These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Submarine canyons  

Microsoft Academic Search

This article discusses the nature and origin of submarine canyons, both the deep canyons crossing the continental slope and their shallower continuation seaward as fan-valleys. The canyons and sediments they contain are discussed in relation to the adjacent land and to the continental rise. Possible origins, including turbidity currents and upbuilding of the continental walls, are dealt with in the

F. P. Shepard

1972-01-01

2

Flushing submarine canyons  

Microsoft Academic Search

The continental slope is a steep, narrow fringe separating the coastal zone from the deep ocean. During low sea-level stands, slides and dense, sediment-laden flows erode the outer continental shelf and the continental slope, leading to the formation of submarine canyons that funnel large volumes of sediment and organic matter from shallow regions to the deep ocean1. During high sea-level

Miquel Canals; Pere Puig; Xavier Durrieu de Madron; Serge Heussner; Albert Palanques; Joan Fabres

2006-01-01

3

Flushing submarine canyons.  

PubMed

The continental slope is a steep, narrow fringe separating the coastal zone from the deep ocean. During low sea-level stands, slides and dense, sediment-laden flows erode the outer continental shelf and the continental slope, leading to the formation of submarine canyons that funnel large volumes of sediment and organic matter from shallow regions to the deep ocean(1). During high sea-level stands, such as at present, these canyons still experience occasional sediment gravity flows(2-5), which are usually thought to be triggered by sediment failure or river flooding. Here we present observations from a submarine canyon on the Gulf of Lions margin, in the northwest Mediterranean Sea, that demonstrate that these flows can also be triggered by dense shelf water cascading (DSWC)-a type of current that is driven solely by seawater density contrast. Our results show that DSWC can transport large amounts of water and sediment, reshape submarine canyon floors and rapidly affect the deep-sea environment. This cascading is seasonal, resulting from the formation of dense water by cooling and/or evaporation, and occurs on both high- and low-latitude continental margins(6-8). DSWC may therefore transport large amounts of sediment and organic matter to the deep ocean. Furthermore, changes in the frequency and intensity of DSWC driven by future climate change may have a significant impact on the supply of organic matter to deep-sea ecosystems and on the amount of carbon stored on continental margins and in ocean basins. PMID:17108962

Canals, Miquel; Puig, Pere; de Madron, Xavier Durrieu; Heussner, Serge; Palanques, Albert; Fabres, Joan

2006-11-16

4

Influence of San Gabriel submarine canyon on narrow-shelf sediment dynamics, southern California  

USGS Publications Warehouse

A conceptual model attributes the PTC to modification of shelf circulation patterns by San Gabriel Canyon. Surface waves diverge over the canyon head resulting in differential wave set up at the shore face. This forces back turbid nearshore water for a distance of a few kilometers toward the canyon. At some point on the shelf, seaward nearshore flow overlaps offshore currents generated or modified by internal waves focused onto the shelf by the canyon and/or turbulent eddies produced by flow separation in currents moving across the canyon axis. At times, these subtle processes overprint tidal and wind-driven currents and thereby create the PTC. The model suggests that canyons heading several kilometers from shore can have a regulatory effect on narrow-shelf sediment dynamics.

Karl, Herman A.

1980-01-01

5

Sedimentary facies in submarine canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons are the major conduits by which sediment, pollutants and nutrients are transported from the continental shelf out into the deep sea. The sedimentary facies within these canyons are remarkably poorly understood because it has proven difficult to accurately sample these heterogeneous and bathymetrically complex environments using traditional ship-based coring techniques. This study exploits a suite of over 100 precisely located vibracores collected using remotely operated vehicles in ten canyons along the northern Californian margin, enabling better understanding of the facies that exist within submarine canyons, their distribution, and the processes responsible for their formation. The dataset reveals three major facies types within the submarine canyons: extremely poorly sorted, coarse-grained sands and gravels with complex and indistinct internal grading patterns and abundant floating clasts; classical normally graded thin bedded turbidites; and a variety of fine-grained muddy deposits. Not all facies are observed within individual canyons, in particular coarse-grained deposits occur exclusively in canyons where the canyon head cuts up to the modern day beach, whereas finer grained deposits have a more complex distribution that relates to processes of sediment redistribution on the shelf. Pairs of cores collected within 30 meters elevation of one another reveal that the coarse-grained chaotic deposits are restricted to the basal canyon floor, with finer-grained deposits at higher elevations on the canyon walls. The remarkable heterogeneity of the facies within these sediment cores illustrate that distinctive processes operate locally within the canyon. In the authors' experience the canyon floor facies represent an unusual facies rarely observed in ancient outcrops, which potentially results from the poor preservation of ancient coarse-grained canyon deposits in the geological record.

Sumner, E.; Paull, C. K.; Gwiazda, R.; Anderson, K.; Lundsten, E. M.; McGann, M.

2013-12-01

6

Currents in monterey submarine canyon  

USGS Publications Warehouse

Flow fields of mean, subtidal, and tidal frequencies between 250 and 3300 m water depths in Monterey Submarine Canyon are examined using current measurements obtained in three yearlong field experiments. Spatial variations in flow fields are mainly controlled by the topography (shape and width) of the canyon. The mean currents flow upcanyon in the offshore reaches (>1000 m) and downcanyon in the shallow reaches (100-m amplitude isotherm oscillations and associated high-speed rectilinear currents. The 15-day spring-neap cycle and a ???3-day??? band are the two prominent frequencies in subtidal flow field. Neither of them seems directly correlated with the spring-neap cycle of the sea level.

Xu, J.P.; Noble, M.A.

2009-01-01

7

Tidal motions and tidally induced fluxes through La Línea submarine canyon, western Alboran sea  

Microsoft Academic Search

Detailed observations from two mooring lines deployed in La Línea submarine canyon, western Alboran Sea, are presented. This is a narrow canyon in the sense that its width is always less than the internal radius of deformation. Tidal currents within the canyon are polarized in the along-canyon direction according to its narrow nature. They have considerable amplitude (values of around

Jesús García Lafuente; Tarek Sarhan; Manuel Vargas; Juan M. Vargas; Francisco Plaza

1999-01-01

8

Habitat associations of deep-water rockfishes in a submarine canyon: an example of  

E-print Network

625 Habitat associations of deep-water rockfishes in a submarine canyon: an example of a natural (genus Se- bastes) and associated habitats in deep water was conducted in Soquel Sub- marine Canyon of high relief interspersed with mud in deep water of narrow submarine canyons are less accessible

9

Primary Initiation of Submarine Canyons  

E-print Network

The discovery of close-to-star gas-giant exo-planets lends support to the idea of Earth's origin as a Jupiter-like gas-giant and to the consequences of its compression, including whole-Earth decompression dynamics that gives rise, without requiring mantle convection, to the myriad measurements and observations whose descriptions are attributed to plate tectonics. I propose here another, unanticipated consequence of whole-Earth decompression dynamics: namely, a specific, dominant, non-erosion, underlying initiation-mechanism precursor for submarine canyons that follows as a direct consequence of Earth's early origin as a Jupiter-like gas-giant.

Herndon, J Marvin

2011-01-01

10

Primary Initiation of Submarine Canyons  

E-print Network

The discovery of close-to-star gas-giant exo-planets lends support to the idea of Earth's origin as a Jupiter-like gas-giant and to the consequences of its compression, including whole-Earth decompression dynamics that gives rise, without requiring mantle convection, to the myriad measurements and observations whose descriptions are attributed to plate tectonics. I propose here another, unanticipated consequence of whole-Earth decompression dynamics: namely, a specific, dominant, non-erosion, underlying initiation-mechanism precursor for submarine canyons that follows as a direct consequence of Earth's early origin as a Jupiter-like gas-giant.

J. Marvin Herndon

2011-02-02

11

Geomorphic process fingerprints in submarine canyons  

USGS Publications Warehouse

Submarine canyons are common features of continental margins worldwide. They are conduits that funnel vast quantities of sediment from the continents to the deep sea. Though it is known that submarine canyons form primarily from erosion induced by submarine sediment flows, we currently lack quantitative, empirically based expressions that describe the morphology of submarine canyon networks. Multibeam bathymetry data along the entire passive US Atlantic margin (USAM) and along the active central California margin near Monterey Bay provide an opportunity to examine the fine-scale morphology of 171 slope-sourced canyons. Log–log regression analyses of canyon thalweg gradient (S) versus up-canyon catchment area (A) are used to examine linkages between morphological domains and the generation and evolution of submarine sediment flows. For example, canyon reaches of the upper continental slope are characterized by steep, linear and/or convex longitudinal profiles, whereas reaches farther down canyon have distinctly concave longitudinal profiles. The transition between these geomorphic domains is inferred to represent the downslope transformation of debris flows into erosive, canyon-flushing turbidity flows. Over geologic timescales this process appears to leave behind a predictable geomorphic fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may be a proxy for the volume of sediment released during geomorphically significant failures along the upper continental slope. Focused studies of slope-sourced submarine canyons may provide new insights into the relationships between fine-scale canyon morphology and down-canyon changes in sediment flow dynamics.

Brothers, Daniel S.; ten Brink, Uri S.; Andrews, Brian D.; Chaytor, Jason D.; Twichell, David C.

2013-01-01

12

"Internal Waves" Advancing along Submarine Canyons.  

PubMed

Patterns of alternating up- and downcanyon currents have been traced along the axes of submarine canyons off California. The patterns arrive later at stations nearer the heads of coastal canyons. Where a canyon heads between two islands, the patterns advance down the axis. The propagation speeds of these patterns were estimated as 25 to 88 centimeters per second. Internal waves are the probable explanation. PMID:17777263

Shepard, F P; Marshall, N F; McLoughlin, P A

1974-01-18

13

Seismic expression of Late Quaternary Banda submarine canyon and fan offshore northern Baja California  

SciTech Connect

High-resolution seismic reflection profiles obtained throughout the inner California continental borderland offshore northwestern Baja California, Mexico, show the presence of numerous modern submarine canyons and associated fans. One set of these, the Banda submarine canyon/fan, is of relatively recent origin, as demonstrated by onlap of the basal fan sediments against an acoustically transparent, presumably hemipelagic deposit. Late Quaternary sedimentation rates inferred from isotopically dated piston core samples place the age of the postulated hemipelagic unit at approximately 650,000 years ago. The Banda submarine canyon heads within the Bahia Todos Santo and passes through a narrow gorge between Punta Banda and Islas Todos Santos. It is proposed that this submarine canyon and fan system formed entirely during late Quaternary time, following the breach of the Punta Banda ridge during a late Pleistocene high sea level stand. The presence of an ancient, buried channel exiting to the north out of Bahia Todos Santos probably marks the head of an earlier submarine canyon which acted as the conduit of clastic sediments from Valle Maneadero to the deep borderland basins. The now active Banda submarine canyon pirated the supply of terrigenous clastics from this older canyon. The active Agua Blanca fault zone cuts across the head of Banda submarine canyon, suggesting that tectonic movements may have played a role in the development of the Banda submarine canyon and fan system.

Legg, M.R.

1987-05-01

14

Flow dynamics around downwelling submarine canyons  

NASA Astrophysics Data System (ADS)

Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (northwestern Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby and Burger numbers were used to determine the significance of Coriolis acceleration and stratification (respectively) and their impacts on flow dynamics. A new non-dimensional parameter (?) was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10-day model period; however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation, and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. The offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m). Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate), as well as stronger vorticity within the canyon. Results from previous studies are explained within this new dynamic framework.

Spurgin, J. M.; Allen, S. E.

2014-10-01

15

Internal modes in a submarine canyon  

SciTech Connect

A simple analytical model is presented for internal waves in a slot of variable width. This model is used to explain the vertical wave length, directional character, and amplitude enhancement of internal waves observed near the axis of La Jolla Submarine Canyon, offshore of San Diego, California.

Gordon, R.L.

1982-01-20

16

ROV Tiburon Investigation of Hawaiian Submarine Canyons  

NASA Astrophysics Data System (ADS)

MBARI conducted ROV dives around the Hawaiian Islands during an expedition of the R/V Western Flyer and Tiburon in the spring of 2001. Eight ROV dives were made to investigate five major submarine canyons offshore of Oahu, Molokai, and Hawaii in up to 3,434 m water depths. Four of these canyons are located off the windward (northern) side of these islands where onshore canyons are also well developed. Those canyons located offshore of Molokai and Oahu incise the head scars of the giant Nuuanu and Wailai submarine landslides. ROV observations and sediment and rock outcrop sampling were made in these canyons to determine their origin and present-day activity. The fifth canyon investigated is located on the leeward (southern) side of Molokai. The canyons along the windward side expose extensive stratigraphic sections that reveal the history of the islands' formation. In composite, these sections contain marine pillow basalt overlain by a substantial sequence of alternating subaerial lava flows, rounded boulder conglomerates, shallow water carbonates, and hyaloclastites that indicate coastal and marine deposition. These sequences illustrate the accretion and subsequent subsidence of the islands' flanks. These canyons also have morphologically distinct upper and lower sections. The upper reaches of the canyons are incised into the shallow water marine facies and contain broad axial channels through which active sediment transport is occurring. In contrast, the morphology of the lower canyons are strongly influenced by the giant landslides that massively altered the northern flanks of the Hawaiian chain. The lower canyons contain plunge pools and steep headwall scarps that are generally comprised of mechanically competent subaerial lava flows. The presence of multiple plunge pools with differentially eroded head scarps suggests retrogressive erosion (bottom-up process) with headward advancement of the various heads. Undercutting of the headwalls also produce periodic rockfalls and debris flows that in combination with the sediment supplied from the upper parts of the canyons is both lengthening and deepening the canyons. This progressive advancement of the erosion along the weaker haloclastite beds has produced a stair-step configuration. In contrast, the canyon we investigated on the leeward side of Molokai showed no evidence of active sediment transport and appears to be filling.

Paull, C. K.; Greene, H. G.; Caress, D. W.; Clague, D. A.; Ussler, W.; Maher, N. M.

2001-12-01

17

Flow near submarine canyons driven by constant winds  

Microsoft Academic Search

Circulation over coastal submarine canyons driven by constant upwelling or downwelling wind stress is simulated and analyzed with a primitive equation ocean model. Astoria Canyon, on the west coast of North America, is the focus of this study, and model results are consistent with most major features of mean canyon circulation observed in Astoria Canyon. Near-surface flow crosses over the

Jun She; John M. Klinck

2000-01-01

18

Wilmington Submarine Canyon: a marine fluvial-like system.  

USGS Publications Warehouse

Midrange sidescan sonar data show that a system of gullies and small channels feeds into large submarine canyons on the Middle Atlantic Continental Slope of the US. The surveyed canyons all have relatively flat floors, but they have different channel morphologies. Wilmington Canyon has a meandering channel that extends down the Continental Slope and across the Continental Rise, whereas two canyons south of Wilmington Canyon have straight channels that trend directly downslope onto the rise. The morphology of these submarine canyon systems is remarkably similar to that of terrestrial fluvial systems.-Authors

McGregor, B.; Stubblefield, W.L.; Ryan, William B. F.; Twichell, D.C.

1982-01-01

19

Modelling the flow over submarine canyons  

NASA Astrophysics Data System (ADS)

The aim of this work is within EUROSTRATAFORM project and consists on developing a model for sedimentary processes and their forcing conditions on the European continental margin (main concern on Nazaré and Setúbal Canyons), constrained by the requirement of considering the continental margin as a continuum and of following the sediments from their source to their settling and accumulation sites. The work will be based on MOHID modelling system (http://www.mohid.com), which includes modules for hydrodynamics, sediment transport and ecology and permits eulerian and lagrangian simulations. The model allows the use of several vertical discretizations and variable horizontal grids, including nested models. Canyons are local geographical accidents where currents are forced both by regional circulation and local forcing mechanisms. Simulation of physical and sedimentary processes requires a fine local discretizaton embedded into a regional model in order to describe accurately their topography. Inside canyons topography and currents interact non-linearly. Their simulation requires adequate vertical grids. A lagrangian grid will be used to minimize numerical diffusion associated to high frequency vertical oscillation generated by internal tides. Sediment transport will be simulated using eulerian and lagrangian formulations. Effects of windstorm waves will be simulated explicitly on re-suspension along submerse beaches. Preliminary results will be presented for the real canyons in a coarse grid. Real topography simulations are forced by density and wind. The results show that canyons by one way or another are likely to induce upwelling in the water column and thus are very productive locals. For the particular case of Nazaré canyon it is shown that flow interacts both with the submarine canyon and with coastal morphology.

Coelho, H. S.; Neves, R.; Leitao, P. C.; Garcia, A. C.

2003-04-01

20

Contemporary sediment-transport processes in submarine canyons.  

PubMed

Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures. PMID:23937169

Puig, Pere; Palanques, Albert; Martín, Jacobo

2014-01-01

21

Contemporary Sediment-Transport Processes in Submarine Canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures.

Puig, Pere; Palanques, Albert; Martín, Jacobo

2014-01-01

22

A submarine canyon as the cause of a mud volcano Liuchieuyu Island in Taiwan  

E-print Network

A submarine canyon as the cause of a mud volcano Ð Liuchieuyu Island in Taiwan J. Chowa,*, J, we also discuss the relationship between a nearby submarine canyon (Kaoping Submarine Canyon¯ection; Submarine canyon; Mud volcano 1. Introduction In the early Pliocene, the paleoenvironment of the offshore

Lin, Andrew Tien-Shun

23

An Experimental Study of Submarine Canyon Evolution on Continental Slopes  

NASA Astrophysics Data System (ADS)

Submarine canyons define the morphology of many continental slopes and are conduits for the transport of sediment from shallow to deep water. Though the origin and evolution of submarine canyons is still debated, there is general agreement that sediment gravity flows play an important role. Here we present results from a simple, reduced-scale sandbox experiment designed to investigate how sediment gravity flows generate submarine canyons. In the experiments, gravity flows were modeled using either sediment-free or turbid saline currents. Unconfined flows were released onto an inclined bed of sand bounded on the downstream end by a movable floor that was incrementally lowered during the course of an experiment to produce an escarpment. This design was developed to represent the growth of relief across the continental slope. To monitor canyon evolution on the slope, we placed an overhead DSLR camera to record vivid time-lapse videos. At the end of each experimental stage we scanned the topography by imaging a series of submerged laser stripes, each projected from a motor-driven transverse laser sheet, onto a calibrated Cartesian coordinate system to produce high resolution bathymetry without draining the ambient water. In areas unaffected by the flows, we observe featureless, angle-of-repose submarine slopes formed by retrogressive breaching processes. In contrast, areas influenced by gravity flows cascading across the shelf break are deeply incised by submarine canyons with well-developed channel networks. Our results show that downslope gravity flows and submarine falling base level are both required to produce realistic canyon morphologies at laboratory scale. Though our mechanism for generating relief may be a rather crude analogue for the processes driving slope evolution, we hope our novel approach can stimulate new questions about the coevolution of canyons and slopes and motivate further experimental work to address them.

Lai, S. Y.; Gerber, T. P.; Amblas, D.

2013-12-01

24

Depositional framework and genesis of Wilcox Submarine Canyon systems, Northwest Gulf Coast  

SciTech Connect

Wilcox (late Paleocene-early Eocene) slope systems of the Texas coastal plain contain two families of paleosubmarine canyons that exhibit distinctly different characteristics and stratigraphic settings: Yoakum and Lavaca type canyons occur as widely separated features within the generally retrogradational middle Wilcox interval. Four such canyons exhibit high length to width ratios, extend far updip of the contemporaneous shelf edge, were excavated deeply into paralic and coastal-plain deposits, and were filled primarily by mud. Fills consist of a lower onlapping unit and capping progradational deposits that are genetically related to deposition of the upper Wilcox fluvial-deltaic sequence. Significantly, the canyon fills correlate with widespread transgressive marine mudstones (the Yoakum shale-Sabinetown Formation and ''Big Shale''). In contrast, Lavaca-type canyons form a system of erosional features created along the rapidly prograding, unstable lower Wilcox continental margin. Comparative analysis of the two canyon system suggests a general process model for submarine canyon formation on prograding basin margins. Key elements are depositional loading of the continental margin creating instability, initiation of a large-scale slump, family of slumps, or listric bedding-plane fault creating a depression or indentation in the margin, and headward and lateral expansion of the depression by slumping and density-underflow erosion. Extent of canyon evolution varies according to time and submerged space available for maturation; short, broad canyons form on narrow shelves of actively prograding margins, and elongate mature canyons form in retrogradational or transgressive settings.

Galloway, W.F.; Dinqus, W.F.; Paige, R.E.

1988-01-01

25

Regional impact of submarine canyons during seasonal upwelling  

NASA Astrophysics Data System (ADS)

numerical model of the northern California Current System along the coasts of Washington and British Columbia is used to quantify the impact of submarine canyons on upwelling from the continental slope onto the shelf. Comparisons with an extensive set of observations show that the model adequately represents the seasonal development of near-bottom density, as well as along-shelf currents that are critical in governing shelf-slope exchange. Additional model runs with simplified coastlines and bathymetry are used to isolate the effects of submarine canyons. Near submarine canyons, equatorward flow over the outer shelf is correlated with dense water at canyon heads and subsequent formation of closed cyclonic eddies, which are both associated with cross-shelf ageostrophic forces. Lagrangian particles tracked from the slope to midshelf show that canyons are associated with upwelling from depths of ˜140-260 m. Source depths for upwelling are shallower than 150 m at locations away from canyons and in a model run with bathymetry that is uniform in the along-shelf direction. Water upwelled through canyons is more likely to be found near the bottom over the shelf. Onshore fluxes of relatively saline water through submarine canyons are large enough to increase volume-averaged salinity over the shelf by 0.1-0.2 psu during the early part of the upwelling season. The nitrate input from the slope to the Washington shelf associated with canyons is estimated to be 30-60% of that upwelled to the euphotic zone by local wind-driven upwelling.

Connolly, Thomas P.; Hickey, Barbara M.

2014-02-01

26

Morphotectonics and incision of the Kaoping submarine canyon, SW Taiwan orogenic wedge  

E-print Network

Morphotectonics and incision of the Kaoping submarine canyon, SW Taiwan orogenic wedge Cheng February 2006 Available online 24 March 2006 Abstract The Kaoping submarine canyon developed on the frontal; Incision; Submarine canyon; Taiwan 1. Introduction 1.1. Geological settings The island of Taiwan is located

Lin, Andrew Tien-Shun

27

Origin of Izu-Bonin forearc submarine canyons  

SciTech Connect

Submarine canyons on the Izu-Bonin forearc are morphologically divided from north to south into four types based on their morphology, long profiles, and seismic profiles: Mikura, Aogashima, Sofu, and Chichijima types, respectively. These types of canyons are genetically different from each other. Mikura group is formed by the faults related to bending of the subducting Philippine Sea Plate. Aogashima type genetically relates to the activity of large submarine calderas that supply large amounts of volcaniclastic material to the consequent forearc slope. The third, Sofu group, is thought to be formed by the large-scale mega mass wasting in relation to the recent movement of the Sofugan tectonic line. The last, Chichijima group, is formed by collision of the Uyeda Ridge and the Ogasawara Plateau on the subducting Pacific Plate with Bonin Arc. Long profiles of four types of submarine canyons also support this.

Fujioka, Kantaro (Univ. of Tokyo (Japan)); Yoshida, Haruko (Chiba Univ. (Japan))

1990-06-01

28

Numerical simulations of the internal tide in a submarine canyon  

NASA Astrophysics Data System (ADS)

Three-dimensional numerical simulations of the generation and propagation of the semidiurnal internal tide in a submarine canyon with dimensions similar to those of the Monterey Canyon are carried out using a primitive equation model. Forcing with just sea level at the offshore boundary in an initially horizontally homogeneous ocean with realistic vertical stratification, internal tides are generated at the canyon foot and rim, and along portions of the canyon floor. The results compare favorably with observations, both indicating enhancement of energy along the canyon floor propagating at an angle consistent with linear internal wave theory. Due to the earth's rotation, internal tide energy is distributed asymmetrically in the cross-canyon direction, favoring the southern side. The effect of canyon floor slope is explored, with the finding that small changes in the slope result in large changes in the amount and distribution of the internal tide energy. Canyons whose floors are subcritical with respect to the semidiurnal frequency along their entire length have very little baroclinic energy, whereas canyons that are near-critical along much of their length, such as the Monterey Canyon, develop strong internal tides that propagate shoreward. Canyons that are near-critical at their mouths but supercritical further inshore generate the most internal tidal energy overall, although little of it makes it onto the continental shelf shoreward of the canyon head. The effects of internal tides within the canyons can be seen outside the canyons as well. Water is transported from depth onto the adjacent continental shelf along the canyon rims. This tidal pumping can be responsible for alongshore internal tide propagation and tidal-period surface currents with relatively small horizontal scales of variability.

Petruncio, Emil T.; Paduan, Jeffrey D.; Rosenfeld, Leslie K.

2002-06-01

29

Anatomy of La Jolla submarine canyon system; offshore southern California  

USGS Publications Warehouse

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 (< 10 cm) turbidites, they are inferred to be part of a veneer of recent sediment covering pre-canyon host sediments that underpin the terraces. The combined use of state of the art seafloor mapping and exploration tools provides a uniquely detailed view of the morphology within an active submarine canyon.

Paull, C.K.; Caress, D.W.; Lundsten, E.; Gwiazda, R.; Anderson, K.; McGann, M.; Conrad, J.; Edwards, B.; Sumner, E.J.

2013-01-01

30

Physical modeling of tidal resonance in a submarine canyon  

NASA Astrophysics Data System (ADS)

observations in submarine canyons poleward of 30° are usually dominated by the semidiurnal (M2) tidal frequency, which is superinertial at these latitudes. Observations from a submarine canyon at 44°N (the Gully, Nova Scotia) suggest that canyons can be dominated by the subinertial (K1) tidal frequency if length scales are correct for resonance of the K1 frequency. A model of the Gully was constructed in a tank on a rotating table and tidal currents generated to determine factors that influence resonance. Resonance curves were fit to measurements from the laboratory canyon for a range of stratifications, background rotation rates, and forcing amplitudes. Dense water was observed upwelling onto the continental shelf on either side of the laboratory canyon and traveled at least one canyon width along the shelf. Friction values measured in the laboratory were much higher than expected, probably due to upwelled water surging onto the shelf on each tidal cycle, similar to a tidal bore. By scaling observations from the laboratory to the ocean and assuming friction in the ocean is also affected by water traveling onto the shelf, a resonance curve for the ocean was created. Because of the broad resonance curve, the diurnal tide remains strong year round at the Gully, even as stratification at the shelf break changes. Dense water surging onto the shelf on tidal frequencies may affect friction and mixing at other nonresonant canyons.

Souëf, K. E.; Allen, S. E.

2014-02-01

31

Evolution of surface gravity waves over a submarine canyon  

E-print Network

The effects of a submarine canyon on the propagation of ocean surface waves are examined with a three-dimensional coupled-mode model for wave propagation over steep topography. Whereas the classical geometrical optics approximation predicts an abrupt transition from complete transmission at small incidence angles to no transmission at large angles, the full model predicts a more gradual transition with partial reflection/transmission that is sensitive to the canyon geometry and controlled by evanescent modes for small incidence angles and relatively short waves. Model results for large incidence angles are compared with data from directional wave buoys deployed around the rim and over Scripps Canyon, near San Diego, California, during the Nearshore Canyon Experiment (NCEX). Wave heights are observed to decay across the canyon by about a factor 5 over a distance shorter than a wavelength. Yet, a spectral refraction model predicts an even larger reduction by about a factor 10, because low frequency components c...

Magne, R; Herbers, T H C; Ardhuin, F; O'Reilly, W C; Rey, V; Magne, Rudy; Belibassakis, Kostas; Herbers, Thomas H. C.; Ardhuin, Fabrice; Reilly, William C. O'; Rey, Vincent

2006-01-01

32

Topographic steering of dense currents with application to submarine canyons  

Microsoft Academic Search

The influence of a submarine canyon on a dense bottom current flowing along the continental shelf is considered. It is shown that the front of the current moves forward with the Nof velocity, establishing a stationary plume parallel to the depth contours behind it. The stationary flow has a frictional transport directed downhill, perpendicular to the depth contours. This transport

A. K. Wåhlin

2002-01-01

33

Submarine canyon erosion: contribution of marine rock burrowers.  

PubMed

Rocks of the rim and upper walls of Scripps Submarine Canyon are intensely burrowed by marine invertebrates. Important excavators are bivalves, polychaetes, and sipunculoids whose activities culminate in a network of passageways and eventual disintegration of the rocks. In many localities erosion by animals is more important than erosion by physical and chemical processes. PMID:17836602

Warme, J E; Scanland, T B; Marshall, N F

1971-09-17

34

Geology and biology of Oceanographer submarine canyon.  

USGS Publications Warehouse

Santonian beds more than 100 m thick are the oldest rocks collected from the canyon. Quaternary silty clay veneers the canyon walls in many places and is commonly burrowed by benthic organisms that cause extensive erosion of the canyon walls, especially in the depth zone (100-1300 m) inhabited by the crabs Geryon and Cancer. Bioerosion is minimal on high, near-vertical cliffs of sedimentary rock, in areas of continual sediment movement, and where the sea floor is paved by gravel. A thin layer of rippled, unconsolidated silt and sand is commonly present on the canyon walls and in the axis. Shelf sediments are transported from Georges Bank over the E rim and in the Canyon by the SW drift and storm currents; tidal currents and internal waves move the sediment downcanyon along the walls and axis.- from Authors

Valentine, P.C.; Uzmann, J.R.; Cooper, R.A.

1980-01-01

35

Role of submarine canyons in shaping the rise between Lydonia and Oceanographer canyons, Georges Bank  

USGS Publications Warehouse

Three large submarine canyons, Oceanographer, Gilbert, and Lydonia, indent the U.S. Atlantic continental shelf and, with four additional canyons, dissect the continental slope in the vicinity of Georges Bank. On the upper rise, these canyons merge at a water depth of approximately 3100 m to form only two valleys. Differences in channel morphology of the canyons on the upper rise imply differences in relative activity, which is inconsistent with observations in the canyon heads. At present, Lydonia Canyon incises the upper rise more deeply than do the other canyons: however, seismic-reflection profiles show buried channels beneath the rise, which suggests that these other six canyons were periodically active during the Neogene. The rise morphology and the thickness of inferred Neogene- and Quaternary-age sediments on the rise are attributed to the presence and activity of the canyons. The erosional and depositional processes and the morphology of these canyons are remarkably similar to those of fluvial systems. Bear Seamount, which has approximately 2000 m of relief on the rise, has acted as a barrier to downslope sediment transport since the Late Cretaceous. Sediment has piled up on the upslope side, whereas much less sediment has accumulated in the "lee shadow" on the downslope side. Seismic-reflection profile data show that Lydonia Canyon has not eroded down to the volcanic rock of Bear Seamount. ?? 1985.

McGregor, B.A.

1985-01-01

36

Space-for-time substitution and the evolution of a submarine canyon-channel system in a passive progradational margin  

NASA Astrophysics Data System (ADS)

Space-for-time substitution is a concept that has been widely applied, but not thoroughly tested, in some fields of geomorphology. The objective of this study is to test whether the concept of space-for-time substitution is valid in reconstructing the evolution of a submarine canyon-channel system in a passive progradational margin. We use multibeam echosounder data and in situ measurements from the south Ebro Margin to analyse the morphology and morphometry of a sequence of submarine valleys ordered in terms of increasing valley thalweg length. The morphological model of submarine valley evolution that we can propose from this analysis is very similar to established models in the literature, which leads us to conclude that time can be substituted by space when reconstructing the evolution of submarine canyon and channel systems in the south Ebro Margin. By extracting morphometric information from the application of the space-for-time substitution model to our data, we identify a series of morphological patterns as a submarine canyon evolves in a passive progradational margin. These include the geometric similarity of canyon planform shape, an increase in canyon draining efficiency and in the influence of flank slope failures, and an evolution towards equilibrium between canyon form and imposed water and sediment load without net erosion or deposition taking place. We also observe that canyon elongation is higher downslope and that the canyon undergoes an early stage of rapid incision similar to the process of "erosion narrowing" reported in terrestrial rivers. We demonstrate that the conclusions of our study are not limited to submarine valleys in the south Ebro Margin but are applicable to other margins around the world.

Micallef, Aaron; Ribó, Marta; Canals, Miquel; Puig, Pere; Lastras, Galderic; Tubau, Xavier

2014-09-01

37

Giant submarine canyons: is size any clue to their importance in the rock record?  

USGS Publications Warehouse

Submarine canyons are the most important conduits for funneling sediment from continents to oceans. Submarine canyons, however, are zones of sediment bypassing, and little sediment accumulates in the canyon until it ceases to be an active conduit. To understand the potential importance in the rock record of any given submarine canyon, it is necessary to understand sediment-transport processes in, as well as knowledge of, deep-sea turbidite and related deposits that moved through the canyons. There is no straightforward correlation between the final volume of the sedimentary deposits and size o fthe associated submarine canyons. Comparison of selected modern submarine canyons together with their deposits emphasizes the wide range of scale differences between canyons and their impact on the rock record. Three of the largest submarine canyons in the world are incised into the Beringian (North American) margin of the Bering Sea. Zhemchug Canyon has the largest cross-section at the shelf break and greatest volume of incision of slope and shelf. The Bering Canyon, which is farther south in the Bering Sea, is first in length and total area. In contrast, the largest submarine fans-e.g., Bengal, Indus, and Amazon-have substantially smaller, delta-front submarine canyons that feed them; their submarine drainage areas are one-third to less than one-tenth the area of Bering Canyon. some very large deep-sea channells and tubidite deposits are not even associated with a significant submarine canyon; examples include Horizon Channel in the northeast Pacific and Laurentian Fan Valley in the North Atlantic. Available data suggest that the size of turbidity currents (as determined by volume of sediment transported to the basins) is also not a reliable indicator of submarine canyon size.

Normark, William R.; Carlson, Paul R.

2003-01-01

38

Macrofaunal communities within and adjacent to a detritus-rich submarine canyon system  

Microsoft Academic Search

Macrofaunal abundance, biomass, diversity and species assemblages within Scripps and La Jolla Submarine Canyons are compared with those on the nearby continental shelf and slope. Our primary objective was to examine the effect of detrital aggregates on infaunal communities within canyons. Two submarines, a remotely operated vehicle (ROV), and a Soutar box-corer were used to collect samples. Within the canyons,

E. W. Vetter; P. K. Dayton

1998-01-01

39

Measuring currents in submarine canyons: Technological and scientific progress in the past 30 years  

USGS Publications Warehouse

The development and application of acoustic and optical technologies and of accurate positioning systems in the past 30 years have opened new frontiers in the submarine canyon research communities. This paper reviews several key advancements in both technology and science in the field of currents in submarine canyons since the1979 publication of Currents in Submarine Canyons and Other Sea Valleys by Francis Shepard and colleagues. Precise placements of high-resolution, high-frequency instruments have not only allowed researchers to collect new data that are essential for advancing and generalizing theories governing the canyon currents, but have also revealed new natural phenomena that challenge the understandings of the theorists and experimenters in their predictions of submarine canyon flow fields. Baroclinic motions at tidal frequencies, found to be intensified both up canyon and toward the canyon floor, dominate the flow field and control the sediment transport processes in submarine canyons. Turbidity currents are found to frequently occur in active submarine canyons such as Monterey Canyon. These turbidity currents have maximum speeds of nearly 200 cm/s, much smaller than the speeds of turbidity currents in geological time, but still very destructive. In addition to traditional Eulerian measurements, Lagrangian flow data are essential in quantifying water and sediment transport in submarine canyons. A concerted experiment with multiple monitoring stations along the canyon axis and on nearby shelves is required to characterize the storm-trigger mechanism for turbidity currents. ?? 2011 Geological Society of America.

Xu, J.P.

2011-01-01

40

Deep-marine tidal bottom currents and their reworked sands in modern and ancient submarine canyons  

Microsoft Academic Search

Submarine canyons provide a unique setting for tidal processes to operate from shallow-marine to deep-marine environments. In modern canyons, current-meter measurements at varying water depths (46–4200 m) show a close correlation between the timing of up- and down-canyon currents and the timing of semi-diurnal tides. These tidal bottom currents in submarine canyons commonly attain maximum velocities of 25–50 cm\\/s. Based

G. Shanmugam

2003-01-01

41

Submarine canyons as important habitat for cetaceans, with special reference to the Gully: A review  

NASA Astrophysics Data System (ADS)

There has been much research interest in the use of submarine canyons by cetaceans, particularly beaked whales (family Ziphiidae), which appear to be especially attracted to canyon habitats in some areas. However, not all submarine canyons are associated with large numbers of cetaceans and the mechanisms through which submarine canyons may attract cetaceans are not clearly understood. This paper reviews some of the cetacean associations with submarine canyons that have been anecdotally described or presented in scientific literature and discusses the physical, oceanographic and biological mechanisms that may lead to enhanced cetacean abundance around these canyons. Particular attention is paid to the Gully, a large submarine canyon and Marine Protected Area off eastern Canada for which there exists some of the strongest evidence available for submarine canyons as important cetacean habitat. Studies demonstrating increased cetacean abundance in the Gully and the processes that are likely to attract cetaceans to this relatively well-studied canyon are discussed. This review provides some limited evidence that cetaceans are more likely to associate with larger canyons; however, further studies are needed to fully understand the relationship between the physical characteristics of canyons and enhanced cetacean abundance. In general, toothed whales (especially beaked whales and sperm whales) appear to exhibit the strongest associations with submarine canyons, occurring in these features throughout the year and likely attracted by concentrating and aggregating processes. By contrast, baleen whales tend to occur in canyons seasonally and are most likely attracted to canyons by enrichment and concentrating processes. Existing evidence thus suggests that at least some submarine canyons are important foraging areas for cetaceans, and should be given special consideration for cetacean conservation and protection.

Moors-Murphy, Hilary B.

2014-06-01

42

Sandwave migration in Monterey Submarine Canyon, Central California  

USGS Publications Warehouse

Repeated high-resolution multibeam bathymetric surveys from 2002 through 2006 at the head of the Monterey Submarine Canyon reveal a sandwave field along the canyon axis between 20 and 250??m water depth. These sandwaves range in wavelength from 20 to 70??m and 1 to 3??m in height. A quantitative measure was devised to determine the direction of sandwave migration based on the asymmetry of their profiles. Despite appreciable spatial variation the sandwaves were found to migrate in a predominantly down-canyon direction, regardless of season and tidal phases. A yearlong ADCP measurement at 250??m water depth showed that intermittent internal tidal oscillations dominated the high-speed canyon currents (50-80??cm/s), which are not correlated with the spring-neap tidal cycle. Observed currents of 50??cm/s or higher were predominantly down-canyon. Applying a simple empirical model, flows of such magnitudes were shown to be able to generate sandwaves of a size similar to the observed ones. ?? 2007 Elsevier B.V. All rights reserved.

Xu, J.P.; Wong, F.L.; Kvitek, R.; Smith, D.P.; Paull, C.K.

2008-01-01

43

Origin of Florida Canyon and the role of spring sapping on the formation of submarine box canyons  

USGS Publications Warehouse

Florida Canyon, one of a series of major submarine canyons on the southwestern edge of the Florida Platform, was surveyed using GLORIA, SeaBeam, and Deep-Tow technologies, and it was directly observed during three DSRV Alvin dives. Florida Canyon exhibits two distinct morphologies: a broad V-shaped upper canyon and a deeply entrenched, flat-floored, U-shaped lower canyon. The flat- floored lower canyon extends 20 km into the Florida Platform from the abyssal Gulf. The lower canyon ends abruptly at an ?3 km in diameter semicircular headwall that rises 750 m with a >60° slope angle to the foot of the upper canyon. The sides of the lower canyon are less steep than its headwall and are characterized by straight faces that occur along preferred orientations and indicate a strong joint control. The upper canyon is characterized by a gently sloping, straight V-shaped central valley cut into a broad terrace. The flat floor of the upper canyon continues as terraces along the upper walls of the lower canyon. On the flanks of the upper canyon, there are five >50-m-deep, >0.5-km-wide, closed sink-hole-like depressions which indicate subsurface dissolution within the platform. The origin of the lower canyon is difficult to explain with traditional models of submarine canyon formation by external physical processes. The movement of ground water, probably with high salinities and reduced compounds along regional joints, may have focused the corrosive force of submarine spring sapping at the head of the lower canyon to produce the canyon's present shape.

Paull, Charles K.; Spiess, Fred N.; Curray, Joseph R.; Twichell, David C.

1990-01-01

44

The eect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in  

E-print Network

The e¡ect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements 2001 Abstract This study examines the influence of a submarine canyon on the dispersal of sediments the head region of the Kao-ping Submarine Canyon whose landward terminus is located approximately 1 km

Lin, Andrew Tien-Shun

45

Internal tidal currents in the Gaoping (Kaoping) Submarine Canyon  

USGS Publications Warehouse

Data from five separate field experiments during 2000-2006 were used to study the internal tidal flow patterns in the Gaoping (formerly spelled Kaoping) Submarine Canyon. The internal tides are large with maximum interface displacements of about 200??m and maximum velocities of over 100cm/s. They are characterized by a first-mode velocity and density structure with zero crossing at about 100??m depth. In the lower layer, the currents increase with increasing depth. The density interface and the along-channel velocity are approximately 90?? out-of-phase, suggesting a predominant standing wave pattern. However, partial reflection is indicated as there is a consistent phase advance between sea level and density interface along the canyon axis. ?? 2008 Elsevier B.V. All rights reserved.

Lee, I.-H.; Wang, Y.-H.; Liu, J.T.; Chuang, W.-S.; Xu, J.

2009-01-01

46

SCLERACTINIAN CORAL RECRUITMENT PATTERNS AT SALT RIVER SUBMARINE CANYON  

Microsoft Academic Search

Abstract. Scleractinian,coral,recruitment,patterns,were studied at depths of 9, 18, 27 and 37 m on the east and west walls of Salt River submarine canyon, St . Croix, U.S . Virgin Islands, by censusing coral juveniles which settled,on experimental,settling,plates,placed,on the,reef for,3-26 months,as well,as coral,juveniles,within,quadrats on the,reef. The most,common,species,in the,juvenile,pop- ulation within quadrats were Agaricia agaricites, Porites astreoides, Madracis decactis, Stephanocoenia michelinii, and,A

St. Croix; Caroline S. Rogers; H. Carl Fitz III; Marcia Gilnack; James Beets; John Hardin

47

The buried Afiq Canyon (eastern Mediterranean, Israel): a case study of a Tertiary submarine canyon exposed in Late Messinian times  

Microsoft Academic Search

The Afiq submarine canyon was one of a series of canyons initially incised in a drowned shelf edge and slope of the eastern Mediterranean margins in early Oligocene times (P19 zone). During most of the Early Miocene submarine erosion or non-deposition prevailed. This was followed by deposition of pelagic marls and debris flows in early Middle Miocene (N8) times. Large-scale

Y. Druckman; B. Buchbinder; G. M. Martinotti; R. Siman Tov; P. Aharon

1995-01-01

48

Depth Distribution for the Order Cydippid (Phylum Ctenophora, Class Tentaculata) in the Monterey Submarine Canyon  

Microsoft Academic Search

This paper will discuss depth distribution analysis of cydippids in the Monterey Bay Submarine Canyon. Cydippids in the Monterey Canyon have been sighted at many different depths and areas. Since 1989, ten different cydippid species, including two new cydippids this year, were recorded on video using a remotely operated vehicle in ten sites within the Monterey Canyon. Because most of

Laura Dippold; Judith Connor; Nancy Jacobsen

49

Hydrodynamics and particle transport associated with a submarine canyon off Blanes (Spain), NW Mediterranean Sea  

Microsoft Academic Search

Particle transport rates were observed to be higher in a submarine canyon in the NW Mediterranean Sea than in areas surrounding the canyon. Velocity and particle profiles were used to reconstruct a three-dimensional (2-layer) grid of the flow field and resulting particle transport. Canyon topography enhanced both horizontal and downward transport of particles in an anticyclonic flow region over the

Timothy C. Granata; Beatriz Vidondo; Carlos M. Duarte; Maria Paola Satta; Marc Garcia

1999-01-01

50

Ascension Submarine Canyon, California - Evolution of a multi-head canyon system along a strike-slip continental margin  

USGS Publications Warehouse

Ascension Submarine Canyon, which lies along the strike-slip (transform) dominated continental margin of central California, consists of two discrete northwestern heads and six less well defined southeastern heads. These eight heads coalesce to form a single submarine canyon near the 2700 m isobath. Detailed seismic stratigraphic data correlated with 19 rock dredge hauls from the walls of the canyon system, suggest that at least one of the two northwestern heads was initially eroded during a Pliocene lowstand of sea level ???3.8 m.y. B.P. Paleogeographic reconstructions indicate that at this time, northwestern Ascension Canyon formed the distal channel of nearby Monterey Canyon and has subsequently been offset by right-lateral, strike-slip faulting along the San Gregorio fault zone. Some of the six southwestern heads of Ascension Canyon may also have been initially eroded as the distal portions of Monterey Canyon during late Pliocene-early Pleistocene sea-level lowstands (???2.8 and 1.75 m.y. B.P.) and subsequently truncated and offset to the northwest. There have also been a minimum of two canyon-cutting episodes within the past 750,000 years, after the entire Ascension Canyon system migrated to the northwest past Monterey Canyon. We attribute these late Pleistocene erosional events to relative lowstands of sea level 750,000 and 18,000 yrs B.P. The late Pleistocene and Holocene evolution of the six southeastern heads also appears to have been controlled by structural uplift of the Ascension-Monterey basement high at the southeastern terminus of the Outer Santa Cruz Basin. We believe that uplift of this basement high sufficiently oversteepened submarine slopes to induce gravitational instability and generate mass movements that resulted in the erosion of the canyon heads. Most significantly, though, our results and interpretations support previous proposals that submarine canyons along strike-slip continental margins can originate by tectonic trunction and lateral offset. ?? 1986.

