon reaching the top of a relatively shallow (∼10 m depth) bedrock saddle that occurs ∼45 m upstream of the main sluiceway gates. Based on acoustic telemetry (fine‐scale tracking and presence–absence data) and supplemental information, such as trash rack spacing and spill conditions, 7 of 11 (64%) observed downstream‐passage events were concluded to have occurred via bottom‐draw regulating sluices located in the northeastern end of the powerhouse. At least 91% of the observed downstream‐passage events were survived. Results suggest that protection initiatives at hydroelectric facilities could exploit the Lake Sturgeon's bottom‐oriented nature, with bottom‐draw sluice gates likely providing a feasible way to facilitate safe downstream passage.Received June 28, 2013; accepted January 28, 2014

Integration of detrital zircon geochronology and three-dimensional (3D) seismic-reflection data from the Molasse basin of Austria yields new insight into Oligocene-early Miocene paleogeography and patterns of sediment routing within the Alpine foreland of central Europe. Three-dimensional seismic-reflection data show a network of deep-water tributaries and a long-lived (>8 Ma) foredeep-axial channel belt that transported Alpine detritus greater than 100 km from west to east. We present 793 new detrital zircon ages from ten sandstone samples collected from subsurface cores located within the seismically mapped network of deep-water tributaries and the axial channel belt. Grain age populations correspond with major pre-Alpine orogenic cycles: the Cadomian (750-530 Ma), the Caledonian (490-380 Ma), and the Variscan (350-250 Ma). Additional age populations correspond with Eocene-Oligocene Periadriatic magmatism (40-30 Ma) and pre-Alpine, Precambrian sources (>750 Ma). Although many samples share the same age populations, the abundances of these populations vary significantly. Sediment that entered the deep-water axial channel belt from the west (Freshwater Molasse) and southwest (Inntal fault zone) is characterized by statistically indistinguishable age distributions that include populations of Variscan, Caledonian, and Cadomian zircon at modest abundances (15-32% each). Sandstone from a shallow marine unit proximal to the northern basin margin consists of >75% Variscan (350-300 Ma) zircon, which originated from the adjacent Bohemian Massif. Mixing calculations based on the Kolmogorov-Smirnoff statistic suggest that the Alpine fold-thrust belt south of the foreland was also an important source of detritus to the deep-water Molasse basin. We interpret evolving detrital zircon age distributions within the axial foredeep to reflect a progressive increase in longitudinal sediment input from the west (Freshwater Molasse) and/or southwest (Inntal fault zone) relative to transverse sediment input from the fold-thrust belt to the south. We infer that these changes reflect a major reorganization of catchment boundaries and denudation rates in the Alpine Orogen that resulted in the Alpine foreland evolving to dominantly longitudinal sediment dispersal. This change was most notably marked by the development of a submarine canyon during deposition of the Upper Puchkirchen Formation that promoted sediment bypass eastward from Freshwater Molasse depozones to the Molasse basin deep-water axial channel belt. The integration of 3D seismic-reflection data with detrital zircon geochronology illustrates sediment dispersal patterns within a continental-scale orogen, with implications for the relative role of longitudinal versus transverse sediment delivery in peripheral foreland basins. This article is protected by copyright. All rights reserved.

This article analyzes the effects of key physical oceanographic conditions on underwater propagation in a shallow water environment. Signals at 2 kHz were transmitted and received over ranges of 1–10 km, and the variability in the sound-speed profile, bathymetry, position of the instruments, and sea surface roughness was measured and the uncertainty on each parameter was estimated. The acoustic channel characteristics, including the transmission loss, delay spread, and coherence time, were calculated between a moored five-element vertical line array and a vessel deployed source. The measurement results were modeled using a Bellhop's ray tracing algorithm. The sensitivity of the simulator output was evaluated as a function of the environmental conditions, and the observed variability in the transmission loss was reproduced by varying the input parameters to the model within the observed and estimated bounds. The relative importance of the physical properties of the environment in terms of their impact on the acoustic channel is determined through a comparison of modeled and measured transmission loss variability.

Liman Tepe-Clazomenae, located in the southern Bay of Izmir, Turkey, was an important Early Bronze Age to Classical Period trading port and cultural centre in the eastern Aegean. The mainland harbour, now submerged similar to 1.5-2 m below present sea level, is one of the best-preserved examples of an Iron Age (Archaic Period; ca. 7th-6th c. BCE) semi-enclosed harbour (>5 ha) with engineered breakwater structures. A multi-proxy study (micropalaeontology, micro-XRF core scanning) was conducted on seven harbour sediment cores and integrated with geophysical data to map the harbour structures and document coastal palaeoenvironmental changes. Bathymetry and side-scan mapping revealed two broad (>35 m) rubble-constructed breakwater structures and a submerged headland that divided the harbour into two separate sub-basins. Linear magnetic anomalies within the eastern breakwater indicate a buried pier structure, recording possible augmentation of a Late Bronze Age (LBA) or Early Iron Age (EIA) proto-harbour embayment. The harbour basin stratigraphy comprises foreshore and upper shoreface deposits overlying terrigenous clays across a marine transgressive surface. A distinctive siltrich chemofacies with increased Ti/Ca and decreased Si marks a transition from a sandy marine shoreface to a low energy, sheltered LBA proto-harbour embayment. The Iron Age harbour construction (ca. 7th-6th c. BCE) is recorded by a rise in Rosalina, decreased Ti/Ca and the appearance of Archaic pottery. The harbour was in use from the Archaic to early Classical periods and served as Clazomenae's mainland commercial port.