Nagel, D.K.; Mullins, H.T.; Greene, H. Gary

1986-01-01

51

Hudson Submarine Canyon Head Offshore New York and New Jersey: A Dynamic Interface  

NASA Astrophysics Data System (ADS)

Hudson Canyon is the largest submarine canyon on the U. S. Atlantic continental margin. Having completed a surface ship multi-beam bathymetric map of the Hudson Canyon region (resolution 100m; http://pubs.usgs.gov/of/2004/1441/index/html), we report preliminary results of mapping portions of the canyon head (75 square km, water depth 200-500 m) using the Eagle Ray autonomous underwater vehicle (Explorer 27- BO1-2200 AUV, ISE Ltd.) of the University of Southern Mississippi. The AUV was equipped with a Simrad EM2000 multi-beam sonar system and flown 50 m above the seafloor for resolution (3 m), and with a CTD to map water column properties. Shipboard CTD casts were also made and water sampled from the shelf break (depth 200 m) to the upper continental rise (3000 m) for detection of methane. The canyon head is of interest as an essential fish habitat (squid, hake, tilefish, and lobster) that may contribute to sustain a regional fishery and that may conduct sediment to the ocean basin. A shallow trough, the Hudson Shelf Valley, extends ~185 km across the continental shelf connecting the mouth of the Hudson River to the canyon head where it indents the seaward edge of the shelf. The canyon head bifurcates with branch 1 (6 km-long) oriented NW-SE aligned with the Shelf Valley, and branch 2 (4 km-long) oriented N-S. The two branches merge into a segment 10 km-long oriented NW-SE aligned with branch 1. Branch 1 has symmetric walls with mean inclinations of 10 degrees and smooth seafloor, suggesting that it is presently inactive and accumulating a cover of hemipelagic sediment. In contrast, the walls of both the N-S branch 2 and of the contiguous NW-SE segment are asymmetric. The walls of the NW-SE segment have a mean inclination of 15 degrees and exhibit semicircular escarpments 800-900 m long and 600-700 m wide, separated by narrow ravines perpendicular to the canyon axis. Slump blocks with sharp rims occur where N-S branch 1 joins the NW- SE segment. Two circular depressions (diameter 100 and 300 m; relief c.15 m; depths 345 m and 390 m) occur at the base of the SW wall of the segment and may be collapse features related to gas discharge evidenced by a high methane anomaly at the shelf edge. The head of Hudson Canyon encompasses diverse habitats and is a dynamic interface between shelf and slope processes. We thank NOAA's National Undersea Research Program for support.

Rona, P.; Guida, V.; Sullivan, M.; Haag, S.; Macelloni, L.; Sweeney, E.; Scranton, M.; Hobbs, J.; Asper, V.

2007-12-01

52

A submarine canyon as the cause of a mud volcano — Liuchieuyu Island in Taiwan  

Microsoft Academic Search

In this paper, based on 3.5kHz, UNIBOOM and conventional seismic data, we propose a model for the creation of Liuchieuyu Island, a near-shore mud volcano off the southwestern coast of Taiwan. In support of this model, we also discuss the relationship between a nearby submarine canyon (Kaoping Submarine Canyon) and the mud diapirs and mud volcanoes in the region. Seismic

J. Chow; J. S. Lee; C. S. Liu; B. D. Lee; J. S. Watkins

2001-01-01

53

Geomorphic process fingerprints in submarine canyons Daniel S. Brothers , Uri S. ten Brink, Brian D. Andrews, Jason D. Chaytor, David C. Twichell  

E-print Network

Geomorphic process fingerprints in submarine canyons Daniel S. Brothers , Uri S. ten Brink, Brian D bathymetry regression power law landslide Submarine canyons are common features of continental margins. Though it is known that submarine canyons form pri- marily from erosion induced by submarine sediment

ten Brink, Uri S.

54

Delaware River: Evidence for its former extension to Wilmington Submarine Canyon  

USGS Publications Warehouse

Seismic-reflection profiles indicate that during the Pleistocene the Delaware River flowed across the continental shelf east of Delaware Bay and emptied into Wilmington Submarine Canyon. The ancestral valley (width, 3 to 8 kilometers; relief, 10 to 30 meters) is buried, is not reflected in the surface topography, and probably predates the formation of the present canyon head.

Twichell, D.C.; Knebel, H. J.; Folger, D.W.

1977-01-01

55

A multidisciplinary approach to the understanding of hydromedusan populations inhabiting Mediterranean submarine canyons  

Microsoft Academic Search

Studies carried out in four submarine canyons in the northwestern Mediterranean Sea have resulted in the discovery of a new fauna composed chiefly of hydromedusae. This finding has led us to postulate the existence of a singular planktonic community in these canyons that is probably maintained by the flux and deposit of organic material from the continental shelf. The specific

J.-M Gili; F. Pages; J. Bouillon; A. Palanques; P. Puig; S. Heussner; A. Calafat; M. Canals; A. Monaco

2000-01-01

56

Delaware river: evidence for its former extension to wilmington submarine canyon.  

PubMed

Seismic-reflection profiles indicate that during the Pleistocene the Delaware River flowed across the continental shelf east of Delaware Bay and emptied into Wilmington Submarine Canyon. The ancestral valley (width, 3 to 8 kilometers; relief, 10 to 30 meters) is buried, is not reflected in the surface topography, and probably predates the formation of the present canyon head. PMID:17734746

Twichell, D C; Knebel, H J; Folger, D W

1977-02-01

57

Accumulation of migratory micronekton crustaceans over the upper slope and submarine canyons of the northwestern Mediterranean  

Microsoft Academic Search

The distribution of migratory micronekton crustaceans in the axis and in the vicinity of three submarine canyons off the Mediterranean coast of France was investigated. Some species accumulated on the upper slope and in canyon heads. The fauna consisted mainly of two pelagic communities: (i) epipelagic, mesopelagic and infrapelagic oceanic fauna (hyperiids, euphausiids), which were advected to shelf waters during

Claude Macquart-Moulin; G. Patriti

1996-01-01

58

Composition and variability of downward particulate matter fluxes in the Palamós submarine canyon (NW Mediterranean)  

Microsoft Academic Search

To study the temporal and spatial variability of downward particle fluxes in the Palamós submarine canyon, seven sediment traps were moored inside and in the vicinity of the canyon from March to November 2001. Total mass fluxes, major constituent (organic carbon, opal, calcium carbonate and lithogenics) contents and fluxes, and 210Pb activity of particulate matter were obtained from two consecutive

J. Martín; A. Palanques; P. Puig

2006-01-01

59

Deep slope currents and suspended particle fluxes in and around the Foix submarine canyon (NW Mediterranean)  

Microsoft Academic Search

Deep slope currents and particulate matter concentrations were studied on the Barcelona continental margin in and around the Foix submarine canyon from May 1993 to April 1994. This year-long moored experiment revealed that near-bottom slope currents are strongly influenced by the bottom topography, being oriented along isobaths and along the canyon axis. The deep slope current fluctuations are controlled by

Pere Puig; Albert Palanques; Jorge Guillén; Emilio Garc??a-Ladona

2000-01-01

60

The Danube submarine canyon (Black Sea): morphology and sedimentary processes  

Microsoft Academic Search

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo–Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath

Irina Popescu; Gilles Lericolais; Nicolae Panin; Alain Normand; Cornel Dinu; Eliane Le Drezen

2004-01-01

61

Tectonically active sediment dispersal system in SW Taiwan margin with emphasis on the Gaoping (Kaoping) Submarine Canyon  

NASA Astrophysics Data System (ADS)

The sediment dispersal system in southwestern Taiwan margin consists of two main parts: the subaerial drainage basin and the offshore receiving marine basin. In plan view, this sediment dispersal system can be further divided into five geomorphic units: (1) the Gaoping (formerly spelled Kaoping) River drainage basin, (2) the Gaoping (Kaoping) Shelf, (3) the Gaoping (Kaoping) Slope, (4) the Gaoping (Kaoping) Submarine Canyon and (5) the Manila Trench in the northernmost South China Sea. The Gaoping River drainage basin is a small (3250 km 2), tectonically active and overfilled foreland basin, receiving sediments derived from the uprising Central Range of Taiwan with a maximum elevation of 3952 m. The Gaoping Submarine Canyon begins at the mouth of the Gaoping River, crosses the narrow Gaoping Shelf (~ 10 km) and the Gaoping Slope, and finally merges into the northern termination of the Manila Trench over a distance of ~ 260 km. The SW Taiwan margin dispersal system is characterized by a direct river-canyon connection with a narrow shelf and frequent episodic sediment discharge events in the canyon head. In a regional source to sink scheme, the Gaoping River drainage basin is the primary source area, the Gaoping Shelf being the sediment bypass zone and the Gaoping Slope being the temporary sink and the Manila Trench being the ultimate sink of the sediment from the Taiwan orogen. It is inferred from seismic data that the outer shelf and upper slope region can be considered as a line source for mass wasting deposits delivered to the lower Gaoping Slope where small depressions between diapiric ridges are partially filled with sediment or are empty. At present, recurrent hyperpycnal flows during the flood seasons are temporarily depositing sediments mainly derived from the Gaoping River in the head of the Gaoping Submarine Canyon. On the decadal and century timescales, sediments temporarily stored in the upper reach are removed over longer timescales probably by downslope-eroding sediment flows within the canyon. Presently, the Gaoping Submarine Canyon serves as the major conduit for transporting terrestrial sediment from the Taiwan orogen to the marine sink of the Manila Trench. Seismic data indicate that the Gaoping Submarine Canyon has been eroding the Gaoping Slope intensely by presumed hyperpycnal flows and transporting sediments from the canyon head to the middle and lower reaches of the canyon. The middle reach is a sediment bypass zone whereas the lower reach serves as either a temporary sediment sink or a sediment conduit, depending on relative prevalence to deposition or erosion during canyon evolution. Contrast differences in channel gradient and travel length between the Gaoping and Amazon sediment dispersal systems suggest that the Gaoping (Kaoping) River-Canyon system is an active sediment dispersal system for transporting terrestrial materials to the deep sea. The fate of the Gaoping River sediment is the northern Manila Trench.

Yu, Ho-Shing; Chiang, Cheng-Shing; Shen, Su-Min

2009-03-01

62

Late Quaternary evolution of the San Antonio Submarine Canyon in the central Chile forearc (?33°S)  

Microsoft Academic Search

Hydrosweep swath-bathymetry and seismic-reflection data reveal the morphology, sedimentary processes, and structural controls on the submarine San Antonio Canyon. The canyon crosses the forearc slope of the central Chile margin for more than 150 km before it empties into the Chile Trench near 33°S latitude. In its upper reaches, the nearly orthogonal segments of the San Antonio Canyon incise ?1

Jane Laursen; William R Normark

2002-01-01

63

Recent sea beam mapping of Ascension-Monterey Submarine Canyon System  

SciTech Connect

Extensive Sea Beam and Bathymetric Swatch Survey System (BS{sup 3}) data covering the Ascension-Monterey Submarine Canyon system and adjoining areas and canyons were collected offshore central California. Many discovered geomorphological features lead to significant new geologic conclusions about the formation and processes of submarine canyons in general and disclose unique sedimentary and tectonic features of the Ascension-Monterey Canyon system. The highly detailed bathymetric maps constructed from the Sea Beam data indicate that the seafloor topographic pattern is influenced by sedimentary and tectonic processes; both remain active along the central California margin. Interpretations of MOAA composite maps, final raw Sea Beam bathymetric maps, and three-dimensional physiographic renditions from bathymetric data indicate a diverse and complex geomorphology for the Ascension-Monterey Submarine Canyon system and adjoining region. Five distinct geomorphologic provinces and four well-defined geographic areas are mapped. Canyons cut by faults and canyon walls actively undergoing mass wasting are prominently displayed in the Sea Beam data. Sedimentary processes illustrating canyon channel capture and the formation of extensive mega-sedimentary wave fields where the canyons debouch onto the abyssal plain are spectacularly well defined. This new tool of seafloor mapping is contributing significant data for the geological interpretation of continental margins and seafloor in the world's oceans.

Greene, H.G. (Geological Survey, Menlo Park, CA (USA))

1990-06-01

64

Transition from partly standing to progressive internal tides in Monterey Submarine Canyon  

NASA Astrophysics Data System (ADS)

Monterey Submarine Canyon is a large, sinuous canyon off the coast of California, the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward-looking moored ADCPs. The mooring observations measured a near-surface stratification change in the upper canyon, likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling. This change in near-surface stratification caused a transition in the behaviour of the internal tide in the upper canyon from a partly standing wave during pre-upwelling conditions to a progressive wave during upwelling conditions. Using a numerical model, we present evidence that either a partly standing or a progressive internal tide can be simulated in the canyon, simply by changing the initial stratification conditions in accordance with the observations. The mechanism driving the transition is a dependence of down-canyon (supercritical) internal tide reflection from the canyon floor and walls on the depth of maximum stratification. During pre-upwelling conditions, the main pycnocline extends down to 200 m (below the canyon rim) resulting in increased supercritical reflection of the up-canyon propagating internal tide back down the canyon. The large up-canyon and smaller down-canyon progressive waves are the two components of the partly standing wave. During upwelling conditions, the pycnocline shallows to the upper 50 m of the watercolumn (above the canyon rim) resulting in decreased supercritical reflection and allowing the up-canyon progressive wave to dominate.

Hall, Rob A.; Alford, Matthew H.; Carter, Glenn S.; Gregg, Michael C.; Lien, Ren-Chieh; Wain, Danielle J.; Zhao, Zhongxiang

2014-06-01

65

Discovery of two new large submarine canyons in the Bering Sea  

USGS Publications Warehouse

The Beringian continental margin is incised by some of the world's largest submarine canyons. Two newly discovered canyons, St. Matthew and Middle, are hereby added to the roster of Bering Sea canyons. Although these canyons are smaller and not cut back into the Bering shelf like the five very large canyons, they are nonetheless comparable in size to most of the canyons that have been cut into the U.S. eastern continental margin and much larger than the well-known southern California canyons. Both igneous and sedimentary rocks of Eocene to Pliocene age have been dredged from the walls of St. Matthew and Middle Canyons as well as from the walls of several of the other Beringian margin canyons, thus suggesting a late Tertiary to Quaternary genesis of the canyons. We speculate that the ancestral Yukon and possibly Anadyr Rivers were instrumental in initiating the canyon-cutting processes, but that, due to restrictions imposed by island and subsea bedrock barriers, cutting of the two newly discovered canyons may have begun later and been slower than for the other five canyons. ?? 1984.

Carlson, P.R.; Karl, Herman A.

1984-01-01

66

A multidisciplinary study of the role of submarine canyons off western Portugal  

Microsoft Academic Search

A multidisciplinary research aimed to characterise the dominant aspects of the Portuguese canyon systems and their role on the shelf-deep ocean sediment exchanges is being conducted in the framework of EU project Eurostrataform. Three contrasting systems are studied: (1) the Nazaré Canyon is a narrow and deep canyon which extends from the deep ocean and completely cuts the NW Portuguese

J. Vitorino; A. Oliveira; A. Rodrigues

2003-01-01

67

Submarine canyons: hotspots of benthic biomass and productivity in the deep sea.  

PubMed

Submarine canyons are dramatic and widespread topographic features crossing continental and island margins in all oceans. Canyons can be sites of enhanced organic-matter flux and deposition through entrainment of coastal detrital export, dense shelf-water cascade, channelling of resuspended particulate material and focusing of sediment deposition. Despite their unusual ecological characteristics and global distribution along oceanic continental margins, only scattered information is available about the influence of submarine canyons on deep-sea ecosystem structure and productivity. Here, we show that deep-sea canyons such as the Kaikoura Canyon on the eastern New Zealand margin (42 degrees 01' S, 173 degrees 03' E) can sustain enormous biomasses of infaunal megabenthic invertebrates over large areas. Our reported biomass values are 100-fold higher than those previously reported for deep-sea (non-chemosynthetic) habitats below 500 m in the ocean. We also present evidence from deep-sea-towed camera images that areas in the canyon that have the extraordinary benthic biomass also harbour high abundances of macrourid (rattail) fishes likely to be feeding on the macro- and megabenthos. Bottom-trawl catch data also indicate that the Kaikoura Canyon has dramatically higher abundances of benthic-feeding fishes than adjacent slopes. Our results demonstrate that the Kaikoura Canyon is one of the most productive habitats described so far in the deep sea. A new global inventory suggests there are at least 660 submarine canyons worldwide, approximately 100 of which could be biomass hotspots similar to the Kaikoura Canyon. The importance of such deep-sea canyons as potential hotspots of production and commercial fisheries yields merits substantial further study. PMID:20444722

De Leo, Fabio C; Smith, Craig R; Rowden, Ashley A; Bowden, David A; Clark, Malcolm R

2010-09-22

68

Submarine canyons: hotspots of benthic biomass and productivity in the deep sea  

PubMed Central

Submarine canyons are dramatic and widespread topographic features crossing continental and island margins in all oceans. Canyons can be sites of enhanced organic-matter flux and deposition through entrainment of coastal detrital export, dense shelf-water cascade, channelling of resuspended particulate material and focusing of sediment deposition. Despite their unusual ecological characteristics and global distribution along oceanic continental margins, only scattered information is available about the influence of submarine canyons on deep-sea ecosystem structure and productivity. Here, we show that deep-sea canyons such as the Kaikoura Canyon on the eastern New Zealand margin (42°01? S, 173°03? E) can sustain enormous biomasses of infaunal megabenthic invertebrates over large areas. Our reported biomass values are 100-fold higher than those previously reported for deep-sea (non-chemosynthetic) habitats below 500 m in the ocean. We also present evidence from deep-sea-towed camera images that areas in the canyon that have the extraordinary benthic biomass also harbour high abundances of macrourid (rattail) fishes likely to be feeding on the macro- and megabenthos. Bottom-trawl catch data also indicate that the Kaikoura Canyon has dramatically higher abundances of benthic-feeding fishes than adjacent slopes. Our results demonstrate that the Kaikoura Canyon is one of the most productive habitats described so far in the deep sea. A new global inventory suggests there are at least 660 submarine canyons worldwide, approximately 100 of which could be biomass hotspots similar to the Kaikoura Canyon. The importance of such deep-sea canyons as potential hotspots of production and commercial fisheries yields merits substantial further study. PMID:20444722

De Leo, Fabio C.; Smith, Craig R.; Rowden, Ashley A.; Bowden, David A.; Clark, Malcolm R.

2010-01-01

69

The effect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in southern Taiwan  

Microsoft Academic Search

This study examines the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and on the sediment movement on the inner shelf. The study area includes the head region of the Kao-ping Submarine Canyon whose landward terminus is located approximately 1 km seaward from the mouth of the Kao-ping River in southern Taiwan. Within

James T. Liu; Kuen-jang Liu; Jeff C. Huang

2002-01-01

70

Geomorphic process fingerprints in submarine canyons1 Daniel S. Brothers*, Uri S. ten Brink, Brian D. Andrews, Jason D. Chaytor, David C.2  

E-print Network

1 Geomorphic process fingerprints in submarine canyons1 Daniel S. Brothers*, Uri S. ten *Corresponding author: dbrothers@usgs.gov; 508-457-229310 11 Abstract12 Submarine canyons are common from the continents to the deep sea.14 Though it is known that submarine canyons form primarily from

ten Brink, Uri S.

71

Submarine canyon and slope processes of the U.S. Atlantic continental margin  

USGS Publications Warehouse

Two regions on the U.S. Atlantic continental margin were surveyed using single-channel, seismic-reflection profiling techniques: the Mid-Atlantic Continental Slope and Rise seaward of New Jersey in the vicinity of Baltimore Canyon and the Continental Slope and upper Rise just north of Cape Hatteras. Submarine canyons are the dominant morphologic feature in both areas. The Continental Slope in the Baltimore Canyon area has a general sea-floor gradient of 3?-4? and a width of approximately 40 km, whereas the study area north of Cape Hatteras has a general sea-floor gradient of approximately 9? and a width of 20 km. The dominant slope process differs in each area. In the Baltimore Canyon area, subbottom reflectors suggest that sediment deposition with progradation of the slope is related to canyon processes. In the study area north of Cape Hatteras, the canyons appear erosional and mass wasting is the dominant erosional process. Dominant slope processes appear to be correlated with the width and sea-floor gradient of the Continental Slope. Although the absolute age of the canyons is difficult to determine without rotary-drill cores for stratigraphic control, Baltimore Canyon is suggested to be older than the shelf-indenting canyon just north of Cape Hatteras. An anomalously large ridge flanking Baltimore Canyon on the upper rise appears to be related to canyon depositional and erosional processes.

McGregor, B.A.

1983-01-01

72

Clast-contact conglomerates in submarine canyons: possible subaqueous sieve deposits  

SciTech Connect

Thick, coarse, clast-contact conglomerates in submarine canyon fill have previously been attributed to rock-fall, grain-flow, or winnowing processes. However, these processes do not adequately explain some thick conglomeratic sequences. The proposed process of subaqueous sieve deposition could account for these clast-contact conglomerates. Subaerial sieve deposition has been documented on small-scale fan models and on alluvial fans. A subaerial sieve deposit begins as a debris flow which at some point freezes up. The matrix is then lost by subsequent filtration or outflow, and the emplacement of a clast-contact gravel ensues. A subaqueous sieve deposit would be slightly modified in that the matrix would not be lost by filtration into the submarine canyon floor, but rather by outflow at the terminus of the lobe immediately after deposition, or possibly from the top and/or sides of the freezing flow mass during transport. Besides forming in submarine canyons, subaqueous sieve deposits might also occur in paralic, submarine fan channel, and base-of-the-slope settings. In substantiating the existence of subaqueous sieve deposits, the sedimentary structures and grain-size data from recent sieve deposits on alluvial fans are compared to those of ancient submarine canyon deposits. Numerous similarities are found supporting this new method of deposition. Some discrepancies are encountered, but these are expected due to modifications caused by an aqueous medium.

Fitzgerald, M.S.

1987-05-01

73

Evolution of Paleogene submarine Canyon-Fan systems, southern Sacramento basin, California  

SciTech Connect

The evolutionary development of the Paleogene Martinez and Meganos Submarine Canyon and Fan systems of the southern Sacramento basin was controlled by a complex interplay of eustatic sea level change and tectonism. In this brief synthesis, the authors postulated that eustatic sea level changes were the dominant or controlling factor, and tectonism, although significant, was of secondary importance. The development of the Paleogene canyon and fan systems is correlated with low sea level stands or regressions at 60 Ma and 56 Ma. Intermittent tectonism, beginning at least 5-10 m.y. earlier, particularly along the western and southwestern margins of the Sacramento basin, controlled the location of the canyon and fan systems. The controlling tectonic elements of the southern basin were north-trending, high-angle faults related to the Kirby Hills and Midland fault zones and the Diablo-Kirby Hills(.) uplift. Both canyons were probably active (that is, channeling coarse sediment to their fans) during most of the late Paleocene. The authors suggest that canyon activity was maintained by south-flowing longshore drift or feeder systems, down-canyon gravity flows (turbidites, etc) and up-down canyon current systems, all of which are typical of modern, active submarine canyon and fan systems. The canyons filled with fine-grained sediments when the canyons were beheaded or separated from the longshore drift system by rising sea level, or when tectonism(.) shifted the major river drainage that supplied the canyon with sediment. Truncation and erosion of the canyon-fill and fan facies of the late Paleocene-early Eocene Meganos Formation along the Diablo outcrop belt was primarily due to the major early middle Eocene lowstand (49.5 Ma).

Fischer, P.J.; Cherven, V.B.; Almgren, A.A.

1986-04-01

74

Sediment dynamics in a submarine canyon: a case of river–sea interaction  

Microsoft Academic Search

This paper presents findings from a 1-month field experiment conducted during the flood season of 2000 on the southern coast of Taiwan to examine the delivery of lithogenic (siliciclastic) sediment to Kao-ping Submarine Canyon from the nearby Kao-ping River and shelf sources and the transport of suspended lithogenic and nonlithogenic particles near the canyon floor. Collected time series data included

James T. Liu; Hui-ling Lin

2004-01-01

75

Morphology of San Antonio submarine canyon on the central Chile forearc  

Microsoft Academic Search

A multibeam survey was conducted over San Antonio submarine canyon, near Valparaiso, Chile, in April and May 1993 using the SeaBeam 2000 system on the R\\/V Melville. The bathymetric data from this survey reveal a canyon with an overall sinuosity of 1.25, a broad, roughly U-shaped cross-section along most of its length, and an almost constant channel slope above the

Rick A. Hagen; Hernán Vergara; David F. Naar

1996-01-01

76

Internal wave behaviour in the submarine canyons of the Celtic Sea Shelf  

NASA Astrophysics Data System (ADS)

The Celtic Sea, located off the south coast of Ireland, is a 100-200m deep shelf sea that is notable for the presence of large tidal currents and strong seasonal fluctuations in surface heating and cooling. The shelf edge is a region of rough topography and barotropic tidal flows generate internal waves and associated baroclinic energy fluxes. These internal tides are reflected if they encounter topographic features. The reflection is dependent on the relative topographic slope and can be subcritical (waves continue to shoal), supercritical (waves are reflected back into deep water) or critical (nonlinear effects, potential wave breaking and turbulent mixing). Submarine canyons are a common bathymetric feature along the Celtic Sea shelf edge and are known to trap and focus internal waves towards the head of the canyon, leading to high levels of turbulent mixing. This mixing may drive vertical nutrient fluxes and enhance primary productivity at the shelf edge. Celtic Sea submarine canyons are typically dendritic and vary in cross sectional profile along the length of their axis, providing many different topographic slope values. Using a numerical model, I will investigate the propagation of internal waves through both idealised canyons and realistic canyon bathymetry from the Celtic Sea shelf edge. Using the results I will attempt to parameterise submarine canyon morphology based on its effect on the internal wave field.

Aslam, Tahmeena; Hall, Rob; Heywood, Karen; Dye, Stephen

2014-05-01

77

Geomorphology and sedimentary features in the Central Portuguese submarine canyons, Western Iberian margin  

NASA Astrophysics Data System (ADS)

The Central Portuguese submarine canyons (Nazaré, Cascais and Setúbal-Lisbon canyons) dissect the Western Iberian margin in an east-west direction from the continental shelf, at water depths shallower than 50 m, down to the Tagus and Iberian abyssal plains, at water depths exceeding 5000 m. We present an analysis of the geomorphology of the canyons and of the sedimentary processes that can be inferred from the observed morphology of the three canyons, based on a compilation of swath bathymetry data and TOBI deep-towed side-scan sonar imagery. This first complete detailed mapping of the Central Portuguese canyons reveals substantial differences in their morphologies and downslope evolution. The canyons are divided into three sections: 1) canyon head and upper reach, 2) middle canyon, and 3) canyon mouth and distal part. The canyon heads and upper reaches are severely indented into the continental shelf, and they are characterised, in the Nazaré and Setúbal-Lisbon canyons, by sinuous V-shaped valleys entrenched within high canyon walls occupied by rock outcrops dissected by gullies. The Cascais upper canyon is complex, with multiple branches with high axial gradients and signs of mass wasting. Middle canyon sections, indented in the slope, display axial incisions with perched, stacked terraces, and are affected by debris avalanches originating from the canyon walls. At the base of slope, the distal Cascais and Setúbal-Lisbon canyons show many characteristics of channel-lobe transition zones: erosional features such as isolated to amalgamated chevron scours, and depositional bedforms such as mud to gravel waves. Pervasive scouring occurs up to 95 km beyond the canyon mouths. By contrast, the Nazaré canyon opens into a 27 km wide and 94 km long channel, whose flat-bottomed thalweg is occupied by sediment waves, irregular, comet-shaped and crescentic scours, and a second-order channel. Transverse, kilometre-scale sediment waves occupy the overbank area of the southern channel margin. The present morphology of the Central Portuguese canyons is the result of erosive processes, subsequent sediment transport and deposition, and sediment instability, whereas inherited tectonic fabric controls their location. Morphological differences between the canyons are explained by the main mechanisms driving their activity. Overall, these morphological features suggest that these canyons have acted as an efficient conduit of sediment to the deep basin, transporting large quantities of material to the deep sea during high-energy events.

Lastras, G.; Arzola, R. G.; Masson, D. G.; Wynn, R. B.; Huvenne, V. A. I.; Hühnerbach, V.; Canals, M.

2009-02-01

78

Distribution, composition, and transport of suspended particulate matter in the vicinity of Willapa submarine canyon, Washington  

Microsoft Academic Search

The distribution and composition of suspended particulate matter in the waters over Willapa submarine canyon and the adjacent continental slope off the coast of Wasington describe an apparently continuous botton nepheloid layer ranging in thickness from 160 to 530 m and composed of particles supplied primarily by the nearby Columbia River. Near-bottom particulate concentrations, estimated by continuous vertical profiles of

EDWARD T. BAKER

1976-01-01

79

Wave-driven setup and alongshore flows observed onshore of a submarine canyon  

Microsoft Academic Search

The effect of alongshore variations in the incident wavefield on wave-driven setup and on alongshore flows in the surfzone is investigated using observations collected onshore of a submarine canyon. Wave heights and radiation stresses at the outer edge of the surfzone (water depth ?2.5 m) varied by up to a factor of 4 and 16, respectively, over a 450 m

Alex Apotsos; Britt Raubenheimer; Steve Elgar; R. T. Guza

2008-01-01

80

Marine Protected Area Design and the Spatial and Temporal Distribution of Cetaceans in a Submarine Canyon  

Microsoft Academic Search

The Gully, the largest submarine canyon off the coast of eastern Canada, is currently under consid- eration as a marine conservation area, primarily because of the increasing interest in oil and gas production on the Scotian Shelf. Cetaceans, as a guild of abundant, large organisms that are relatively sensitive to such threats, provide a reliable means to determine the boundaries

Sascha K. Hooker; Hal Whitehead; Shannon Gowans

1999-01-01

81

Scleractinian coral recruitment patterns at Salt River submarine canyon, St. Croix, U.S. Virgin Islands  

Microsoft Academic Search

Scleractinian coral recruitment patterns were studied at depths of 9, 18, 27 and 37 m on the east and west walls of Salt River submarine canyon, St. Croix, U.S. Virgin Islands, by censusing coral juveniles which settled on experimental settling plates placed on the reef for 3–26 months as well as coral juveniles within quadrats on the reef. The most

Caroline S. Rogers; H. Carl Fitz; Marcia Gilnack; James Beets; John Hardin

1984-01-01

82

Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons  

Microsoft Academic Search

Habitat heterogeneity is a major structuring agent of ecological assemblages promoting beta diversity and ultimately contributing to overall higher global diversity. The exact processes by which heterogeneity increases diversity are scale dependent and encompass variation in other well-known processes, e.g., productivity, disturbance, and temperature. Thus, habitat heterogeneity likely triggers multiple and cascading diversity effects through ecological assemblages. Submarine canyons, a

Craig R. McClain; James P. Barry

2010-01-01

83

Offshore transport of dense shelf water in the presence of a submarine canyon  

Microsoft Academic Search

The formation and offshore transport of dense water over a uniformly sloping shelf crosscut by a submarine canyon is examined using a three-dimensional primitive-equation numerical model. A constant negative buoyancy flux is applied in a limited region adjacent to a straight coast to represent brine rejection from ice production in an idealized coastal polynya. A sharp density front forms at

David C. Chapman; Glen Gawarkiewicz

1995-01-01

84

Burrow construction and behavior of tilefish, Lopholatilus chamaeleonticeps , in Hudson Submarine Canyon  

Microsoft Academic Search

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish

Kenneth W. Able; Churchill B. Grimes; Richard A. Cooper; Joseph R. Uzmann

1982-01-01

85

Headless submarine canyons and fluid flow on the toe of the Cascadia accretionary complex  

USGS Publications Warehouse

Headless submarine canyons with steep headwalls and shallowly sloping floors occur on both the second and third landward vergent anticlines on the toe of the Cascadia accretionary complex off central Oregon (45 ??N, 125?? 30??W). In September 1993, we carried out a series of nine deep tow camera sled runs and nine ALVIN dives to examine the relationship between fluid venting, structure and canyon formation. We studied four canyons on the second and third landward vergent anticlines, as well as the apparently unfailed intercanyon regions along strike. All evidence of fluid expulsion is associated with the canyons; we found no evidence of fluid flow between canyons. Even though all fluid seeps are related to canyons, we did not find seeps in all canyons, and the location of the seeps within the canyons differed. On the landward facing limb of the second landward vergent anticline a robust cold seep community occurs at the canyon's inflection point. This seep is characterized by chemosynthetic vent clams, tube worms and extensive authigenic carbonate. Fluids for this seep may utilize high-permeability flow paths either parallel to bedding within the second thrust ridge or along the underlying thrust fault before leaking into the overriding section. Two seaward facing canyons on the third anticlinal ridge have vent clam communities near the canyon mouths at approximately the intersection between the anticlinal ridge and the adjacent forearc basin. No seeps were found along strike at the intersection of the slope basin and anticlinal ridge. We infer that the lack of seepage along strike and the presence of seeps in canyons may be related to fluid flow below the forearc basin/slope unconformity (overpressured by the impinging thrust fault to the west?) directed toward canyons at the surface.

Orange, D.L.; McAdoo, B.G.; Moore, J.C.; Tobin, H.; Screaton, E.; Chezar, H.; Lee, H.; Reid, M.; Vail, R.

1997-01-01

86

The Barrow submarine Canyon: A drain for the chukehi sea  

Microsoft Academic Search

Oceanographic measurements made in the spring through holes in the ice in an area off Barrow, where the Barrow Canyon forms a sloping trough from the shallow Chukehi Sea into the deep Beaufort Sea, have revealed two interacting water movements: (1) a flow of highly saline water from the shallow Chukehi Sea into the Beaufort Sea through the Barrow Canyon

G. R. Garrison; P. Becker

1976-01-01

87

The structure and origin of the large submarine canyons of the Bering Sea  

USGS Publications Warehouse

Three exceptionally large and long submarine canyons - Bering, Pribilof, and Zhemchug - incise the continental slope underlying the southeastern Bering Sea. Bering Canyon, the world's longest known slope valley, is approximately 400 km long and has a volume of 4,300 km3. The volume of Pribilof Canyon is 1,300 km3 and that of Zhemchug is 8,500 km3; Zhemchug Canyon may well be the world's largest slope valley; most other large submarine canyons have volumes less than 500 km3. Pribilof and Zhemchug canyons are further distinguished by the headward bifurcation of their slope axes to form elongated trough-shaped basins behind the regionally projected position of the shelf edge. These troughs are superimposed over structural depressions formed by down-faulted basement rocks of Mesozoic and older ages. Prior to canyon cutting these depressions were filled with as much as 2,600 m of shallow-water diatomaceous, tuffaceous, and detrital sediments largely of Tertiary age. Deposition of these sediments took place concurrently with general margin subsidence of at least 2,000 m. The data and conclusions presented in this paper stress that the location, trend, and shape of the enormous submarine canyons cutting the Bering margin are structurally determined. However, axial cutting and headward erosion within the relatively unconsolidated Tertiary strata and the older, lithified basement rock is thought to have been caused by basinward-sliding masses of sediment; these unstable sediment bodies accumulated on the upper continental slope and outer shelf, probably near the mouths of major Alaskan rivers. Bering Canyon was periodically cut and filled by axial sedimentation during Late Tertiary and Quaternary time. Pribilof and Zhemchug canyons, however, are thought to have been excavated entirely during the Pleistocene. It is presumed that, during one or more periods of glacially lowered sea level, the Kuskokwim and Yukon rivers emptied into or near the heads of Pribilof and Zhemchug canyons. The enormous size and unusual shape of Zhemchug Canyon resulted from the breaching of the seaward wall of an outer-shelf basement depression and the subsequent removal of nearly 4,500 km3 of Tertiary deposits filling it. ?? 1970.

Scholl, D. W.; Buffington, E.C.; Hopkins, D.M.; Alpha, T.R.

1970-01-01

88

Event-driven sediment flux in Hueneme and Mugu submarine canyons, southern California  

USGS Publications Warehouse

Vertical sediment fluxes and their dominant controlling processes in Hueneme and Mugu submarine canyons off south-central California were assessed using data from sediment traps and current meters on two moorings that were deployed for 6 months during the winter of 2007. The maxima of total particulate flux, which reached as high as 300+ g/m2/day in Hueneme Canyon, were recorded during winter storm events when high waves and river floods often coincided. During these winter storms, wave-induced resuspension of shelf sediment was a major source for the elevated sediment fluxes. Canyon rim morphology, rather than physical proximity to an adjacent river mouth, appeared to control the magnitude of sediment fluxes in these two submarine canyon systems. Episodic turbidity currents and internal bores enhanced sediment fluxes, particularly in the lower sediment traps positioned 30 m above the canyon floor. Lower excess 210Pb activities measured in the sediment samples collected during periods of peak total particulate flux further substantiate that reworked shelf-, rather than newly introduced river-borne, sediments supply most of the material entering these canyons during storms.

Xu, J.P.; Swarzenski, P.W.; Noble, M.; Li, A.-C.

2010-01-01

89

Geotechnical and sedimentological properties of Nice slope and submarine Var canyon deposits  

SciTech Connect

The submarine topography of the Baie des Anges consists of a narrow shelf and a steep slope where about 1,000 m-thick Pliocene-Quaternary deposits overlie the Messinian erosion surface. After a stage of rapid development, this large sedimentary body was submitted during the Quaternary to degradation through active mass-wasting processes. Thirteen piston cores were taken in several parts along the flanks and the floor of the Var canyon. Logging of these cores included gamma-density measurements, sedimentary structure descriptions, and microfacies observations (nannofossils). The cores were also sampled for a first geotechnical analysis. Geotechnical parameters such as water content, bulk density, vane shear strength, and Atterberg limits allowed us to study the response of surficial sediments to the vertical effective pressure and to discriminate several geotechnical groups related to different genetic types of sediment. Particularly the consolidation state was evaluated with the calculated ratio between undrained cohesion and vertical effective pressure (C/sub u//P). The sediment stability was assessed using the infinite slope stability analysis method under undrained conditions. Results of this preliminary analysis show that sedimentary instabilities could occur on important slopes.

Cochonat, P.; Schieb, T.; Guillaume, J.; Kerbrat, R.; Tisot, J.P.; Auffret, G.A.; Mueller, C.

1988-08-01

90

Submarine canyons as the preferred habitat for wood-boring species of Xylophaga (Mollusca, Bivalvia)  

NASA Astrophysics Data System (ADS)

Submarine canyons are often viewed as natural “debris concentrators” on the seafloor. Organic substrates may be more abundant inside than outside canyon walls. To determine the effects of the presence these substrates in the Blanes submarine canyon (NW Mediterranean) and its adjacent western open slope, we deployed wood to study colonizing organisms. Three replicate pine and oak cubes (i.e. most common trees inland) were moored at 900, 1200, 1500 and 1800 m depth and collected after 3, 9 and 12 months. Wood from inside the canyon was significantly more heavily colonized by the five morphotypes of wood-boring bivalves than was wood on the adjacent open slope. Xylophaga sp. A dominated all wood types and locations, with peak abundance at 900 and 1200 m depth. Its growth rate was highest (0.070 mm d-1) during the first three months and was faster (or it recruits earlier) in pine than in oak. Size distribution showed that several recruitment events may have occurred from summer to winter. Xylophaga sp. B, appeared first after 9 months and clearly preferred pine over oak. As the immersion time was the same, this strongly supported a specific association between recruiters and type of substrate. Three morphotypes, pooled as Xylophaga spp. C, were rare and seemed to colonize preferentially oak inside the canyon and pine in the adjacent open slope. Individuals of Xylophaga were more abundant inside the canyon than in nearby off-canyon locations. Blanes Canyon may serve as a long-term concentrator of land-derived vegetal fragments and as a consequence sustain more animals. Are the species richness and abundance of wood-boring bivalves higher inside the canyon than on the adjacent open slope? Do the composition and density of the wood-boring bivalves change with deployment time and depth, as well as on the type of the sunken wood? What is the growth rate of the dominant wood-boring species?

Romano, C.; Voight, J. R.; Company, J. B.; Plyuscheva, M.; Martin, D.

2013-11-01

91

Axial Channel Morphology Fill and Movement Within Submarine Canyons off California  

NASA Astrophysics Data System (ADS)

Axial channels of seven submarine canyons off California have recently been investigated with ultrahigh resolution multibeam surveys. Vibracores collected from remotely operated vehicles (ROVs) provide ground truth data on the materials within the axis of six of these canyons. Acoustic beacons were used to track movement of the seafloor within the axis of Monterey Canyon. Multibeam bathymetry (0.15 m vertical precision and 1.0 m horizontal resolution at 50 m survey altitude) and chirp seismic-reflection profiles (0.11 m vertical resolution) were collected from an autonomous underwater vehicle (AUV). Inertial navigation combined with Doppler velocity sonar allows the AUV to navigate the sinuous canyons at 3 kt on a pre-programmed route ~50 m above the seafloor. Submarine canyons that head near the shoreline (Monterey, Hueneme, Mugu, Redondo and La Jolla) contain similar wave-like bedforms with 20-100 m wavelengths and amplitudes up to 2.5 m oriented roughly perpendicular to the channel axis. These bedforms are asymmetric in profile with a steep down-canyon face and crescent-shaped, concave down-canyon. They are observed throughout the surveys (80-800 m water depth) and appear to form genetically similar packages (0.1 to 3 km long) that terminate upslope at a somewhat higher topographic step. Generally, bedform groups are found within the axial channel, but occasionally extend up the canyon walls. ROV-collected vibracores show that the wave-like bedforms comprise recent, coarse-grained gravity flow deposits, suggesting these canyons are active. In contrast, two submarine canyons with heads on the outer shelf (Soquel and Santa Monica) lack these wave-like bedforms and have relatively smooth axial channel floors. Vibracores show these canyons are filled with generally uniform fine-grained sediments, suggesting they are inactive. Apparently wave-like bedforms are common features of active submarine canyons. To assess whether sediment within a canyon floor is moved by traction currents or mass transport, three acoustic beacons were deployed in Monterey Canyon (~290 m water depth) in February 2007. The beacons were placed in 50-cm-high ~45 kg concrete monuments. These boulder-sized monuments were buried leaving only the top of the beacon extending ~6 cm above the seafloor. The position of these beacons was re-surveyed 8 times between February 2007 and July 2008. While the beacons did not move between most surveys, two down-canyon shifts of ~150 m and >1,200 m were measured. The episodic movement of the buried monuments suggests that the seafloor was remobilized to more than 50-cm- depth during sediment transport events. Four repeat AUV multibeam surveys were also conducted during the first half of 2007. These surveys show that the wave-shaped bedforms occur in the canyon axis down to at least 1,100 m water depth. Because the buried monuments have moved more than two wavelengths down- canyon during an individual event, identification and tracking of individual bedforms between events has proven to be difficult. Apparently, these wave-shaped bedforms are produced during brief, discrete mass transport events.

Paull, C. K.; Caress, D. W.; Ussler, W.; Lundsten, E.; Thomas, H.

2008-12-01

92

Organic geochemistry of submarine canyons: The Portuguese Margin  

NASA Astrophysics Data System (ADS)

The organic geochemistry of the Portuguese Margin of the North-Eastern Atlantic Ocean reveals a highly heterogeneous environment that is strongly influenced by canyons that incise the continental margin. Suspended particulate organic matter (sPOM) is funnelled through the canyons to the deep sea, particularly in the Nazaré Canyon where there are high concentrations of sPOM even at >2000 m water depth. The nature of the sPOM through the water column varies, with that transported through the canyons having higher contributions of terrestrial organic matter (higher C/N and larger contribution of land plant-derived lipids) than sPOM in overlying waters and close to the seafloor on the adjacent slope. Zooplankton-derived lipids dominate sPOM associated with the upper and lower boundaries of the Mediterranean Overflow Water (MOW˜600 and 1500 m, respectively). Canyon sediments are enriched in organic carbon when compared to slope sediments, but sedimentary organic matter also appears to derive from multiple sources and undergoes significant alteration prior to deposition. On the open slope, low sedimentation rates and long oxygen exposure times lead to intensive oxidation of organic matter.

Kiriakoulakis, Kostas; Blackbird, Sabena; Ingels, Jeroen; Vanreusel, Ann; Wolff, George A.

2011-12-01

93

Composition, export and faunal utilization of drift vegetation in the salt river submarine canyon  

NASA Astrophysics Data System (ADS)

Submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water. We studied the composition, export, and faunal utilization of shallow, nearshore benthic vegetation as it was transported to offshore areas via the Salt River submarine canyon on the island of St Croix, U.S. Virgin Islands. The study was conducted using a saturation diving system (NULS-1: Hydrolab) during two missions in April and August, 1980. Using bottom drifters deployed in Salt River Bay and the submarine canyon, we recorded net benthic current flow up to 2 cm s -1 moving out of the lagoon and down the canyon to deeper water. Using bottom nets set up at the canyon head and at the 29 m isobar, and from transect surveys and drift clump samples, we determined drift plant export rates and drift clump biomass and species composition. The dominant drift plants were Thalassia testudinum and Syringodium filiforme and algae in the genera Dictyota, Dictyopterus, and Diloplus. During the second mission, the seagrass Halophila decipiens became more abundant, both in the drift and in large patches along the canyon floor. In both missions, more drift was collected in the nets during high wind conditions than during calmer days. Calculated turnover times ranged from 0·01 to 4·4 days for algae in the order Dictyotales and 4·4 to 18 days for Thalassia blades. Total exported biomass of drift vegetation varied between 1·4 to 65·1 kg wet wt day -1. Samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes, but in relatively low numbers. Faunal numbers were most strongly related to rate of drift movement.

Josselyn, Michael N.; Cailliet, Gregor M.; Niesen, Thomas M.; Cowen, Robert; Hurley, Ann C.; Connor, Judith; Hawes, Sandra

1983-10-01

94

Role of submarine canyons in the US Atlantic Continental Slope and upper Continental rise development  

SciTech Connect

Three areas of the US Atlantic continental slope and rise (seaward of George Bank, Delaware Bay, and Pamlico Sound north of Cape Hatteras) have been studied using seismic reflection profiles and mid-range sidescan-sonar data. The continental slope in all three areas is dissected by numerous submarine canyons. The general sea floor gradient of the slope and the morphology of the rise, however, vary among the areas. Submarine canyons are dominant morphologic features on the slope and have an important function in sediment transport and distribution on the rise. In the study area north of Cape Hatteras, however, the low relief of the rise topography indicates that ocean currents flowing parallel to the margin may also affect sediment distribution on the rise. Morphology and sedimentation patterns suggest that differences in canyon ages exist both within each area and among the areas. Spatial and temporal variability of canyon activity is important in determining sediment sources for the construction of the rise. Although the US Atlantic slope and rise are relatively sediment-starved at present, mid-range sidescan data and submersible observations and samples suggest that periodic sediment transport events occur within the canyons.

McGregor, B.A.

1984-04-01

95

Mechanisms of sandstone deposition in a late Proterozoic submarine canyon, Adelaide geosyncline, South Australia  

SciTech Connect

Late Proterozoic submarine canyon fills the Adelaide Supergroup (Flinders Range, South Australia) are asymmetrical in terms of their facies. Coarse breccia units, commonly associated with coarse-grained channelized turbidite sandstone units, generally occur adjacent to north walls of all the east-west-trending canyon incisions. In contrast, fine-grained sandstones and mudstones within the canyon fill are generally associated with south walls. In one canyon (Patsy-Springs canyon), an additional element of asymmetry is associated with the prevalence of northward-climbing sets of climbing ripples (southward-dipping stoss sides) within channelized turbidites, in what are interpreted to be major thalweg channels and their associated levees. Flute casts at the bases of individual turbidite sandstones invariably indicate initial turbidity current flow to the west throughout the vertical sequences of the channel fills. Parallel laminations above the flute casts in each flow pass upward into climbing ripples with south-dipping stoss sides, implying southward lateral accretion across the channel of a levee or bar as each turbidity current decelerated. The asymmetries outlined could be explained by: Coriolis force acting on the turbidity currents, or the existence on a steep slope of a meandering canyon gorge, confining a thalweg channel developed within subsequent canyon fill. In such a situation, roller-coastering turbidity currents would seek outer bends of the meandering primary gorge.

von der Borch, C.C.; Grady, A.E.

1984-06-01

96

Focused sound from three-dimensional sound propagation effects over a submarine canyon.  

PubMed

Ship noise data reveal an intensification of the near-surface sound field over a submarine canyon. Numerical modeling of sound propagation is used to study the effect. The noise data were collected during an ocean acoustic and physical oceanography experiment northeast of Taiwan in 2009. In situ measurements of water sound-speed profiles and a database of high-resolution bathymetry are used in the modeling study. The model results suggest that the intensification is caused by three-dimensional sound focusing by the concave canyon seafloor. Uncertainties in the model results from unsampled aspects of the environment are discussed. PMID:21682362

Chiu, Linus Y S; Lin, Ying-Tsong; Chen, Chi-Fang; Duda, Timothy F; Calder, Brian

2011-06-01

97

Litter in submarine canyons off the west coast of Portugal  

Microsoft Academic Search

Marine litter is of global concern and is present in all the world's oceans, including deep benthic habitats where the extent of the problem is still largely unknown. Litter abundance and composition were investigated using video footage and still images from 16 Remotely Operated Vehicle (ROV) dives in Lisbon, Setúbal, Cascais and Nazaré Canyons located west of Portugal. Litter was

Gideon Mordecai; Paul A. Tyler; Douglas G. Masson; Veerle A. I. Huvenne

2011-01-01

98

From suspended particles to strata: The fate of terrestrial substances in the Gaoping (Kaoping) submarine canyon  

NASA Astrophysics Data System (ADS)

The river-sea system consisting of the Gaoping (new spelling according to the latest government's directive, formerly spelled Kaoping) River (KPR), shelf, and Submarine Canyon (KPRSC) located off southern Taiwan is an ideal natural laboratory to study the source, pathway, transport, and fate of terrestrial substances. In 2004 during the flood season of the KPR, a system-wide comprehensive field experiment was conducted to investigate particle dynamics from a source-to-sink perspective in the KPRSC with the emphasis on the effect of particle size on the transport, settling, and sedimentation along the pathway. This paper reports the findings from (1) two sediment trap moorings each configured with a Technicap PPS 3/3 sediment trap, and an acoustic current meter (Aquadopp); (2) concurrent hydrographic profiling and water sampling was conducted over 8 h next to the sediment trap moorings; and (3) box-coring in the head region of the submarine canyon near the mooring sites. Particle samples from sediment traps were analyzed for mass fluxes, grain-size composition, total organic carbon (TOC) and nitrogen (TN), organic matter (OM), carbonate, biogenic opal, polycyclic aromatic hydrocarbon (PAH), lithogenic silica and aluminum, and foraminiferal abundance. Samples from box cores were analyzed for grain-size distribution, TOC, particulate organic matter (POM), carbonate, biogenic opal, water content, and 210Pb ex. Water samples were filtered through 500, 250, 63, 10 µm sieves and 0.4 µm filter for the suspended sediment concentration of different size-classes. Results show that the river and shelf do not supply all the suspended particles near the canyon floor. The estimated mass flux near the canyon floor exceeds 800 g/m 2/day, whose values are 2-7 times higher than those at the upper rim of the canyon. Most of the suspended particles in the canyon are fine-grained (finer than medium silt) lithogenic sediments whose percentages are 90.2% at the upper rim and 93.6% in the deeper part of the canyon. As suspended particles settle through the canyon, their size-composition shows a downward fining trend. The average percentage of clay-to-fine-silt particles (0.4-10 µm) in the water samples increases from 22.7% above the upper rim of the canyon to 56.0% near the bottom of the canyon. Conversely, the average percentage of the sand-sized (> 63 µm) suspended particles decreases downward from 32.0% above the canyon to 12.0% in the deeper part of the canyon. Correspondingly, the substrate of the canyon is composed largely of hemipelagic lithogenic mud. Parallel to this downward fining trend is the downward decrease of concentrations of suspended nonlithogenic substances such as TOC and PAH, despite of their affinity to fine-grained particles. On the surface of the canyon, down-core variables (grain size, 210Pb ex activity, TOC, water content) near the head region of the canyon show post-depositional disturbances such as hyperpycnite and turbiditic deposits. These deposits point to the occurrences of erosion and deposition related to high-density flows such as turbidity currents, which might be an important process in submarine canyon sedimentation.

Liu, James T.; Hung, Jia-Jang; Lin, Hui-Ling; Huh, Chih-An; Lee, Chon-Lin; Hsu, Ray T.; Huang, Ya-Wen; Chu, Joel C.

2009-03-01

99

Geospatial variability of krill and top predators within an Antarctic submarine canyon system  

Microsoft Academic Search

The spatial distribution patterns of krill, seabirds (penguin, petrel and albatross), fur seals and baleen whales were mapped\\u000a in nearshore waters (<50 km from land) to investigate their habitat selection within two adjacent submarine canyons near Livingston\\u000a Island, Antarctica. Three shipboard surveys were conducted (February 2005–2007), and an echosounder was used to measure the\\u000a distribution and abundance of krill while simultaneously

Jarrod A. Santora; Christian S. Reiss

100

Sedimentologic evolution of a submarine canyon in a forearc basin, Upper Cretaceous Rosario Formation, San Carlos, Mexico  

SciTech Connect

The walls, floor, and fill of a submarine canyon are well-exposed near San Carlos, Mexico, in forecarc strata of the Upper Cretaceous Rosario Formation. The submarine canyon is about 7 km wide and at least 230 m deep and has eroded a minimum of 150 m into underlying fluvial red beds. It is unclear whether subaerial or submarine processes initiated the canyon cutting; however, marine processes, especially debris flows, modified the morphology of the submarine canyon. The submarine canyon fill and overlying slope deposits form two major fining-upward sequences. The first includes a 120 m thick lower conglomerate-sandstone unit (LCSU) at the base of the canyon fill overlain by a 50-110 m thick middle mudstone-sandstone unit (MMSU). The MMSU consists predominantly of mudstone and thin-bedded sandstone, but includes a channel filled with sandstone beds that form a fining- and thinning-upward sequence. This sequence is overlain by the second major sequence, a 0-60 m thick upper conglomerate-sandstone unit (UCSU), which is confined to three channels within the submarine canyon and passes gradationally upward into slope mudstone. Each of the two major fining-upward sequences records a gradual decrease in supply of coarse-grained sediment to the submarine canyon head. The first fining-upward sequence may correspond to a lowstand and subsequent rise in global sea level or, alternatively, may have resulted from local downdropping of the basin. The second fining-upward sequence does not correspond to global sea level fluctuations but is age-correlative with a drop then rise in relative sea level recognized by other workers 300-400 km to the north in the San Diego-Ensenada area. This sea level drop is inferred to have been a regional-scale tectonic event that affect the forearc basin along its length. 18 figures, 2 tables.

Morris, W.R.; Busby-Spera, C.J.

1988-06-01

101

Submarine sand dunes and sedimentary environments in Oceanographer Canyon.  

USGS Publications Warehouse

Reveals an extensive field of large sand dunes on the canyon floor. The dunes are medium to coarse sand, are oriented across the axis, and the largest of them are as high as 3m and have wavelengths up to 15m. Their asymmetry, grain size, and height suggest that they are formed by axial currents flowing up- and downcanyon and that the largest dunes require flows of at least 70 cm/sec.-from Authors

Valentine, P.C.; Cooper, R.A.; Uzmann, J.R.

1984-01-01

102

Litter in submarine canyons off the west coast of Portugal  

NASA Astrophysics Data System (ADS)

Marine litter is of global concern and is present in all the world's oceans, including deep benthic habitats where the extent of the problem is still largely unknown. Litter abundance and composition were investigated using video footage and still images from 16 Remotely Operated Vehicle (ROV) dives in Lisbon, Setúbal, Cascais and Nazaré Canyons located west of Portugal. Litter was most abundant at sites closest to the coastline and population centres, suggesting the majority of the litter was land sourced. Plastic was the dominant type of debris, followed by fishing gear. Standardised mean abundance was 1100 litter items km -2, but was as high as 6600 litter items km -2 in canyons close to Lisbon. Although all anthropogenic material may be harmful to biota, debris was also used as a habitat by some macro-invertebrates. Litter composition and abundance observed in the canyons of the Portuguese margin were comparable to those seen in other deep sea areas around the world. Accumulation of litter in the deep sea is a consequence of human activities both on land and at sea. This needs to be taken into account in future policy decisions regarding marine pollution.

Mordecai, Gideon; Tyler, Paul A.; Masson, Douglas G.; Huvenne, Veerle A. I.

2011-12-01

103

Dispersal of natural and anthropogenic lead through submarine canyons at the Portuguese margin  

NASA Astrophysics Data System (ADS)

Submarine canyons represent natural conduits for preferential transport of particulate material, including anthropogenic contaminants, from coastal zones directly to the deep sea. To assess related dispersal of natural and anthropogenic lead (Pb), we analyzed Pb concentrations and stable isotope ratios in surface sediments and sediment trap particulate material from the Portuguese margin Nazaré and Setúbal/Lisbon canyons. Geochemical data are integrated with previously obtained data on near-bottom hydrodynamics and processes and pathways of sediment transport. The two canyon systems are located in close geographic proximity to each other, but represent contrasting settings in terms of sediment input and down-canyon sediment transport processes. Concentration-isotope diagrams and three-isotope plots ( 206Pb/ 207Pb vs. 208Pb/ 206Pb) suggest binary mixing between natural and anthropogenic end members. The inferred isotopic signature of pollutant Pb ( 206Pb/ 207Pb=1.143 [1.134-1.149, 95% confidence interval]) is most consistent with industrial Pb; ongoing influence from gasoline Pb additives is at most of minor importance. Two proposed natural end members most likely bracket the isotopic signature of natural Pb. Accordingly, binary mixing calculations indicate that on average 20-45% vs. 35-55% of total Pb is derived from anthropogenic sources in the Nazaré and Setúbal-Lisbon canyon systems, respectively. Enhanced anthropogenic influence in the latter area is consistent with its proximity to heavily populated and industrialized areas and with sediment input from the Tagus and Sado rivers, potential major carriers of pollutant particles. In both canyon systems, the anthropogenic component generally decreases with increasing water depth. Isotopic signatures of sediment trap particulate material are generally consistent with surface sediment data at similar water depth, but show large variability in the upper Nazaré canyon and major deviations from surface sediments in the lower canyon. In the lower canyon, Pb isotopic ratios of sediment trap particulate material mostly reflect low pelagic fluxes from the overlying water column, whereas surface sediment signatures are dominated by episodic down-canyon mass transport events. Such gravity flows appear to incorporate older (pre-industrial) material masking the isotopic signature of pollutant Pb. Large variability in the upper canyon reflects continuous sediment resuspension by bottom currents. Stronger average bottom currents are associated with higher 206Pb/ 207Pb ratios of sediment trap particulate material and hence decreased influence of pollutant Pb. This may reflect preferential resuspension of natural Pb at the canyon floor and/or additional remobilization of older, less-polluted sediment in adjacent areas such as the canyon walls.

Richter, T. O.; de Stigter, H. C.; Boer, W.; Jesus, C. C.; van Weering, T. C. E.

2009-02-01

104

Sedimentary regime of deep submarine canyons around Fylla Banke, northeastern Labrador Sea  

NASA Astrophysics Data System (ADS)

Sedimentary regime of deep submarine canyons around the Fylla Banke, northeastern Labrador Sea Dorthe Paulsen (1), Antoon Kuijpers (2), Marit-Solveig Seidenkrantz (3) and Tove Nielsen (2) 1) Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K 2) Geological Survey of Denmark and Greenland (GEUS), Øster Voldgde 10, DK-1350 Copenhagen K. 3) Centre for Past Climate Studies, Department of Geoscience, Aarhus University. Hoegh-Guldbergs Gade 2, DK-8000 Aarhus C The southern end of the Davis Strait, the comparatively shallow-water area separating the Labrador Sea from the Baffin Bay, is cut by two deep submarine canyons of west Greenland, on the western and eastern side of the Fylla Banke, respectively. The purpose of this study is to investigate Late Pleistocene sedimentary processes governing the area of the two canyons in order to test if gravity flows or ocean currents are the most important factors governing canyon sedimentary processes in this region. Furthermore, an account is given on the formation of the two canyons in order to explain the significant difference between them. The study was carried out based on seismic profiles combined with bathymetric information, and a single sidescan sonar profile from one of the canyons (western canyon). Sedimentary information and an age model are derived from of a 5-m long gravity core (TTR13-AT-479G) collected from the mouth of the western canyon (southern end). The data indicates that the sedimentary regime is today highly affected by northward transport of the ocean currents and that gravity flows (southward from shallower to deep waters) are only of limited significance today. The deep southern end of the canyons are influenced by the upper parts of the deep North Atlantic Deep Water, but the majority of the sediment transport is linked to the strong northward flow of the lower parts of the West Greenland Current. For comparison the sediment transport is held up against earlier studies from the Davis Strait area, where 2D seismic profiles were carried out several places of the west coast of Greenland. These studies are from a contourite drift complex at the Davis Strait and north of Labrador Sea. A further possible process operating in maintaining active sediment transport through the canyon may be the cascading of dense winter water formed on the West Greenland shelf.

Paulsen, Dorthe; Kuijpers, Antoon; Seidenkrantz, Marit-Solveig; Nielsen, Tove

2014-05-01

105

Submarine canyon in a forearc basin, Upper Cretaceous Rosario Group, Baja California, Mexico  

SciTech Connect

Late Cretaceous marine and nonmarine sedimentary rocks of the Rosario Group, deposited in one or more forearc basins, are exposed discontinuously from San Diego to Punta Canoas. Near the southern end of this belt, at San Carlos, mexico, a well-exposed, 6-km wide submarine canyon cuts at least 150 m into a fluvial section. Paleocurrent data indicate a west-southwest-directed sediment transport in the canyon. Large blocks of limestone 3-4 m in size, derived from the Early Cretaceous arc basement complex of the Alisitos group, were transported at least 20 km from the source area in the submarine canyon. The canyon fill consists of a basal and upper conglomerate to sandstone unit separated by a 20 to 45-m thick shale and sandstone unit, and capped by a second shale and sandstone unit of unknown thickness. The lower conglomerate-sandstone unit ranges from 20 to 140 m thick, and cuts into fluvial deposits in a curved or steplike pattern. The upper conglomerate-sandstone unit fills deep channels incised into a sandstone-shale unit and is 35-60 m thick. The conglomerates represent high-density turbidites and debris flows. Sandstones are massive (ungraded or graded), or display Bouma AB or ABC divisions. Shaly slump blocks, derived from channel margins or terraces, were injected by clastic sills and dikes as they were incorporated into the conglomeratic flows. Slump blocks increase in frequency and size near the northern canyon wall. This pattern has been attributed to a meandering channel with slumping on the outer bend of a meander. The abrupt contact between the conglomerate-sandstone units and the overlying shale-sandstone units indicates that on two occasions the canyon head was abruptly denied access to sources of coarse-grained material. This cyclic pattern may be the result of tectonic events or eustatic sea level changes.

Morris, W.R.; Busby-Spera, C.J.; Boles, J.R.

1986-04-01

106

Rejuvenation of submarine canyon associated with ridge subduction, Tenryu Canyon, off Tokai, central Japan  

Microsoft Academic Search

The 130-km-long Tenryu Canyon is an active deep water meandering canyon transversely developed on the tectonically active Tokai (Eastern Nankai) accretionary prism, where the multiple intraplate deformation caused by the arc–arc Izu collision. Over 2000 km of EM 12 data, 3.5-kHz profiles and PASISAR profiles obtained during the KAIKO-TOKAI Project, 1996, IZANAGI data, the bathymetric chart, and the preexisting seismic

Wonn Soh; Hidekazu Tokuyama

2002-01-01

107

Recent sediment transport and deposition in the Lisbon-Setúbal and Cascais submarine canyons, Portuguese continental margin  

NASA Astrophysics Data System (ADS)

Recent sediment transport and deposition in the Lisbon-Setúbal and Cascais submarine canyons, Portuguese continental margin, were investigated on the basis of water column profiles of suspended particulate matter, records of near-bottom currents and settling fluxes of particulate matter obtained with benthic landers, and analysis of surface sediments. The results show that fine-grained predominantly lithogenic sediment derived from adjacent shelf areas accumulates in the upper reaches of the canyons. Sediment deposited further down in the middle and lower reaches of the canyons is essentially similar to the hemipelagic sediment found on the adjacent continental slope, indicating that down-canyon transport of sediment from the upper to the lower canyon is limited. Tidal currents measured at various depths in the Lisbon-Setúbal Canyon appear sufficiently strong to resuspend and transport sediment, but net up-canyon flow of the bottom water may retain shelf-derived lithogenic sediment in the upper canyon. Sediment gravity flows, which in the nearby Nazaré Canyon are an effective mechanism for down-canyon sediment transport, appear rare in the Lisbon-Setúbal Canyon and probably also in the Cascais Canyon. Turbidity current events recorded in the sedimentary record of the canyons may correspond to seismic events of 1969 and 1755 AD.

de Stigter, Henko C.; Jesus, Carlos César; Boer, Wim; Richter, Thomas O.; Costa, Ana; van Weering, Tjeerd C. E.

2011-12-01

108

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin  

NASA Astrophysics Data System (ADS)

Shelf-sourced submarine canyons are common features of continental margins and are fundamental to deep-sea sedimentary systems. Despite their geomorphic and geologic significance, relatively few passive margin shelf-breaching canyons worldwide have been mapped using modern geophysical methods. Between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the US Mid-Atlantic margin: Wilmington, Baltimore, Washington, and Norfolk canyons. More than 5700 km2 of high-resolution multibeam bathymetry and 890 line-km of sub-bottom CHIRP profiles were collected along the outer shelf and uppermost slope (depths of 80-1200 m). The data allowed us to compare and contrast the fine-scale morphology of each canyon system. The canyons have marked differences in the morphology and orientation of canyon heads, steepness and density of sidewall gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles for Washington, Baltimore and Wilmington canyons have linear shapes, and each canyon thalweg exhibits morphological evidence for recent, relatively small-scale sediment transport. For example, Washington Canyon displays extremely steep wall gradients and contains ~100 m wide, 5-10 m deep, v-shaped incisions down the canyon axis, suggesting modern or recent sediment transport. In contrast, the convex axial thalweg profile, the absence of thalweg incision, and evidence for sediment infilling at the canyon head, suggest that depositional processes strongly influence Norfolk Canyon during the current sea-level high-stand. The north walls of Wilmington, Washington and Norfolk canyons are steeper than the south walls due to differential erosion, though the underlying cause for this asymmetry is not clear. Furthermore, we speculate that most of the geomorphic features observed within the canyons (e.g., terraces, tributary canyons, gullies, and hanging valleys) were formed during the Pleistocene, and show only subtle modification by Holocene processes active during the present sea-level high-stand.

Obelcz, Jeffrey; Brothers, Daniel; Chaytor, Jason; Brink, Uri ten; Ross, Steve W.; Brooke, Sandra

2014-06-01

109

A comparison of megafaunal communities in five submarine canyons off Southern California, USA  

NASA Astrophysics Data System (ADS)

Remotely operated vehicle surveys were conducted in five submarine canyons off Southern California during research expeditions in 2005 and 2010. Video transects from a range of depths were analysed to produce presence/absence data of megafauna for each site. A comparison of benthic communities at various depths, locales, and canyons was performed. No significant difference was found between canyon communities based on the level of sediment transport activity, however this may be due to the unbalanced sampling of this opportunistic study. There was significant variation in biological community composition and abundance amongst water depths. These depth-related trends are in agreement with the findings of the previous studies and are likely tied to depth-correlated variables such as hydrostatic pressure, temperature, salinity, and oxygen concentration. Species richness was found to initially increase with depth before declining rapidly at the mouths of the studied canyons. Low oxygen levels in the Santa Monica Basin, into which four of the surveyed canyons empty, may explain this.

Duffy, Grant A.; Lundsten, Lonny; Kuhnz, Linda A.; Paull, Charles K.

2014-06-01

110

Sediment deposition in a modern submarine canyon: Eel Canyon, northern California  

Microsoft Academic Search

Previous studies on the Eel margin have shown that a substantial amount of terrigenous sediment may be rapidly transported and deposited seaward of the shelf break during the Eel River flooding season. Eel Canyon, located ?10 km seaward of the Eel River mouth, has been investigated to determine its role in seaward escape of sediment over seasonal timescales. In order

B. L. Mullenbach; C. A. Nittrouer; P. Puig; D. L. Orange

2004-01-01

111

Hudson Submarine Canyon Head Offshore New York and New Jersey: a Dynamic Interface II  

NASA Astrophysics Data System (ADS)

Hudson Canyon is the largest submarine canyon on the US Atlantic continental margin. Our multidisciplinary study focuses on the canyon head from where it begins as an indentation in the outer continental shelf (water depth 100 m) to 75 km seaward along the canyon axis (water depth 2000 m). A shallow trough, the Hudson Shelf Valley extends about 185 km across the continental shelf and connects the mouth of the Hudson River where the river discharges into New York Bay to the head of the canyon. Our study comprises high-resolution bathymetry using Autonomous Underwater Vehicle (AUV) Eagle Ray (100 square km area),and delineation of interacting shelf and slope water masses using shipboard and AUV hydrocasts including water samples for methane analysis. The initial 10 km of the canyon head (axial depth 100 m to 300 m) bifurcates where it indents the outer shelf, with one branch aligned NW-SE with the Hudson Shelf Valley and a second branch aligned N-S along the shelf. The walls and floor of the NW-SE branch are smoothed by sediment accumulation and appear inactive in terms of sediment transport. The N-S branch is rough and appears active. Ravines orthogonal to the axis progressively increase in frequency and relief seaward through successive 10 km-long N-S and NW-SE trending sections of the canyon attaining a 1 km spacing. Two circular depressions (diameters 100 m and 300 m; relief c.15 m; depths 345 m and 390 m) occur at the base of the W wall of the N-S segment. The depressions may be collapse features related to gas discharge evidenced by a high methane anomaly (50 nM) detected in the adjacent canyon axis (water depth 421 m). Multiple layers of inter-leaved shelf (fresh) and slope (warm, salty) water masses were observed in the canyon head in summer 2007 and 2008. The dynamic interaction of these water masses is being studied in context of shelf-slope exchange and potential influence on canyon topography and ecosystems. We thank NOAA for support.

Rona, P.; Guida, V.; Scranton, M.; Gong, D.; Sullivan, M.; Haag, S.; Diercks, A.; Asper, V.

2008-12-01

112

ccsd-00089326,version1-17Aug2006 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/, Evolution of surface gravity waves over a submarine canyon  

E-print Network

.1029/, Evolution of surface gravity waves over a submarine canyon R. Magne1,5 , K. A. Belibassakis2 , T. H. C. Herbers3 , Fabrice Ardhuin1 , W. C. O'Reilly4 , and V. Rey5 Abstract. The effects of a submarine canyon

Paris-Sud XI, Université de

113

Tectonic controls on nearshore sediment accumulation and submarine canyon morphology offshore La Jolla, Southern California  

USGS Publications Warehouse

CHIRP seismic and swath bathymetry data acquired offshore La Jolla, California provide an unprecedented three-dimensional view of the La Jolla and Scripps submarine canyons. Shore-parallel patterns of tectonic deformation appear to control nearshore sediment thickness and distribution around the canyons. These shore-parallel patterns allow the impact of local tectonic deformation to be separated from the influence of eustatic sea-level fluctuations. Based on stratal geometry and acoustic character, we identify a prominent angular unconformity inferred to be the transgressive surface and three sedimentary sequences: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. Beneath the transgressive surface, steeply dipping reflectors with several dip reversals record faulting and folding along the La Jolla margin. Scripps Canyon is located at the crest of an antiform, where the rocks are fractured and more susceptible to erosion. La Jolla Canyon is located along the northern strand of the Rose Canyon Fault Zone, which separates Cretaceous lithified rocks to the south from poorly cemented Eocene sands and gravels to the north. Isopach and structure contour maps of the three sedimentary units reveal how their thicknesses and spatial distributions relate to regional tectonic deformation. For example, the estuarine unit is predominantly deposited along the edges of the canyons in paleotopographic lows that may have been inlets along barrier beaches during the Holocene sea-level rise. The distribution of the infilling unit is controlled by pre-existing relief that records tectonic deformation and erosional processes. The thickness and distribution of the upper transparent unit are controlled by long-wavelength, tectonically induced relief on the transgressive surface and hydrodynamics. ?? 2009 Elsevier B.V.

Le, Dantec N.; Hogarth, L.J.; Driscoll, N.W.; Babcock, J.M.; Barnhardt, W.A.; Schwab, W.C.

2010-01-01

114

Spatial distribution of phytoplankton assemblages in the Nazaré submarine canyon region (Portugal): HPLC-CHEMTAX approach  

NASA Astrophysics Data System (ADS)

The distribution and composition of phytoplankton assemblages were studied in the Nazaré submarine canyon, during an upwelling event, using high-performance liquid chromatography (HPLC) pigment analysis, complemented by microscopic qualitative observations. High chlorophyll a (Chl a) concentrations were recorded in the canyon head, near the coast, where values greater than 4 ?g L - 1 were observed. In contrast, Chl a was relatively low in offshore regions, with values below 0.5 ?g L - 1 . The most abundant accessory pigments were fucoxanthin, peridinin, diadinoxanthin and 19'-hexanoyloxyfucoxanthin. Pigment data information was analyzed using the CHEMTAX software to estimate the contribution of different taxonomic groups to total Chl a. North of the canyon head, an area with high concentration of peridinin-containing dinoflagellates was identified (with presence of chain-forming toxic dinoflagellates). The presence of these organisms was associated with mixed water columns and phosphate values lower than the ones south of the canyon head, where a dominance of diatoms was recorded. The rest of the study region showed a dominance of prymnesiophytes and a significant contribution of cyanobacteria at oceanic stations. This study demonstrates the usefulness of using pigment analysis to study spatial distribution of phytoplankton groups in relation to a complex physical environment.

Mendes, Carlos Rafael; Sá, Carolina; Vitorino, João; Borges, Carlos; Tavano Garcia, Virginia Maria; Brotas, Vanda

2011-07-01

115

Biodiversity of macrofaunal assemblages from three Portuguese submarine canyons (NE Atlantic)  

NASA Astrophysics Data System (ADS)

The macrofaunal assemblages from three Portuguese submarine canyons, Nazaré, Cascais and Setúbal were studied from samples collected at their upper (900-1000 m), middle (3200-3500 m) and lower sections (4200-4500 m) and at the adjacent open slopes (˜1000 m), during the HERMES cruises D297 (R.R.S. Discovery, 2005) CD179 (R.R.S. Charles Darwin, 2006) and 64PE252 (R.V. Pelagia, 2006). The taxonomic composition and patterns in biodiversity, abundance and community structure of the benthic macrofauna were described. Annelida (42.1% of total abundance; 137 species) and Arthropoda (20.6%; 162 species) were, respectively, the most abundant and the most species-rich Phyla among the 342 taxa identified during this study. Multivariate analyses showed significant differences between and within canyons and between canyons and open slope assemblages. At their upper section, canyons supported higher macrofauna abundance but slightly lower biodiversity than the adjacent slopes at similar depth. In all canyons abundance reached the highest value in the middle section and the lowest in the upper section, with marked fluctuations in Nazaré (474-4599 ind. m -2) and lower variability in Cascais (583-1125 ind. m -2). The high abundance and dominance of the assemblages in the middle section of Nazaré and Setúbal was accompanied by depressed biodiversity, while in Cascais, Hurlbert's expected species richness showed increasing values from the upper to the middle canyon, and maintained the high values at the lower section. Overall, the Nazaré Canyon showed the lowest expected species richness (ES (100): 16-39) and the Cascais Canyon the highest (39-54). There was a significant negative Kendall's correlation between total organic carbon concentrations in the superficial sediments and ES (100) and a significant positive correlation between total nitrogen and macrofauna density. The influences of organic enrichment, sediment heterogeneity and hydrodynamic regime on the abundance, diversity and community structure of the macrofauna are discussed. It is suggested that altered and localised environmental conditions in the Portuguese canyons play an important role in modifying more common abundance and diversity bathymetric patterns evident in many continental slope environments.

Cunha, Marina R.; Paterson, Gordon L. J.; Amaro, Teresa; Blackbird, Sabena; de Stigter, Henko C.; Ferreira, Clarisse; Glover, Adrian; Hilário, Ana; Kiriakoulakis, Konstadinos; Neal, Lenka; Ravara, Ascensão; Rodrigues, Clara F.; Tiago, Áurea; Billett, David S. M.

2011-12-01

116

Near-bottom particulate matter dynamics in the Nazaré submarine canyon under calm and stormy conditions  

NASA Astrophysics Data System (ADS)

Two mooring lines equipped with near-bottom sediment traps were deployed in the axis of the Nazaré submarine canyon at ˜1600 and ˜3300 m depth, respectively. We studied time-series of particle flux, composition (biogenic silica, carbonates, organic matter and lithogenic fractions), granulometry, mineralogy and 210Pb concentration of particulate matter over five sediment trap deployments between October 2002 and December 2004. Current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow, temperature, salinity and suspended particle concentration. The composition of the collected particles was fairly constant year-round, dominated by the lithogenic fraction and with OC/N ratios in the range 11-21, suggesting an important terrigenous influence inside the canyon. The results show contrasting dynamic environments in the upper (1600 m depth) and middle (3300 m depth) canyon. High current speeds (spring tides up to 80 cm s -1) and high apparent mass fluxes of particulate matter (mean 65 g m -2 d -1; maximum 265 g m -2 d -1) are permanent at the shallowest station. At the deepest site, fluxes were below 10 g m -2 d -1 most of the time and the annual flux was governed by events of sharp flux increase. Storms affecting the continental shelf during autumn and winter are a major driver of down-canyon dispersal of sediments to the middle canyon and beyond. Important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m, as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth. On three occasions during the study period, significant wave heights of incident storms surpassed 7 m, leading to notable episodes of down-canyon transport that were clearly observed in the middle canyon. During one of these stormy periods (January 2003) a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m. However, a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon. The role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding.

Martín, Jacobo; Palanques, Albert; Vitorino, João; Oliveira, Anabela; de Stigter, Henko C.

2011-12-01

117

The propagation of sound in narrow street canyons.  

PubMed

This paper addresses an important problem of predicting sound propagation in narrow street canyons with width less than 10 m, which are commonly found in a built-up urban district. Major noise sources are, for example, air conditioners installed on building facades and powered mechanical equipment for repair and construction work. Interference effects due to multiple reflections from building facades and ground surfaces are important contributions in these complex environments. Although the studies of sound transmission in urban areas can be traced back to as early as the 1960s, the resulting mathematical and numerical models are still unable to predict sound fields accurately in city streets. This is understandable because sound propagation in city streets involves many intriguing phenomena such as reflections and scattering at the building facades, diffusion effects due to recessions and protrusions of building surfaces, geometric spreading, and atmospheric absorption. This paper describes the development of a numerical model for the prediction of sound fields in city streets. To simplify the problem, a typical city street is represented by two parallel reflecting walls and a flat impedance ground. The numerical model is based on a simple ray theory that takes account of multiple reflections from the building facades. The sound fields due to the point source and its images are summed coherently such that mutual interference effects between contributing rays can be included in the analysis. Indoor experiments are conducted in an anechoic chamber. Experimental data are compared with theoretical predictions to establish the validity and usefulness of this simple model. Outdoor experimental measurements have also been conducted to further validate the model. PMID:12186035

Iu, K K; Li, K M

2002-08-01

118

Submarine canyon deposits, central California coast, and their possible relation to an Eocene low sea-level stand  

SciTech Connect

A cliff exposure in the northern Santa Lucia Range is interpreted to represent the north margin of an Eocene submarine canyon. The exposure shows an unconformity between The Rocks Sandstone Member of the Reliz Canyon Formation and the underlying crystalline basement rocks. Sandstone beds overlie the unconformity at an angle of about 20/sup 0/. Stratigraphic relations exposed nearby show that about 220 m of the Reliz Canyon and Church Creek Formations pinches out northward against the basement across a distance of about 900 m of the Reliz Canyon and Church Creek Formations pinches out northward against the basement across a distance of about 900 m. This corresponds to an original southward slope of the unconformity of about 14/sup 0/. Farther south, an even steeper slope to the north may be indicated, but a fault of uncertain horizontal displacement intervenes. The Reliz Canyon Formation seems to have been deposited in a small northwest-trending submarine canyon in the vicinity of the exposed unconformity; elsewhere in the region the Reliz Canyon Formation may have been deposited in two other canyons or restricted basins. Fossil data show that the voluminous sand of The Rocks Sandstone Member was deposited near the early-middle Eocene boundary, a postulated time of worldwide low sea level. 20 refs., 7 figs.

Seiders, V.M.; Joyce, J.M.

1984-01-01

119

Upwelling of subsurface water into the rim of the Biob??o submarine canyon as a response to surface winds  

Microsoft Academic Search

The submarine canyon of the Biob??o River (36°50?S; 73°15?W) is located in the vicinity of a zone of intense seasonal upwelling off Central Chile. This zone conforms a coastal ecosystem that produces more than 50% of the Chilean fish catch and approximately 4% of the world fish captures. As the small- and mesoscale oceanographic processes associated to this canyon are

M. Sobarzo; M Figueroa; L Djurfeldt

2001-01-01

120

The surface sediment distribution and sedimentary environment of the Pearl River Submarine Canyon  

NASA Astrophysics Data System (ADS)

The grain size composition, particle size parameters, clay mineral, and detrital mineral of surface sediment of this The Pearl River Submarine Canyon (the PRSC, for short) area have been measured and analyzed, which were took sampling in 2005 and 2006 in the northern South China Sea. The results show that the isolines distribution features of these parameters have very good corresponding relation with the geomorphology of the PRSC. On the continental-shelf slope break of the PRSC head (123m-1500m water depth), the close interval isolines of the surface sediment particle size percentage content and size parameters nearly parallel with the water depth isolines. The data of sand percentage content and mean grain size, sorting coefficient and skewness decreases with the increase of water depth. The other way around, the silt and clay percentage content and kurtosis value increase with deeper water. These show that in the canyon head sediment distribution was controlled by the material source (mainly comes from the Pearl River), slope and the northern South China Sea offshore current. In the main PRSC area, the surface sediment grain size composition content and grain size parameter numerical isolines have become a isoline platform which has the similar shape with the main PRSC and extended to the northeast and southwest deep sea basin. This means that the sedimentary environment of main canyon is apparently different with the head environment, that is affected by the high-temperature and high-salt the South China Sea Branch of by the Kuroshio along the 3500 m water depth isoline and alone the canyon to bending. The 25% percentage content isoline of the calcium biological and 45% percentage content isoline of the light mineral show a broadband distribution along the head and upside of the PRSC, and reduces in the entrance with the water depth isolines, apparently influenced by the South China Sea Branch of the Kuroshio. A high value area of the silt, clay mineral, light mineral, heavy mineral, silicon biological, and calcium biological appears to the entrance of the PRSC, which may be controlled by a perennial anticlockwise current. But how the materials passed through the South China Sea Branch of the Kuroshio and sediment here still is not be solved. The distribution of clay minerals close to the distribution of grain size, around the main canyon with more loose and uniform interval value isolines. It is lower of the percentage content isolines value of the Illite, Kaolinite and Chlorite in the canyon than the values around the canyon (specially at northeast, northwest, southwest ). And the Smectite percentage content has the opposite distribution, the value is higher in the canyon than out the canyon. Which means that the Traditional knowledge about ocean clay minerals distribution is influenced by the latitude is not adaptive at submarine canyon area. To sum up, the existence of the PRSC has changed the material transport mode from land to deep ocean basin in the northern South China Sea. Not only it played a transfer passageway, but also it played the role of the sorting and aggregation, which is beneficial to the formation and gathering of certain minerals. This work were supported by the NSFC (41106046), the Youth Ocean Science Fund Project, SOA(2011333) and the Basic Scientific Researching Specific Funds of SIO, SOA (JT1002)

Han, X.; Chu, F.; Li, J.; Xu, D.; Zhang, W.

2012-12-01

121

A multidisciplinary study of the role of submarine canyons off western Portugal  

NASA Astrophysics Data System (ADS)

A multidisciplinary research aimed to characterise the dominant aspects of the Portuguese canyon systems and their role on the shelf-deep ocean sediment exchanges is being conducted in the framework of EU project Eurostrataform. Three contrasting systems are studied: (1) the Nazaré Canyon is a narrow and deep canyon which extends from the deep ocean and completely cuts the NW Portuguese shelf, with no local riverine sources; (2) the Setubal-Lisbon canyon system affects an area marked by complex topography and coastline configuration and with riverine contributions provided by the Tagus and Sado rivers; (3) the Oporto canyon is restricted to the outer shelf, with a major local riverine source (Douro river). We present preliminary results from the ongoing program of observations, which includes multidisciplinary surveys (CTD, suspended particle matter measurments, shallow seismic) and both long- and short-term moorings. Process studies are extended with the use of system MOCASSIM, an operational system for the forecast of oceanographic conditions off the Portuguese coast, which is presently being developped at Instituto Hidrografico. The system integrates wave and circulation models and makes use of data assimilation methods to provide numerical results which are consistent with the observed conditions.

Vitorino, J.; Oliveira, A.; Rodrigues, A.

2003-04-01

122

Large-scale teleoperation approach to exploration of the Hudson submarine canyon  

NASA Astrophysics Data System (ADS)

Teleoperation provides a means for in-situ continuous observation of, and interaction with, remote sites that are difficult and potentially hazardous to access directly. The Hudson submarine canyon, with its proximity to a large population center is an ideal test bed for an on-going teleoperation approach to its exploration and observation. To facilitate a long duration mission and freedom from an expensive and weather dependent surface support ship, an underwater electrical recharge site is proposed. A power line/fiber optic cable is placed from shoreline facilities to the recharge site, located on the upper rim of the canyon at approximately 100 meter depth. Here, free flying remotely piloted vehicles periodically recharge batteries and send video/data back to the surface. The entire venture is located underwater and remains there for the duration of the mission. The recharge site can be relocated to expand the exploration area. Various alternate canyon sites worldwide are considered. Internet access, and an access fee structure for the general public, presents the possibility of an economically self-supporting venture when conducted on a sufficiently large scale.

Konesky, Gregory A.

2002-01-01

123

Habitat heterogeneity, disturbance, and productivity work in concert to regulate biodiversity in deep submarine canyons.  

PubMed

Habitat heterogeneity is a major structuring agent of ecological assemblages promoting beta diversity and ultimately contributing to overall higher global diversity. The exact processes by which heterogeneity increases diversity are scale dependent and encompass variation in other well-known processes, e.g., productivity, disturbance, and temperature. Thus, habitat heterogeneity likely triggers multiple and cascading diversity effects through ecological assemblages. Submarine canyons, a pervasive feature of the world's oceans, likely increase habitat heterogeneity at multiple spatial scales similar to their terrestrial analogues. However, our understanding of how processes regulating diversity, and the potential for cascading effects within these important topographic features, remains incomplete. Utilizing remote-operated vehicles (ROVs) for coring and video transects, we quantified faunal turnover in the deep-sea benthos at a rarely examined scale (1 m-1 km). Macrofaunal community structure, megafaunal density, carbon flux, and sediment characteristics were analyzed for the soft-bottom benthos at the base of cliff faces in Monterey Canyon (northeast Pacific Ocean) at three depths. We documented a remarkable degree of faunal turnover and changes in overall community structure at scales < 100 m, and often < 10 m, related to geographic features of a canyon complex. Ultimately, our findings indicated that multiple linked processes related to habitat heterogeneity, ecosystem engineering, and bottom-up dynamics are important to deep-sea biodiversity. PMID:20462112

McClain, Craig R; Barry, James P

2010-04-01

124

Tales of Two Turbidity Currents Recorded in Monterey Submarine Canyon, USA  

NASA Astrophysics Data System (ADS)

The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in submarine environment has attracted the attention of researchers from different disciplines. Yet not only field measurements of oceanic turbidity currents are a rare achievement but also when such measurements do occur they consist mostly of velocity records with very limited or no data of suspended sediment concentration and grain size distribution. This work focus on two turbidity currents measured in the Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, defined by the source of the gravity flows, play a significant role in shaping the characteristics of the currents as they travel downstream the canyon. Before the flows reach their normal state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through an adjusting preliminary stage where they are subject to capacity-driven deposition releasing heavy material in excess. Flows composed with fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm the different flow patterns between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology.

Xu, J.; Sequeiros, O.; Noble, M. A.