Abstract. The benefit of autonomous vehicles in hydrography is largely based on the ability of these platforms to carry out survey campaigns in a fully autonomous manner. One solution is to have real-time processing onboard the survey vessel. To meet this real-time processing goal, deep learning based-models are favored. Although Artificial Intelligence (AI) is booming, the main studies have been devoted to optical images and more recently, to LIDAR point clouds. However, little attention has been paid to the underwater environment. In this paper, we present an investigation into the adaptation of deep neural network to multi-beam echo-sounder (MBES) point cloud in order to classify sea-bottom morphology. More precisely, the paper investigates whether fully convolutional network can be trained while using the native 3D structure of the point cloud. A preprocessing approach is provided in order to overcome the lack of adequate training data. The results reported from the test data sets show the level of complexity related to natural, underwater terrain features where a classification accuracy no better than 65% can be reached when 2 micro topographic classes are used. Point density and resolution have a strong impact on the seabed morphology thereby affecting the classification scheme.

International audience; Swath bathymetry data and seismic profiles collected in the NW Gulf of St Lawrence reveal a series of wedge-shaped depositional systems interpreted as grounding zone wedges (GZWs). Some segments of the GZWs change locally to form frontal moraines, or morainal banks, and subaqueous ice-contact fans, reflecting changes in either the nature of the ice margin or the rate of sediment input. These grounding zones (GZ) of the ice margin extend laterally along three isobaths at depths of 180 (GZ1), 120 (GZ2) and 80 (GZ3) m (±20 m) along the Québec North Shore shelf, the 120 m-deep GZ2 system being traceable over a distance of >300 km. Associated GZWs can occur in three geometries along a same isobath system: curvilinear, lobate and shelf-break. GZ systems were built during three distinct stages of stabilization of the marine-based southeastern margin of the Laurentide Ice Sheet following its rapid retreat across the deeper waters of the Laurentian Channel in the Gulf of St Lawrence after 14.8 cal ka BP. The occurrence of GZ along distinct isobaths indicates that bathymetry exerted a strong control on ice stabilization during deglaciation by reducing the relative water depth at the ice margin and thereby the buoyancy and rate of iceberg calving. However, fluctuations and re-advances of the ice margin are also recorded by the overprinting of a portion of the GZ2 system by the younger GZ3 system, potentially suggesting an additional response to climate-driven forcing.

Abstract Variations in environmental physicochemical parameters result in corresponding changes in seawater rare earth element (REE) distributions. For an archive to be utilized in paleoceanographic and paleoenvironmental reconstructions, it should record these variations. Therefore, an archive's proxy potentiality should be assessed analogous to modern oceanic settings. Articulated brachiopods of several shallow water localities ( The mean REE SN pattern of shallow-water brachiopods is significantly different from that of their deep-water counterparts, with lower enrichments in LREEs and MREEs, and depletion in HREEs. Depth exercises a major control on the LREE and MREE fractionation with a milder one on HREE fractionation. The Ce/Ce* anomaly is not affected by either of these parameters in shallow-water settings, but in deep settings the depth effect dominates. Due to the importance of depth on REE fractionation in the shells from shallow settings, their LREE SN to HREE SN ratios (L:H) were divided into six discrete intervals for the bathymetric sensor. The bathymetric sensor was applied to some fossils and whole rock in order to estimate their paleodepths. The evaluation was successful in placing the Permian Gyanyima, the Pennsylvanian Naco, Boggy and the Silurian Chicotte, Becscie and Jupiter Formations in shallow depths (

AbstractCurrent understanding of bedform dynamics is largely based on field and laboratory observations of bedforms in steady flow environments. There are relatively few investigations of bedforms in flows dominated by unsteadiness associated with rapidly changing flows or tides. As a consequence, the ability to predict bedform response to variable flow is rudimentary. Using high‐resolution multibeam bathymetric data, this study explores the dynamics of a dune field developed by tidally modulated, fluvially dominated flow in the Fraser River Estuary, British Columbia, Canada. The dunes were dominantly low lee angle features characteristic of large, deep river channels. Data were collected over a field ca 1·0 km long and 0·5 km wide through a complete diurnal tidal cycle during the rising limb of the hydrograph immediately prior to peak freshet, yielding the most comprehensive characterization of low‐angle dunes ever reported. The data show that bedform height and lee angle slope respond to variable flow by declining as the tide ebbs, then increasing as the tide rises and the flow velocities decrease. Bedform lengths do not appear to respond to the changes in velocity caused by the tides. Changes in the bedform height and lee angle have a counterclockwise hysteresis with mean flow velocity, indicating that changes in the bedform geometry lag changes in the flow. The data reveal that lee angle slope responds directly to suspended sediment concentration, supporting previous speculation that low‐angle dune morphology is maintained by erosion of the dune stoss and crest at high flow, and deposition of that material in the dune trough.