2013-12-01

125

Modeled alongshore circulation and morphologic evolution onshore of a large submarine canyon  

NASA Astrophysics Data System (ADS)

Alongshore circulation and morphologic evolution observed at an ocean beach during the Nearshore Canyon Experiment, onshore of a large submarine canyon in San Diego, CA (USA), are investigated using a two-dimensional depth-averaged numerical model (Delft3D). The model is forced with waves observed in ~500 m water depth and tidal constituents derived from satellite altimetry. Consistent with field observations, the model indicates that refraction of waves over the canyon results in wave focusing ~500 m upcoast of the canyon and shadowing onshore of the canyon. The spatial variability in the modeled wave field results in a corresponding non-uniform alongshore circulation field. In particular, when waves approach from the northwest the alongshore flow converges near the wave focal zone, while waves that approach from the southwest result in alongshore flow that diverges away from the wave focal zone. The direction and magnitude of alongshore flows are determined by a balance between the (often opposing) radiation stress and alongshore pressure gradients, consistent with observations and previous results. The largest observed morphologic evolution, vertical accretion of about 1.5 m in about 3 m water depth near the wave focal zone, occurred over a one-week period when waves from the northwest reached heights of 1.8 m. The model, with limited tuning, replicates the magnitude and spatial extent of the observed accretion and indicates that net accretion of the cross-shore profile was owing to alongshore transport from converging alongshore flows. The good agreement between the observed and modeled morphology change allows for an in-depth examination of the alongshore force balance that resulted in the sediment convergence. These results indicate that, at least in this case, a depth-averaged hydrodynamic model can replicate observed surfzone morphologic change resulting from forcing that is strongly non-uniform in the alongshore. Funding was provided by the Office of Naval Research, The National Science Foundation, a Woods Hole Oceanographic Institution and United States Geological Survey joint postdoctoral fellowship, and a National Security Science and Engineering Faculty Fellowship.

Hansen, J. E.; Raubenheimer, B.; List, J. H.; Elgar, S.; Guza, R. T.; Lippmann, T. C.

2012-12-01

126

The summer assemblage of large pelagic Crustacea in the Gully submarine canyon: Major patterns  

NASA Astrophysics Data System (ADS)

We describe the trawl-vulnerable crustacean micronekton and macrozooplankton of the Gully, a large, shelf-incising submarine canyon off Nova Scotia, Canada, and a Marine Protected Area. Over 68 species of pelagic crustacea were collected with an International Young Gadoid Pelagic Trawl during three annual summer surveys at one fixed station in the canyon. Depths sampled ranged from the surface to the upper bathypelagic zone, concentrated in the upper 1250 m, with a maximum depth of 1500 m. The crustacean fauna was dominated by cold temperate species typical of mid- to higher-latitudes in the North Atlantic. Meganyctiphanes norvegica and Eusergestes arcticus were particularly dominant in terms of both observed biomass and abundance above 750 m depth. At least 17 species were new records for Canadian waters. The species assemblage of the station varied primarily with depth and diel cycle, the only dominant members of the assemblage showing pronounced inter-annual variations in catch being M. norvegica and Themisto gaudichaudii, both relatively shallow living species.

MacIsaac, K. G.; Kenchington, T. J.; Kenchington, E. L. R.; Best, M.

2014-06-01

127

Morphology of submarine canyon system and geotechnical properties of surficial sediments across the Peru-Chile forearc  

SciTech Connect

During August 1987, a SeaMARC II side-scan and sampling survey was conducted across the Peru-Chile forearc from 17/degrees/30'S to 19/degrees/30'S. Side-scan images reveal a complex submarine canyon system. Incised canyons meander across the Arequipa basin; their sinuosity results from erosion and cutbank slumping of the basin sediments. Lenticular packets of strata visible in reprocessed digital single-channel seismic profiles are interpreted to be buried channels. Tributary canyons coalesce into a single canyon at the structural high that deviates from its north-south course to a northeast-southwest course as a result of stream piracy. A dendritic drainage basin forming on the midslope may be the rejuvenation of an abandoned channel. Sediment properties were measured on 42 free-fall cores and 7 piston cores recovered both in and around the submarine canyon. Olive-gray (5Y 3/2) hemipelagic mud is the predominant sediment across the forearc. Most cores exhibit a small degree of bioturbation and thin laminae of sand; the number of sand laminae increases as the distance away from the canyon decreases. Shear strengths, averaged over a 1-m core length, decrease slightly with water depth. Carbonate content in all samples from this area is negligible with the exception of one piston core recovered from the upper reaches of the canyon, the bottom of which is composed of gravel- and sand-size shell fragments. Bulk mineralogy, determined from semiquantitative analysis of x-ray diffraction patterns, shows a decrease in relative feldspar percent and an increase in total clay content with increasing water depth. Preliminary analysis of core tops shows a mean grain size in the medium to very fine silt class, with increasing grain size toward the canyon. Smear slide counts generally show a surprisingly low abundance of volcanic glass and biogenic material, particularly diatoms.

Bergersen, D.D.; Coulbourn, W.T.; Moberly, R.

1989-03-01

128

Slope basins, headless canyons, and submarine palaeoseismology of the Cascadia accretionary complex  

USGS Publications Warehouse

A combination of geomorphological, seismic reflection and geotechnical data constrains this study of sediment erosion and deposition at the toe of the Cascadia accretionary prism. We conducted a series of ALVIN dives in a region south of Astoria Canyon to examine the interrelationship of fluid flow and slope failure in a series of headless submarine canyons. Elevated head gradients at the inflection point of canyons have been inferred to assist in localized failures that feed sediment into a closed slope basin. Measured head gradients are an order of magnitude too low to cause seepage-induced slope failure alone; we therefore propose transient slope failure mechanisms. Intercanyon slopes are uniformly unscarred and smooth, although consolidation tests indicate that up to several metres of material may have been removed. A sheet-like failure would remove sediment uniformly, preserving the observed smooth intercanyon slope. Earthquake-induced liquefaction is a likely trigger for this type of sheet failure as the slope is too steep and short for sediment flow to organize itself into channels. Bathymetric and seismic reflection data suggest sediment in a trench slope basin between the second and third ridges from the prism's deformation is derived locally. A comparison of the amounts of material removed from the slopes and that in the basin shows that the amount of material removed from the slopes may slightly exceed the amount of material in the basin, implying that a small amount of sediment has escaped the basin, perhaps when the second ridge was too low to form a sufficient dam, or through a gap in the second ridge to the south. Regardless, almost 80% of the material shed off the slopes around the basin is deposited locally, whereas the remaining 20% is redeposited on the incoming section and will be re-accreted.

McAdoo, B.G.; Orange, D.L.; Screaton, E.; Lee, H.; Kayen, R.

1997-01-01

129

Analysis of Submarine Landslides and Canyons along the U.S. Atlantic Margin Using Extended Continental Shelf Mapping Data  

NASA Astrophysics Data System (ADS)

U.S. Geological Survey (USGS) studies of the U.S. Atlantic continental slope and rise aim to understand the: 1) the role of submarine landslides in tsunami generation, and 2) the linkages between margin morphology and sedimentary processes, particularly in and around submarine canyon systems. Data from U.S. Extended Continental Shelf (ECS) and numerous subsequent mapping surveys have facilitated the identification and characterization of submarine landslides and related features in fine detail over an unprecedented spatial extent. Ongoing analysis of USGS collected piston cores, sub-bottom and multichannel seismic (MCS) reflection profiles, and an extensive suite of legacy MCS data from two landslides, the Southern New England landslide zone and the Currituck Landslide, suggest that the most recent major landslide events are pre-Holocene, but that failures were complex and most likely multi-phase, at times resulting in extensive overlapping debris deposits. Piston core records plus visual observations of the seafloor from recent TowCam deployments and NOAA Ship Okeanos Explorer ROV dives reveal ongoing development of colluvial wedge-style debris aprons at the base of scarps within these landslides, showing that these regions continue to evolve long after the initial failure events. Multibeam bathymetry data and MCS profiles along the upper slope reveal evidence for vertical fluid migration and possible seabed gas expulsion. These observations underscore the need to reevaluate the sources of pore fluid overpressure in slope sediments and their role in landslide generation. ECS and more recent multibeam mapping have provided the opportunity to investigate the full extent of submarine canyon morphology and evolution from Cape Hatteras up to the US-Canadian EEZ, which has led to better understanding of the important role of antecedent margin physiography on their development. Six submarine canyon systems along the margin (Veatch, Hydrographer, Hudson, Wilmington-Baltimore, Norfolk-Washington, and Hatteras) are being investigated from the canyon heads down to their deep-water submarine fans in an effort to characterize their sediment transport history and constrain the influences of external processes on their morphology. Each canyon-fan system is morphologically unique and is strongly controlled by source region, antecedent margin morphology, landslide and debris flow processes, and the long-term influence of deep-water (along-slope) currents.

Chaytor, J. D.; Brothers, D. S.; Ten Brink, U. S.; Hoy, S. K.; Baxter, C.; Andrews, B.

2013-12-01

130

Suspended sediment fluxes and transport processes in the Gulf of Lions submarine canyons. The role of storms and dense water cascading  

Microsoft Academic Search

Contemporary suspended sediment transport was studied in seven submarine canyons of the Gulf of Lions (GoL). Current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from November 2003 to May 2004. Sediment transport events were monitored and studied in relation to forcing conditions. There was a large flood in early December,

Albert Palanques; Xavier Durrieu de Madron; Pere Puig; Joan Fabres; Jorge Guillén; Antoni Calafat; Miquel Canals; Serge Heussner; Jerôme Bonnin

2006-01-01

131

Submarine canyon morphologies in the Gulf of Palermo (Southern Tyrrhenian Sea) and possible implications for geo-hazard  

Microsoft Academic Search

The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from\\u000a 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons\\u000a are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth

Claudio Lo Iacono; Attilio Sulli; Mauro Agate; Valeria Lo Presti; Fabrizio Pepe; Raimondo Catalano

2011-01-01

132

Composition and provenance of terrigenous organic matter transported along submarine canyons in the Gulf of Lion (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Previous projects in the Gulf of Lion have investigated the path of terrigenous material in the Rhone deltaic system, the continental shelf and the nearby canyon heads. This study focuses on the slope region of the Gulf of Lion to further describe particulate exchanges with ocean’s interior through submarine canyons and atmospheric inputs. Nine sediment traps were deployed from the heads to the mouths of Lacaze-Duthiers and Cap de Creus submarine canyons and on the southern open slope from October 2005 to October 2006. Sediment trap samples were analyzed by CuO oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin-derived phenols and cutin acids. Sediment trap data show that the Dense Shelf Water Cascading event that took place in the months of winter 2006 (January, February and March) had a profound impact on particle fluxes in both canyons. This event was responsible for the majority of lignin phenol (55.4%) and cutin acid (42.8%) inputs to submarine canyons, with lignin compositions similar to those measured along the mid- and outer-continental shelf, which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons. The highest lithogenic-normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations (i.e., 193.46 ?g VP g-1 lithogenic at deep slope station), when river flow, wave energy and total particle fluxes were relatively low. During this period, lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios (>3) at almost all stations, high p-coumaric to ferulic acid ratios (>3) and high yields of cutin acids relative to vanillyl phenols (>1), all trends that are consistent with high pollen inputs. Our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons, mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer.

Pasqual, Catalina; Goñi, Miguel A.; Tesi, Tommaso; Sanchez-Vidal, Anna; Calafat, Antoni; Canals, Miquel

2013-11-01

133

3D seismic interpretation of Plio-Pleistocene headless submarine canyons on the Ebro margin: implications for deepwater sand transport  

NASA Astrophysics Data System (ADS)

Recently acquired 3D seismic data from the Ebro continental margin (Eastern Spain) have been used to study a series of spectacular buried post-Messinian submarine canyons that are restricted to the slope i.e. they do not link to incised valleys on the shelf. Understanding the origin of this type of ‘headless’ canyon is important for overall considerations of shelf by-pass and supply of reservoir-prone sediments to the lower parts of slope systems. In particular, the key question is, at what stage in the relative sea level cycle are headless canyons cut? Previous work has documented headless submarine canyons on several continental slopes, but these studies have been mainly based on bathymetric data or on 2D seismic profiles, and are therefore mostly restricted to analysis of the modern seabed topography. This study is the first analysis of this type of canyon system based entirely on 3D seismic data, tied to industry exploration wells. Integrated 3D seismic techniques (structure and attribute maps, time slices and 3D visualisation) allowed us to define in detail the main erosional and depositional features on the continental slope, and their evolution through time. The headless canyons are developed within at least 14 discrete stratigraphic intervals within the Pliocene and Pleistocene succession of the Ebro margin. They are typically 0.5-2km wide, 10-15km long, and incise at least 50m into the slope units. Their most astounding characteristic is an upslope branching geometry in their head area, and single channel morphology downslope. The upslope branching involves three orders of channel bifurcation. The downslope channel development is mainly controlled by the dominance of inherited topography from underlying canyons, and the confinement this imposes on downslope traction currents. The analysis of the phases of activity of the canyons, and the comparison with shelf margin geometry and lithostratigraphy has allowed us to develop a local margin growth model for the Ebro delta system. This model is based on the interplay between internal (sediment supply, tectonic setting, inherited topography) and external controls (sea-level, climate changes). Adjacent headless canyons exhibit considerable diachroneity in their evolution from erosion to deposition and backfilling. In such a complex three-dimensional system, the mode of sand transport to the canyon heads is the most critical factor determining the development of slope reservoir fairways. This study casts doubt on the applicability of idealised lowstand wedge models for exploration on this type of deltaic margin.

Bertoni, C.; Cartwright, J.; Fernandez, J.

2003-04-01

134

The engineering and geological constraints of the intraslope basins and submarine canyons of the northwestern Gulf of Mexico  

SciTech Connect

It is well realized that future hydrocarbon discoveries on the upper and lower continental slope and rise off Texas and Louisiana necessitate innovative methods for the construction of platforms and pipelines in a very difficult engineering and complex geological environment. There are 105 intraslope basins and 5 major submarine canyons on the continental slope of the northwestern Gulf of Mexico, many of which may be prime targets for hydrocarbon production. Examination of the physiographic, geophysical and geotechnical characteristics of the intraslope basins of Pigmy and Vaca basins and the Alaminos submarine canyon are used as examples to typify the various engineering and geological constraints that are most likely to be encountered on the continental slope and rise and along the Sigsbee Escarpment in the northwestern Gulf of Mexico. High-resolution bathymetry identifies such constraints as high-angle intraslope basin walls, walls that exceed 40 degrees are not uncommon. Sediment slumps and other instabilities, such as long-term sediment creep and other affects of halokenesis and contemporaneous faulting, are illustrated and evaluated from high-resolution geophysics. The small canyons and large gullies that dissect the parameter flanks of Alaminos Canyon, that may be the results of both recent and old turbidity currents and debris flows, are structures that require engineering consideration in the implement of seafloor structures in, near or down slope of these features.

Bryant, W.R.; Yuh Liu, J. [Texas A& M Univ., College Station, TX (United States); Ponthier, J. [Louisiana State Univ., Baton Rouge, LA (United States)

1995-10-01

135

Microbial communities in sunken wood are structured by wood-boring bivalves and location in a submarine canyon.  

PubMed

The cornerstones of sunken wood ecosystems are microorganisms involved in cellulose degradation. These can either be free-living microorganisms in the wood matrix or symbiotic bacteria associated with wood-boring bivalves such as emblematic species of Xylophaga, the most common deep-sea woodborer. Here we use experimentally submerged pine wood, placed in and outside the Mediterranean submarine Blanes Canyon, to compare the microbial communities on the wood, in fecal pellets of Xylophaga spp. and associated with the gills of these animals. Analyses based on tag pyrosequencing of the 16S rRNA bacterial gene showed that sunken wood contained three distinct microbial communities. Wood and pellet communities were different from each other suggesting that Xylophaga spp. create new microbial niches by excreting fecal pellets into their burrows. In turn, gills of Xylophaga spp. contain potential bacterial symbionts, as illustrated by the presence of sequences closely related to symbiotic bacteria found in other wood eating marine invertebrates. Finally, we found that sunken wood communities inside the canyon were different and more diverse than the ones outside the canyon. This finding extends to the microbial world the view that submarine canyons are sites of diverse marine life. PMID:24805961

Fagervold, Sonja K; Romano, Chiara; Kalenitchenko, Dimitri; Borowski, Christian; Nunes-Jorge, Amandine; Martin, Daniel; Galand, Pierre E

2014-01-01

136

Microbial Communities in Sunken Wood Are Structured by Wood-Boring Bivalves and Location in a Submarine Canyon  

PubMed Central

The cornerstones of sunken wood ecosystems are microorganisms involved in cellulose degradation. These can either be free-living microorganisms in the wood matrix or symbiotic bacteria associated with wood-boring bivalves such as emblematic species of Xylophaga, the most common deep-sea woodborer. Here we use experimentally submerged pine wood, placed in and outside the Mediterranean submarine Blanes Canyon, to compare the microbial communities on the wood, in fecal pellets of Xylophaga spp. and associated with the gills of these animals. Analyses based on tag pyrosequencing of the 16S rRNA bacterial gene showed that sunken wood contained three distinct microbial communities. Wood and pellet communities were different from each other suggesting that Xylophaga spp. create new microbial niches by excreting fecal pellets into their burrows. In turn, gills of Xylophaga spp. contain potential bacterial symbionts, as illustrated by the presence of sequences closely related to symbiotic bacteria found in other wood eating marine invertebrates. Finally, we found that sunken wood communities inside the canyon were different and more diverse than the ones outside the canyon. This finding extends to the microbial world the view that submarine canyons are sites of diverse marine life. PMID:24805961

Fagervold, Sonja K.; Romano, Chiara; Kalenitchenko, Dimitri; Borowski, Christian; Nunes-Jorge, Amandine; Martin, Daniel; Galand, Pierre E.

2014-01-01

137

Spatial scale-dependent habitat heterogeneity influences submarine canyon macrofaunal abundance and diversity off the Main and Northwest Hawaiian Islands  

NASA Astrophysics Data System (ADS)

The mapping of biodiversity on continental margins on landscape scales is highly relevant to marine spatial planning and conservation. Submarine canyons are widespread topographic features on continental and island margins that enhance benthic biomass across a range of oceanic provinces and productivity regimes. However, it remains unclear whether canyons enhance faunal biodiversity on landscape scales relevant to marine protected area (MPA) design. Furthermore, it is not known which physical attributes and heterogeneity metrics can provide good surrogates for large-scale mapping of canyon benthic biodiversity. To test mechanistic hypotheses evaluating the role of different canyon-landscape attributes in enhancing benthic biodiversity at different spatial scales we conducted 34 submersible dives in six submarine canyons and nearby slopes in the Hawaiian archipelago, sampling infaunal macrobenthos in a depth-stratified sampling design. We employed multivariate multiple regression models to evaluate sediment and topographic heterogeneity, canyon transverse profiles, and overall water mass variability as potential drivers of macrobenthic community structure and species richness. We find that variables related to habitat heterogeneity at medium (0.13 km2) and large (15-33 km2) spatial scales such as slope, backscatter reflectivity and canyon transverse profiles are often good predictors of macrobenthic biodiversity, explaining 16-30% of the variance. Particulate organic carbon (POC) flux and distance from shore are also important variables, implicating food supply as a major predictor of canyon biodiversity. Canyons off the high Main Hawaiian Islands (Oahu and Moloka'i) are significantly affected by organic enrichment, showing enhanced infaunal macrobenthos abundance, whereas this effect is imperceptible around the low Northwest Hawaiian Islands (Nihoa and Maro Reef). Variable canyon alpha-diversity and high rates of species turnover (beta-diversity), particularly for polychaetes, suggest that canyons play important roles in maintaining high levels of regional biodiversity in the extremely oligotrophic system of the North Pacific Subtropical Gyre. This information is of key importance to the process of MPA design, suggesting that canyon habitats be explicitly included in marine spatial planning. The low-islands of Nihoa and Maro Reef in the NWHI showed a lack of sustained input of terrestrial and macrolagae detritus, likely having an influence on the observed low macrofaunal abundances (see further discussion of ‘canyon effects’ in Section 4.3), and showing the fundamental role of coastal landscape characteristics in determining the amount and nature of allochthonous organic matter entering the system. Total and highly-mobile invertebrate megafauna abundances were two to three times higher in the submarine canyons and slopes of the MHI contrasted with the NWHI (Vetter et al., 2010), also demonstrating the role of this larger contribution of terrestrial and coastal organic enrichment in the MHI contrasted with the NWHI.

De Leo, Fabio C.; Vetter, Eric W.; Smith, Craig R.; Rowden, Ashley A.; McGranaghan, Matthew

2014-06-01

138

A delta-fed submarine ramp alternative to the canyon-fed depositional model of the Stevens submarine fan system, southeastern San Joaquin basin, Kern County, California  

SciTech Connect

Deep-marine sands of the Upper Miocene Stevens Sandstone, one of the most important hydrocarbon-producing units in the United States, were deposited by sediment-gravity flows in the Bakersfield Arch area of the southern San Joaquin basin. The Stevens Sandstone has historically been considered to be a thick turbidite succession shed off the southern Sierra Nevada as four fans in a long-lived submarine fan system fed by several large submarine canyons. Access to previously unavailable proprietary 2-D and 3-D seismic data sets, carefully calibrated by well-log and core data, permits a more complete understanding of the depositional architecture of this highly petroliferous, deep-marine depositional system. This study concludes that these units were deposited in a delta-fed, line- sourced deep-sea system, whose distribution was structurally-controlled. Seismic lines examined in this study show evidence for a large fault-controlled slump feature in the area that has been referred to as {open_quotes}Rosedale Canyon,{close_quotes} and no evidence supports the existence of submarine canyons feeding the system. The highly progradational Stevens interval consists of thick siliciclastic units separated by thin, intervening biosiliceous shales. Seismically, the upper bounding surfaces of these biosiliceous shales represent major downlap surfaces. As sands were deposited by high-density turbidity currents, the area of the present Bakersfield Arch developed into a deep-sea braid plain. Smaller-scale linear features detected on horizon slices through the 3-D seismic data cube have been interpreted in this study as braided channelform features deposited on the deep-sea braid plain. Hydrocarbon production along these linear trends may be associated with porosity and permeability variations resulting from channelized versus non-channelized sedimentation.

Harrison, C.P. [Amoco Production Co., Houston, TX (United States)

1996-12-31

139

A delta-fed submarine ramp alternative to the canyon-fed depositional model of the Stevens submarine fan system, southeastern San Joaquin basin, Kern County, California  

SciTech Connect

Deep-marine sands of the Upper Miocene Stevens Sandstone, one of the most important hydrocarbon-producing units in the United States, were deposited by sediment-gravity flows in the Bakersfield Arch area of the southern San Joaquin basin. The Stevens Sandstone has historically been considered to be a thick turbidite succession shed off the southern Sierra Nevada as four fans in a long-lived submarine fan system fed by several large submarine canyons. Access to previously unavailable proprietary 2-D and 3-D seismic data sets, carefully calibrated by well-log and core data, permits a more complete understanding of the depositional architecture of this highly petroliferous, deep-marine depositional system. This study concludes that these units were deposited in a delta-fed, line- sourced deep-sea system, whose distribution was structurally-controlled. Seismic lines examined in this study show evidence for a large fault-controlled slump feature in the area that has been referred to as [open quotes]Rosedale Canyon,[close quotes] and no evidence supports the existence of submarine canyons feeding the system. The highly progradational Stevens interval consists of thick siliciclastic units separated by thin, intervening biosiliceous shales. Seismically, the upper bounding surfaces of these biosiliceous shales represent major downlap surfaces. As sands were deposited by high-density turbidity currents, the area of the present Bakersfield Arch developed into a deep-sea braid plain. Smaller-scale linear features detected on horizon slices through the 3-D seismic data cube have been interpreted in this study as braided channelform features deposited on the deep-sea braid plain. Hydrocarbon production along these linear trends may be associated with porosity and permeability variations resulting from channelized versus non-channelized sedimentation.

Harrison, C.P. (Amoco Production Co., Houston, TX (United States))

1996-01-01

140

Limited depth zonation among bathyal epibenthic megafauna of the Gully submarine canyon, northwest Atlantic  

NASA Astrophysics Data System (ADS)

The Gully is a large submarine canyon incised into the Scotian Shelf, in the northwest Atlantic. A submersible-mounted camera was used to collect 17 km of high resolution video imagery of the soft sediment flanks and floor of the canyon between 1000 and 2500 m depth. A depth-stratified random survey design with two transects per stratum was followed. Depth strata were drawn at 1000-1500 m, 1500-2000 m and 2000-2500 m reflecting global and regional faunal boundaries. The 47,614 individuals or colonies observed on the transects were identified into 49 unique taxa drawn from 7 phyla, while 21 additional taxa were observed between the transect lines. Cnidaria was the most diverse phylum (22 taxa) on the transects, followed by the Echinodermata (15 taxa). Most fauna were sessile or sedentary suspension feeders. A species of Xenophyophorida, likely Syringammina sp., was the most abundant taxon. Cluster analysis of transects based on a Bray-Curtis (BC) matrix of species abundance identified one cluster of five transects and one independent transect - the deepest transect (2406 m average depth). A similarity profile test indicated that this structure is not random. There was a significant change in the megafaunal assemblage with depth over scales of 10s of kilometers, accounting for 65% of the variation in the BC matrix. Both total organic carbon and labile carbon were higher in cores from the 1000-1500 m stratum than at greater depth, consistent with transport of food and sediments into the canyon from shallower waters. The first principal component calculated from species abundances separated the two transects from the 1000-1500 m depth stratum from the others indicating that sediment food supply influences community structure and composition. Over small spatial scales (?10 m), eight groups of species associations were identified. However, the associations between the species within each group were not strong with the highest correlation between the Xenophyophorida and the Pennatulacea (?=0.66). At this spatial scale substrate type was an important factor, with hard and soft bottom species associations being identified.

Kenchington, E. L.; Cogswell, A. T.; MacIsaac, K. G.; Beazley, L.; Law, B. A.; Kenchington, T. J.

2014-06-01

141

Epibiotic relationships on Zygochlamys patagonica (Mollusca, Bivalvia, Pectinidae) increase biodiversity in a submarine canyon in Argentina  

NASA Astrophysics Data System (ADS)

The continental slope of the southern SW Atlantic Ocean has many distinguishable deep submarine canyons, varying in depth and extension. The benthic fauna within one of them, detected in April 2005 by means of a multibeam SIMRAD EM1002 sonar, and located at 43°35?S to 59°33?W, 325 m depth, was studied to discuss faunal affinities with the neighbouring Patagonian scallop fishing grounds located at upper slope depths. In order to add faunal information to the previous general study, we studied the epibiotic species settled on Patagonian scallops (the dominant species in the area) collected in the reference sampling site using a 2.5-m mouth-opening dredge, 10 mm mesh size. We sampled 103 scallops with shell heights between 22 and 69 mm; epibionts were recorded on both valves. We found 53 epibiotic taxa, which were most conspicuous on the upper valve. Bryozoa was the most diverse group (34 species) while Polychaeta was the most abundant group, recorded on 94% of the scallops. Stylasteridae (2 species) and Clavulariidae (Cnidaria) conform newly recorded epibionts on Z. patagonica and the sponge Tedania (Tedaniopsis) infundibuliformis also represents a new record for the SW Atlantic Ocean.

Schejter, Laura; López Gappa, Juan; Bremec, Claudia Silvia

2014-06-01

142

Distribution of Pasiphaea japonica larvae in submarine canyons and adjacent continental slope areas in Toyama Bay, Sea of Japan  

NASA Astrophysics Data System (ADS)

The horizontal and vertical distribution of Pasiphaea japonica larvae, which included larval stages and postlarval or later stages, were investigated in Toyama Bay located in central Japan. The horizontal distributions in the inner part of the bay were investigated by oblique hauls from 10 m above the sea-bottom to the surface using a Remodeled NORPAC net (LNP net) in May, August, November 2005, January, March, April, July, September, December 2006, March-September, November-December 2007, and January-March 2008. The vertical distributions were investigated by concurrent horizontal hauls at the depths of 0, 50, 100, 150, 200, and 250 m using a Motoda net (MTD net) in January, March, April, July, September, and December 2006. Mean density of larvae was higher in submarine canyons which dissect the continental shelf and run to the mouth of river, than adjacent continental slope areas. Larvae densely aggregated in the canyon head. Vertical distribution of the larval stages concentrated in the depth range of 100-150 m in both daytime and nighttime, and larvae in the postlarval or later stages showed diel vertical distribution over a wider depth range than larval stages. Our results indicate the possibility of a larval aggregation in energy-rich habitats, and indicated two important roles of submarine canyons, which were larval retention and high food supply.

Nanjo, Nobuaki; Katayama, Satoshi

2014-09-01

143

A western thalweg of the Princeton Valley submarine canyon system as a reservoir and a trap near Willows, California  

SciTech Connect

The Princeton Valley submarine canyon system has long been an important reservoir and trapping mechanism in the northern Sacramento Valley, California. Recently a western thalweg of the system, identified north of Willows, California, has proven to be a significant trapping mechanism for gas in truncated Kione Formation sandstones. Both Upper Cretaceous Kione Formation and Paleocene Princeton Valley sandstones are exploratory objectives in the area and are productive in existing wells. The Kione Formation, a sand-rich deltaic sequence approximately 2,000 ft thick, has been truncated to the west by the Princeton Valley submarine canyon system. The canyon (gorge) has been subsequently filed with primarily impermeable shales, providing a trap for migrating gases in the truncated sands. The trend was discovered in 1977 by Shell Oil Company based on seismic and was the first substantiated evidence of a western thalweg of the Princeton Gorge in the Willows area. To date, four wells have been completed along the trend and current exploratory efforts are attempting to follow the gorge trend.

Blake, R.G. (Fleet Oil Co., Irvine, CA (USA)); Bainer, R.W.

1990-05-01

144

Scleractinian coral recruitment patterns at Salt River submarine canyon, St. Croix, U.S. Virgin Islands  

NASA Astrophysics Data System (ADS)

Scleractinian coral recruitment patterns were studied at depths of 9, 18, 27 and 37 m on the east and west walls of Salt River submarine canyon, St. Croix, U.S. Virgin Islands, by censusing coral juveniles which settled on experimental settling plates placed on the reef for 3 26 months as well as coral juveniles within quadrats on the reef. The most common species in the juvenile population within quadrats were Agaricia agaricites, Porites astreoides, Madracis decactis, Stephanocoenia michelinii, and A. lamarcki. The only species settling on settling plates were Agaricia spp., Madracis decactis, Porites spp., Stephanocoenia michelinii and Favia fragum. A total of 271 corals settled on 342 plates, with 51% of the juveniles on the east wall and 49% on the west wall. Of these 34% settled on horizontal surfaces and 66% on vertical surfaces. Based on results from quadrats, Agaricia agaricites and Porites astreoides had high recruitment rates relative to their abundance on the reef. In contrast, Agaricia lamarcki, Montastraea annularis, M. cavernosa and Siderastrea siderea had high amounts of cover compared to their abundance as juveniles within quadrats. The mean number of juveniles per m2 within quadrats ranged from 3 to 42. In general, there was a decrease in the mean number of juveniles and the number of species with depth. Total number of juveniles on settling plates was highest at 18 m on both walls. The largest number within quadrats was at 18 m on the east wall, followed by 9 m and 18 m on the west wall. High rates of coral recruitment tended to be associated with low algal biomass and relatively high grazing pressure by urchins and fishes.

Rogers, Caroline S.; Fitz, H. Carl; Gilnack, Marcia; Beets, James; Hardin, John

1984-10-01

145

Submarine canyon morphologies in the Gulf of Palermo (Southern Tyrrhenian Sea) and possible implications for geo-hazard  

NASA Astrophysics Data System (ADS)

The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth of around 1,300 m. The canyons evolved through concurrent top-down turbiditic processes and bottom-up retrogressive mass failures. Most of the mass failure features of the area are related to canyon-shaping processes and only few of them are not confined to the upper slope. In general, these features probably do not represent a significant tsunami hazard along the coast. The geological element that controls the evolution of the canyons and induces sediment instability corresponds to the steep slope gradient, especially in the western sector of the Gulf, where the steepest canyons are located. The structural features mapped in the Palermo offshore contributed to the regulation of mass failure processes in the area, with direct faults and antiform structures coinciding with some of the canyon heads. Furthermore, the occurrence of pockmarks and highs that probably consist of authigenic carbonates above faulted and folded strata suggests a local relationship between structural control, fluid escape processes and mass failure. This paper presents a valuable high-resolution morphologic dataset of the Gulf of Palermo, which constitutes a reliable base for evaluating the geo-hazard potential related to slope failure in the area.

Lo Iacono, Claudio; Sulli, Attilio; Agate, Mauro; Lo Presti, Valeria; Pepe, Fabrizio; Catalano, Raimondo

2011-03-01

146

Sedimentary features and processes in the Nazaré and Setúbal submarine canyons, west Iberian margin  

Microsoft Academic Search

Here we present part of the first complete sidescan sonar dataset of the Nazaré and Setúbal Canyons, west Iberian margin, which, in combination with multibeam bathymetry, shallow seismic profiles and precise piston coring of intra-canyon targets, are used to characterise the sedimentary dynamics of these deep-sea settings. The results show that Nazaré and Setúbal Canyons are highly complex environments. They

Raquel G. Arzola; Russell B. Wynn; Galderic Lastras; Douglas G. Masson; Philip P. E. Weaver

2008-01-01

147

Biological and physical processes in and around Astoria submarine Canyon, Oregon, USA  

Microsoft Academic Search

Astoria Canyon represents the westernmost portion of the Columbia River drainage system, with the head of the canyon beginning just 16 km west of the mouth of the Columbia River along the northern Oregon and southern Washington coasts. During the summer of 2001, physical, chemical, and biological measurements in the canyon were taken to better understand the hydrodynamic setting of,

Keith L. Bosley; J. William Lavelle; Richard D. Brodeur; W. Waldo Wakefield; Robert L. Emmett; Edward T. Baker; Kara M. Rehmke

2004-01-01

148

Sources and distribution of polycyclic aromatic hydrocarbons in the sediments of Kaoping River and submarine canyon system, Taiwan.  

PubMed

In this study, we measured and analyzed polycyclic aromatic hydrocarbons (PAHs) in surface sediment samples collected from the Kaoping river and submarine canyon (KPSC) system to determine the compositional patterns and characteristic distributions of PAH and to elucidate the transport and fate of these land-derived particles. Concentrations of total PAH (sum of 28 PAH compounds) ranged from 22.6 to 45,100 ngg(-1) dry weight (dw) and the highest concentrations were found in the sediments of Donggang Harbor. The ratio of perylene to sum of penta-aromatic PAH isomers (47-55%) was higher in off-shore stations, suggesting a diagenetic PAH source. Various isomeric ratios also indicated that combustion was a significant source of PAH to the sediment at stations located along the Kaoping river and the north-western shelf of the Kaoping estuary. However, in the south-eastern shelf and some canyon sites, petroleum-derived PAHs were a more significant source of these compounds. Principal component analysis and hierarchical cluster analysis suggest PAHs in the sediments from the north-western shelf, and river and canyon sediments might be a pyrogenic product of coal and diesel-burning vehicles, while those of the south-eastern shelf may be petrogenic. PAH concentrations and compositional patterns are effective tracers of particulate transport in KPSC system. The seaward transport of riverine particulates was found to be mostly directed to NW-shelf and/or canyon. PMID:17574277

Fang, Meng-Der; Hsieh, Ping-Chieh; Ko, Fung-Chi; Baker, Joel E; Lee, Chon-Lin

2007-08-01

149

Internal geometry, seismic facies, and petroleum potential of canyons and inner fan channels of the Indus submarine fan  

SciTech Connect

The Indus Fan, the second largest submarine fan in the world, covers 1,250,000 km/sup 2/ (500,000 mi/sup 2/) and contains sediment more than 7 km (23,000 ft) thick. Multichannel (24-fold) CDP seismic data provide the bases for evaluating the Indus Fan and consist of four seismic facies. Of these, only the high-amplitude, discontinuous (H-D) facies is thought to contain reservoir-quality sandstones. The H-D facies is confined to the axes of leveed channels. Canyon-channel systems that fed the fan in the past can be divided into three zones. The degradational zone is composed of an erosional canyon complex filled by prodelta mud. The transitional zone, located near the canyon mouth, consists of superimposed channels that initially were erosional but eventually aggraded and developed levees. The headward termination of the H-D facies occurs in this zone. The aggradational zone consists of superimposed leveed channels confined solely by their own levees. The proximal termination of the H-D facies near canyon mouths implies the presence of reservoir-quality sandstone surrounded by source/seal mudstone in the transitional zone. This stratigraphic trapping geometry and structural leads may represent a vast, untapped petroleum province.

McHargue, T.R.; Webb, J.E.

1986-02-01

150

Accumulation of dioxins in deep-sea crustaceans, fish and sediments from a submarine canyon (NW Mediterranean)  

NASA Astrophysics Data System (ADS)

Submarine canyons are efficient pathways transporting sediments and associated pollutants to deep sea. The objective of this work was to provide with the first assessment of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) levels and accumulation in deep-sea megafauna (crustacean and fish) and sediments in the Blanes submarine canyon (North-Western Mediterranean Sea). The influence of the selected species habitats (pelagic, nektobenthic, and benthic) and the trophic chain level on the accumulation of dioxins was also investigated. Bottom sediment and biota samples were collected at different depths and locations inside the canyon and in the adjacent slope outside the canyon influence. ?2,3,7,8-PCDD/F concentrations in sediments varied from 102 to 680 pg g-1 dry weight (d.w.) (1-6 WHO98-TEQ pg g-1 d.w.). Dioxins are enriched in bottom sediments at higher depths inside the canyon and in particular in the deepest parts of the canyon axis (1700 m depth), whereas no enrichment of dioxins was verified at the deepest sediments from the adjacent open slope outside the canyon influence. The proportion of ?2,3,7,8-PCDF (furans) to ?2,3,7,8-PCDD (dioxins) increased for sediments with higher soot carbon content consistent with the higher affinity of PCDF for sorption onto soot carbon. Higher ?2,3,7,8-PCDD/F levels were found in crustaceans than in fish, ranging from 220 to 795 pg g-1 lipid weight (l.w.) (13-90 WHO98-TEQ pg g-1 l.w.) and 110 to 300 pg g-1 l.w. (22-33 WHO98-TEQ pg g-1 l.w.) in crustaceans and fish, respectively. Dioxin highest concentrations were found in nektobenthic organisms, i.e., benthic organism with swimming capabilities (both fish and crustaceans). These higher levels are consistent with the higher trophic level and predicted biomagnification factors (BMFs) of nektobenthic species. The reduced availability of sediment-bound PCDD/F for benthic species mainly due to soot and organic carbon sorption of these contaminants most probably influenced this result too. While biomagnification exerts a clear influence on the total dioxin concentrations in biota, life habits seem to exert an influence in the differential congener-specific accumulation of dioxins rather than in the total concentration. Thus, pelagic species reflected the estimated congener pattern from the surface water dissolved phase and phytoplankton, whereas the dioxin pattern in benthic and nektobenthic species was more similar to the estimated pattern in the deep-water dissolved phase and the sediment. The three crustacean species considered in this study bioaccumulated higher amounts of other dioxin congeners (non-2,3,7,8-PCDD/Fs) compared to fish. An interplay of several factors, such as biota habitats, differential uptake of water column dioxin (dissolved and particle-bound fractions), and different metabolization capabilities and rates (CYP-mediated metabolism) may explain the differences observed in dioxin patterns among crustacean species and between fish and crustaceans in the Blanes submarine canyon.

Castro-Jiménez, Javier; Rotllant, Guiomar; Ábalos, Manuela; Parera, Jordi; Dachs, Jordi; Company, Joan B.; Calafat, Antoni; Abad, Esteban

2013-11-01

151

Formation of pockmarks and submarine canyons associated with dissociation of gas hydrates on the Joetsu Knoll, eastern margin of the Sea of Japan  

NASA Astrophysics Data System (ADS)

This study, based on 3.5 kHz SBP, 3D seismic data and long piston cores obtained during MD179 cruise, elucidated the timing and causes of pockmark and submarine canyon formation on the Joetsu Knoll in the eastern margin of the Sea of Japan. Gas hydrate mounds and pockmarks aligned parallel to the axis on the top of the Joetsu Knoll are associated with gas chimneys, pull-up structures, faults, and multiple bottom-simulating reflectors (BSRs), suggesting that thermogenic gas migrated upward through gas chimneys and faults from deep hydrocarbon sources and reservoirs. Seismic and core data suggest that submarine canyons on the western slope of the Joetsu Knoll were formed by turbidity currents generated by sand and mud ejection from pockmarks on the knoll. The pockmark and canyon formation probably commenced during the sea-level fall, lasting until transgression stages. Subsequently, hydropressure release during the sea level lowering might have instigated dissociation of the gas hydrate around the base of the gas hydrate, leading to generation and migration of large volumes of methane gas to the seafloor. Accumulation of hydrate caps below mounds eventually caused the collapse of the mounds and the formation of large depressions (pockmarks) along with ejection of sand and mud out of the pockmarks, thereby generating turbidity currents. Prolonged pockmark and submarine canyon activities might have persisted until the transgression stage because of time lags from gas hydrate dissociation around the base of the gas hydrate until upward migration to the seafloor. This study revealed the possibility that submarine canyons were formed by pockmark activities. If that process occurred, it would present important implications for reconstructing the long-term history of shallow gas hydrate activity based on submarine canyon development.

Nakajima, Takeshi; Kakuwa, Yoshitaka; Yasudomi, Yukihito; Itaki, Takuya; Motoyama, Isao; Tomiyama, Takayuki; Machiyama, Hideaki; Katayama, Hajime; Okitsu, Osamu; Morita, Sumito; Tanahashi, Manabu; Matsumoto, Ryo

2014-08-01

152

Trawling-induced daily sediment resuspension in the flank of a Mediterranean submarine canyon  

NASA Astrophysics Data System (ADS)

Commercial bottom trawling is one of the anthropogenic activities causing the biggest impact on the seafloor due to its recurrence and global distribution. In particular, trawling has been proposed as a major driver of sediment dynamics at depths below the reach of storm waves, but the issue is at present poorly documented with direct observations. This paper analyses changes in water turbidity in a tributary valley of the La Fonera (=Palamós) submarine canyon, whose flanks are routinely exploited by a local trawling fleet down to depths of 800 m. A string of turbidimeters was deployed at 980 m water depth inside the tributary for two consecutive years, 2010-2011. The second year, an ADCP profiled the currents 80 m above the seafloor. The results illustrate that near-bottom water turbidity at the study site is heavily dominated, both in its magnitude and temporal patterns, by trawling-induced sediment resuspension at the fishing ground. Resuspended sediments are channelised along the tributary in the form of sediment gravity flows, being recorded only during working days and working hours of the trawling fleet. These sediment gravity flows generate turbid plumes that extend to at least 100 m above the bottom, reaching suspended sediment concentrations up to 236 mg l-1 close to the seafloor (5 m above bottom). A few hours after the end of daily trawling activities, water turbidity progressively decreases but resuspended particles remain in suspension for several hours, developing bottom and intermediate nepheloid layers that reach background levels ˜2 mg l-1 before trawling activities resume. The presence of these nepheloid layers was recorded in a CTD+turbidimeter transect conducted across the fishing ground a few hours after the end of a working day. These results highlight that deep bottom trawling can effectively replace natural processes as the main driving force of sediment resuspension on continental slope regions and generate increased near-bottom water turbidity that propagates from fishing grounds to wider and deeper areas via sediment gravity flows and nepheloid layer development.

Martín, Jacobo; Puig, Pere; Palanques, Albert; Ribó, Marta

2014-06-01

153

Submarine canyons of north-western Sicily (Southern Tyrrhenian Sea): Variability in morphology, sedimentary processes and evolution on a tectonically active margin  

NASA Astrophysics Data System (ADS)

Swath-bathymetry, mono-channel and multi-channel seismic reflection records acquired during the last two decades on the northern Sicilian margin have unveiled a dense network of submarine canyons within the depth range of 80-2100 m. The canyons display a relevant variability in their geometry, morphology and sedimentary processes. The margin shows a young, tectonically active shelf to slope setting, linking the Sicilian-Maghrebian Thrust Belt to the Tyrrhenian oceanic realm, developed during the Neogene-Quaternary time span. The aim of this study is to highlight the main governing factors that contributed to the evolution and differentiation of the northern Sicilian canyons, mainly focusing on the Gulf of Palermo and on the Gulf of Castellammare. Tectonic control is more evident in the canyons of the Gulf of Palermo, with submarine landslides retrograding on a steep slope and mainly controlling their evolution. Otherwise, canyons, tributaries and gullies mapped in the Gulf of Castellammare developed on a less steep substrate and display sinuous to meandering paths, with a relevant role of coastal/shelf sedimentary inputs and downslope turbidity processes in their formation. Results suggest that, despite the geographically close proximity of the two study areas, the different structural settings of the Castellammare and Palermo Basins are mainly responsible for canyon variability. Data indicate likely on-going uplift and tilting movements along the Sicilian margin, influencing the development of the studied canyons, which have probably been more active during the Quaternary glacial maxima than they are in the present day.

Lo Iacono, Claudio; Sulli, Attilio; Agate, Mauro

2014-06-01

154

On vertical advection truncation errors in terrain-following numerical models: Comparison to a laboratory model for upwelling over submarine canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons which indent the continental shelf are frequently regions of steep (up to 45°), three-dimensional topography. Recent observations have delineated the flow over several submarine canyons during 2-4 day long upwelling episodes. Thus upwelling episodes over submarine canyons provide an excellent flow regime for evaluating numerical and physical models. Here we compare a physical and numerical model simulation of an upwelling event over a simplified submarine canyon. The numerical model being evaluated is a version of the S-Coordinate Rutgers University Model (SCRUM). Careful matching between the models is necessary for a stringent comparison. Results show a poor comparison for the homogeneous case due to nonhydrostatic effects in the laboratory model. Results for the stratified case are better but show a systematic difference between the numerical results and laboratory results. This difference is shown not to be due to nonhydrostatic effects. Rather, the difference is due to truncation errors in the calculation of the vertical advection of density in the numerical model. The calculation is inaccurate due to the terrain-following coordinates combined with a strong vertical gradient in density, vertical shear in the horizontal velocity and topography with strong curvature.

Allen, S. E.; Dinniman, M. S.; Klinck, J. M.; Gorby, D. D.; Hewett, A. J.; Hickey, B. M.

2003-01-01

155

Megafauna of vulnerable marine ecosystems in French mediterranean submarine canyons: Spatial distribution and anthropogenic impacts  

NASA Astrophysics Data System (ADS)

Vulnerable Marine Ecosystems (VME) in the deep Mediterranean Sea have been identified by the General Fisheries Commission for the Mediterranean as consisting of communities of Scleractinia (Lophelia pertusa and Madrepora oculata), Pennatulacea (Funiculina quadrangularis) and Alcyonacea (Isidella elongata). This paper deals with video data recorded in the heads of French Mediterranean canyons. Quantitative observations were extracted from 101 video films recorded during the MEDSEACAN cruise in 2009 (Aamp/Comex). Qualitative information was extracted from four other cruises (two Marum/Comex cruises in 2009 and 2011 and two Ifremer cruises in 1995 and 2010) to support the previous observations in the Cassidaigne and Lacaze-Duthiers canyons. All the species, fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using GIS. The abundances and distributions of benthic fishing resources (marketable fishes, Aristeidae, Octopodidae), Vulnerable Marine Species, trawling scars and litter of 17 canyons were calculated and compared, as was the open slope between the Stoechades and Toulon canyons. Funiculina quadrangularis was rarely observed, being confined for the most part to the Marti canyon and, I. elongata was abundant in three canyons (Bourcart, Marti, Petit-Rhône). These two cnidarians were encountered in relatively low abundances, and it may be that they have been swept away by repeated trawling. The Lacaze-Duthiers and Cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold-water corals, whose distribution was mapped in detail. These colonies were often seen to be entangled in fishing lines. The alcyonacean Callogorgia verticillata was observed to be highly abundant in the Bourcart canyon and less abundant in several other canyons. This alcyonacean was also severely affected by bottom fishing gears and is proposed as a Vulnerable Marine Species. Our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the Gulf of Lion and to long lines where rocky substrates are present. The bauxite residue (red mud) expelled in the Cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks. Litter was present in all of the canyons and especially in considerable quantities in the Ligurian Sea, where the heads of the canyons are closer to the coast. Three Marine Protected Areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems.

Fabri, M.-C.; Pedel, L.; Beuck, L.; Galgani, F.; Hebbeln, D.; Freiwald, A.

2014-06-01

156

Abundance and biomass of macrobenthos in the vicinity of Carson Submarine Canyon, northwest Atlantic Ocean  

Microsoft Academic Search

The abundance, biomass and mean weight of macrofauna in the Carson Canyon region (Lat. 45°30'N, Long. 48°40'W) of the Grand Banks were estimated from 40 quantitative infaunal samples taken at 15 stations in June 1980. In contrast to other areas, there were no significant differences in these values between samples taken in and outside of the canyon. Abundance (\\u000a$$\\\\bar

K. A. Houston; R. L. Haedrich

1984-01-01

157

Typhoon- and earthquake-enhanced concentration and inventory of dissolved and particulate trace metals along two submarine canyons off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The influence of typhoon and earthquake events on the distributions of dissolved and particulate trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn) is evaluated along the Gaoping Canyon and Fangliao Canyon in a tectonically active margin off southwestern Taiwan. The Fangliao Canyon was mightily struck by a large Pingtung Earthquake (ML 7.0) in winter when terrestrial inputs were insignificant. This large earthquake clearly enhanced the concentration and inventory of total suspended matter (TSM), dissolved and particulate metals by 2-5 fold in Fangliao Canyon and nearby Gaoping Canyon, as compared to those in normal winter conditions. The Gaoping Canyon is typically inundated with massive amounts of terrestrial materials during summer typhoons from the mountainous Gaoping River. Strong contrast of particle and metal distributions can be found between summer and winter and between typhoon and regular summer periods in the Gaoping Canyon, which was apparently caused by various strengths of river inputs followed by sediment resuspension and lateral advection at intermediate and near-bottom depths along the canyon. The water-column and canyon-wide inventories of TSM, dissolved and particulate metals increased up to 2-fold higher during the post-typhoon period than during the rainy period in summer in the Gaoping Canyon. After extreme events, most metals tend to increase their release into the dissolved phase through the increase of TSM concentration. In addition to huge river inputs during typhoon, both typhoon and earthquake induce energetic sea conditions that cause sediment resuspension and enhance the concentration and inventory of particles and metals in submarine canyons.

Hung, J.-J.; Ho, C.-Y.

2014-01-01

158

Muscular and hepatic pollution biomarkers in the fishes Phycis blennoides and Micromesistius poutassou and the crustacean Aristeus antennatus in the Blanes Submarine Canyon (NW Mediterranean).  

PubMed

Submarine canyons are regarded as a sink for pollutants. In order to determine if this theory applied to deep-sea species from an important fishing ground (the Blanes submarine canyon) located in the NW Mediterranean, we sampled the commercial fish Phycis blennoides and Micromesistius poutassou and the crustacean Aristeus antennatus. Specimens were sampled inside and outside (in the open continental slope) the submarine canyon; both are regarded as potentially affected by exposure to different anthropogenic chemicals. Several pollution biomarkers in muscle (activity of cholinesterases) and liver/hepatopancreas (catalase, glutathione S-transferases, carboxylesterases, ethoxyresorufin O-deethylase in fish or mixed function oxygenase (MFO)-related reductases in crustacean, and lipid peroxidation levels) were measured. Chemical analysis of the persistent organic pollutants, namely polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) was also performed on the fish and crustacean muscle. Biomarker activities and levels were discussed in relation to pollutant exposure, habitat, and parameters including sex, size, and species. Biochemical responses and chemical analysis of PCBs evidenced interspecies differences as well as sex and size-related ones, mainly in A. antennatus. An indication of higher exposure to pollutants inside the canyon was observed, which was more clearly reflected in the fish than in the crustacean. However, further research is required to confirm this observation. PMID:18941829

Solé, Montserrat; Hambach, Bastian; Cortijo, Verónica; Huertas, David; Fernández, Pilar; Company, Joan B

2009-07-01

159

Stratigraphic and lithologic relationships: lateral outcrop profiles and architectural elements of middle Eocene Torrey submarine canyon, La Jolla, California  

SciTech Connect

Heterogeneous fills within similar subsurface systems are problematic for hydrocarbon exploration and production. Diagramming the stratigraphic and lithologic associations of the Torrey Canyon on photomosaics demonstrates the complexities. Many elements resemble fluvial fills; others are unique to the submarine setting. The basal (first-order) bounding surface is an unconformity, at least 2 mi wide, truncating paralic to slope units. Internally, the canyon comprises channels on a variety of scales. Large (second-order) cuts are up to 300 ft deep and 1/2 mi wide. Within these are (third-order) crosscutting, meandering to braided channels, 5 ft to more than 60 ft deep and 10 ft to more than 1500 ft wide. A variety of (fourth order) bed forms, lithofacies, and fabrics embody the fill. Conglomerates occur as bars, channels, and sheets. They range from clast to matrix supported and disorganized to imbricated. Sandstones include sheets with turbidite or dish structures; channels of structureless to faintly laminated crosscutting units; and crevasse-splay wedges, sheets, and channels of laminated, cross-bedded, or rippled fabrics. Fine-grained deposits are sheets or channel fills and encompass intercalated sandstone and mudstone, mudstone with starved ripples, and laminated mudstone. Lithologically diverse slump masses add further complexities. The predominance of conglomerates and interconnected sandstones downdip vs. mudstone channels and segregated sandstones updip provides a model for predicting subsurface reservoir types, geometries, and permeability trends in similar systems.

May, J.A.; Warme, J.E.

1989-03-01

160

Subaqueous grain flows at the head of Carmel Submarine Canyon, California  

USGS Publications Warehouse

Very coarse sand is the predominate material on the beach, adjacent shelf, and upper canyon-head slopes, while silt and clay cover the surface below a water depth at about 35 m. On angle-of-repose slopes in the upper canyon head, downslope-coarsening deposits are similar to a type of sediment gravity flow deposit formed by grain flows (sand avalanches). Using three sand fractions that were dyed different fluorescent colors, scuba divers generated sand avalanches that produced deposits similar to the natural deposits. -from Authors

Dingler, J.R.; Anima, R.J.

1989-01-01

161

Axial incision: The key to understand submarine canyon evolution (in the western Gulf of Lion)  

Microsoft Academic Search

A detailed morphological analysis of the outer shelf and continental slope of the Western Gulf of Lion is presented, based on swath bathymetry data together with sub-bottom profiles and high resolution seismic reflection profiles. These data reveal two main erosive features, of very different dimensions: the axial incision and the canyon's major valley. The height of axial incisions' flanks with

J. Baztan; S. Berné; J.-L Olivet; M. Rabineau; D. Aslanian; M. Gaudin; J.-P. Réhault; M. Canals

2005-01-01

162

Laboratory observations of rotating, stratified flow in the vicinity of a submarine canyon  

Microsoft Academic Search

Laboratory experiments are conducted concerning an oscillatory, along-isobath flow of a linearly stratified fluid along a continuous continental shelf, shelf-break, and continental slope model topography interrupted only by a single isolated canyon. The model topography is located along the periphery of a circular tank, which is placed at the center of a turntable. Modulating the turntable rotation rate drives the

Don L. Boyer; Xiuzhang Zhang; Nicholas Pérenne

2000-01-01

163

Bioluminescence in the Monterey Submarine Canyon: image analysis of video recordings from a midwater submersible  

Microsoft Academic Search

Video images of bioluminescence were recorded in situ during a 1985 study of the midwater environment of the Monterey Canyon, using a single-person, untethered submersible. Gelatinous organisms were responsible for the most brilliant bioluminescent displays, often exhibiting elaborate kinetics in response to mechanical stimulation. Images of bioluminescent displays recorded from identified organisms are shown and display patterns are described. All

E. A. Widder; S. A. Bernstein; D. F. Bracher; J. F. Case; K. R. Reisenbichler; J. J. Torres; B. H. Robison

1989-01-01

164

Provenance and fate of organic carbon in three submarine canyons from the Portuguese Margin: Implications for transport processes of material in continental margins  

NASA Astrophysics Data System (ADS)

Submarine canyons are key environments on the continental margin that are affected by unique and dynamic but often episodic and complex processes, and are difficult to study. Canyons are considered hotspots of biodiversity and enhancement of primary productivity at canyon heads has often been postulated to support this, although the evidence is sparse. Additionally canyons are considered to be fast-track corridors for material transported from the land to the deep sea and they are considered major pathways for the transportation and burial of organic carbon, acting as buffers for sediment and carbon storage. Organic geochemical and isotopic markers are often used as reliable indicators for the supply, quality and fate of organic matter in marine systems. In this study they have been used to test the above hypotheses in three contrasting submarine canyons (Nazaré, Setubal/Lisbon and Cascais) of the Portuguese Margin. The elemental and lipid biomarker composition of suspended particulate organic matter of surface waters close to the studied canyon heads had a fresh phytoplankton signal, however there was no clear evidence for enhanced primary productivity by comparison to the neighbouring open slope. By contrast, mid-depth waters (700-1600 m), that are dominated by the northward flowing Mediterranean Outflow Water, had high lipid content and abundant mesozooplankton biomarkers, perhaps reflecting zooplankton activity focused at the boundaries of distinct water masses. In the waters close to the floor of the Nazaré Canyon the presence of elemental sulphur (a product of sediment diagenesis) and high molecular weight hydrocarbons (recalcitrant, terrestrial markers) indicated high levels of resuspended material, particularly at the Upper section (

Kiriakoulakis, Kostas; Wolff, George; Blackbird, Sabena

2010-05-01

165

Cleaning behavior of Bodianus rufus, Thalassoma bifasciatum, Gobiosoma evelynae , and Periclimenes pedersoni along a depth gradient at Salt River Submarine Canyon, St. Croix  

Microsoft Academic Search

Synopsis  Cleaning activity at specific cleaning stations was monitored over a depth range of 15–45 m at Salt River Submarine Canyon,\\u000a St. Croix using the HYDROLAB underwater habitat. We observed over 4600 cleaning events involving 32 host species. Cleaners\\u000a included the fishesGobiosoma evelynae (cleaning goby), juvenileBodianus rufus (Spanish hogfish) and juvenileThalassoma bifasciatum (bluehead wrasse) and the shrimpPericlimenes pedersoni, often active simultaneously

William S. Johnson; Peter Ruben

1988-01-01

166

Geological exploration in an East Coast submarine canyon from a research submersible  

USGS Publications Warehouse

Large talus blocks litter the flat floor of Oceanographer Canyon at a depth of 1460 meters; they indicate down-axis mass transport of floor sediment at an unknown time and rate. From 1460 to 1310 meters the sidewall is covered by unconsolidated sediment lying at 35?? to 40?? from the horizontal. An outcrop of Pleistocene or younger sediment at 1460 meters is probably a remnant of a former fill.

Trumbull, J.V.A.; McCamis, M.J.

1967-01-01

167

Geological exploration in an East coast submarine canyon from a research submersible.  

PubMed

Large talus blocks litter the flat floor of Oceanographer Canyon at a depth of 1460 meters; they indicate down-axis mass transport of floor sediment at an unknown time and rate. From 1460 to 1310 meters the sidewall is covered by unconsolidated sediment lying at 35 degrees to 40 degrees from the horizontal. An outcrop of Pleistocene or younger sediment at 1460 meters is probably a remnant of a former fill. PMID:17794318

Trumbull, J V; McCamis, M J

1967-10-20

168

A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon  

PubMed Central

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin. PMID:22194903

Huvenne, Veerle A. I.; Tyler, Paul A.; Masson, Doug G.; Fisher, Elizabeth H.; Hauton, Chris; Hühnerbach, Veit; Le Bas, Timothy P.; Wolff, George A.

2011-01-01

169

A picture on the wall: innovative mapping reveals cold-water coral refuge in submarine canyon.  

PubMed

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked--quite literally--and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin. PMID:22194903

Huvenne, Veerle A I; Tyler, Paul A; Masson, Doug G; Fisher, Elizabeth H; Hauton, Chris; Hühnerbach, Veit; Le Bas, Timothy P; Wolff, George A

2011-01-01

170

Defining biological assemblages (biotopes) of conservation interest in the submarine canyons of the South West Approaches (offshore United Kingdom) for use in marine habitat mapping  

NASA Astrophysics Data System (ADS)

In 2007, the upper part of a submarine canyon system located in water depths between 138 and 1165 m in the South West (SW) Approaches (North East Atlantic Ocean) was surveyed over a 2 week period. High-resolution multibeam echosounder data covering 1106 km2, and 44 ground-truthing video and image transects were acquired to characterise the biological assemblages of the canyons. The SW Approaches is an area of complex terrain, and intensive ground-truthing revealed the canyons to be dominated by soft sediment assemblages. A combination of multivariate analysis of seabed photographs (184-1059 m) and visual assessment of video ground-truthing identified 12 megabenthic assemblages (biotopes) at an appropriate scale to act as mapping units. Of these biotopes, 5 adhered to current definitions of habitats of conservation concern, 4 of which were classed as Vulnerable Marine Ecosystems. Some of the biotopes correspond to descriptions of communities from other megahabitat features (for example the continental shelf and seamounts), although it appears that the canyons host modified versions, possibly due to the inferred high rates of sedimentation in the canyons. Other biotopes described appear to be unique to canyon features, particularly the sea pen biotope consisting of Kophobelemnon stelliferum and cerianthids.

Davies, Jaime S.; Howell, Kerry L.; Stewart, Heather A.; Guinan, Janine; Golding, Neil

2014-06-01

171

Impact of bottom trawling on deep-sea sediment properties along the flanks of a submarine canyon.  

PubMed

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y-1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. PMID:25111298

Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

2014-01-01

172

Impact of Bottom Trawling on Deep-Sea Sediment Properties along the Flanks of a Submarine Canyon  

PubMed Central

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400–800 m depth range. To explore the degree of alteration of surface sediments (0–50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y?1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. PMID:25111298

Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

2014-01-01

173

From Kings Peak to the Delgado submarine canyon: Tracking littoral inputs to the deep sea at the Mendocino Triple Junction, California  

NASA Astrophysics Data System (ADS)

Gravel coarse enough to overcome viscous damping and impact bedrock underwater is thought prerequisite for incision of submarine canyons, yet with few exceptions, canyons off the California coast have headwalls >2 km offshore at the shelf edge and below storm wave base. This suggests effective disconnection from modern coarse littoral sediment fluxes, and implies they are relict Pleistocene features only actively incised during glacial periods. North of the Transverse Ranges only five submarine canyons approach shore closer than 500 m, and are coincident areas of rapid uplift. Although canyons occur adjacent to major upland-draining streams that transport coarse sediment, submarine canyon headwalls are often laterally offset from stream mouths by ~1-2 km. Coarse stream sediment thus requires littoral transport to enter canyon heads and induce incision. To better understand the evolution of coarse sediment through the littoral system, we measured the texture and composition of coarse sediment in streams and beaches directly onshore of the Delgado submarine canyon, which lies offshore of the fastest uplifting segment of the King Range and onshore the Mendocino Triple Junction. Adjacent to the Delgado Canyon inlet, coarse (d50 > 360 mm) sediment enters the littoral zone from three streams, and is transported alongshore in a predominantly southeast direction. Stream-derived alluvium is comprised of a poorly to moderately sorted mixture of angular to subrounded clasts of well-cemented sandstone (d50 = 256-725 mm) and fissile siliciclastic mudstone (d50 = 90-256 mm). Well sorted and rounded beach gravels adjacent to stream mouths are similarly coarse, and clasts larger than 1 m diameter extend 200-400 meters eastward from stream mouths. In contrast, sediment entering the littoral zone from hillslope erosion between streams is finer (d50 ~16 mm) and is exclusively comprised of pervasively-folded siliciclastic mudstone. Immediately adjacent the Delgado canyon headwall, beach sediments are nearly two orders of magnitude finer than sediment at stream mouths (d50 = 16 mm). However, sandstone clasts are coarser (d50 = 32 mm), comprise ~30% of the total mass, and approximately 10% of these clasts exceed 128 mm in diameter. The mudstone fraction in contrast is much finer (d50 = 4 mm). Particles finer than 0.25 mm represent less than 10% of beach sediment, consistent with effective removal of fines from the littoral environment. Lithologic contrast between sandstone and mudstone rock types is the basis for a multi-lithologic downstream fining model that routes sediment through the littoral system. Inputs of sediment are calculated according to upstream catchment area for 200 m segments of coastline and scaled according to lithologically based erosion rates, with differential diminuation as it is routed through the littoral zone. Initial model results indicate that differential abrasion of mudstone clasts relative to sandstone clasts is important to achieving grain size and lithologic distributions observed at the canyon head, and the presence of clasts >100 mm diameter ~1 km from their input via stream to the littoral zone provides tools needed for incision submarine bedrock.

Davidson, C. J.; Di Fiori, R. V.; Smith, M. E.; Mueller, E. R.

2011-12-01

174

Megalodicopia hians in the Monterey submarine canyon: Distribution, larval development, and culture  

NASA Astrophysics Data System (ADS)

The exclusively deep-sea ascidian family Octacnemidae comprises several genera in which the oral siphon has hypertrophied to form two large lips which create an "oral hood" capable of capturing motile prey. Megalodicopia hians is typical of this carnivorous family and has been reported to prey upon small epibenthic crustaceans. Distribution of M. hians in the Monterey Canyon system (36°45'N, 122°00'W) (California) was determined with remotely operated vehicles. M. hians was found sparsely to depths of at least 3800 m throughout the canyon; however, abundance was greatest within the oxygen-minimum zone (400-800 m). Eggs, sperm, and recently fertilized embryos were obtained repeatedly from adults returned to the laboratory in vivo, indicating that this species free-spawns routinely. Overall egg diameter (ovum plus chorion, plus follicle cells) was 175-190 ?m—considerably smaller than previously reported for this species. Embryonic development at temperature and oxygen concentrations equivalent to the oxygen-minimum zone was 2-4 d and, embryos gave rise to typical phlebobranch "simple" tadpole larvae. Larval period was extremely variable, and settlement/metamorphosis occurred up to 3 months post-hatching. These results are discussed within the context of settlement-site selection and fertilization ecology of the species.

Havenhand, Jon. N.; Matsumoto, George I.; Seidel, Ed

2006-02-01

175

Deposition rates, mixing intensity and organic content in two contrasting submarine canyons  

NASA Astrophysics Data System (ADS)

The hydrographically different conditions characterising the Western Iberian Margin (NE Atlantic) and the Gulf of Lions (Mediterranean) may play an important role in determining the biogeochemical characteristics of the sediments. To investigate this, we compared the Nazaré and Cap de Creus canyons, and their respective adjacent open slopes in terms of the organic carbon (C org) contents, chlorophyll- a (chl- a) concentrations, C:N and chl- a:phaeopigment ratios, and also in terms of modelled mixing intensities, chl- a and 210Pb deposition and background concentrations in sediments. Chlorophyll- a and 210Pb profiles were fitted simultaneously with a reactive transport model to estimate mixing intensity, deposition and background concentrations. Further, to account for the possibility that the decay of chl- a may be lower in the deep sea than in shallow areas, we estimated the model parameters with two models. In one approach (model 1), the temperature dependent decay rate of chl- a as given by Sun et al. [Sun, M.Y., Lee, C., Aller, R.C. (1993) Laboratory Studies of Oxic and Anoxic Degradation of chlorophyll- a in Long-Island sound sediments. Geochimica et Cosmochimica Acta, 57, 147-157] for estuaries was used. In the other approach (model 2), an extra parameter was estimated to derive the chlorophyll- a degradation rate. An F-test, taking into account the different number of parameters in the models, was used to single out the model that significantly fitted the data best. In most cases, the model parameters were best-explained with model 1, indicating the empirical relationship by Sun et al. (1993) is a valid means to estimate the chlorophyll- a degradation rate in deep sea sediments. To assess the robustness with which the model parameters were estimated we provide a first application of Bayesian analysis in the modelling of tracers in sediments. Bayesian analysis allows calculating the mean and standard deviation for each model parameter and correlations among parameters. The model parameters for stations for which 210Pb and chlorophyll- a profiles were available were robustly fitted as evidenced by an average coefficient of variation of 0.22. C org contents, chl- a concentrations, chl- a:phaeo ratios, mixing intensities, depositions and background concentrations of chl- a and 210Pb indicated that the Cap de Creus canyon and adjacent slope were less active in terms of organic matter accumulation and burial than the Nazaré canyon and respective open slope.

García, R.; van Oevelen, D.; Soetaert, K.; Thomsen, L.; De Stigter, H. C.; Epping, E.

2008-02-01

176

Swept away by a turbidity current in Mendocino submarine canyon, California  

NASA Astrophysics Data System (ADS)

present unique observations and measurements of a dilute turbidity current made with a remotely operated vehicle in 400 m water depth near the head of Mendocino Canyon, California. The flow had a two-layer structure with a thin (0.5 to 30 m), relatively dense (<0.04 vol %) and fast (up to ~1.7 m/s) wedge-shaped lower layer overlain by a thicker (up to 89 m) more dilute and slower current. The fast moving lower layer lagged the slow moving, dilute flow front by 14 min, which we infer resulted from the interaction of two initial pulses. The two layers were strongly coupled, and the sharp interface between the layers was characterized by a wave-like instability. This is the first field-scale data from a turbidity current to show (i) the complex dynamics of the head of a turbidity current and (ii) the presence of multiple layers within the same event.

Sumner, E. J.; Paull, C. K.

2014-11-01

177

Spatial and temporal infaunal dynamics of the Blanes submarine canyon-slope system (NW Mediterranean); changes in nematode standing stocks, feeding types and gender-life stage ratios  

NASA Astrophysics Data System (ADS)

Despite recent advances in the knowledge of submarine canyons ecosystems, our understanding of the faunal patterns and processes in these environments is still marginal. In this study, meiobenthic nematode communities (from 300 m to 1600 m depth) obtained in November 2003 and May 2004 at eight stations inside and outside Blanes submarine canyon were analysed for nematode standing stocks (SSs), feeding types and gender-life stage distributions. Environmental data were obtained by sediment traps and current meters, attached to moorings (April 2003-May 2004), and sediments samples analysed for biogeochemistry and grain size (May 2004). In November 2003, nematode SSs decreased with increasing depth (367.2 individuals and 7.31 ?g C per 10 cm2 at 388 m water depth to 7.7 individuals and 0.18 ?g C per 10 cm2 at 1677 m water depth), showing a significant negative relation (abundance: R2 = 0.620, p = 0.020; biomass: R2 = 0.512, p = 0.046). This was not the case in May 2004 (283.5 individuals and 3.53 ?g C per 10 cm2 at 388 m water depth to 490.8 individuals and 4.93 ?g C per 10 cm2 at 1677 m water depth; abundance: R2 = 0.003, p = 0.902; biomass: R2 = 0.052, p = 0.587), suggesting a temporal effect that overrides the traditional decrease of SSs with increasing water depth. Both water depth and sampling time played a significant role in explaining nematode SSs, but with differences between stations. No overall differences were observed between canyon and open slope stations. Nematode standing stock (SS) patterns can be explained by taking into account the interplay of phytodetrital input and disturbance events, with station differences such as topography playing an important role. Individual nematode size decreased from November 2003 to May 2004 and was explained by a food-induced genera shift and/or a food-induced transition from a ‘latent’ to a ‘reproductive’ nematode community. Our results suggest that size patterns in nematode communities are not solely governed by trophic conditions over longer periods of time in relatively food-rich environments such as canyons. We hypothesize that food pulses in a dynamic and topographical heterogeneous environment such as canyons regulate nematode size distributions, rather than long-term food availability. Feeding type distributions in the Blanes Canyon did not clearly resemble those from other canyon systems, apart from the spring assemblage at one station in the head of the canyon.

Ingels, Jeroen; Vanreusel, Ann; Romano, Chiara; Coenjaerts, Johan; Mar Flexas, M.; Zúñiga, Diana; Martin, Daniel

2013-11-01

178

Demography and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon along the open coast of southern California, USA  

USGS Publications Warehouse

The demography, spatial distribution, and movement patterns of leopard sharks (Triakis semifasciata) aggregating near the head of a submarine canyon in La Jolla, California, USA, were investigated to resolve the causal explanations for this and similar shark aggregations. All sharks sampled from the aggregation site (n=140) were sexually mature and 97.1 % were female. Aerial photographs taken during tethered balloon surveys revealed high densities of milling sharks of up to 5470 sharks ha-1. Eight sharks were each tagged with a continuous acoustic transmitter and manually tracked without interruption for up to 48 h. Sharks exhibited strong site-fidelity and were generally confined to a divergence (shadow) zone of low wave energy, which results from wave refraction over the steep bathymetric contours of the submarine canyon. Within this divergence zone, the movements of sharks were strongly localized over the seismically active Rose Canyon Fault. Tracked sharks spent most of their time in shallow water (?2 m for 71.0 % and ?10 m for 95.9 % of time), with some dispersing to deeper (max: 53.9 m) and cooler (min: 12.7 °C) water after sunset, subsequently returning by sunrise. These findings suggest multiple functions of this aggregation and that the mechanism controlling its formation, maintenance, and dissolution is complex and rooted in the sharks' variable response to numerous confounding environmental factors.

Nosal, D.C.; Cartamil, D.C.; Long, J.W.; Luhrmann, M.; Wegner, N.C.; Graham, J.B.

2013-01-01

179

Paleocene Sepultura Formation: submarine canyon at La Mesa, Baja California, Mexico  

SciTech Connect

The Paleocene Sepultura Formation has been interpreted as the result of both deposition in a basin that varied in depth from strandline to at least 30-40 fathoms, and to widely distributed fluvial deposition. At La Mesa, east of Puerto Santa Catarina, Baja California, an excellent exposure exhibits canyon-fed sediments not reported in other places for this formation. The sediments at La Mesa consist of a sequence of alternating clastics and resedimented carbonate materials. The sequence begins with fine sandstone cut by channels, which indicates gravity-induced catastrophic sedimentation, such as debris flows. The channels are filled with massive nodular algal limestone with rip-up clasts of sandstone, some of them 1 m wide, with abundant Turritella pachecoensis and Venericardia sp. The massive limestone is overlain by clastic sediments that, in places, exhibit slumping and laminar bedding with limestone rip-ups. Apparently this unit is an upper-fan deposit. The nodular limestone grades laterally into thin-bedded calcarenites. These allodapic limestones exhibit A and B divisions of the Bouma sequence, similar to overbank levee deposits.

Tellez-Duarte, M.A.; Navarro-Fuentes, J.C.; Valdez-Noriega, M.A.

1988-03-01

180

Tectono-climatic signals in linear, confined, point-sourced, deep-marine siliciclastic systems as analog for submarine-canyon fills, Eocene, Spanish Pyrenees  

NASA Astrophysics Data System (ADS)

The linear, confined geometry, and point-sourced nature, of the deep-marine siliciclastic systems in the Eocene Ainsa-Jaca basin, Spanish Pyrenees, provides a useful ancient spatial-temporal comparison and partial analog for the architecture and controls on the sedimentary infill of large submarine canyons / multiple canyons at continental margins with active tectonics, including salt and shale diapirism. The cumulative ~4 km of stratigraphy contains 8 sandy systems with a total of ~25 discrete channelized sandbodies that accumulated over ~10 Myr in water depths of ~400 to 800 m, that were controlled by the ~400-kyr Milkankovitch frequency with modes, at ~100 kyr and ~41 kyr (possibly stacked ~23-kyr) influencing bottom- water conditions, causing periodic stratification in the water column across a submarine sill within the western part of the more proximal depositional systems. Local tectonics defined and controlled the position and stacking patterns of the 8 sandy systems and their constituent channelized sandbodies, in a process of "seesaw tectonics" by: (i) Westward lateral offset-stacking of channelized sandbodies due to growth of the eastern side of the basin, and (ii) Eastward (orogenwards) "back-stepping" of the depositional axis of each sandy system, due to phases of relative uplift of the opposing lateral margin. Thus, the first-order control on accommodation for deep-marine sedimentation was tectonic, with the pacing of the supply of coarse siliciclastics being driven by global climatic processes, particularly Milankovitch-type frequencies. The dominance of eccentricity and obliquity is similar to results from the continental lacustrine, Eocene Green River Formation. The age model for the Ainsa basin yields an average sediment accumulation rate of ~40 cm kyr-1, that is consistent with that inferred from the spectral analysis on bioturbation intensity for fine-grained sedimentation (~30 cm kyr-1). This paper compares and contrasts depositional patterns and controls for submarine canyons with this ancient linear, confined, point-sourced deep-marine system.

Pickering, K.

2008-12-01

181

Large-scale stratigraphic architecture and sequence analysis of an early Pleistocene submarine canyon fill, Monte Ascensione succession (Peri-Adriatic basin, eastern central Italy)  

NASA Astrophysics Data System (ADS)

The Monte Ascensione succession (c. 2.65-2.1 Ma) is a well-exposed example of an exhumed submarine canyon fill embedded within slope hemipelagic mudstones. This gorge represented a long-lasting pathway for sediment transport and deposition and during the Gelasian delivered Apennine-derived clastic sediment to the adjacent Peri-Adriatic basin. A total of six principal lithofacies types, representing both canyon-confining hemipelagic deposits and canyon-filling turbidity current and mass-transport deposits, can be delineated in the studied sedimentary succession. The canyon-fill deposits display a marked cyclic character and the component lithofacies succeed one another to form at least fifteen fining-upward stratal units, which are interpreted to represent high-frequency, unconformity-bounded depositional sequences. Variability in the vertical repetition of constituent lithofacies allows the identification of three basic styles of sequence architecture that can be interpreted in terms of differing positions along a conceptual down-canyon depositional profile. An integrated chronology, based on biostratigraphic data and on palaeomagnetic polarity measurements, strongly supports a one-to-one correlation between the sequence-bounding surfaces and oxygen isotope stages G2-78, suggesting that the most feasible sequence-engendering mechanism is that of orbitally dictated glacio-eustatic changes in sea level, which regulated timing of sediment storage on the shelf and its redistribution beyond the shelf edge. One of the most significant aspects of this study is the demonstration that processes occurring within upper slope canyons can be expected to be strongly influenced by variations in sea level; that is, the erosional and depositional features evident in these deposits can be strongly controlled by allocyclic processes rather than autocyclic or random processes.

Di Celma, Claudio; Teloni, Riccardo; Rustichelli, Andrea

2014-04-01

182

Hazard assessment for a submarine landslide generated local-source tsunami from Kaikoura Canyon  

NASA Astrophysics Data System (ADS)

The Kaikoura Canyon, sediment sink for the Canterbury rivers north of Christchurch, comes to within 500 meters of shore at Goose Bay and accumulates approximately 1.5x106 m3 of sediment each year (Lewis and Barnes, 1999). This sediment, which has accumulated to about seventy meters in thickness (Walters et al., 2006), exhibits tensional fractures, is located in a tectonically active area and could result in catastrophic failure and potentially a local-source tsunami (Lewis and Banes, 1999; Lewis, 1998; Walters et al, 2006). Evidence suggests that this may have happened in the last two hundred years (Lewis, 1998; Lewis and Barnes 1999) and with a return period on the nearby Alpine and Hope faults also in the range of a one to two hundred years (Walters et al, 2006) could happen again relatively soon. A review of the historical record and oral traditions for Kaikoura shows that historically Kaikoura has been affected by 11 events of which 10 are from distant sources and one, though debatable, is possibly from a local source. There are some preserved traditions for the Kaikoura area. These taniwha stories from near Oaro and from the Lyell Creek have been repeated and changed though time though the general essence remains the same. These taniwha legends, though not conclusive, indicate a dangerous shoreline where people have been killed in the past, possibly by flooding or tsunami. Archaeological investigations at Kaikoura found evidence of a Maori occupational layers interrupted by water-worn stones, a "lens of clean gravel between occupation layers" and in other areas of the excavation, the gravels separate discontinuous periods of occupation (Fomison 1963; Foster, 2006). Additionally "pea-gravel" sized greywacke pebbles were found dispersed throughout sections of the South Bay shore platforms, though they were attributesd to slopewash (Duckmanton, 1974) this is less likely since the nearby hills are limestone. A geological investigation along the Kaikoura Coast, at five sites from South Bay to Oara, corroborates this. At four of the sites a similar greywacke pebble bearing layer was found which was not present at test sites to the North and South of the peninsula (Kiwa Rd Campsites and Claverly respectively). These deposits contain diatoms indicating marine provenance. Surveys of Kaikoura peninsula households and businesses showed low levels of preparedness for a local source event. In regards to local-source tsunamis the district council has indicated that they "are unpredictable [and] it is impractical to include rules to mitigate their effects. Instead, the Council is committed to a Civil Defence network which provides an educative role and which sets in place a process for dealing with the results of any tsunami" (Kaikoura District Plan, 2010). Plans and an education strategy need to be formulated and implemented. They need to address considerations such as the fact that about 60% of those surveyed expect some sort of siren warning and the limitations inherent in such a warning system along with signage and public tsunami hazard maps and evacuation zones.

DuBois, J.

2012-04-01

183

Role of submarine canyons in sediment transport on active Taiwan and passive Chinese margins in northernmost South China Sea  

NASA Astrophysics Data System (ADS)

The basin floor of the northernmost South China Sea (SCS) is manifested by flexure of the Chinese margin under the westward migrating overthrust belt of Taiwan, forming two distinct slopes facing each other: the SCS Slope to the Chinese margin and the Kaoping Slope to the Taiwan orogen, respectively. The oblique arc-continental collision being actively propagating from north to south, and consequently the basin floor of the northernmost SCS deepens and tilts towards south, forming a linear marine transport route along the basin axis. The Penghu Canyon is located along the tilting basin axis where is the physiographic boundary separating the SCS and Kaoping slopes. This canyon extends southward and continues to a deep-sea Penghu Channel around 21°N, and finally merges into the northern Manila Trench. The Kaoping Canyon is a distinctive canyon on the Kaoping Shelf/Slope and is the major sediment conduit for delivering Taiwan orogenic sediment to the SCS basin. On the passive margin, the Formosa Canyon is the major sediment pathway on the SCS Slope where it extends from the upper slope to the lower slope and merges into the lower Penghu Canyon. These three main canyons are draining sediment flows southward to the basin floor of SCS and finally to the Manila Trench. Longitudinal profiles for these three canyons are presented to interpret conditions of sedimentary processes in canyon floors. The longitudinal profile of Kaoping Canyon is characterized by linear geometry which is suggested to be erosion dominated. Similarly, the Penghu Canyon shows a linear curve in longitudinal profile indicating the canyon to be erosion type. In contrast, the longitudinal profile of Formosa Canyon shows nearly concave shape which indicates to be deposition dominated. Erosion of these three canyons is suggested to be removal of sediments on the canyon floor and transport down-canyon rather than to be down-cutting of canyon floor. These three main canyons provide sediment input from different sources to the tilting basin floor. The Kaoping Canyon plays the most important role in transport sediment to the Manila Trench, the ultimate sediment sink. A large amount of sediments is transported by Kaoping Canyon because of the canyon head connecting to the Kaoping River mouth, linking a small mountainous river drainage basin and receiving sediments directly. Sediment supply from the Penghu Canyon is suggested to be low, as there is no direct sediment supply from tributary canyons located on both the Kaoping and SCS slopes. The Formosa Canyon feeds limited sediment to the Penghu Canyon because the canyon head neither connects to a river nor links to assumed sediment depocenter at shelf edge, resulting in limited input of sediment to the canyon and consequently limited sediment supply to the Manila Trench.

Wu, Y.; Hsiung, K.; Yu, H.

2011-12-01

184

Seismic Analysis across the Deformation Front: implications for channel migration in the upper reach of the Penghu Submarine Canyon, Offshore Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

This study analyzes both 2D and 3D seismic images in the upper reach of the Penghu Submarine Canyon to investigate sedimentary and structural processes in this tectonically active zone. The study area lies across the deformation front which separates the rifted South China Sea (SCS) continental slope to the west from the submarine Taiwan accretionary wedge to the east. Using 3D seismic images, several structural and sedimentary features have been identified: in the rifted SCS slope domain, besides the paleo-slope surface, buried submarine channels and mass transport deposits (MTDs), a reverse reactivated normal fault system is recognized, while in the accretionary wedge domain, the fold and thrust structures are dominate. The reverse fault system we interpreted in the rifted SCS slope domain was a normal fault in the past, and then reactivated to become a reverse fault through the arc-continent collision processes. Since the deformation front is defined as the location of the most frontal contractional structures along a convergent plate boundary, no contractional structures should appear west of it. We thus suggest to move the location of the previously mapped deformation front further west to where the reactivated fault lies. High resolution 2D seismic and bathymetry data reveal that the directions of the paleo-submarine channels ran in an across-slope direction, while the present submarine channels head down slope in the study area. The channel migration model we proposed suggests that this might be the result of the fault reactivation. The interactions of down-slope processes and active structural controls affect the channel paths in our study area.

Han, Wei-Chung; Liu, Char-Shine; Chi, Wu-Cheng; Wang, Yun-shuen

2014-05-01

185

Mapping the Canyon  

NSDL National Science Digital Library

In this activity, students will learn about the bathymetry of Hudson Canyon, a submarine canyon on the Atlantic coast of North America. As they study Hudson Canyon, they will compare and contrast topographic maps and bathymetric maps, investigate the various ways in which bathymetric maps are made, and learn how to interpret bathymetric maps.

186

Structure-Forming Corals and Sponges and Their Use as Fish Habitat in Bering Sea Submarine Canyons  

Microsoft Academic Search

Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids

Robert J. Miller; John Hocevar; Robert P. Stone; Dmitry V. Fedorov

2012-01-01

187

Flow modification and shelf-slope exchange induced by a submarine canyon off the northeast Spanish coast  

Microsoft Academic Search

We present results from a study of the modifications induced by the short-timescale response of a shelf break baroclinic jet to the presence of a downstream canyon. The field site was the Canyon of Palamós, located in the northeastern edge of Spain. To determine the short time scale variability of the area, three intensive surveys were carried out at approximately

A. Alvarez; J. Tintoré; A. Sabatés

1996-01-01

188

Structure-forming corals and sponges and their use as fish habitat in Bering Sea submarine canyons.  

PubMed

Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide. PMID:22470486

Miller, Robert J; Hocevar, John; Stone, Robert P; Fedorov, Dmitry V

2012-01-01

189

Biophysical Factors Affecting the Distribution of Demersal Fish around the Head of a Submarine Canyon Off the Bonney Coast, South Australia  

PubMed Central

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100–1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small suites of species with narrow depth distributions, were identified on the shelf, upper slope and mid slope. The assemblage groupings were largely explained by depth (?w?=?0.78). Compared to the depth gradient, canyon-related effects are weak or occur at spatial or temporal scales not sampled in this study. A conceptual physical model displayed features consistent with the depth zonational patterns in fish, and also indicated that canyon upwelling can occur. The depth zonation of the fish assemblage was associated with the depth distribution of water masses in the area. Notably, the mid-slope community (1,000 m) coincided with a layer of Antarctic Intermediate Water, the upper slope community (500 m) resided within the core of the Flinders Current, and the shelf community was located in a well-mixed layer of surface water (<450 m depth). PMID:22253907

Currie, David R.; McClatchie, Sam; Middleton, John F.; Nayar, Sasi

2012-01-01

190

Biophysical factors affecting the distribution of demersal fish around the head of a Submarine Canyon off the Bonney Coast, South Australia.  

PubMed

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100-1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small suites of species with narrow depth distributions, were identified on the shelf, upper slope and mid slope. The assemblage groupings were largely explained by depth (?w?=?0.78). Compared to the depth gradient, canyon-related effects are weak or occur at spatial or temporal scales not sampled in this study. A conceptual physical model displayed features consistent with the depth zonational patterns in fish, and also indicated that canyon upwelling can occur. The depth zonation of the fish assemblage was associated with the depth distribution of water masses in the area. Notably, the mid-slope community (1,000 m) coincided with a layer of Antarctic Intermediate Water, the upper slope community (500 m) resided within the core of the Flinders Current, and the shelf community was located in a well-mixed layer of surface water (<450 m depth). PMID:22253907

Currie, David R; McClatchie, Sam; Middleton, John F; Nayar, Sasi

2012-01-01

191

Storm-induced sediment gravity flows at the head of the Eel submarine canyon, northern California margin  

Microsoft Academic Search

As part of the STRATAFORM program, a bottom-boundary layer (BBL) tripod was deployed at 120 m depth in the northern thalweg of the Eel Canyon during winter 2000. Increases of the near-bottom suspended-sediment concentrations (SSC) recorded at the canyon head were not directly related to the Eel River discharge, but were clearly linked to the occurrence of storms. BBL measurements

P. Puig; A. S. Ogston; B. L. Mullenbach; C. A. Nittrouer; J. D. Parsons; R. W. Sternberg

2004-01-01

192

Mechanisms of vegetation-induced channel narrowing of an unregulated canyon river: Results from a natural field-scale experiment  

NASA Astrophysics Data System (ADS)

The lower Yampa River in Yampa Canyon, western Colorado serves as a natural, field-scale experiment, initiated when the invasive riparian plant, tamarisk (Tamarix spp.), colonized an unregulated river. In response to tamarisk's rapid invasion, the channel narrowed by 6% in the widest reaches since 1961. Taking advantage of this unique setting, we reconstructed the geomorphic and vegetation history in order to identify the key mechanisms for which, in the absence of other environmental perturbations, vegetation alters fluvial processes that result in a narrower channel. From our reconstruction, we identified a distinct similarity in the timing and magnitude of tamarisk encroachment and channel change, albeit with a lag in the channel response, thus suggesting tamarisk as the driving force. Within a decade of establishment, tamarisk effectively trapped sediment and, as a result, increased floodplain construction rates. Increasing tamarisk coverage over time also reduced the occurrence of floodplain stripping. Tamarisk recruitment was driven by both hydrologic and hydraulic variables, and the majority of tamarisk plants (84%) established below the stage of the 2-year flood. Thus, upon establishment nearly all plants regularly interact with the flow and sediment transport field. Our analyses were predicated on the hypothesis that the flow regime of the Yampa River was stationary, and that only the riparian vegetation community had changed. While not heavily impacted by water development, we determined that some aspects of the flow regime have shifted. However, this shift, which involved the clustering in time of extremely wet and dry years, did not influence fluvial processes directly. Instead these changes directly impacted riparian vegetation and changes in vegetation cover, in turn, altered fluvial processes. Today, the rate of channel change and new tamarisk recruitment is small. We believe that the rapid expansion of tamarisk and related floodplain construction that led to a narrower channel pushed the Yampa River into a new stable state, characterized by a relatively static channel.

Manners, Rebecca B.; Schmidt, John C.; Scott, Michael L.

2014-04-01

193

Habitat associations of deep-water rockfishes in a submarine canyon: an example of a natural refuge  

Microsoft Academic Search

Abstract.?A multidisciplinary assess- ment,of benthic ,rockfishes,(genus Se- bastes) and associated,habitats,in deep water,was ,conducted ,in Soquel ,Sub- marine Canyon, Monterey Bay, Califor- nia. Rock habitats,at depths,to 300 m

Mary M. Yoklavich; H. Gary Greene; Gregor M. Cailliet; Deidre E. Sullivan; Robert N. Lea; Milton S. Love

194

Are deep-sea organisms dwelling within a submarine canyon more at risk from anthropogenic contamination than those from the adjacent open slope? A case study of Blanes canyon (NW Mediterranean)  

NASA Astrophysics Data System (ADS)

Due to their geomorphological structure and proximity to the coastline, submarine canyons may act as natural conduit routes for anthropogenic contaminants that are transported from surface waters to the deep-sea. Organisms dwelling in these canyon environments might thus be at risk of experiencing adverse health effects due to higher pollution exposure. To address this question, chemical and biochemical analyses were conducted on two of the most abundant deep-sea fish species in the study area, namely Alepocephalus rostratus and Lepidion lepidion, and the most abundant deep-sea commercial decapod crustacean Aristeus antennatus sampled inside Blanes canyon (BC) and on the adjacent open slope (OS). Persistent organic pollutants (POPs) levels, including polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and derivatives, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were determined in muscle tissue of selected samples from 900 m and 1500 m depth. Potential effects resulting from contaminant exposure were determined using hepatic biomarkers such as ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-deethylase (PROD), catalase (CAT), carboxylesterase (CbE), glutathione-S-transferase (GST), total glutathione peroxidase (GPX), glutathione reductase (GR) and superoxide-dismutase (SOD) enzyme activities and lipid peroxidation levels (LP). L. lepidion and A. antennatus tissues exhibited higher POP levels inside BC compared to the OS at 900 m depth. These findings were consistent with biomarker data (i.e. enzymatic response to presence of contaminant agents). Elevated xenobiotic-metabolizing (EROD and PROD) and antioxidant enzymes (CAT and GPX) indicated higher contaminant exposure in both species caught within BC. No difference in POP accumulation between sites was observed in L. lepidion at 1500 m depth, nor in biomarker data, suggesting that the pollution gradient was less pronounced at greater depths. This trend was further corroborated by the results obtained for A. rostratus at 1500 m depth. Hence, the present findings suggest the, at least temporary, existence of a pollution gradient between Blanes canyon and the open slope at shallower depths and this resulted in alterations of the physiology of deep-sea organisms dwelling within this area.

Koenig, Samuel; Fernández, Pilar; Company, Joan B.; Huertas, David; Solé, Montserrat

2013-11-01

195

FINAL REPORT CANYON AND SLOPE  

E-print Network

fisheries. Many of these canyons provide habitats for a variety of deep water corals . They have also been#12;FINAL REPORT CANYON AND SLOPE PROCESSES STUDY VOLUME I EXECUTIVE S(2@lARY Prepared for United . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...11 #12;Introduction The eastern U.S. continental margin is incised by numerous submarine canyons

Mathis, Wayne N.

196

The Dnepr Canyon: evidence for a continuous submarine channel link between the outer shelf and the deep-sea basin of the northwestern Black Sea  

NASA Astrophysics Data System (ADS)

Multibeam bathymetric surveys and single-beam profiles were collected in 2003-2010 from aboard the Ukrainian RV Professor Vodyanitskiy (cruises PV-58 and PV-60, 2003 and 2004), and the German RV Meteor (cruise M-72, legs 1 and 4, 2007) and RV Maria S. Merian (cruise MSM-15, leg 2, 2010) along the continental margin of the NW Black Sea. Integrating published, reprocessed and novel data has revealed the existence of a major continuous channel extending from the Dnepr paleo-delta into greater water depths. It is more than 90 km long, 1.1 km wide and up to 125 m deep. On the upper slope (120-960 m water depth), a number of smaller channels merge into the large, Y-shaped Dnepr Canyon, which then continues obliquely downslope via this submarine channel to at least 1,815 m water depth off the Crimean continental margin, NW Black Sea. The channel could be an important, hitherto unknown link between the shallow oxic and deep anoxic environments of the Black Sea, along which sediment and organic matter could be funneled into the deep-sea basin. This would have far-reaching implications for investigations dealing with marine geology and biology, climate change, as well as oil and natural gas exploitation. The unusual alignment of the channel along the margin of the basin, as well as the location and mode of channel termination in deeper waters deserve future research.

Gulin, Sergei B.; Artemov, Yuriy G.; Egorov, Viktor N.; Evtushenko, Dmitriy B.

2013-08-01

197

Submarine canyon, slope, and shelf sedimentation in an upper Eocene-Oligocene progradational system (Limnos Island, north Aegean Sea, Greece)  

SciTech Connect

The only well-exposed outcrops of a post-Alpine late Eocene-Oligocene basin in the north Aegean Sea are at Limnos Island. These mostly consist of typical slope deposits overlain by remnants of shallow marine shelf and continental (braided-river) deposits. Three main slope lithofacies are distinguished. Canyon deposits consist of thick-bedded, massive, and pebbly sandstones (facies B), conglomerates (facies A), pebbly mudstone where the matrix shows flow (facies F), rock falls (nummulitic limestones), and zones of slump folds in sandstones (facies F). Channelized facies of massive sandstones, classical turbidites, and thin interbeds of sandstone and mudstone (facies E - probably overbank or levee deposits) are associated with canyon deposits. Pelagic and hemipelagic slope deposits consist of mudstone (facies G) and thin-bedded sandstone (facies D) with occasional small to medium-scale slump folds. These mud-rich slope deposits are incised by several channels filled with conglomerates, thick massive sandstones with well-developed dish structures, and turbidites interbedded with thin layers of mudstone (facies C). This unit composes a typical thinning and fining-upward sequence.

Roussos, N. (Public Petroleum Corp. of Greece, Athens)

1988-08-01

198

Canyon dynamics and related sedimentary impacts off western Portugal  

NASA Astrophysics Data System (ADS)

Submarine canyons are areas of increased exchanges between the continental shelf and the deep ocean. We present preliminary results from a multidisciplinary research focussing the dynamics of several canyon systems that occur along the Portuguese continental margin. The research is being conducted in the framework of EU project Eurostrataform and aims to understand the dominant aspects of the interaction between shelf/slope flows and canyons and to relate those aspects with the exportation of sediments from the shelf. The present work is intended to complement results from previous projects that were focussed on the quasi-inertial dynamics of the Portuguese canyon systems. Three contrasting systems are studied: (1) the Nazaré Canyon, a narrow and deep canyon which completely cuts the shelf, with no local riverine sources; (2) the Setubal-Lisbon canyon system, located in an area of complex topography and coastline configuration, with local riverine sources (Tagus and Sado rivers) and (3) the Oporto canyon, which is restricted to the outer shelf and affected by a major riverine source (Douro river). The ongoing program of observations includes multidisciplinary surveys (CTD, ADCP, suspended particle matter measurements, shallow seismic) and both long-term and short-term currentmeter moorings. The observations will cover both the summer upwelling regime as well as the highly energetic winter conditions. Process studies will combine observations and numerical modeling tools through the use of MOCASSIM system, which is presently being developed at Instituto Hidrografico. The system integrates several numerical models and is intended to characterise the wave and current conditions over the study areas.

Vitorino, J.; Oliveira, A.; Silva, R.; Quaresma, L.; Marreiros, R.

2003-04-01

199

The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon  

Microsoft Academic Search

Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV

T. Amaro; S. Bianchelli; D. S. M. Billett; M. R. Cunha; A. Pusceddu; R. Danovaro

2010-01-01

200

Variation in canyon morphology on the Great Barrier Reef margin, north-eastern Australia: The influence of slope and barrier reefs  

NASA Astrophysics Data System (ADS)

New high-resolution bathymetry, seismic reflection profiles, and existing sidescan data have revealed the presence of a series of submarine canyons in the slope off the Noggin Passage region, north-eastern Australia. The morphology of the Noggin Canyons contrasts with that of the canyons in the Ribbon Reef region, further north along the north-eastern Australia margin. The Noggin Canyons are mostly slope-confined, with canyon heads located at water depths between 200 and 400 m. These narrow and straight canyons show a decrease in canyon relief with depth, and have incision values and canyon gradients lower than the Ribbon Reef Canyons. New findings on the Ribbon Reef Canyons reveal an increase of canyon relief with depth in the shelf-incised canyons, as well as complex relationships between geomorphic parameters, such as canyon gradient, incision, canyon width and canyon wall gradient. The main factors controlling the differences in canyon morphology are the shape of the continental slope and the presence of barrier reefs at the shelf-edge. Steep exponential and linear slope profiles, and the presence of an extensive shelf-edge barrier system in the Ribbon Reef region, are related to large shelf-incised canyons. In contrast, the slope-confined canyons of the Noggin region are linked to sigmoidal slopes, and more open outer-shelf conditions lacking barrier reefs. These conditions allow higher overall sediment supply to the upper slope, and the resulting formation of sigmoidal slope profiles. In the Ribbon Reef region, the physical barriers provided by the shelf-edge barrier reefs reduce the amount of shelf-to-basin sediment transport, thereby forming exponential slopes. Further, sediment gravity flow deposition through the canyons is more prominent in the Ribbon Reef region, as a direct consequence of the more frequent breaching of the shelf by the canyons, otherwise infrequent in the Noggin region. Our results highlight this particular relationship between canyon and slope morphology, and the importance of the variable shelf-edge morphology in controlling the shelf-to-basin sediment transport. This aspect is especially relevant for understanding the margin development in modern and ancient mixed carbonate-siliciclastic continental settings.

Puga-Bernabéu, Ángel; Webster, Jody M.; Beaman, Robin J.; Guilbaud, Vincent

2013-06-01

201

Unusual occurrence and stratigraphic significance of the Glossifungites ichnofacies in a submarine paleo-canyon — Example from a Pliocene shelf-edge delta, Southeast Trinidad  

NASA Astrophysics Data System (ADS)

Sedimentary rocks belonging to the upper-slope shelf-margin delta of the Paleo-Orinoco River are present at the southeast coastline of Trinidad in the Columbus Basin. The Pliocene Mayaro Formation, exposed as foreshore cliffs, represents the wave-influenced delta front and mouth bar of this system. These deposits consist of thick to very thick hummocky cross-stratified sandstone beds and thin-bedded to laminated heterolithic sediments. They also contain abundant soft-sediment deformation structures and sparse well-preserved softground burrows (e.g. Ophiomorpha nodosa). Towards the north-central part of the outcrop, the delta front deposits are cut across by a paleo-canyon filled with younger mud-dominated prodeltaic sediments. The rare exposure of the canyon-wall exhibits an unusual occurrence of Glossifungites ichnofacies. Contrastingly distinct from archetypal examples, this monospecific suite contains a low abundance of firmground Thalassinoides filled with mud rather than sand. The tracemakers burrowed into a firm medium-grained sandy substrate of the delta front, and the burrows were subsequently passively filled by the mud from the overlying prodeltaic sediments filling the canyon. The deep-tier firmground Thalassinoides suite crosscuts the pre-existing softground trace fossils. Integration of ichnologic, sedimentologic and sequence-stratigraphic datasets indicates that the older delta front sediments are separated from the prodeltaic deposits by distinct episodes of fluctuating relative sea-level controlled by the basin-bounding growth-fault activities and the development of the canyon. Whereas the entire shelf-margin megasequence might have been deposited through a regional scale sea-level lowstand, the local fluctuations in accommodation space resulting from the growth-fault movements and the incision of the canyon were responsible for the shifting positions of the depositional architectural elements of the shelf-edge delta.

Dasgupta, Sudipta; Buatois, Luis A.

2012-08-01

202

Shallow-water longshore drift-fed submarine fan deposition (Moisie River Delta, Eastern Canada)  

E-print Network

ORIGINAL Shallow-water longshore drift-fed submarine fan deposition (Moisie River Delta, Eastern Submarine canyons and associated submarine fans are in some cases located at the end of a littoral cell to the discovery of an unusu- ally shallow submarine fan (60 m) located at the end of a littoral cell. Sediment

St-Ong, Guillaume

203

Let's Bet on Sediments! Hudson Canyon Cruise--Grades 9-12. Focus: Sediments of Hudson Canyon.  

ERIC Educational Resources Information Center

These activities are designed to teach about the sediments of Hudson Canyon. Students investigate and analyze the patterns of sedimentation in the Hudson Canyon, observe how heavier particles sink faster than finer particles, and learn that submarine landslides are avalanches of sediment in deep ocean canyons. The activity provides learning…

National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

204

Morphology, evolution and fill: Implications for sand and mud distribution in filling deep-water canyons and slope channel complexes  

Microsoft Academic Search

A survey of the northeastern margin of the Rockall Trough on the Irish margin examined the transition from shelf edge to basin floor, in morphology and sedimentary activity, of a deeply incised submarine canyon system, the Donegal Bay submarine canyon. The survey produced superb 3D profiling of the canyon along its entire length, marking a transition from ‘cauliflower’ shaped head

Bryan T. Cronin; Andrey M. Akhmetzhanov; Adriano Mazzini; Grigorii Akhmanov; Michael Ivanov; Neil H. Kenyon

2005-01-01

205

The segmentations and the significances of the Central Canyon System in the Qiongdongnan Basin, northern South China Sea  

NASA Astrophysics Data System (ADS)

The submarine canyons as the important element of the source to sink have attracted the widespread interests in studying their morphologic features, stratigraphic frames, depositional architectures, as well as the related depositional model, hydrodynamic simulation, and hydrocarbon exploration. The Central Canyon System, a large axial submarine canyon, in the Qiongdongnan Basin is developed in Neogene passive continental margin of northern South China Sea, which is paralleled to the shelf break with an "S-shaped" geometry and an NE-NEE orientation. Based on the integrated analysis of high-resolution 2D/3D seismic data and well log data, the whole canyon could be divided into three segments from west to east through its distinct morphological and depositional architecture characteristics, the head area, the western segment and the eastern segment. The canyon shows the classical U-shaped morphology in seismic profiles, and the infillings are composed of a suit of turbidite channel complex in the head area. In the western segment, the canyon demonstrates the sinuous geometry and multiple-shaped morphology in seismic profiles. Four complexes of turbidite channel and mass transport complex (MTC) are observed, which could constitute into two stratigraphic cycles. The canyon in the eastern segment shows V-shaped morphology with steep flanks and a narrow and straight course, which is composed of collapse deposits in the flanks and the sheet sand-MTC complex. The sediment supply, northern continental slope system, paleo-geomorphic characteristics and tectonic setting in the Qiongdongnan Basin are considered as the controlling factors on the development and evolution of the Central Canyon System, each of them have different influences in the three segments. The turbidite channel in the head area was triggered by the abundant sediment supply from western source together with the fault activity at 5.7 Ma of the Red River Fault. The evolution of the canyon in the western segment should be the combined effects of the turbidite channel from western source, the mass transport complex from the northern continental slope, and the paleo-seafloor geomorphology. In the eastern segment, the canyon should be constrained by the semi-closed subbasin in eastern Qiongdongnan Basin corresponding to the tectonic transformation at about 11.6 Ma. This unique submarine canyon in the Qiongdongnan Basin is suggested to be characterized by axial gravity flow, ascribing to different gravity deposits originated from different sediment supplies and the tectonic activities.

Su, Ming; Xie, Xinong; Xie, Yuhong; Wang, Zhenfeng; Zhang, Cheng; Jiang, Tao; He, Yunlong

2014-01-01

206

The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon  

NASA Astrophysics Data System (ADS)

Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m-2 d-1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

Amaro, T.; Bianchelli, S.; Billett, D. S. M.; Cunha, M. R.; Pusceddu, A.; Danovaro, R.

2010-08-01

207

Attack submarines  

SciTech Connect

This issue discusses missions for submarines, technology proliferation; implications for U.S. security; U.S. SSN-21 Seawolf versus other submarines; stability and arms control; nuclear propulsion and nuclear proliferation; air independent propulsion.

Not Available

1991-01-01

208

Linking subaerial erosion wih submarine geomorphology in the northern Ionian Sea, Italy  

NASA Astrophysics Data System (ADS)

The supply of sediment from continental sources is commonly suspected to have exerted a strong influence on the development of canyons and other morphological features on the continental slopes, but rarely is the sediment supply known quantitatively to make this link. Here, we outline an area where offshore morphology, in the northern Ionian Sea, may be linked to supply of sediment from subaerial erosion in NE Sicily and SW Calabria. Shelves in this area are very narrow (< 1 km), and the bathymetry shows that rivers and adjacent submarine channels are almost directly connected. Integrated topographic analyses were performed on a merged digital evelation model (DEM) of ASTER data for subaerial topography and multibeam sonar data for submarine bathymetry. Spatial variations in onshore erosion were assesed using a variety of methods, namely: long-term sediment flux from Pleistocene uplift rates, decadal sediment flux from landslides; published long-term exhumation rates from 10Be cosmogenic nuclide concentrations and published recent sediment yields determined using the Gavrilovic Method. Submarine channels associated with rivers delivering larger sediment fluxes have broad channels, high relief and smooth concave-upward longitudinal profiles. Conversely, submarine channels that lie offshore small-flux rivers have straight longitudinal profiles, low relief and steep gradients. Where river catchments supply a greater sediment flux offshore, shelves tend to be wider (~400 m) and submarine channels have gentler gradients. In contrast, where catchments supply less sediment flux, shelves are narrow (250-300 m) and offshore channel gradients are steeper. How morphology varies with tectonic uplift rate was also studied, but we find that, unlike onshore terrains where tectonics is commonly an important factor influencing channel morphology, in the submarine landscapes, sediment flux appears to dominate.

Goswami, Rajasmita; Mitchell, Neil C.; Argnani, Andrea

2014-05-01

209

SUBMARINE GEOLOOY REP  

E-print Network

SUBMARINE GEOLOOY REP. Investigation of bead of Monterey Submarine Canyon. Contract N6ori-lll. March 1948. 36p. 2. Shepard, Francis P Erosion '8o."U"d. Teshnieal Hemo- rand'IIJil No.2.3, July 1951. 10. Inman, Douglas L. SUbmarine topoerapey

Russell, Lynn

210

Interacting ocean waves explain powerful seafloor canyon flows  

NASA Astrophysics Data System (ADS)

Off the southwestern coast of Taiwan the Gaoping Submarine Canyon meanders in a giant backward S shape as it stretches southwestward toward the South China Sea. In the canyon, a 200-meter-deep cut into the seafloor that lies 300 meters below the sea's surface, the waters carry an usually large amount of internal tidal power—9.1 megawatts from the canyon's mouth to its head. Along with the strong flows a region of enhanced vertical mixing sits at the canyon's head. Researchers had previously attributed the anomalous flows to internal waves pushing through the Gaoping Canyon, though the source of the energy remained an open question.

Schultz, Colin

2012-02-01

211

Calcareous nannoplankton and benthic foraminiferal assemblages from the Nazar Canyon  

E-print Network

Calcareous nannoplankton and benthic foraminiferal assemblages from the Nazaré Canyon (Portuguese, Portugal E-mail: catarina.guerreiro@hidrografico.pt Abstract. Submarine canyons are assumed to play as preferential conduits between the littoral and deep oceanic domain. Here we present first results

212

Canyon dynamics and related sedimentary impacts off western Portugal  

Microsoft Academic Search

Submarine canyons are areas of increased exchanges between the continental shelf and the deep ocean. We present preliminary results from a multidisciplinary research focussing the dynamics of several canyon systems that occur along the Portuguese continental margin. The research is being conducted in the framework of EU project Eurostrataform and aims to understand the dominant aspects of the interaction between

J. Vitorino; A. Oliveira; R. Silva; L. Quaresma; R. Marreiros

2003-01-01

213

Development of the Astoria Canyon-Fan physiography and comparison with similar systems  

USGS Publications Warehouse

A detailed bathymetric study of Astoria Canyon and Astoria Fan provides a model for typical submarine canyon-fan systems. The present canyon head is 9 miles (17 km) west of the Columbia River mouth but buried Pleistocene channels appear to have connected the two features in the past. The canyon, which is distinguished by its relief, V-shaped profiles, and numerous tributaries, winds sinuously and is coincident with apparent structural trends across the continental shelf and slope. At the fan apex, the canyon mouth merges smoothly into Astoria Channel, which is characterized by its U-shaped profiles, lower walls of even height, and levee development. Astoria Channel and the fan valley at the base of the continental slope are the most recently active of a series of main fan valleys that appear to have: (1) progressively "hooked left"; (2) migrated from north to south across the fan during its formation; and (3) been partly responsible for the asymmetrical shape of the fan. The deep, narrow upper fan valleys that characterize the steep (> 1:100, or 0??35???) and rough (10-30 fathoms, or 18-55 m) upper fan surface break into distributaries on the middle fan, where there is the sharpest change in gradient. The main valleys become broader and shallower down the fan, while the generally concave fan surface grades to nearly a flat seafloor (to gradients < 1:1000, or 0??0.5???), (< 10 fathoms, or 18 m relief). Similarity of Astoria Canyon-Fan system with other deep-sea fan and alluvial fan systems, suggests the hypothesis that size of drainage basin, sediment size, and sediment load control the size, gradient, and valley development of any fan system. Data from bathymetry, seismic refraction stations, and sediment load of the Columbia River indicate that the cutting of Astoria Canyon and the deposition of the unconsolidated sediment layer forming Astoria Fan could have been accomplished during the Pleistocene. A similar history can be suggested for other major submarine canyon-fan systems. ?? 1970.

Nelson, C.H.; Carlson, P.R.; Byrne, J.V.; Alpha, T.R.

1970-01-01

214

Pleistocene entrenched valley/canyon systems, Gulf of Mexico  

SciTech Connect

The Mississippi Submarine Canyon is the seaward extension of the late Wisconsin entrenched alluvial valley. Geophysical and geologic data provide evidence for the continuity of the Mississippi entrenched valley, the Timbalier channel, and the submarine canyon. The Mississippi entrenched valley/canyon system is one of several systems recognized in the Pleistocene section of offshore Louisiana. Most of these systems were produced by the ancestral Mississippi River. They typically exhibit a three-gradient profile with their maximum erosional relief at the preexisting shelf margin. The canyons extend onto the pre-existing shelf for 20 to 50 mi, with erosion commonly exceeding 1000 ft. All of these systems delivered large quantities of sediment to the Pleistocene slope and abyssal plain. The fan deposits are the products of sediment passing through and being removed from the entrenched valley/canyon systems.

Steffens, G.S.

1986-09-01

215

North Atlantic slope and canyon study. Volume 1. Executive summary  

SciTech Connect

A field program to investigate the currents and sediment transport along the outershelf and upper slope along the southern flank of Georges Bank was conducted between 1980 and 1984. A major part of the field experiment was conducted in Lydonia Canyon, a large submarine canyon which cuts northward about 20 km into the continental shelf from the shelfbreak. A smaller experiment was conducted in Oceanographer Canyon to compare the currents in these two major canyons. The long-term current observations made in Lydonia and Oceanographer Canyons show that the current regime in these topographic features differs from the adjacent slope, and between canyons. Sediments near the head (depths shallower than about 600 m) in both Lydonia and Oceanographer are frequently resuspended. This frequent resuspension may allow the sediments to strip pollutants from the water column. Currents in Oceanographer Canyon are stronger and the sediments coarser than in Lydonia at comparable depths.

Butman, B.

1986-12-01

216

The Nearshore Canyon Experiment  

NASA Astrophysics Data System (ADS)

Observations collected in Fall 2003 during the Nearshore Canyon Experiment (NCEX) will be used to test hypotheses about the effect of complex continental-shelf bathymetry on surface gravity waves and on wave-driven circulation. Refraction, diffraction, reflection, scattering, and trapping by abrupt shelf bathymetry can result in dramatic alongshore variations in wave height and direction. Onshore of the irregular bathymetry, alongcoast changes in breaking waves can force complicated circulation, including alongshore flows that reverse direction across the surf zone and along the shoreline, and strong offshore-directed rip currents that may be an important mechanism for transport of water, sediment, and pollution between the surf zone and inner shelf. Observations for NCEX will be obtained along the southern California coast near two steep submarine canyons (separated alongshore by a few km) that cross the shelf from about 300-m water depth to just seaward of the surfzone near Black's Beach (famous for large waves) and La Jolla Shores (well known as a calm area with small waves). Frequency-directional spectra of incident waves estimated from observations offshore of the canyons will be used to initialize models that predict the effect of the canyons on infragravity waves, swell, sea, and wave-driven circulation. Model predictions will be tested with observations from alongshore arrays deployed near, between, and onshore (including the surf and swash zones) of the canyons. Arrays also will be deployed to investigate wave reflection and scattering from the steep canyon walls, and cross-shore changes in surf and swash zone circulation. Additional instrumentation will be used to study alongcoast changes in wave breaking and set-up, details of surface currents in the surf and swash, and breaking-induced turbulence and dissipation. The NCEX instrument arrays will be designed in collaboration with modelers, and near-real time data will be used to initialize and test model predictions. In addition, model forecasts will be used to guide placement of movable sensors, allowing predictions of nearshore waves and currents to be tested during the observational period. NCEX~team~members~are~listed~on http://science.whoi.edu/PVLAB/NCEX/ncex.html. Funding for NCEX is provided by the US Office of Naval Research and the National Science Foundation.

Elgar, S.

2002-12-01

217

Exploration models for submarine slope sandstones  

SciTech Connect

Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully/channel fill, slope spillover sand sheets, and intraslope basin fill. Submarine canyon fill is mainly shale, but sandstone beds that form stratigraphic traps may be present. Canyon shale fill juxtaposed against older sandstones can also form stratigraphic traps. Gully/channel fills are sandstones deposited on shallow-gradient slopes or ramps. The proximity of these sandstones to slope shales provides opportunities for stratigraphic traps to develop. Spillover sand sheets are resedimented from a shelf to a shallow-gradient slope and are associated with gully/channel fills. Intraslope basin fill is mainly shale, but elongate, sheetlike, or fan-shaped turbidite sandstones can provide stratigraphic traps. In all of these deposits, slope shales may be sufficiently enriched in organic carbon to be potential hydrocarbon source rocks; the potential for organic-rich shales to accumulate is highest in intraslope basin fill.

Slatt, R.M.

1986-09-01

218

Genotype, soil type, and locale effects on reciprocal transplant vigor, endophyte growth, and microbial functional diversity of a narrow sagebrush hybrid zone in Salt Creek Canyon, Utah  

USGS Publications Warehouse

When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F1 hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F1 hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden-by-soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F1 hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes.

Miglia, K.J.; McArthur, E.D.; Redman, R.S.; Rodriguez, R.J.; Zak, J.C.; Freeman, D.C.

2007-01-01

219

Grand Canyon  

... (lower) half of the images, other landmarks include Lake Powell, on the left, and Humphreys Peak and Sunset Crater National Monument on ... December 31, 2000 - Grand Canyon and Lake Powell. project:  MISR category:  gallery ...

2014-05-15

220

Upwelling flow dynamics in long canyons at low Rossby number  

NASA Astrophysics Data System (ADS)

Submarine canyons, topographic features incising the continental slope, vary in both shape and size. The dynamics of short canyons have been observed and described in the field, in the laboratory, and with numerical simulations. Flow within long canyons, such as Juan de Fuca canyon, located between Vancouver Island and Washington State in the Pacific Northwest, is less well understood. Physical models of both long and short canyons have been constructed to understand the upwelling dynamics in long canyons and how upwelling changes, as compared with the dynamics of short canyons, at low Rossby number. Stratification and rotation, both important parameters in determining the dynamics in canyons, can be controlled and scaled accordingly for replication of oceanic conditions. The physical model is spun up to an initial rotation rate, and the flow is forced by increasing the rotation rate over the equivalent of several days. Flow visualization is used to determine the strength and location of upwelling, the strength and mechanisms generating vorticity, as well as the differences between the flow within the long and short canyons. The pattern of upwelling between the two canyons is significantly different in the horizontal with upwelling occurring through the canyon head in the short canyon and upwelling occurring close to the mouth along the downstream rim in the long canyon. At high Rossby number, upwelling is similar in both the long and short canyon and is driven by advection. However, as Rossby number decreases, the flow in the long canyon is more strongly affected by the strong convergence of the isobaths near the canyon than by advection alone.

Waterhouse, Amy F.; Allen, Susan E.; Bowie, Alexander W.

2009-05-01

221

The Congo deep-sea fan: how far and for how long? A basin-wide view of the interaction between a giant submarine fan  

E-print Network

a giant submarine fan and a mature passive margin Zahie Anka 1,* , Michel Séranne 2,** , Michel Lopez 2 submarine fan systems in the world and one of the most important depocentre in the eastern south Atlantic through an impressive submarine canyon, which cuts down about 950 m at the shelf-break and more than 1300

Demouchy, Sylvie

222

Simple Submarine  

NSDL National Science Digital Library

Using simple, inexpensive items, students build and test submarine models in a single class period. They gain insight into the engineering that's required to make these machines ascend, descend, and hover safely in extreme environments. The printable eight-page handout includes a series of inquiry-based questions that get students thinking about the complex engineering required for submersibles, illustrated experiment directions, and a worksheet that includes thought-provoking questions along with areas for recording experiment data.

223

Influence of submarine morphology on bottom water flow across the western Ross Sea continental margin  

USGS Publications Warehouse

Multibeam sonar bathymetry documents a lack of significant channels crossing outer continental shelf and slope of the western Ross Sea. This indicates that movement of bottom water across the shelf break into the deep ocean in this area is mainly by laminar or sheet flow. Subtle, ~20 m deep and up to 1000 m wide channels extend down the continental slope, into tributary drainage patterns on the upper rise, and then major erosional submarine canyons. These down-slope channels may have been formed by episodic pulses of rapid down slope water flow, some recorded on bottom current meters, or by sub-ice melt water erosion from an icesheet grounded at the margin. Narrow, mostly linear furrows on the continental shelf thought to be caused by iceberg scouring are randomly oriented, have widths generally less than 400 m and depths less than 30m, and extend to water depths in excess of 600 m.

Davey, F.J.; Jacobs, S.S.

2007-01-01

224

Hot Canyon  

ScienceCinema

This historical film footage, originally produced in the early 1950s as part of a series by WOI-TV, shows atomic research at Ames Laboratory. The work was conducted in a special area of the Laboratory known as the "Hot Canyon."

None

2013-03-01

225

Mapping the True 3D Morphology of Deep-Sea Canyons  

Microsoft Academic Search

The importance of submarine canyons as ecosystem hotspots and sediment transport pathways has been recognised for decades (e.g. Heezen et al., 1955; Vetter & Dayton, 1998). However, studying canyon systems in detail is a challenge, because of the complexity and steepness of the terrain. Acoustic surveys are hampered by side-echoes, while the high slope angles cause most types of sampling

V. A. Huvenne; D. Masson; P. A. Tyler; V. Huehnerbach

2010-01-01

226

Potential for SGD induced submarine geohazard off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The submarine groundwater discharge (SGD) is not only play important roles on material exchange between land and sea, it may also trigger liquefaction process and induce further submarine geohazards in coastal zone. Since 2006, Southern Taiwan was experienced a series of natural hazards including earthquakes and typhoon that induced severe landslides and flooding and caused huge human lives and economics losses. These natural hazards also touched off submarine cable-break incidents off southwestern Taiwan from Gaoping Slope to the northern terminus of the Manila Trench. After the 2006 Pingtung Earthquake, the local fishermen reported disturbed waters at the Fangliao submarine canyon head. Although many researches conjectured the disturbed waters may caused by the eruption of submarine volcanoes which has been widely discovered off the southwestern Taiwan. The subbottom profiles reveal a series of faults and liquefaction strata exist near the head of Fanliao submarine canyon and acoustically transparent sediments with doming structures also observed at the adjacent area. Moreover, we also found pockmarks with acoustic blanking under it on the Gaoping Shelf and a series of gaseous pluming gushed from the seafloor was also observed in the shallow waters. Integrate all these data, we may reasonably infer the disturbed waters which reported by the fishermen may caused by the liquefaction process on the seafloor. In addition to geophysical observations, natural geochemical tracers (radon and radium) in conjunction with side-scan sonar were used to evaluate the distribution of SGD system in the study area. All the evidences indicate that the large earthquake in conjunction with high pore fluid pressures in the surface sediment might have easily triggered liquefaction process and generated large debris flow and swept the submarine cables away from the Fangliao submarine canyon head to the abyss.

Su, C.; Lin, C.; Cheng, Y.; Chiu, H.

2013-12-01

227

How Submarines Work  

NSDL National Science Digital Library

In this article, presented by HowStuffWorks.com, shows how a submarine dives and surfaces in the water. It also shows how life support is maintained, how the submarine gets its power, how a submarine finds its way in the deep ocean and how submarines might be rescued. The article addresses many points effectively and is a good survey of the topic.

Brain, Marshall

228

North Atlantic slope and canyon study. Volume 2. Final report  

SciTech Connect

A field program to investigate the currents and sediment transport along the outershelf and upper slope along the southern flank of Georges Bank was conducted between 1980 and 1984. A major part of the field experiment was conducted in Lydonia Canyon, a large submarine canyon which cuts northward about 20 km into the continental shelf from the shelfbreak. A smaller experiment was conducted in Oceanographer Canyon to compare the currents in these two major canyons. Long-term current observations were made at 20 locations in or adjacent to Lydonia Canyon, and at 9 stations on the continental slope. Detailed semi-synoptic hydrographic observations were made on 9 cruises. The currents associated with Gulf Stream warm core rings (WCR's) strongly affect the flow along the outer shelf and upper slope; eastward currents in excess of 75cm/s were associated with WCR's.

Butman, B.

1986-12-01

229

Tectonic control of Cretaceous gravity deposits and submarine Valleys in the subalpine basin, French western Alps  

SciTech Connect

The Late Jurassic-Early Cretaceous series of the French subalpine basin is characterized by alternating limestones and marls with numerous, thick gravity-flow deposits (carbonate debris flows and slumps, siliciclastic grain flows, turbidites). These gravity deposits originate from platforms and slopes and come through the basin via several parallel canyons and submarine valleys. Some carbonate (Berriasian) and siliciclastic (Aptian) deep-sea fans are built at the canyon mouth during intense activity of the canyons and reworking of the sediments. The tectonic control of the gravity deposits is demonstrated by the position and filling of the submarine valleys all along the Cretaceous. The submarine valleys correspond systematically to the lower part of extensional tilted blocks; the gravity deposits come along the main syn-sedimentary normal faults delimiting these tilted blocks. The gravity deposits go from one tilted block to another through some synsedimentary passes which are induced by slight folding, perhaps related to an early diapirism at some nodes of extensional faults. The canyon-like valleys are due to very strong erosion when a submarine valley cuts of the higher part of a tilted block. The gravity deposits are stacked atop each other and progressively fill the valleys. Thus the cutting and filling of the submarine valleys and canyons on occasions during the Early Cretaceous are explained by a permanent synsedimentary activity. These Jurassic and Cretaceous extensional structures are later reactivated by inversion during Tertiary compressional movements.

Philippe, J.; Beaudoin, B.; Fries, G.; Parize, O.

1988-08-01

230

An insight into the feeding ecology of deep-sea canyon nematodes — Results from field observations and the first in-situ 13C feeding experiment in the Nazaré Canyon  

Microsoft Academic Search

Submarine canyon systems provide a heterogeneous habitat for deep-sea benthos in terms of topography, hydrography, and the quality and quantity of organic matter present. Enhanced meiofauna densities as found in organically enriched canyon sediments suggest that nematodes, as the dominant metazoan meiobenthic taxon, may play an important role in the benthic food web of these sediments. Very little is known

Jeroen Ingels; David S. M Billett; Saskia Van Gaever; Ann Vanreusel

2011-01-01

231

Sediment storage and reworkingon the shelf and in the Canyon of the Indus River-Fan Systemsince the  

E-print Network

Sediment storage and reworkingon the shelf and in the Canyon of the Indus River-Fan Systemsince on to the deep-water submarine fan is complicated by temporary storage within large clinoforms on the shelf on either side of the submar- ine canyon, where most of the sedimentation since the start of the Holocene

Clift, Peter

232

Deep Research Submarine  

E-print Network

The Deep Sea Research Submarine (Figure 1) is a modified VIRGINIA Class Submarine that incorporates a permanently installed Deep Sea Operations Compartment (Figure 2). Table 1 summarizes the characteristics of the Deep ...

Woertz, Jeff

2002-02-01

233

Design a Submarine  

NSDL National Science Digital Library

Learners act as engineers and design mini submarines that move in the water like real submarines. The submarines must be able to float, sink, and hover steadily without touching the top of the water or resting on the bottom. Use this activity to introduce learners to density and buoyancy.

Museum of Science and Industry, Chicago

2012-01-01

234

Bioavailability of sinking organic matter in the Blanes canyon and the adjacent open slope (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Submarine canyons are sites of intense energy and material exchange between the shelf and the deep adjacent basins. To test the hypothesis that active submarine canyons represent preferential conduits of available food for the deep-sea benthos, two mooring lines were deployed at 1200 m depth from November 2008 to November 2009 inside the Blanes canyon and on the adjacent open slope (Catalan Margin, NW Mediterranean Sea). We investigated the fluxes, biochemical composition and food quality of sinking organic carbon (OC). OC fluxes in the canyon and the open slope varied among sampling periods, though not consistently in the two sites. In particular, while in the open slope the highest OC fluxes were observed in August 2009, in the canyon the highest OC fluxes occurred in April-May 2009. For almost the entire study period, the OC fluxes in the canyon were significantly higher than those in the open slope, whereas OC contents of sinking particles collected in the open slope were consistently higher than those in the canyon. This result confirms that submarine canyons are effective conveyors of OC to the deep sea, particles transferred are predominantly of inorganic origin, significantly higher than that reaching the open slope at a similar water depth. Using multivariate statistical tests, two major clusters of sampling periods were identified: one in the canyon that grouped trap samples collected in December 2008, concurrently with the occurrence of a major storm at the sea surface, and associated with increased fluxes of nutritionally available particles from the upper shelf. Another cluster grouped samples from both the canyon and the open slope collected in March 2009, concurrently with the occurrence of the seasonal phytoplankton bloom at the sea surface, and associated with increased fluxes of total phytopigments. Our results confirm the key ecological role of submarine canyons for the functioning of deep-sea ecosystems, and highlight the importance of canyons in linking episodic storms and primary production occurring at the sea surface to the deep sea floor.

Lopez-Fernandez, P.; Bianchelli, S.; Pusceddu, A.; Calafat, A.; Sanchez-Vidal, A.; Danovaro, R.

2012-12-01

235

Bioavailable organic matter in surface sediments of the Nazaré canyon and adjacent slope (Western Iberian Margin)  

NASA Astrophysics Data System (ADS)

The distribution of bioavailable organic matter in surface sediments of the Nazaré submarine canyon and adjacent open slope was investigated. The concentration of chlorophyll a (chl a), phaeopigments (phaeo), chloroplastic pigment equivalents (CPE) and total hydrolyzable amino acids (THAA) decreased with increasing water depth, and were in general higher within the canyon (specially in the upper regions) than on the open slope. The concentrations were low on the canyon walls, increasing towards the canyon axis. The chl a:phaeo ratio, degradation index (DI), asp:?-ala and glu:?-aba ratios were highest in the upper canyon, and similarly low in the deeper canyon and along the open slope. On the canyon axis and walls these lability indices were similar. chl a:OM ratio indicated that the quality of the bulk organic matter in the upper canyon was higher than on the slope and deeper canyon regions. Bioavailable organic matter enters the canyon through the upper region; it is transported down canyon by the tide circulation, where it is dispersed across a bigger area under a more refractory state. Flume experiments demonstrate that arborescent foraminifera and polychaete pellet mounds, as found in the head of the canyon; increase deposition of phytodetritus under critical shear velocities by a 50%.

García, R.; Thomsen, L.

2008-11-01

236

Seismic stratigraphy and development of Avon canyon in Benin (Dahomey) basin, southwestern Nigeria  

NASA Astrophysics Data System (ADS)

Interpretation of a grid of high resolution seismic profiles from the offshore eastern part of the Benin (Dahomey) basin in southwestern Nigeria area permitted the identification of cyclic events of cut and fill associated with the Avon canyon. Seismic stratigraphic analysis was carried out to evaluate the canyon morphology, origin and evolution. At least three generations of ancient submarine canyons and a newly formed submarine canyon have been identified. Seismic reflection parameters of the ancient canyons are characterized by transparent to slightly transparent, continuous to slightly discontinuous, high to moderate amplitude and parallel to sub-parallel reflections. Locally, high amplitude and chaotic reflections were observed. The reflection configurations consist of regular oblique, chaotic oblique, progradational and parallel to sub-parallel types. These seismic reflection characteristics are probably due to variable sedimentation processes within the canyons, which were affected by mass wasting. Canyon morphological features include step-wise and spoon-shaped wall development, deep valley incision, a V-shaped valley, similar orientation in the southeast direction, and simple to complex erosion features in the axial floor. The canyons have a composite origin, caused partly by lowering of the sea level probably associated with the formation of the Antarctic Ice Sheet about 30 Ma ago and partly by complex sedimentary processes. Regional correlation with geological ages using the reflectors show that the canyons cut through the Cretaceous and lower Tertiary sediments while the sedimentary infill of the canyon is predominantly Miocene and younger. Gravity-driven depositional processes, downward excavation by down slope sediment flows, mass wasting from the canyon walls and variation in terrigenous sediment supply have played significant roles in maintaining the canyons. These canyons were probably conduits for sediment transport to deep-waters in the Gulf of Guinea during their period of formation.

Olabode, S. O.; Adekoya, J. A.

2008-03-01

237

1 INTRODUCTION Turbidity currents are a dominant driving  

E-print Network

of submarine canyons and associated fans. A typical canyon-fan configuration is illustrated in Figure 1 (Pirmez, 1994). It encompasses a) a relatively steep-slope, narrow submarine canyon excavated by net erosive: Turbidity currents emanating from a submarine canyon and debouching onto an associated submarine fan often

Parker, Gary

238

Application of a Lagrangian transport model to organo-mineral aggregates within the Nazaré canyon  

NASA Astrophysics Data System (ADS)

In this study, a hydrodynamic model was applied to the Nazaré submarine canyon with boundary forcing provided by an operational forecast model for the West Iberian coast. After validation, a Lagrangian transport model was coupled to the hydrodynamic model to study the transport patterns of the organo-mineral aggregates along the Nazaré canyon comparing three different classes of organo-mineral aggregates. The results showed that the transport in the canyon is neither constant, nor unidirectional and that there are preferential areas where suspended matter is resuspended, transported and deposited. The results showed that the transport of the larger size classes of organo-mineral aggregates is less pronounced, and that there is a decrease in the phytodetrital carbon flux along the canyon. The Nazaré canyon acts as depocenter of sedimentary organic matter and the canyon is not a conduit of organo-mineral aggregates to the deep sea.

Pando, S.; Juliano, M.; Garcia, R.; Mendes, P. A. de Jesus; Thomsen, L.

2013-01-01

239

Shelf-to-canyon sediment-transport processes on the Eel continental margin (northern California)  

Microsoft Academic Search

To investigate the processes by which sediment is supplied to the head of a submarine canyon, an instrumented tripod and a mooring were deployed in the northern thalweg of the Eel Canyon during autumn and winter 1999–2000. This was done as part of the STRATAFORM program, and in combination with a long time-series benthic-tripod data collection on the Eel continental

P. Puig; A. S. Ogston; B. L. Mullenbach; C. A. Nittrouer; R. W. Sternberg

2003-01-01

240

Submarine fans in a sequence stratigraphic framework  

SciTech Connect

Submarine fans are fan- or cone-shaped turbiditic deposits formed in upper bathyal or deeper water depths. Within a sequence stratigraphic framework, these basin-floor turbidites can occur during lowstand-fan or lowstand-wedge systems tract time. During lowstand fan time, streams are rejuvenated and depocenters shift from the coastal plain to the upper slope, causing retrogradational slope failure and canyon formation. The sediment delivered here bypasses the canyon and continues down the slope as a succession of gravity flows and is deposited as fan-shaped turbiditic deposits at the base of the slope. Seismic and outcrop evidence suggest that these sand-prone deposits are abruptly introduced into the basin and are generally characterized by subtle external mounding and internal bidirectionally down lapping seismic reflections where seismically resolvable. Deep-water sediment deposited during this interval has no coeval shelf equivalent. During lowstand wedge time, streams cease down cutting and valleys which have been freshly incised begin to fill. Because coarse sediment will preferentially be deposited within these incised valleys, the sand-to-mud ratio delivered to the upper slope will be decreased and, consequently, there is an inherent difference between submarine fans deposited at this time and those deposited during lowstand fan time. Deposition during lowstand wedge time is characterized seismically by slope front fill or wedge-shaped geometries down lapping the earlier submarine fan (i.e., deposited during lowstand fan time). These shale-prone deposits are largely comprised of thinner-bedded turbidites as well as the occasional leveed channel.

Posamentier, H.W.; Erskine, R.D.; Mitchum, R.M.; Vail, P.R.

1987-05-01

241

Submarine cable route survey  

SciTech Connect

The growth of telecommunication market is very significant. From the beginning of the nineties, more and more the use of optical fiber submarine cables is privileged to that of satellites. These submarine telecommunication highways require accurate surveys in order to select the optimum route and determine the cable characteristics. Advanced technology tools used for these surveys are presented along with their implementation.

Herrouin, G.; Scuiller, T.

1995-12-31

242

Paint-Stirrer Submarine  

ERIC Educational Resources Information Center

In this article, the authors discuss a unique and challenging laboratory exercise called, the paint-stir-stick submarine, that keeps the students enthralled. The paint-stir-stick submarine fits beautifully with the National Science Education Standards Physical Science Content Standard B, and with the California state science standards for physical…

Young, Jocelyn; Hardy, Kevin

2007-01-01

243

Morphology, paleogeographic setting, and origin of the middle Wilcox Yoakum Canyon, Texas coastal plain  

SciTech Connect

The Yoakum canyon is the largest of the Gulf Coast Eocene erosional gorges and is interpreted as a buried submarine channel. The canyon can be traced for 67 mi (108 km) from the Wilcox fault zone, which defines the position of the early Eocene shelf edge, nearly to present outcrop. In this paper, the authors expand on previously published descriptions of the canyon and use a more extensive subsurface database. Decompaction of the canyon shale-fill reveals that original depths of the canyon exceeded 3,500 ft (1,067 m). Apparent canyon-wall slump scarps and a peripheral chaotic zone, interpreted as an incipient slump feature, are comparable to similar features of the late Quaternary Mississippi submarine canyon. The Yoakum canyon formed within the Garwood subembayment to the west of and adjacent to the middle Wilcox Rockdale delta system. Quantitative mapping of facies adjacent to the Yoakum shale indicate the following sequence of events. (1) Muddy, distal deltaic and shelf facies of the lower middle Wilcox subgroup were deposited during a retrogradation. (2) A resurgence of progradation deposited upper middle Wilcox deltaic facies atop the unconsolidated, lower middle Wilcox continental margin muds, loading the shelf edge and initiating slump failure of the continental margin. (3) Headward erosion of the canyon across the shelf occurred contemporaneously with a subsidence-induced transgression that coincided with a disruption in sediment supply. The Yoakum canyon was excavated by a combination of slumping and current scour. (4) The canyon was filled by hemipelagic and prodelta muds of the upper Wilcox subgroup. 19 figs.

Dingus, W.F. (Exxon Co., Midland, TX (USA)); Galloway, W.E. (Univ. of Texas, Austin (USA))

1990-07-01

244

The Black Canyon of the Gunnison: Today and Yesterday  

USGS Publications Warehouse

Since the early visit of Captain John William Gunnison in the middle of the last century, the Black Canyon of the Gunnison has stirred mixed apprehension and wonder in the hearts of its viewers. It ranks high among the more awesome gorges of North America. Many great western canyons are as well remembered for their brightly colored walls as for their airy depths. Not so the Black Canyon. Though it is assuredly not black, the dark-gray tones of its walls and the hazy shadows of its gloomy depths join together to make its name well deserved. Its name conveys an impression, not a picture. After the first emotional impact of the canyon, the same questions come to the minds of most reflective viewers and in about the following order: How deep is the Black Canyon, how wide, how does it compare with other canyons, what are the rocks, how did it form, and how long did it take? Several western canyons exceed the Black Canyon in overall size. Some are longer; some are deeper; some are narrower; and a few have walls as steep. But no other canyon in North American combines the depth, narrowness, sheerness, and somber countenance of the Black Canyon. In many places the Black Canyon is as deep as it is wide. Between The Narrows and Chasm View in the Black Canyon of the Gunnison National Monument (fig. 15) it is much deeper than wide. Average depth in the monument is about 2,000 feet, ranging from a maximum of about 2,700 feet, north of Warner Point (which also is the greatest depth anywhere in the canyon), to a minimum of about 1,750 feet at The Narrows. The stretch of canyon between Pulpit Rock and Chasm View, including The Narrows, though the shallowest in the monument, is also the narrowest, has some of the steepest walls, and is, therefore, among the most impressive segments of the canyon (fig. 3). Profiles of several well-known western canyons are shown in figure 1. Deepest of these by far is Hells Canyon of the Snake, on the Idaho-Oregon border. Clearly, it dwarfs the Black Canyon in the immensity of its void, though its flaring walls lack the alarming verticality of the Black Canyon. Arizona's Grand Canyon of the Colorado is acknowledged as the greatest of them all; it is not as deep as Hells Canyon, but it is wider, longer, more rugged, and far more colorful. Its depth is two to three times that of the Black Canyon. Zion Canyon, Utah, combines depth, sheerness, serenity, and color in a chasm that ranges from capacious to extremely narrow. Its Narrows have a depth-to-width ratio unmatched by any other major American canyon. California's Yosemite Valley, in a setting of sylvan verdure, is unique among the gorges shown in profile in figure 1 in being the only glacial trough; its monolithic walls bear witness to the abrasive power of moving ice. Few cliffs in the world match the splendor of its El Capitan. Lodore Canyon, on the Green River in Dinosaur National Monument, Colorado, is best known, perhaps, for its noisy splashy rapids, first made famous by John Wesley Powell. Lodore Canyon also features towering cliffs of deep-red quartzite. Grand Canyon of the Yellowstone River, Wyoming, is noted for its great waterfalls, dashing river, and bright coloration. The Royal Gorge of the Arkansas River, Colorado, features the 'world's highest suspension bridge'. The profiles shown in figure 1 afford some basis for comparing one canyon with another. They cannot abstract in two dimensions the overall impression that each canyon makes. Color, vegetation, outcrop habit, vantage point, season of year, length of visit - even the roar of the river or lack thereof - all contribute to this highly personal effect. For a river of its size, the Gunnison has an unusually steep gradient through the Black Canyon. The river falls about 2,150 feet from the head of the canyon at Sapinero to the mouth at its junction with North Fork - a distance of about 50 miles and an average rate of fall of about 43 feet per mile. By comparison, the Green

Hansen, Wallace R.

1965-01-01

245

THE SUBMARINE REVIEW SUMMER 2012  

E-print Network

THE SUBMARINE REVIEW 1 SUMMER 2012 SPURRING INNOVATION AT THE DECKPLATE LEVEL IN THE SUBMARINE FORCE LT Ryan P. Hilger, USN Submarine Student at the Naval Postgraduate School he phenomenal success to alter how we design and operate our submarines. Vice Admiral Richardson happily announced after

246

Reflection and tunneling of ocean waves observed at a submarine Jim Thomson  

E-print Network

Reflection and tunneling of ocean waves observed at a submarine canyon Jim Thomson WHOI-MIT Joint Received 24 February 2005; accepted 7 April 2005; published 17 May 2005. [1] Ocean surface gravity waves: Thomson, J., S. Elgar, and T. H. C. Herbers (2005), Reflection and tunneling of ocean waves observed

Kirby, James T.

247

Clay Mineral Formation in Sea Water by Submarine Weathering of K-Feldspar  

Microsoft Academic Search

A SU1TE of granodiorite samples was collected by dredging from depths of about 1000 m from the walls of Carmel and Monterey submarine canyons, Monterey Bay, California. One surface of each of the various granodiorite slabs was weathered and encrusted with marine organisms. The weathering is maximum at the surface and penetrates to a depth of about 20 em and

R. W. Rex; B. D. MART

1966-01-01

248

Canyon conditions impact carbon flows in food webs of three sections of the Nazaré canyon  

NASA Astrophysics Data System (ADS)

Submarine canyons transport large amounts of sediment and organic matter (OM) from the continental shelf to the abyssal plain. Three carbon-based food web models were constructed for the upper (300-750 m water depth), middle (2700-3500 m) and lower section (4000-5000 m) of the Nazaré canyon (eastern Atlantic Ocean) using linear inverse modeling to examine how the food web is influenced by the characteristics of the respective canyon section. The models were based on an empirical dataset consisting of biomass and carbon processing data, and general physiological data constraints from the literature. Environmental conditions, most notably organic matter (OM) input and hydrodynamic activity, differed between the canyon sections and strongly affected the benthic food web structure. Despite the large difference in depth, the OM inputs into the food webs of the upper and middle sections were of similar magnitude (7.98±0.84 and 9.30±0.71 mmol C m -2 d -1, respectively). OM input to the lower section was however almost 6-7 times lower (1.26±0.03 mmol C m -2 d -1). Carbon processing in the upper section was dominated by prokaryotes (70% of total respiration), though there was a significant meiofaunal (21%) and smaller macrofaunal (9%) contribution. The high total faunal contribution to carbon processing resembles that found in shallower continental shelves and upper slopes, although the meiofaunal contribution is surprisingly high and suggest that high current speeds and sediment resuspension in the upper canyon favor the role of the meiofauna. The high OM input and conditions in the accreting sediments of the middle canyon section were more beneficial for megafauna (holothurians), than for the other food web compartments. The high megafaunal biomass (516 mmol C m -2), their large contribution to respiration (56% of total respiration) and secondary production (0.08 mmol C m -2 d -1) shows that these accreting sediments in canyons are megafaunal hotspots in the deep-sea. Conversely, carbon cycling in the lower canyon section was strongly dominated by prokaryotes (86% of respiration) and the food web structure therefore resembled that of lower slope and abyssal plain sediments. This study shows that elevated OM input in canyons may favor the faunal contribution to carbon processing and create hotspots of faunal biomass and carbon processing along the continental shelf.

van Oevelen, Dick; Soetaert, Karline; Garcia, R.; de Stigter, Henko C.; Cunha, Marina R.; Pusceddu, Antonio; Danovaro, Roberto

2011-12-01

249

Submarine neutrino communication  

E-print Network

We discuss the possibility to use a high energy neutrino beam from a muon storage ring to provide one way communication with a submerged submarine. Neutrino interactions produce muons which can be detected either, directly when they pass through the submarine or by their emission of Cerenkov light in sea water, which, in turn, can be exploited with sensitive photo detectors. Due to the very high neutrino flux from a muon storage ring, it is sufficient to mount either detection system directly onto the hull of the submersible. The achievable data transfer rates compare favorable with existing technologies and do allow for a communication at the usual speed and depth of submarines.

Patrick Huber

2010-08-20

250

Submarine neutrino communication  

E-print Network

We discuss the possibility to use a high energy neutrino beam from a muon storage ring to provide one way communication with a submerged submarine. Neutrino interactions produce muons which can be detected either, directly when they pass through the submarine or by their emission of Cerenkov light in sea water, which, in turn, can be exploited with sensitive photo detectors. Due to the very high neutrino flux from a muon storage ring, it is sufficient to mount either detection system directly onto the hull of the submersible. The achievable data transfer rates compare favorable with existing technologies and do allow for a communication at the usual speed and depth of submarines.

Huber, Patrick

2009-01-01

251

Movements and Swimming Behavior of Three Species of Sharks in La Jolla Canyon, California  

Microsoft Academic Search

We tracked six individuals of three shark species, the shortfin mako, Isurus oxyrinchus, great white, Carcharodon carcharias, and blue, Prionace glauca, near the submarine canyon off La Jolla, southern California during the summers of 1995 and 1997. The duration of tracking ranged from 2 to 38 h per shark. The mode of travel differed in one respect among species. The

A. Peter Klimley; Sallie C. Beavers; Tobey H. Curtis; Salvador J. Jorgensen

2002-01-01

252

Submarine: Lift Bag Lander  

NSDL National Science Digital Library

In this activity (on page 4), learners create a submarine using a plastic sandwich bag. This is a fun way to learn about buoyancy and how captured gas can cause objects to float.
Note: You will also need access to a tank or swimming pool to watch your submarine dive.
Safety note: Learners will need an adult's help to drill holes in the film canister.

2014-04-24

253

Bryce Canyon Hoodoo  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

254

Hoodoos of Bryce Canyon  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

255

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

256

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

257

Bryce Canyon's Cedar Valley  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

258

Bryce Canyon Sandstone  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

259

Bryce Canyon Cedars  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

260

Bryce Canyon Vistas  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

261

Bryce Canyon Hoodoo  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

262

Bryce Canyon Benchmark  

USGS Multimedia Gallery

A USGS elevation benchmark in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that ...

263

Bryce Canyon Rim  

USGS Multimedia Gallery

The rim of Bryce Canyon, viewed from Rainbow Point. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms ...

264

Bryce Canyon Amphitheater  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

265

Bryce Canyon Amphitheater Panorama  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

266

Bryce Canyon Amphitheater  

USGS Multimedia Gallery

Views along the Queen's Garden Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sands...

267

Bryce Canyon Amphitheater Hoodoos  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

268

Bryce Canyon Natural Bridge  

USGS Multimedia Gallery

The Bryce Canyon Natural Bridge. Technically, this is not a natural bridge, which forms when running water erodes a tunnel into a rock formation. Instead, this is a natural arch, similar to the ones in nearby Arches National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is...

269

Bryce Canyon Natural Bridge  

USGS Multimedia Gallery

Bryce Canyon's Natural Bridge is technically a natural arch, similar to those in the nearby Arches National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates...

270

Glen Canyon Dam  

USGS Multimedia Gallery

The USGS Glen Canyon Adaptive Management Working Group took a trip in August from Glen Canyon Dam to Lees Ferry on Friday, August 31, 2012. This spot at Four Mile (four miles downstream from the dam) is where a lot of people fish: There were fishermen that day that claimed to have c...

271

Bryce Canyon Hoodoos  

USGS Multimedia Gallery

Sandstone hoodoos in Bryce Canyon National Park. In the background, Grand Staircase-Escalante National Monument can be seen. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different er...

272

Hoodoos of Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

273

Le Canyon du Var: Case study of a modern active proximal channel  

SciTech Connect

The Var Canyon and the continental slope along the French Riviera were investigated using SAR, a new deeply towed high-resolution side-scan sonar and 3.5-kHz subbottom profiler package. Later on, a ground-truth operation using the CYANA submersible and Kuellenberg cores provided in-situ observations and samples. The main characteristics of this area are the narrow shelf, the steep continental slope, and very coarse superficial materials. During the Pliocene, an alluvial cone was built on the floor of a deep ria located at the present Var alluvial plain. This detritic cone overlies the Messinian erosion surface. It is totally submarine and formed by pudding stones, conglomerates, and marls. Since the early Quaternary, this large sedimentary body has been dismantled by gravity processes (mass wasting, debris flows, turbidites). The bed form at the head of the Var Valley (500 m depth) is marked by an anastomosed network eroding the spurs that give the typical herringbone facies of the canyon's flanks. Downslope from this area begins a gravel wave field extending to a water depth of 2,100 m. Wavelength and height appear to be directly controlled by the topography. Downward and according to a break in the slope, the sea floor is characterized by a rhythmic alternance of gravel fields and mud fields (to 2,400 m). The muddy areas are always located on relatively high points of the sea bottom. The significance of these bed forms will be discussed and related to the sedimentary processes which may have operated in this area.

Savoye, B.; Voisset, M.; Cochonat, P.; Auffret, G.A.; Bourillet, J.; Droz, L.; Ollier, G.; Coutelle, A.; Le Cann, C.; Auzende, J.; Serge, R. (IFREMER, Brest (France))

1988-08-01

274

Snake Hells Canyon Subbasin Inventory  

E-print Network

Snake Hells Canyon Subbasin Inventory May 2004 Prepared for the Northwest Power and Conservation .................................................................................................................................. 62 8 APPENDIX A APRE SUMMARIES FOR HELLS CANYON SUBBASIN.................. 63 Snake Hells Canyon Subbasin Inventory i May 2004 #12;LIST OF FIGURES FIGURE 1.LAND MANAGEMENT IN THE SNAKE HELLS CANYON

275

Bioavailability of sinking organic matter in the Blanes canyon and the adjacent open slope (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Submarine canyons are sites of intense energy and material exchange between the shelf and the deep adjacent basins. To test the hypothesis that active submarine canyons represent preferential conduits of available food for the deep-sea benthos, two mooring lines were deployed at 1200 m depth from November 2008 to November 2009 inside the Blanes canyon and on the adjacent open slope (Catalan Margin, NW Mediterranean Sea). We investigated the fluxes, biochemical composition and food quality of sinking organic carbon (OC). OC fluxes in the canyon and the open slope varied among sampling periods, though not consistently in the two sites. In particular, while in the open slope the highest OC fluxes were observed in August 2009, in the canyon the highest OC fluxes occurred in April-May 2009. For almost the entire study period, the OC fluxes in the canyon were significantly higher than those in the open slope, whereas OC contents of sinking particles collected in the open slope were consistently higher than those in the canyon. This result confirms that submarine canyons are effective conveyors of OC to the deep sea. Particles transferred to the deep sea floor through the canyons are predominantly of inorganic origin, significantly higher than that reaching the open slope at a similar water depth. Using multivariate statistical tests, two major clusters of sampling periods were identified: one in the canyon that grouped trap samples collected in December 2008, concurrently with the occurrence of a major storm at the sea surface, and associated with increased fluxes of nutritionally available particles from the upper shelf. Another cluster grouped samples from both the canyon and the open slope collected in March 2009, concurrently with the occurrence of the seasonal phytoplankton bloom at the sea surface, and associated with increased fluxes of total phytopigments. Our results confirm the key ecological role of submarine canyons for the functioning of deep-sea ecosystems, and highlight the importance of canyons in linking episodic storms and primary production occurring at the sea surface to the deep sea floor.

Lopez-Fernandez, P.; Bianchelli, S.; Pusceddu, A.; Calafat, A.; Sanchez-Vidal, A.; Danovaro, R.

2013-05-01

276

Application of a lagrangian transport model to organo-mineral aggregates within the Nazaré canyon  

NASA Astrophysics Data System (ADS)

In this study, a hydrodynamic model was applied to the Nazaré submarine canyon with boundary forcing provided by an operational forecast model for the west Iberian coast for the spring of 2009. After validation, a lagrangian transport model was coupled to the hydrodynamic model to study and compare the transport patterns of three different classes of organo-mineral aggregates along the Nazaré canyon. The results show that the transport in the canyon is neither constant, nor unidirectional and that there are preferential areas where deposited matter is resuspended and redistributed. The transport of the larger class size of organo-mineral aggregates (2000 ?m and 4000 ?m) is less pronounced, and a decrease in the phytodetrital carbon flux along the canyon is observed. During the modelled period, the Nazaré canyon acts as a depocentre of sedimentary organic matter rather than a conduit of organo-mineral aggregates to the deep sea, as has been reported by other authors. The results of this study are crucial for the understanding of the oceanic carbon sequestration at the continental margin, and therefore important for evaluating the role of submarine canyons within the global carbon cycle.

Pando, S.; Juliano, M. F.; García, R.; Mendes, P. A. de Jesus; Thomsen, L.

2013-06-01

277

The Grand Canyon  

NSDL National Science Digital Library

The first site from PBS.org, called Lost in the Canyon (1), offers an excellent online learning experience. Visitors learn about John Wesley Powell's expedition down the Colorado River, covered in transcripts from the companion television show and a timeline of Powell's life. Other features include an interactive lesson on running rapids and a look at the unique geologic history of the area. Next, from StudyWorks! Online comes the lesson entitled Sleuthing at the Grand Canyon: Using Rocks to Tell Us About the Past (2). Through basic descriptions, photographs, and illustrations, students learn how rocks form, how scientists use them to find out about past environments, and much more. The third site is provided by the Grand Canyon Monitoring and Research Center called The Grand Canyon Monitoring and Research Center Fiscal Year 2000-2004 Monitoring and Research Strategic Plan (3). Readers will discover the mission of the center, history of monitoring in the area, management strategies, research activities, and much more. Next is a site offered by Richard S. Naylor of Northeastern University's Department of Geology called Unconformities in the Grand Canyon (4). Visitors will find descriptions and photographs of several sites in the Grand Canyon that exhibit geologic unconformities or surfaces that represent a break in the geologic record. The fifth site is maintained by kaibob.org called the Geology of Grand Canyon (5). This site contains basic information on how the canyon was formed, where all the rock came from, why it looks like it does, and when it all happened. From NASA's Visible Earth Web site comes the 3-D View of Grand Canyon (6) page. The canyon can be viewed in a low or high resolution JPEG format, which shows the surrounding area, part of the Colorado river, and the canyon itself in dynamic colors. Part of Northern Arizona University, the seventh site is entitled Canyons, Culture, and Environmental Change: An Introduction to the Land Use History of the Colorado Plateau (7). The site provides an introduction to the environmental history of the Colorado Plateau and summarizes a vast body of research from multiple disciplines in an easily accessible format. The last site from NOAA's Colorado River Basin Forecast Center is the River Forecasts and Data page (8). Provided are data from various sites along the river that offer a wide range of relevant information such as simulated hydrographs.

Brieske, Joel A.

2002-01-01

278

Constraining the timing of turbidity current driven sediment transport down Monterey Canyon, offshore California  

NASA Astrophysics Data System (ADS)

Turbidity currents are responsible for transport of sand down the Monterey Submarine Canyon, offshore California, from the shoreline to Monterey Fan. However the timing of sediment transport events and their frequencies are not fully understood despite recent monitoring of canyon events and AMS 14C dating of foraminifera from hemipelagic sediments bracketing sand deposited during turbidity flows. Quartz optically stimulated luminescence (OSL) dating in sand sequences provides a complementary means of dating sand transport. OSL dates reflect the time interval since the sand grains were last exposed to sunlight. However, the technique has never been applied extensively to canyon sediments before. Here we report both quartz OSL ages of sand deposits and benthic foraminifera ages sampled from the axial channel within Monterey Submarine Canyon and Fan via ROV-collected vibracores. This allows a rare opportunity to directly test the frequency and timing of turbidity current events at different points in the canyon. We use both single-grain and small (~2 mm area) single aliquot regeneration OSL approaches on vibracore samples from various water depths to determine sand transport frequency. Within the upper canyon (<2,000 m water depths) the OSL data require sub-decadal to decadal transit times. Sand bearing fining upward sequences yielding middle Holocene to last few hundred year ages indicate turbidity currents occur at 150 to 250 year event frequencies within the fan channel out to 3,600 m water depth. We suggest that turbidity currents have been active during the current sea-level high stand and that the submarine fan has recorded turbidity currents over the entire Holocene. The increased age spread in single grain OSL dates with water depth provides evidence of sediment mixing and reworking during turbidity flows. Apparently, sand is stored within the canyon for various amounts of time while it is in route to its current location on the fan.

McGann, M.; Stevens, T.; Paull, C. K.; Ussler, W.; Buylaert, J.

2013-12-01

279

Distribution and transport of suspended particulate matter in Monterey Canyon, California  

USGS Publications Warehouse

From August 1993 to August 1994, six moorings that measure current, temperature, salinity, and water clarity were deployed along the axis of Monterey Canyon to study the circulation and transport of water and suspended particulate matter through the canyon system. The moorings occupied three sites that are morphologically different: a narrow transverse section (axis width 900 m) at 1450 m water depth, a wide transverse section at 2837 m, and a third site in the fan valley axis farther offshore at 3223 m that recorded for 3 yr. In addition, CTD/transmissometer casts were conducted within and near the Monterey Canyon during four cruises. Our data show a mainly biogenic, surface turbid layer, a limited intermediate nepheloid layer, and a bottom nepheloid layer. There is a consistent presence of a turbid layer within the canyon at a water depth of about 1500 m. Tidal flow dominates at all sites, but currents above the canyon rim and within the canyon appear to belong to two distinct dynamic systems. Bottom intensification of currents plays an important role in raising the near-bottom shear stress high enough that bottom sediments are often, if not always, resuspended. Mean flow pattern suggests a convergence zone between the narrow and wide site: the near-bed (100 m above bottom where the lowest current meter was located) mean transport is down-canyon at the 1450-m site, while the near-bottom transport at the 2837-m site is up-canyon, at a smaller magnitude. Transport at the 3223-m site is dominantly NNW, cross-canyon, with periods of up-canyon flow over 3 yr. A very high-turbidity event was recorded 100 m above the canyon bottom at the narrow site. The event started very abruptly and lasted more than a week. This event was not detected at either of the deeper sites. A canyon head flushing event is likely the cause. ?? 2002 Elsevier Science B.V. All rights reserved.

Xu, J.P.; Noble, M.; Eittreim, S.L.; Rosenfeld, L.K.; Schwing, F.B.; Pilskaln, C.H.

2002-01-01

280

Submarine Coaxial Cable Pressure Characteristics  

Microsoft Academic Search

In equalization design of submarine coaxial cable system, the cable attenuation deviation due to pressure in deep sea bottom has significant weight. This paper treats the submarine coaxial cable characteristics pressure dependency. By using an artificial ocean test facility, 1.7 inch submarine coaxial cable attenuation, phase, capacitance and insulator core diameter were studied and their pressure coefficients under a pressure

K. Aida; M. Aiki

1978-01-01

281

Tlie Submarine Caves of Bermuda  

E-print Network

Tlie Submarine Caves of Bermuda ThomasM. Iliffe Bermuda Biological Station, Ferry Reach 1-15 #12;The SubmarineCavesofBermuda ThomasM.Iliffe BermudaBiological Station,Ferry Reach 1-15 Abstract Bermuda the volcanic pedistal. Three types of submarine limestone cave morphology have so far been identified

Iliffe, Thomas M.

282

Flow in bedrock canyons.  

PubMed

Bedrock erosion in rivers sets the pace of landscape evolution, influences the evolution of orogens and determines the size, shape and relief of mountains. A variety of models link fluid flow and sediment transport processes to bedrock incision in canyons. The model components that represent sediment transport processes are increasingly well developed. In contrast, the model components being used to represent fluid flow are largely untested because there are no observations of the flow structure in bedrock canyons. Here we present a 524-kilometre, continuous centreline, acoustic Doppler current profiler survey of the Fraser Canyon in western Canada, which includes 42 individual bedrock canyons. Our observations of three-dimensional flow structure reveal that, as water enters the canyons, a high-velocity core follows the bed surface, causing a velocity inversion (high velocities near the bed and low velocities at the surface). The plunging water then upwells along the canyon walls, resulting in counter-rotating, along-stream coherent flow structures that diverge near the bed. The resulting flow structure promotes deep scour in the bedrock channel floor and undercutting of the canyon walls. This provides a mechanism for channel widening and ensures that the base of the walls is swept clear of the debris that is often deposited there, keeping the walls nearly vertical. These observations reveal that the flow structure in bedrock canyons is more complex than assumed in the models presently used. Fluid flow models that capture the essence of the three-dimensional flow field, using simple phenomenological rules that are computationally tractable, are required to capture the dynamic coupling between flow, bedrock erosion and solid-Earth dynamics. PMID:25254474

Venditti, Jeremy G; Rennie, Colin D; Bomhof, James; Bradley, Ryan W; Little, Malcolm; Church, Michael

2014-09-25

283

Paint-Stirrer Submarine  

NSDL National Science Digital Library

In today's fast-paced, technological world, it is a constant struggle for teachers to find new and exciting ways to challenge and engage our students. The Paint-Stirrer Submarine is a unique and challenging laboratory exercise that keeps the students enthralled. They won't even realize they are learning because they will be having too much fun. This inquiry-based, hands-on experience in building a submarine allows the students to learn about buoyancy, buoyant force, Archimedes' principle, and motion in an engaging manner. It will be an experience neither you nor your students will ever forget.

Young, Jocelyn; Hardy, Kevin

2007-02-01

284

Submarine: Soda Cup Lander  

NSDL National Science Digital Library

In this activity (on page 2), learners create a submarine using a plastic cup. This is a fun way to learn about buoyancy and density. Extensions for this activity, such as adding a propeller or manometer, are also included.
Note: You will also need access to a tank or swimming pool to watch your submarine dive.
Safety note: Learners will need an adult's help to drill holes in the film canister. Learners will also need an adult's help if they use a glue gun to attach the film canister to the plastic cup.

2014-04-24

285

Sedimentology and regional correlation of a basinally restricted deepwater siliciclastic wedge: Brushy Canyon Formation-Cherry Canyon Tongue (Lower Guadalupian), Delaware basin  

SciTech Connect

Sedimentologic data and a new regional correlation based on seismic and field data constrain depositional models for basinally restricted siliciclastics of the Brushy Canyon Formation and sandstones of the immediately overlying Cherry Canyon Tongue. In the Guadalupe Mountains, the Brushy Canyon thins at the basin margin, from 300 m to pinch-out, by onlap onto a basinward-sloping submarine unconformity. The onlapping wedge contains numerous basinward-trending channels (up to 50 m deep and 1 km wide). Laminated siltstones comprise interchannel areas and occur in channels as draping units of constant thickness. Sandstones (rippled, parallel laminated, and massive beds) are restricted to channels and onlap channel walls. Density-driven currents flowing into a density-stratified basin as interflows and underflows best explain these geometries. Concentration of sandstones in vertically stacked, 20 to 50-m deep channels suggests sands were point-sourced into the basin. Increasing proportions of high-energy deposits in successive sandstone channel fills indicate progradation of the Brushy Canyon wedge. Correlation of the Brushy Canyon unconformity shelfward to an interpreted disconformity within the San Andres Formation suggests that the shelf was subaerially exposed. Allochthonous fossils in Brushy Canyon sandstones indicate existing submerged shallow, upper slope areas were normal marine. Updip portions of the lower Cherry Canyon Sandstone Tongue are confined within paleocanyons and are deltaic in origin, suggesting fluvial delivery of sand across the shelf. These regional constraints suggest that density-driven currents were turbidity currents rather than saline density currents sourced by hypersaline shelf waters.

Rossen, C.; Sarg, J.F.

1987-05-01

286

Coastal and submarine instabilities distribution in the tectonically active SW margin of the Corinth Rift (Psathopyrgos, Achaia, Greece)  

NASA Astrophysics Data System (ADS)

The Corinth Rift, one of the most active rifts in the world as local extension trending NE-SW reaches the amount of 14±2 mm/yr, corresponds to one of the largest zones of seismically active normal faulting. The formation, growth and migration southwards of the prevailing fault systems, which evolve simultaneously with the intense morphogenetic processes, are overprinted in the age, facies and thickness of the Plio-Pleistocene sequences constructing the south margin of the western Gulf of Corinth. The dominant fault blocks, defined by east-west trending, north dipping normal faults, are accompanied by several morphological features and anomalies, noticed in both the terrestrial and the marine environment. Our main aim has been to examine how the tectonic evolution, in combination with the attendant fierce erosional and sedimentary processes, has affected the morphology through geodynamic processes expressed as failures in the wider coastal area. High resolution multibeam bathymetry in combination with the available land surface data have contributed to submarine and subaerial morphological mapping. These have been used as a basis for the detection of all those geomorphic features that indicate instabilities probably triggered, directly or indirectly, by the ongoing active tectonic deformation. The interpretation of the combined datasets shows that the southwestern margin of the Corinth Rift towards Psathopyrgos fault zone is characterized by intense coastal relief and a narrow, almost absent, continental shelf, which passes abruptly to steep submarine slopes. These steep slope values denote the effects of the most recent brittle deformation and are related to coastal and submarine instabilities and failures. High uplift rates and rapid sedimentation, indicative of the regional high-energy terrestrial and submarine environment, are subsequently balanced by the transportation of the seafloor currents, especially where slope gradients decrease, disintegrating the probable slide deposits. Conversely, the nearby active -but older- tectonic structure of the Heliki fault, is related to less steep slopes. Canyons are extensive and sediment mass failures appear as retrogressive landslide scars identified near the headwalls. The mass movements evolving near the coastal and shallow marine areas may have a high tsunamigenic potential, which depends on the volumes of the mobilized materials. As a special interest has been arisen nowadays concerning risk assessment and management, the results of our study can be further evaluated from a geohazard perspective.

Simou, Eirini; Papanikolaou, Dimitrios; Lykousis, Vasilios; Nomikou, Paraskevi; Vassilakis, Emmanuel

2014-05-01

287

Stresses in a submarine topography under ocean waves  

SciTech Connect

The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, to obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular the dynamic pore pressure and the combined static and dynamic effective stresses are presented. 10 references, 11 figures.

Mei, C.C.; McTigue, D.F.

1984-01-01

288

Stresses in a submarine topography under ocean waves  

SciTech Connect

The problem of submarine slope stability is of interest to both offshore engineering and geology. In an uneven topography, the weight above a horizontal plane induces two-dimensional variation in the static stress field. The action of wave pressure, which changes with depth, further introduces excess pore pressure and dynamic stresses in the sea bottom. In the present paper, we combine a simple analytical theory for the static stress by the present authors, and the recent solution by Mei and Foda for wave-induced stresses in a plane poro-elastic sea bed to account for mild bottom slope and wave shoaling, and obtain the effective stress field in a submarine topography under sea waves. Sample results are given for a ridge and a canyon. In particular, the dynamic pore pressure and the combined static and dynamic effective stresses are presented.

Mei, C.C.; McTigue, D.F.

1984-09-01

289

Giant submarine landslides off NW-Africa  

NASA Astrophysics Data System (ADS)

The passive continental margin off Northwest Africa is dominated by high terrigenous sediment input (fluvial and aeolian) and high primary production in upwelling areas. The redeposition of these sediments is controlled by both gravitational and bottom current induced along slope sediment transport. Some sections of the margin show repeated instabilities, while other regions are stable for a long time. Two prominent examples for large scale landslides are the Dakar Slide offshore Senegal and Sahara Slide offshore West-Sahara. High resolution seismic and hydro-acoustic data acquired during Cruise MSM11/2 in spring 2009 in addition to data from cruise M65/2 in 2005 reveal an giant submarine slide offshore Senegal named Dakar Slide. The slide shows a headwall with a length of at least 90km along slope in between water depths of 3.100 to 3.400m. The slide is confined by the Dakar Canyon in the north and the Diola Canyon in the south. The northern sidewall runs for 90 km into the deep-sea where it crosses the distal part of the Dakar Canyon. Seismic data show that the distal part of the Canyon was repeatedly destroyed and filled by slide deposits. Erosion structures in former canyon fill shows reactivation of the Canyon in the past. The area above the slide does not show major mass-wasting events even though the slope gradient there with 3° is steeper than the slope angle of 0.5-1° in the headwall region of the slide. Beneath the northern headwall and sidewall of the Dakar Slide the seismic data show a large scale wavy sediment structure, which covers at least 400 km² and is up to 1km thick. The crests of the waves strike in an along slope direction, and we interpret this feature as listric faults, which might have originated from creeping prior to the main catastrophic failure event. Furthermore upslope of this area between 1.300 and 2.000 meters bathymetric and high resolution seismic data show additional signs for (active/recent) creeping in the form of down slope orientated bulges. Until now, however, it is unclear if there is a relation between the creeping and the slope failure. The Dakar and the Diola Canyon seem to limit the slide to this area and therefore restrict the expansion of the slide further along the slope. As indicated by the repeated slide deposits filling the Dakar Canyon and the abundance of deeper lying chaotic to transparent sediment structures in the seismic data, mass-wasting events prior to Dakar Slide were common. Seismic data from cruise M58/1 in 2003 and new bathymetric data of the headwall area of the Sahara-Slide also collected during Cruise MSM11/2 show a mega slide with a length of ~700km and an estimated volume of ~600km. The age of the main slide event is 50-60ka. The distal part of this slide complex is well studied, while data in the source-area are sparse. Available data of the source area indicate vertically stacked slide deposits and a relatively recent reactivation of the headwall. To investigate this observation in more detail additional data will be acquired during the upcoming Poseidon P395 Cruise in February 2010.

Meyer, Mathias; Geersen, Jacob; Schwenk, Tillmann; Krastel, Sebastian

2010-05-01

290

Geological overview of the Angola-Congo Margin, the Congo deep-sea fan and its submarine valleys  

E-print Network

connection between the Congo River estuary and the Congo canyon head that allows relatively continuous.1016/j.dsr2.2009.04.001 #12;.1 Introduction The accumulation of marine sediment seaward of the Congo River estuary is probably one of the greatest in the world for a submarine system that is still active

Boyer, Edmond

291

Fiber Optic Submarine Cables  

NASA Astrophysics Data System (ADS)

Submarine communication cables have one of the longest history in the field of technics. During the last 20 years their importance showed a drastic decay in favour of satellites. Presently their future looks bright again as they contain now optical fibers instead of coaxial pairs.

Oestreich, Ulrich H. P.

1990-01-01

292

Making a Submarine.  

ERIC Educational Resources Information Center

Describes Archimedes principle and why a ship sinks when it gets a hole in it. Suggests an activity for teaching the concept of density and water displacement through the construction of a simple submarine. Includes materials and procedures for this activity. (KHR)

Cornacchia, Deborah J.

2002-01-01

293

Canyon and channel networks of Peru-Chile fore arc at Arica Bight  

SciTech Connect

Canyons and channels of the Peru-Chile fore arc between 17{degree}30'S to 19{degree}30'S form a complex, integrated network revealed in SeaMARC II side-scan mosaics. The largest canyon, incised 200-600 m, is bordered by a series of sidewall slumps, producing a sinuosity that mimics subaerial meanders. The canyon courses across the Arequipa fore-arc basin floor, across a structural high and onto the middle trench slope to about 4,000 m where it disappears into a background of complex small-scale structures, From 500-2,500 m depth the canyon strikes north-south oblique to the regional slope. At 2,500 m, it abruptly turns to the southwest toward the trench axis. At this elbow, a second canyon heads on the midslope and also trends north-south until 3,500 m, where it too abruptly changes to a southwest course. A history of stream piracy analogous to subaerial systems is implied in this geometry. Tributaries join this main canyon from the landward side, forming a dendritic pattern. These channels have levees which are linked by submarine crevasse splays to sediment waves on the Arequipa basin floor. The orientation of the waves is reminiscent of bow waves from a passing ship, oblique to channel and pointing downslope, and may provide an indication of the vertical extent of passing turbidity currents. Sediments are dominantly olive gray, hemipelagic silts with sands present only immediately adjacent to the canyons. Boulders of mudstone line portions of the canyon floor. Sands are absent from the lowermost slope and trench axis, as are any indications of submarine fans. Sands may be rare in this system, with those that are present kneaded into the active margin system along the lower trench slope.

Coulbourn, W.T. (Hawaii Institute of Geophysics, Honolulu (USA))

1990-05-01

294

Deep Canyon and Slope Suspended Sediment Transport in the Western Gulf of Lions During the 2006 Intense Cascading Period  

Microsoft Academic Search

Recent studies have demonstrated that most of the off-shelf suspended sediment transport in the Gulf of Lions occurs in its westernmost sector, preferentially through the Cap de Creus submarine canyon. Based on this previous knowledge, a focussed monitoring strategy was designed within the HERMES project, to better constrain the contemporary sediment transport processes in this region. A network of mooring

A. Palanques; P. Puig; X. Durrieu de Madron; A. Calafat; M. Canals; S. Heussner

2008-01-01

295

The turbidity currents records of Kaoping Canyon during past 32000 yrs  

NASA Astrophysics Data System (ADS)

Taiwan is both located in East Asia Monsoon area and plate collision boundary; as the result, frequently episodic rainfall and fractal geologic setting will cause Taiwan become a high potential area that gravity flows happen. When the high density terristrial flows were exported to the sea, it will become the hyperpycnal flow and perhaps can cause submarine geo-hazard happen (i.e. In 2010 Typhoon Morakot, there are numerous terrestrial sediments be delivered to the southwestern offshore Taiwan along the Kaoping Canyon and causing submarine cable be broken). Additionally, turbidite will also be triggered by earthquakes and it will also have the chance to cause submarine geo-hazard. For an example, Pintung earthquake happened in Hengchun, Taiwan in 1996; this earthquake triggered very huge magnitude submarine landslide happened and damaged several hundred kilometers submarine cable along the Kaoping Canyon. Taiwan is a island surrounded by ocean, and there are lots of submarine cables across these seas, especially along the Kaoping Canyon in southwestern offshore Taiwan. In order to avoid too much economic and safety waste, the risk estimation of geo-hazard is very important, and the frequency of turbidity currents happened is a very visible index. Hence, we collected a core located at the downstream of Kaoping Canyon in 2800 meters water depth. Its length is about 39 meters and we can divide this core into two different lithofacies roughly by core description. The upper part is dominated by mud and silt inter-bedded, and the lower part is dominated by massive mud. By the 14C dating, the age of lithofacies change is about 11000 yrs BP. According to the previous studies, We supposed due to Kaoping Canyon is connected with Kaoping river directly and the terrestrial materials of Pintong plain can be delivered from the land to deep ocean directly via the high energy flooding events. In other words, the lithoface change is related to the high energy events happened in land; hence, we propose that from 32000 yrs BP to 11000 yrs BP, the weather in southwestern Taiwan was dryer, and after 11000 yrs BP, it became wetter and frequently turbidity currents happened in Kaoping canyon system.

Yu, S.; Lin, A. T.; Tsai, L.

2013-12-01

296

The canyon hypothesis.  

PubMed

The three-dimensional structure of human rhinovirus 14 has a deep surface depression or "canyon" encircling each of the twelve fivefold vertices. The canyon's surface is inaccessible to the broad antigen binding region of antibodies, permitting conservation of residues that might be required for host cell receptor recognition without danger of attack by the host's immune system. In contrast, the exposed surface features, where neutralizing antibodies are known to bind, change rapidly under pressure from the host's immune system. It was, therefore, hypothesized that this depression was the site of receptor attachment. Similar, but smaller, depressions had been observed previously on both the hemagglutinin and neuraminidase spikes of influenza virus. These have also been shown to be the site of host cell interaction. Although support for the canyon hypothesis was only circumstantial in the first place, there are now extensive confirmatory data. These include site-specific mutations of residues in the canyon and conformational changes induced in the canyon by the binding of small organic molecules, all of which alter receptor attachment. The strategy used in human rhinovirus 14 to protect the viral receptor attachment site from immune surveillance may be utilized not only in other picornaviruses but also in many other types of viruses including human immunodeficiency virus. PMID:2560913

Rossmann, M G

1989-01-01

297

Fluvial features in the deep-sea: new insights from the glacigenic submarine drainage system of the Northwest Atlantic Mid-Ocean Channel in the Labrador Sea  

Microsoft Academic Search

Side-scan sonar imagery and seismic profiles from the submarine drainage system of the Northwest Atlantic Mid-Ocean Channel (NAMOC) of the Labrador Sea reveal the presence of a variety of fluvial features in the deep-sea. The analogies extend from meso-scale features to the basin-wide drainage pattern. At basin-scale, the NAMOC submarine drainage system consists of downslope converging tributary canyons on the

Ingo Klaucke; Reinhard Hesse

1996-01-01

298

Paleogene canyons of Tethyan margin and their hydrocarbon potential, Czechoslovakia  

SciTech Connect

Two Paleogene canyons buried below the Neogene foredeep and the Carpathian thrust belt in Southern Moravia have been outlined by drilling and seismic profiling. The features, as much as 12 km wide and over 1000 m deep, have been traced for 40 km. They are cut into Mesozoic and Paleozoic carbonate and clastic deposits and underlying Precambrian crystalline rocks. The sedimentary fill is made of late Eocene and early oligocene marine deposits, predominantly silty mudstones and siltstones. Sandstones and conglomerates are distributed mainly in the lower axial part of the valleys. Proximal and distal turbidites, grain-flow and debris-flow deposits have been identified in the fill. The common occurrence of slump folds, pebbly mudstones, and chaotic slump deposits indicate that mass movement played a significant role in sediment transport inside the canyons. The canyons are interpreted as being cut by rivers, then submerged and further developed by submarine processes. The organic rich mudstones of the canyon fill are significant source rocks (1-10% TOC). They reached the generative stage only after being tectonically buried below the Carpathian thrust belt in middle Miocene time. Channelized sandstones and proximal turbidities provide reservoirs of limited extent, although more substantial accumulations of sands are possible further downslope at the mouth of these canyons. Several oil fields have been discovered both within the canyon fill and the surrounding rocks. Similar Paleogene valleys may be present elsewhere along the ancient Tethyan margins buried below the Neogene foredeeps and frontal zones of the Alps and Carpathians. Their recognition could prove fruitful in the search for hydrocarbons.

Picha, F.J. (Chevron Overseas Petroleum Inc., San Ramon, CA (United States))

1991-03-01

299

Anomalous topography on the continental shelf around Hudson Canyon  

USGS Publications Warehouse

Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

Knebel, H. J.

1979-01-01

300

Snake Hells Canyon Subbasin Assessment  

E-print Network

Snake Hells Canyon Subbasin Assessment May 2004 Prepared for the Northwest Power and Conservation, Ecovista Angela Sondenaa, Nez Perce Tribe Darin Saul, Ecovista #12;Snake Hells Canyon Subbasin Assessment Table of Contents 0 INTRODUCTION TO SNAKE HELLS CANYON SUBBASIN ASSESSMENT............ 1 1 SUBBASIN

301

Evidence of hyperpycnal flows at the head of the meandering Kaoping Canyon off SW Taiwan  

NASA Astrophysics Data System (ADS)

Using seismic and Chirp sonar profiles, this paper tests the hypothesis that hyperpycnal flows are the main factor controlling the formation and maintenance of the meandering Kaoping submarine canyon off SW Taiwan. Cross-section geometries, and erosional as well as depositional features vary along the canyon course. In the proximal, sinuous part of the canyon, down-cutting into the shelf strata has created a relief of 340 m. The cause of this intense erosion of the seafloor is suggested to be the frequent development of hyperpycnal flows. A seismic section across a meander in the distal part of the canyon shows levees formed by overspilled sediments at the outer bend, and a terrace characterized by relatively flat stratified facies at the inner bend. The geological setting and climatic conditions in SW Taiwan (e.g. earthquakes, typhoons, floods), as well as major river-canyon connections (for example, direct input of highly concentrated suspended sediment) would all promote hyperpycnal flow generation. This causes axial incision, canyon wall slumping, and the formation of levees by spill-over deposition in the upper reach of the Kaoping Canyon.

Chiang, Cheng-Shing; Yu, Ho-Shing

2008-06-01

302

Experiments on hydraulic jumps in turbidity currents near a canyon-fan transition.  

PubMed

The point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by a drop in channel slope. Turbidity currents of the kind responsible for the genesis of the canyon and fan should display an internal hydraulic jump near the slope transition. No direct field observations of any such jump appear, however, to have been made. Experiments on the nature of the jump and the resulting sedimentary deposits indicate that the thickness of the deposits just downstream of the jump tends to increase as the ratio of bed shear velocity immediately behind the jump to particle fall velocity decreases. PMID:17744147

Garcia, M; Parker, G

1989-07-28

303

Grand Canyon Explorer  

NSDL National Science Digital Library

Maintained by Bob Ribokas, Grand Canyon Explorer is quite extraordinary for a unaffiliated Web site. Updated regularly, it contains everything from stunning photography and geologic descriptions to information about hiking permits and park trials for users planning a trip. A highlight of the site is the guided tour, which provides descriptions and pictures from the park entrance to the Grand Canyon's spectacular formations like Mohave Point on the South Rim. The author has even provided a downloadable version of the Web site for Pocket PC's and PDA's, enabling users to have all the information at their finger tips when visiting the park.

1994-01-01

304

Glen Canyon Dam  

USGS Multimedia Gallery

The Glen Canyon Dam on the Colorado River in Arizona. At noon Monday, Nov. 19, U.S. Interior Secretary Ken Salazar will open the dam’s river outlet tubes, releasing controlled flows larger than the usual 8,000-25,000 cubic feet per second that flows through the turbines of the Glen...

305

Homogenizing Coastal Canyons  

Microsoft Academic Search

We consider coastal waves that are weakly nonlinear due to rapid bottom variations along the coast and, in particular, due to the presence of a series of deep canyons on the shelf break with their crests lying perpendicular to the coast. In addition, the bottom topography may vary slowly in both horizontal coordinates. Starting with the rigid lid shallow water

O. Bokhove

2002-01-01

306

Naval Submarine Support Facility: Submarine Base New London (A)  

Microsoft Academic Search

n a beautiful 1999 New England summer day, while driving north on I-95, Cap- tain Jack Pine crossed the Thames River above Groton, Connecticut, and glanced down at the east bank and the New London Submarine Base. It had been a little over six years since he had commanded the attack submarine USS Boise (SSN 764), homeported in New London.

DOUGLAS A. YESENSKY

307

Morphology, evolution and fill: Implications for sand and mud distribution in filling deep-water canyons and slope channel complexes  

NASA Astrophysics Data System (ADS)

A survey of the northeastern margin of the Rockall Trough on the Irish margin examined the transition from shelf edge to basin floor, in morphology and sedimentary activity, of a deeply incised submarine canyon system, the Donegal Bay submarine canyon. The survey produced superb 3D profiling of the canyon along its entire length, marking a transition from 'cauliflower' shaped head region with numerous tributary gullies feeding into one main canyon, to a single trunk canyon. This canyon, with an initial combined width and depth of > 17 km and > 800 m in the 'cauliflower' head area, decreases rapidly to > 4.5 km wide and > 450 m deep after the zone of tributary confluence. Eighteen kilometers further down dip, the canyon loses topographic expression as it approaches the lower rise and floor of the Rockall Trough. Degrees of recent sedimentary activity are evaluated by comparing side scan sonar systems of different frequency, and thus of different penetration sub sea, and by ground-truthing using drop (gravity) cores. The canyon was a very active system, dominated by sand transportation towards the floor of the Rockall Trough, along the slope as coarse-grained contourite, or as sand spillover from the shelf. Sand was also deposited as overbank deposits outside the main head region of the canyon, presumably by large volume turbidity currents and more active lateral gullies. The head area of the canyon system has been progressively cut off from sand source by progressive sea level rise since the last glaciation. Sand was locally deposited on terraces but not in the overbank area. Less frequent, lower volume and finer grained turbidity currents have become more common in the system. The initial sand and bypass-dominated system with small sediment waves, which may be gravels, has become dominated by muddy debrites in the lower reaches and by slumps in the upper reaches. Slumping in those upper reaches leads to ponding of sand in the head and upper reach areas, with only very occasional turbidity currents transporting sand further down the system in small channels. A model is produced to explain the mechanism and expression of backfilling in a large deep-water canyon system whose hinterland has been flooded back since glacial drawdown of sea level in the eastern Rockall Trough area. This model explains how sand may be trapped in large volumes in the upper reaches of a canyon system, due to slumping from the canyon margins and nearby upper slope regions. The focusing of sand deposition in areas where this is not usually expected will have important implications for hydrocarbon explorationists who wish to map the distribution of potential reservoir sand bodies within large, confined deep-water canyon systems.

Cronin, Bryan T.; Akhmetzhanov, Andrey M.; Mazzini, Adriano; Akhmanov, Grigorii; Ivanov, Michael; Kenyon, Neil H.; TTR-10 Shipboard Scientists

2005-08-01

308

The narrow, shallow, low-accommodation shelf of central Brazil: Sedimentology, evolution, and human uses  

NASA Astrophysics Data System (ADS)

The continental shelf off the coast of central Brazil, extending from 10 to 16°S, is unusually narrow (~ 20 km) and rests on the São Francisco craton. The shelf break is located between the 45 and 50 m isobaths and coincides with major hinge-lines of the marginal basins. The shelf was exposed for most of the Quaternary period, particularly during the last 1 my, when the average sea level was - 62 m. Submarine geomorphology is strongly influenced by this extended sub-aerial exposure and reduced subsidence, resulting in widespread incisions on the shelf. During the limited episodes of shelf inundation, as is the case today, a few meters of non-framework grain assemblages dominated by coralline algae accumulated on the outer shelf, while quartz sands were restricted to water depths of less than 10-15 m. Mud accumulation on this unusually shallow shelf is aided by additional accommodation space provided by incisions and canyon heads indenting the shelf. Artisanal fisheries, targeting high-value commercial species associated with hard bottoms located on the outer shelf and shelf break, are the most important human use of this shelf. Data used in this study have been compiled from theses and previously conducted surveys and consist of four piston cores, 509 km of chirp subbottom profiles and side scan recordings, and 711 bottom grab samples that have been analyzed for various textural and compositional aspects.

Dominguez, José Maria Landim; da Silva, Rian Pereira; Nunes, Alina Sá; Freire, Antonio Fernando Menezes

2013-12-01

309

Sedimentary processes in the middle Nazaré Canyon  

NASA Astrophysics Data System (ADS)

Nazaré Canyon extends from a water depth of 50 m near the Portuguese coast to 5000 m at the edge of the Iberian Abyssal Plain. The system is not connected to a modern river and instead obtains its present day sediment input by capture of along-shelf sediment transport. Much of this sediment is deposited in the middle canyon between about 2700 and 3800 m. However, the middle canyon is a highly heterogeneous environment, with areas of both high and low sedimentation rates, exposed rock outcrop, erosion and stable and unstable slopes in close juxtaposition. This paper explores how the various sedimentary processes interact to create the observed heterogeneous canyon environment, which will influence benthic biodiversity in the canyon. Seafloor heterogeneity is investigated using a nested approach to data interpretation, using local high-resolution data to calibrate regional lower resolution data. Six different data types, ship and ROV-mounted swath bathymetry, 30 kHz sidescan sonar images, sediment cores, seafloor video/photographs and current metre/acoustic backscatter data, were incorporated into the analysis. The main morphological characteristic of the middle canyon is a narrow, steep-sided, axial channel flanked by gently sloping terraces. Small-scale landsliding, active at the present day, is the main process that exposes a variety of substrates, ranging from semi-consolidated Holocene sediments to rock of probable Mesozoic age, on the steep axial channel walls. The axial channel floor is characterised in part by large-scale sediment bedforms and in part by landslide debris, suggesting some reworking of landslide debris by currents within the channel. The terraces are interpreted as inner levees with high sedimentation rates. Cores show a dominantly muddy sequence interrupted by thin turbidite sands emplaced on decadal to centennial timescales. The fine-grained sedimentation is the product of continuous settling from fine-grained flows that range from gravity currents to lateral advection of nepheloid layers. The close proximity of areas of high sedimentation and erosion creates a highly heterogeneous seafloor, with the highest heterogeneity on the steepest slopes.

Masson, D. G.; Huvenne, V. A. I.; de Stigter, H. C.; Arzola, R. G.; LeBas, T. P.

2011-12-01

310

Mapping the True 3D Morphology of Deep-Sea Canyons  

NASA Astrophysics Data System (ADS)

The importance of submarine canyons as ecosystem hotspots and sediment transport pathways has been recognised for decades (e.g. Heezen et al., 1955; Vetter & Dayton, 1998). However, studying canyon systems in detail is a challenge, because of the complexity and steepness of the terrain. Acoustic surveys are hampered by side-echoes, while the high slope angles cause most types of sampling equipment, deployed from surface vessels, to fail. Ship-borne bathymetric surveys tend to represent the canyon topography in an overly smoothed way as a result of their limited resolution in deep water compared to the scale of the terrain variability. Moreover, it is clear that overhanging cliffs cannot be mapped correctly with traditional, downward looking multibeam echosounders. The increasing availability of underwater vehicles, however, opens new opportunities. During summer 2009, we mapped several submarine canyon habitats in detail, using the UK deep-water Remotely Operated Vehicle (ROV) ISIS. In particular, we developed a new methodology to map vertical cliffs and overhangs by placing the high-resolution Simrad SM2000 multibeam system of the ROV in a forward-looking position rather than in the traditional downward-looking configuration. The cliff morphology was then mapped by moving the ROV laterally in parallel passes at different depths. Repeating this approach at different distances from the cliff face, we obtained maps of varying resolution and extent. The low resolution maps provide an overview of the general geological framework, while individual strata and faunal colonies can be recognised on the highest resolution maps. Using point-cloud models, we combined the ship-borne bathymetry with the ROV-based data, in order to obtain a true 3D seabed morphology of the canyon study site, which can be used for fly-throughs, geomorphological analysis or habitat mapping. With this approach, we could visualise the spatial structure and density distribution of a unique and previously unknown cold-water coral reef, formed as a hanging garden under a 1600 m long and 120 m high overhanging wall, at 1350 m water depth in the Whittard Canyon, NE Atlantic margin. Heezen, B.C., Ewing, M. and Menzies, R. (1955). The influence of submarine turbidity currents on abyssal productivity. Oikos, 6, 170-182. Vetter, E.W. & Dayton, P.K. (1998). Macrofaunal communities within and adjacent to a detritus-rich submarine canyon system. Deep-Sea Research II, 45, 25-54.

Huvenne, V. A.; Masson, D.; Tyler, P. A.; Huehnerbach, V.

2010-12-01

311

Submarine landslides: advances and challenges  

Microsoft Academic Search

Due to the recent development of well-integrat ed surveying techniques of the sea-floor, significant improvements were achieved in mapping and describing the morphology of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as found on land. Submarine mass movements however, can have run out

Jacques Locat; Homa J. Lee

2002-01-01

312

Seismic depth conversion problems associated with the Mississippi Canyon in the vicinity of Ewing Bank Block 305 field, offshore Louisiana  

SciTech Connect

Ewing Bank Block 305 field is located on the outermost edge of the continental shelf, approximately 145 km south of New Orleans, Louisiana. The geology of the field is fairly typical of other fields found offshore of Louisiana, except there is a huge, partly filled, Pleistocene submarine canyon that overlies the field. This canyon, which is commonly referred to as the Mississippi Canyon, causes a large seismic depth conversion problem that makes it virtually impossible to correctly map the structure of the field using normally processed marine seismic data The Mississippi Canyon is a large erosional feature that was formed at the mouth of the ancestral Mississippi River during the last glacial sea level lowstand. In the vicinity of the field, the canyon is about 10 km wide and 1 km deep, which is approximately two-thirds the size of the Grand Canyon of the Colorado River, and is filled mostly with Holocene sediments. Because the sediments that fill the canyon are very young, their interval velocities are much lower than the interval velocities of the sediments that form the canyon walls. This creates abrupt near surface lateral velocity variations that distort the geometry of seismic reflectors such that the time geometries seen on seismic lines are not at all indicative of the structure of the subsurface. Using a model-based processing technique and available well control, the authors have been able to solve this difficult depth conversion problem and have gained a better understanding of the geology of this field.

Leveille, G.P. (Conoco Inc., New Orleans, LA (USA)); Sahai, K.S.; McDaniel, P.G.

1990-05-01

313

Current submarine atmosphere control technology.  

PubMed

Air purification in submarines was introduced towards the end of World War II and was limited to the use of soda lime for the removal of carbon dioxide and oxygen candles for the regeneration of oxygen. The next major advances came with the advent of nuclear-powered submarines. These included the development of regenerative and, sometimes, energy-intensive processes for comprehensive atmosphere revitalization. With the present development of conventional submarines using air-independent propulsion there is a requirement for air purification similar to that of the nuclear-powered submarines but it is constrained by limited power and space. Some progress has been made in the development of new technology and the adoption of air purification equipment used in the nuclear-powered submarines for this application. PMID:11876194

Mazurek, W

1998-01-01

314

Submarine slumps, slides, and flows dominate sculpting of Beringian Margin, Alaska  

SciTech Connect

The 1,400 km long Beringian margin is characterized by several very large submarine canyons and by a large oceanic plateau at the southern end. GLORIA sidescan-sonar imagery provides a perspective of this margin that is unattainable with conventional acoustic profiles. The broad coverage of GLORIA images emphasizes that, of all the sedimentary processes affecting this vast margin, mass movement is clearly the dominant shaping process. Styles of failure include mud and debris flows, slumps, and massive block slides, some covering areas greater than 1,500 km{sup 2}. GLORIA imagery and seismic-reflection profiles show evidence for a wide variety of slides and slumps in the canyons of the northern margin, Navarin and Pervenets. The 100 km long shelf edge between these two canyons is characterized by a series of scalloped slide scars and incipient scars associated with blocks of sedimentary material, 1 to 2 km across. One of the largest single slide masses is a huge block tens of kilometers wide that occurs on the rise in the central part of the margin beyond the mouth of Zhemchug Canyon. Sliding of this block may have initiated the incision of the world's largest submarine canyon. The removal of this block accelerated headward erosion by retrograde failure until Zhemchug Canyon was cut back to a fault parallel to the shelf edge. Mass movement along the southern margin is widespread at the edges of Umnak Plateau. One mass failure, well-defined by GLORIA, is about 30 km wide and 55 km long. This and other slides along the plateau are associated with diapiric-like structures, suggesting relatively recent tectonism.

Carlson, P.R.; Karl, H.A.; Edwards, B.D.; Gardner, J.V.; Hall, R. (Geological Survey, Menlo Park, CA (USA))

1990-06-01

315

The Grand Canyon  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on the ecology of the Grand Canyon area. Students act as scientists investigating the damming of the Colorado River by the Glen Canyon dam and experimental flooding that took place in 1996. They then write a proposal as to whether or not more experimental flooding should be done on the area considering the ecological effects. It includes objectives, materials, procedures, discussion questions, evaluation ideas, extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

316

Influence of the Nazaré Canyon, central Portuguese margin, on late winter coccolithophore assemblages  

NASA Astrophysics Data System (ADS)

This paper presents a first attempt to characterize coccolithophore assemblages occurring in the context of an active submarine canyon. Coccolithophores from the upper-middle sections of the Nazaré Canyon (central Portuguese margin) - one of the largest canyons of the European continental margin - were investigated during a late winter period (9-12 March 2010). Species distributions were analyzed in a multiparameter environmental context (temperature, salinity, turbidity, Chl-a and nutrient concentrations). Monthly averaged surface water Chl-a concentrations between 2006 and 2011 assessed from satellite data are also presented, as a framework for interpreting spatial and temporal distribution of phytoplankton in the Nazaré Canyon. The Nazaré Canyon was observed to act as a conduit for advection of relatively nutrient-poor oceanic waters of ENACWst origin into nearshore areas of the continental shelf (less than 10 km off the coast), whilst at the surface a nutrient-rich buoyant plume resulting from intensive coastal runoff prior and during the beginning of the cruise was spreading in oceanward direction. Two distinct coccolithophore assemblages appear representative for the coast to open-ocean gradient: (1) Emiliania huxleyi together with Gephyrocapsa ericsonii and Coronosphaera mediterranea dominated the more productive assemblage present within coastal-neritic surface waters; and (2) Syracosphaera spp. and Ophiaster spp. displayed a higher affinity with open-ocean conditions, and also generally a broader vertical distribution. Local “hotspots” of coccolithophore and phytoplankton biomass potentially associated with perturbations of surface water circulation by the canyon are discussed.

Guerreiro, Catarina; Sá, Carolina; de Stigter, Henko; Oliveira, Anabela; Cachão, Mário; Cros, Llu?sa; Borges, Carlos; Quaresma, Luis; Santos, Ana I.; Fortuño, José-Manuel; Rodrigues, Aurora

2014-06-01

317

Optimizing submarine berthing with a persistence incentive  

Microsoft Academic Search

Submarine berthing plans reserve mooring locations for inbound U.S. Navy nuclear submarines prior to their port entrance. Once in port, submarines may be shifted to different berthing locations to allow them to better receive services they require or to make way for other shifted vessels. However, submarine berth shifting is expensive, labor inten- sive, and potentially hazardous. This article presents

Gerald G. Brown; Kelly J. Cormican; Siriphong Lawphongpanich; Daniel B. Widdis

1997-01-01

318

Evidence for submarine landslides and continental slope erosion related to fault reactivation during the last glaciation offshore eastern Canada  

NASA Astrophysics Data System (ADS)

Many studies have proposed that reactivation of dormant faults during deglaciation is a source of neotectonic activity in glaciated regions, but few have demonstrated the relationship to submarine landslides. In this study, seabed morphology and shallow geology of the outer continental margin adjacent to the Charlie Gibbs Fracture Zone off Newfoundland, Canada was investigated for evidence of this relationship. The glacial history and morphology of the margin suggest that the entire continental shelf in the area, coincident with major continental crustal lineaments, was ice-covered during the Last glacial cycle, and transverse troughs delineate the paleo-icestream drainage patterns. A recent investigation of Notre Dame Trough revealed the existence of large sediment failures on the shelf. The current study investigates complex seafloor erosion and widespread mass transport deposition (MTD) on the continental slope seaward of Notre Dame Trough, using recently-acquired high resolution seismic reflection data and piston cores. The new data reveal that a trough mouth fan (TMF) is present on the slope seaward of Notre Dame Trough. The Notre Dame TMF is characterized by a succession of stacked debris flows, but does not show a lobate shape in plan view like other classic TMFs. Instead, the Notre Dame TMF has abruptly-truncated margins suggesting post-depositional failure and erosion of the fan deposits. Seismic reflection data show that the locations of the failures along the TMF margin are coincident with a set of shallow faults; however the current dataset does not image the deeper portion of the faults. On the upper slope immediately south of the TMF, a narrow and deeply incised canyon is located along-trend with the Notre Dame Trough. The location of this canyon appears to be controlled by a fault. Downslope from this canyon, along the southern margin of the TMF, a 25 km wide, flat-floored, U-shaped valley was eroded into a succession of stacked MTD-filled channels. Seismic stratigraphic analysis shows that the valley developed around the same time as the adjacent TMF, however, the valley morphology and evidence for repeated slope failure suggests that the processes responsible for its formation were different than the processes that formed the nearby TMF. Age control provided from piston cores suggest that the last major slope failure that contributed to valley formation probably occurred at ~29 ka. Geotechnical measurements from piston cores show slightly underconsolidated sediments. The results indicate that this part of the margin is more unstable than Orphan Basin and Labrador slope regions. Given the low factor of safety and the complex fault system, low energy earthquake from the surrounding area could be enough to potentially trigger landslides.

Saint-Ange, F.; Campbell, C.; MacKillop, K.; Mosher, D. C.; Piper, D. J.; Roger, J.

2012-12-01

319

Flow structure in submarine meandering channels, a continuous discussion on secondary flow  

NASA Astrophysics Data System (ADS)

The understanding of the flow structure in deep-sea turbidity currents is important for the formation of submarine meandering channels. Similarly to the case of subaerial channels, several types of secondary flows include turbulence-, curvature- and bed morphodynamic-driven flow structures that modulate sediment transport and channel bed morphodynamics. This study focuses on [1] a review of long-time research effort (Abad et al., 2011) that tackles the description of the secondary flow associated with a subaqueous bottom current (saline) in a high-curvature meandering channel and [2] ongoing numerical simulations of similar settings as the experiments to describe the entire flow structure. In the case of subaerial channels, the classical Rozovskiian paradigm is often invoked which indicates that the near-bottom secondary flow in a bend is directed inward. It has recently been suggested based on experimental and theoretical considerations, however, that this pattern is reversed (near-bottom secondary flow is directed outward) in the case of submarine meandering channels. Experimental results presented here, on the other hand, indicate near-bottom secondary flows that have the same direction as observed in a river (normal secondary flow). The implication is an apparent contradiction between experimental results. This study combines theory, experiments, reconstructions of field flows and ongoing simulations to resolve this apparent contradiction based on the flow densimetric Froude number. Three ranges of densimetric Froude number are found, such that a) in an upper regime, secondary flow is reversed, b) in a middle regime, it is normal and c) in a lower regime, it is reversed. These results are applied to field scale channel-forming turbidity currents in the Amazon submarine canyon-fan system (Amazon Channel) and the Monterey canyon and a saline underflow in the Black Sea flowing from the Bosphorus. Our analysis indicates that secondary flow should be normal throughout most of the Amazon submarine fan reach, lower-regime reversed in the case of the Black Sea underflow, and upper-regime reversed in the case of the Monterey canyon. The analysis predicts both normal and reversed regimes in the Amazon submarine canyon reach. This research presents insights on the importance of flow structure not only to describe subaqueous bed morphodynamics, but also to understand evolution of submarine meandering channels, therefore its importance for developing accurate morphodynamic models. Reference: Abad, J. D., Sequeiros, O. E., Spinewine, B., Pirmez, C., Garcia, M. H., Parker, G. (2011). SECONDARY CURRENT OF SALINE UNDERFLOW IN A HIGHLY MEANDERING CHANNEL: EXPERIMENTS AND THEORY. In press, Journal of Sedimentary Research

Abad, J. D.; Parker, G.; Sequeiros, O.; Spinewine, B.; Garcia, M. H.; Pirmez, C.

2011-12-01

320

Active submarine volcano sampled  

NASA Astrophysics Data System (ADS)

On June 4, 1982, two full dredge hauls of fresh olivine basalt were recovered from the upper flanks of Kavachi submarine volcano, Solomon Islands, from water depths of 400 and 900 m. The shallower dredge site was within one-half mile of the active submarine vent evidenced at the surface by an area of slick water, probably caused by gas emissions. Kavachi is a composite stratovolcano located on the ‘trench-slope break’ or ‘outer-arc high’ of the New Georgia Group, approximately 35 km seaward of the main volcanic line and only 30 km landward of the base of the trench inner wall. The volcano has been observed to erupt every year or two for at least the last 30 years (see cover photographs). An island formed in 1952, 1961, 1965, and 1978, but in each case it rapidly eroded below sea level. The latest eruption was observed by Solair pilots during the several weeks up to and including May 18, 1982.

Taylor, Brian

321

Ancient Observatories: Chaco Canyon  

NSDL National Science Digital Library

Located in the northwest corner of New Mexico, Chaco Canyon is a shallow, ten-mile canyon accessible only by washboard dirt roads. It is an area of tremendous cultural importance, as it was once the center of an elaborate system of buildings, roadways, and other construction. Intense building activity continued at the site until about AD 1150, and then it was quickly abandoned. Today, it is a National Historic Park and a UNESCO World Heritage Site. On this site created by the Exploratorium in San Francisco, visitors can learn about this unique place via sections that provide insight into its layout, its history of human habitation, and also its various celestial alignments. First-time visitors can click on the Sense of Place tab to view a time-lapse video of the site. The Time area is remarkable, as visitors can read an essay titled "How Old Is It?" and then watch "Migration Stories," which talks about the experiences that humans have had there over the centuries. The site is rounded out by the Observation area, which allows users to learn about how the canyon's unique qualities have fascinated visitors, explorers, and others.

322

Exo-enzymatic activities and organic matter properties in deep-sea canyon and slope systems off the southern Cretan margin  

NASA Astrophysics Data System (ADS)

Enzymatic activities of aminopeptidase and ?- D-glucosidase were investigated in sediments collected from deep-sea canyon (Samaria) and slope systems of the unexplored southern Cretan margin (Eastern Mediterranean Sea). Stations were grouped in defined regions, inside the canyon, in nearby slopes and in open slope systems. Redox potential values, organic carbon concentrations, C/N ratios, chlorophyll- a, phaeopigments, prokaryotic abundances and carbon (C) mineralization rates were also estimated. The main aim of this investigation was to examine the links among prokaryotic abundance and activities and organic matter parameters along the axis of a submarine canyon (Samaria), and laterally along the slopes of the deep southern Cretan margin (Eastern Mediterranean Sea). The recorded aminopeptidase activities exhibited elevated values near the mouth of the canyon and the nearby slope systems and were found to be comparable to those reported for mesotrophic ecosystems. Statistical comparisons revealed that chloroplastic pigment equivalents, C/N ratios and carbon mineralization rates did not differ significantly between the deep stations in and outside the canyon (of either 2000 or 3500 m water depth). On the other hand, organic carbon and nitrogen content, prokaryotic abundances, and enzymatic activities differ substantially between the canyon and slope stations. It is suggested that the deep basins at the outlet of the submarine canyon of Samaria and the nearby slope systems are promising targets for the identification of microbial hotspots.

Polymenakou, Paraskevi N.; Lampadariou, Nikolaos; Tselepides, Anastasios

2008-10-01

323

Photomosaics and logs of trenches on the San Andreas Fault at Mill Canyon near Watsonville, California  

USGS Publications Warehouse

We present photomosaics and logs of the walls of trenches excavated for a paleoseismic study at Mill Canyon, one of two sites along the San Andreas fault in the Santa Cruz Mtns. on the Kelley-Thompson Ranch. This site was a part of Rancho Salsipuedes begining in 1834. It was purchased by the present owner’s family in 1851. Remnants of a cabin/mill operations still exist up the canyon dating from 1908 when the area was logged. At this location, faulting has moved a shutter ridge across the mouth of Mill Canyon ponding Holocene sediment. Recent faulting is confined to a narrow zone near the break in slope.

Fumal, Thomas E.; Dawson, Timothy E.; Flowers, Rebecca; Hamilton, John C.; Heingartner, Gordon F.; Kessler, James; Samrad, Laura

2004-01-01

324

Submitted to Journal of Hydraulic Research, June, 2004 The Response of Turbidity Currents to a Canyon-Fan Transition: Internal Hydraulic  

E-print Network

Turbidity currents often carve canyons into the continental slope, and then deposit submarine fans on lower of sediment brought in by rivers or littoral drift to the ocean floor. On relatively steep slopes they can fans are commonly found at and beyond the transition between the continental slope and rise (Bouma et

Parker, Gary

325

Metazoan meiofauna in deep-sea canyons and adjacent open slopes: A large-scale comparison with focus on the rare taxa  

Microsoft Academic Search

Metazoan meiofaunal abundance, total biomass, nematode size and the richness of taxa were investigated along bathymetric gradients (from the shelf break down to ca. 5000-m depth) in six submarine canyons and on five adjacent open slopes of three deep-sea regions. The investigated areas were distributed along >2500km, on the Portuguese to the Catalan and South Adriatic margins. The Portuguese and

S. Bianchelli; C. Gambi; D. Zeppilli; R. Danovaro

2010-01-01

326

Submarine ramp facies model for delta-fed, sand-rich turbidite systems  

SciTech Connect

Some sandy turbidite successions contain facies that differ in significant ways from those predicted by the canyonfed submarine fan depositional model. The key differences are the absence of a master slope channel or canyon through which sediment is transported to the basin, and the lack of facies segregation into distinct channel and overbank or interchannel facies associations within the turbidite sequence. These types of sequences can be better described using a delta-fed submarine ramp depositional model. The primary components of this model are: a sandy deltaic system that has prograded to the shelf-slope break; an abbreviated section of mud-rich slope deposits traversed by multiple shallow channels that transport sand from the delta front to the deeper basin; very sandy proximal ramp deposits composed dominantly of laterally continuous sheets of Facies B turbidites; and less sandy distal ramp deposits characterized by an increase in the abundance of Facies C and D turbidites. Ramp turbidites characteristically display statistically random patterns of bed thickness. Submarine ramp development requires rapid sediment accumulation (>800 ft or 250 m/m.y.) in turbidite basins of shallow to moderate depth where deltaic progradation is rapid enough to mask the structural relief along basin margins. The delta-fed submarine ramp facies model may be useful in describing short-lived sandy depositonal episodes in some rapidly aggrading and prograding basinal sequences. As such, they represent one member in a spectrum of submarine fan depositional styles.

Heller, P.L.; Dickinson, W.R.

1985-06-01

327

Stratigraphy and depositional environment of unnamed (lower Miocene) submarine-fan sandstone unit in Sierra Madre and San Rafael Mountains, northeastern Santa Barbara County, California  

SciTech Connect

A relatively thick and extensive, previously unnamed, lower Miocene sandstone unit occurs in the central Sierra Madre and in the Hurricane Deck area of the San Rafael Mountains of northeastern Santa Barbara County, California. It is underlain conformably and interfingers with a dark mudstone that correlates with the Soda Lake Shale Member of the Vaqueros Formation; it is overlain conformably and interfingers with a brown shale that correlates with the Saltos Member of the Monterey Shale. Northeastern exposures along the north flank of the Sierra Madre are almost exclusively medium to coarse-grained, structureless sandstone with scattered pebbly conglomerate beds. Thickness ranges from zero in the southeastern part of the Sierra Madre to 70 m in the northeast, 75 m in the northwest, and 600 m in the central part of the range. Toward the southwest in the Hurricane Deck area of the San Rafael Mountains, the unit becomes thicker and more extensively interbedded with mudstone. Lithology of the unit consists of 0.3-3.5 m thick beds of medium to coarse-grained, structureless to vaguely graded sandstone with scoured contacts at the base. Sandstone beds 0.3-3.0 m thick, which are more distinctly graded from coarse to very fine are also present. The interbedded mudstone commonly is bioturbated, so bedding is indistinct. Thickness ranges from 1020 m in the central part of the area to 750 m toward the southwest and 92 m toward the northwest. The unit most likely represents deposition in a submarine-canyon and fan complex that had its channel head in the northeast and spread southwestward into a thick sequence of submarine-fan sandstone lobes, which were confined in a narrow west-trending trough.

Thomas, G.D.; Fritsche, A.E.; Condon, M.W.

1988-03-01

328

Yucca in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

329

Chollas in Pine Creek Canyon  

USGS Multimedia Gallery

The Mojave Desert, home to drought-tolerant plants like Cholla cacti, gradually mixes with loblolly pine ecosystems in Pine Creek Canyon. Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Roc...

330

Yuccas in Pine Creek Canyon  

USGS Multimedia Gallery

The Mojave Desert, home to drought-tolerant plants like yuccas, gradually mixes with loblolly pine ecosystems in Pine Creek Canyon. Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Cany...

331

Manzanita in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

332

Rainbow Point of Bryce Canyon  

USGS Multimedia Gallery

View of Bryce Canyon National Park from Rainbow Point. In the foreground are sandstone hoodoos. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite ...

333

Bryce Canyon's Navajo Loop Trail  

USGS Multimedia Gallery

Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

334

Cedar Forest in Bryce Canyon  

USGS Multimedia Gallery

A cedar forest in Bryce Canyon National Park, viewed from Rainbow Point. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the ...

335

Cedar Forests of Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

336

Cedar Valley in Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

337

Snow-covered Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

338

Sunset in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

339

Sunset over Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

340

Sunset over Red Rock Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

341

Cedar Tree in Bryce Canyon  

USGS Multimedia Gallery

A cedar tree in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their ba...

342

Bryce Canyon Wall of Windows  

USGS Multimedia Gallery

Bryce Canyon's Wall of Windows, a series of sandstone arches and hoodoos in the Bryce Amphitheater. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolom...

343

Bryce Canyon's Wall of Windows  

USGS Multimedia Gallery

Bryce Canyon's Wall of Windows, a series of sandstone arches and hoodoos in the Bryce Amphitheater. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolom...

344

Rainbow Point of Bryce Canyon  

USGS Multimedia Gallery

View of Bryce Canyon National Park from Rainbow Point. In the foreground are sandstone hoodoos and in the background is the Grand Staircase-Escalante National Monument, which is managed by the Bureau of Land Management. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a ...

345

California State Waters Map Series--Hueneme Canyon and vicinity, California  

USGS Publications Warehouse

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Hueneme Canyon and vicinity map area lies within the eastern Santa Barbara Channel region of the Southern California Bight. The area is part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation - at least 90° - since the early Miocene has been proposed for the Western Transverse Ranges, and the region is presently undergoing north-south shortening. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area, which is offshore of the Oxnard plain and west of and along the trend of the south flank of the Santa Monica Mountains, lies at the east end of the Santa Barbara littoral cell, characterized by west-to-east littoral transport of sediment derived mainly from coastal watersheds. The Hueneme Canyon and vicinity map area in California's State Waters is characterized by two major physiographic features: (1) the nearshore continental shelf, and (2) the Hueneme and Mugu Submarine Canyon system, which, in the map area, includes Hueneme Canyon and parts of three smaller, unnamed headless canyons incised into the shelf southeast of Hueneme Canyon. The shelf is underlain by tens of meters of interbedded upper Quaternary shelf, estuarine, and fluvial deposits that formed as sea level fluctuated in the last several hundred thousand years. Hueneme Canyon extends about 15 km offshore from its canyon head near the dredged navigation channel of the Port of Hueneme. The canyon is relatively deep (about 150 m at the California's State Waters limit) and steep (canyon flanks as steep as 25° to 30°). Historically, Hueneme Canyon functioned as the eastern termination of the Santa Barbara littoral cell by trapping all eastward littoral drift, not only feeding the large Hueneme submarine fan but acting as the major conduit of sediment to the deep Santa Monica Basin; however, recent dredging programs needed to maintain Channel Islands Harbor and the Port of Hueneme have moved the nearshore sediment trapped by jetties and breakwaters to an area southeast of the Hueneme Canyon head. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft sediment and isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Hueneme Canyon and vicinity map area are related directly to the geomorphology and sedimentary processes that are the result of its Quaternary geologic history. The two basic megahabitats in the map area are Shelf (continental shelf) and Flank (continental slope). The flat seafloor of the continental shelf in the Hueneme Canyon and vicinity map area is dynamic, as indicated by mobile sand sheets and coarser grained scour depressions. The active Hueneme Canyon provides considerable relief to the continental shelf in the map area, and its irregular morphology of eroded walls, landslide scarps, and deposits and gullies provide promising habitat for groundfish, crabs, shrimp, and other marine benthic organisms. Most invertebrates observed in the map area durin

Johnson, Samuel Y.; Dartnell, Peter; Cochrane, Guy R.; Golden, Nadine E.; Phillips, Eleyne L.; Ritchie, Andrew C.; Kvitek, Rikk G.; Greene, H. Gary; Krigsman, Lisa M.; Endris, Charles A.; Clahan, Kevin B.; Sliter, Ray W.; Wong, Florence L.; Yoklavich, Mary M.; Normark, William R.

2012-01-01

346

Submarine daylight and ecology  

Microsoft Academic Search

The different parameters acting upon daylight before it reaches underwater organisms are discussed. Methods for measuring these parameters are reviewed, and lightsensing units equipped with hemispherical collectors and possessing a narrow spectral sensitivity band are recommended for use in marine biology. A new formula relating Secchi-disk readings to attenuation coefficients is proposed. A method is suggested which makes it possible

S. Weinberg

1976-01-01

347

Submarine groundwater discharge of nutrients to the ocean along a coastal lagoon barrier, Southern Brazil  

E-print Network

Submarine groundwater discharge of nutrients to the ocean along a coastal lagoon barrier, Southern the southern coast of Brazil is linked to the coastal ocean by a narrow mouth and by groundwater transport through a Holocene barrier. Although other groundwater systems are apparently active in this region

Jahnke, Richard A.

348

Submarine landslides in French Polynesia SUBMARINE LANDSLIDES IN SOCIETY AND AUSTRAL ISLANDS,  

E-print Network

Submarine landslides in French Polynesia 1 SUBMARINE LANDSLIDES IN SOCIETY AND AUSTRAL ISLANDS of numerous submarine landslides in French Polynesia. This inventory shows an evolution of the landslide type with the age of oceanic islands. Submarine active volcanoes are subject to superficial landslides of fragmental

Clouard, Valerie

349

Grand Canyon Explorer: The Geology of the Grand Canyon  

NSDL National Science Digital Library

This site provides an overview of how the Grand Canyon was formed. Concepts discussed include erosion by water, ice and wind, continental drift, and deposition. A photo gallery and stratigraphic figures support the text.

Ribokas, Bob

350

New York Canyon Stimulation  

SciTech Connect

The New York Canyon Stimulation Project was to demonstrate the commercial application of Enhanced Geothermal System techniques in Buena Vista Valley area of Pershing County, Nevada. From October 2009 to early 2012, TGP Development Company aggressively implemented Phase I of Pre-Stimulation and Site/Wellbore readiness. This included: geological studies; water studies and analyses and procurement of initial permits for drilling. Oversubscription of water rights and lack of water needed for implementation of EGS were identified and remained primary obstacles. Despite extended efforts to find alternative solutions, the water supply circumstances could not be overcome and led TGP to determine a "����No Go"��� decision and initiate project termination in April 2012.

Raemy, B. Principal Investigator, TGP Development Company, LLC

2012-06-21

351

An ongoing large submarine landslide at the Japan trench  

NASA Astrophysics Data System (ADS)

This paper deals with an active submarine landslide on a landward trench slope in the Japan trench. Studied area is located on the upper terrace ranging from 400 to 1200 m in water depth, off Sendai, northeast Japan. We have surveyed in detail the seabed topography using a multi narrow beam (hereafter MBES) and a subbottom profiler (hereafter SBP) during the cruise MR12-E02 of R/V Mirai. The survey lines were 12 lines in N-S, and 3 lines in E-W, and situated in the region from 141°45'E, 37°40'N to 142°33'E, 38°32'N. Moreover, we used multi-channel seismic profile by the cruise KR04-10 of R/V Kairei in the interpretation of the SBP results. In general, horseshoe-shaped depressions of about 100 km wide along the trench slope are arrayed along the Japan trench. It has thought that they were formed by large submarine landslides, but we could not understand critically the relationship between the depressions and the submarine landslides. Based on the survey results, we found signals of an active submarine landslide in the depression as follows. 1) We observed arcuate-shaped lineaments, which are sub-parallel to a horseshoe-shaped depression. The lineaments concentrate in the south region from 38°N at about 20 km wide. These lineaments are formed by deformation structures as anticlines, synclines and normal fault sense displacements. 2) Most of the synclines and anticlines are not buried to form the lineaments. 3) Normal faults cutting about 1 km deep are observed in a multi-channel seismic profile. The normal faults are located just below the arcuate-shaped lineaments, and are tilted eastward being the downslope direction. It indicates a large submarine landslide. We concluded that the arcuate-shaped lineaments were generated by surface sediment movement with the submarine landsliding. We think that the submarine landslide of about 20 km wide and about 1 km thick move continuously down the landward trench slope. This would be the formation process of the horseshoe-shaped depression along the Japan trench.

Nitta, S.; Kasaya, T.; Miura, S.; Kawamura, K.

2013-12-01

352

Calcareous nannoplankton and benthic foraminiferal assemblages from the Nazaré Canyon (Portuguese continental margin): Preliminary results  

NASA Astrophysics Data System (ADS)

Submarine canyons are assumed to play an important role in oceanic/neritic circulation, marine productivity and sedimentary processes, acting as preferential conduits between the littoral and deep oceanic domain. Here we present first results of a comparative micropalaeontological study on calcareous nannoplankton and benthic foraminifera from surface sediments from the surroundings of the upper Nazaré Canyon (Portuguese continental margin) and from the shelf north of the canyon. Regardless of the difficulty to distinguish taphonomical from (palaeo)ecological effects in such a complex and still poorly known marine system, the first results suggest that the canyon's hydro-sedimentary dynamic regime act as a prolongation of the shore/inner shelf hydrodynamic conditions towards west, preventing deposition and/or preservation of the smaller and fragile species of calcareous nannoplankton (e.g. E. huxleyi and G. ericsonii) and enhancing the record of the larger and more opportunistic ones (e.g. G. oceanica); and disturbing benthic foraminiferal productivity and/or diversity, or their preservation in the fossil record. Both calcareous nannoplankton and benthic foraminifera are more abundant off the canyon's domain, suggesting that its highly energetic thalweg conditions are probably filtering the fossil record in the sediment. Still, preliminary results suggest that the occurrence of persistent physical phenomena related with the canyon's morphology and proximity to the coast (e.g. solitary internal waves) may be locally promoting favourable conditions for calcareous nannoplankton, as shown by high values of nannoliths, chlorophyll a and 19' hexanoyloxyfucoxantine (unpublished data) north of the canyon's head. It is our goal to test this hypothesis in the near future by (a) studying multicore and surficial sediments from more recent surveys, and (b) calibrating the sediment results with water column data presently in process at the Institute of Oceanography (IO).

Guerreiro, C.; Rosa, F.; Oliveira, A.; Cachão, M.; Fatela, F.; Rodrigues, A.

2009-01-01

353

On sonobuoy placement for submarine tracking  

Microsoft Academic Search

This paper addresses the problem of detecting and tracking an unknown number of submarines in a body of water using a known number of moving sonobuoys. Indeed, we suppose there are N submarines collectively maneuvering as a weakly interacting stochastic dynamical system, where N is a random number, and we need to detect and track these submarines using M moving

Michael A. Kouritzin; David J. Ballantyne; Hyukjoon Kim; Yaozhong Hu

2005-01-01

354

Submarine Warfare in the A Bibliography  

E-print Network

Submarine Warfare in the 20th & 21st Centuries: A Bibliography Compiled by Michaele Lee Huygen 3D, 1966. p. 205. This bibliography is a revised edition of the bibliography Submarine Warfare in the 20th & 21st Centuries, 2003, which is in turn a revised and expanded version of Submarine Warfare in the 20

355

Direct measures of Submarine Groundwater Discharge (SGD)  

E-print Network

Page: 1 Direct measures of Submarine Groundwater Discharge (SGD) over a fractured rock aquifer of submarine groundwater discharge (SGD) have been made, but measurements along the South American coast of submarine, freshwater springs have been recognized in the folk wisdom of millennia, the scientific inquiry

356

Northern Current variability and its impact on the Blanes Canyon circulation: A numerical study  

NASA Astrophysics Data System (ADS)

A high-resolution (?1.2 km) 3D numerical model was used to analyze the interaction of the Northern Current (a right-bounded flow) with the Blanes submarine canyon (BC, NW Mediterranean). Although it refers to a climatological simulation the model properly suites our purpose since it simulates the Northern Current (NC) mesoscale variability, as well as its seasonal variability. Model results were validated with satellite sea surface temperature and current-meter data. The simulated NC tends to be faster and deeper in winter, and slower and shallower in summer. According to our results, NC meanders and eddies are recurrent in the BC area and produce highly fluctuating three-dimensional circulation patterns within the canyon. We found that NC meanders and anticyclonic eddies propagating along the current pathway tend to be deep and, consequently, their effects extend down to the deeper part of the BC. We also found that the meandering of the NC plays a key role in enhancing vertical motions inside the BC. Upwelling and downwelling events occurring on timescales of 4-20 days are associated with NC meanders crests and troughs passing over the BC. Net upwelling/downwelling events are accordingly influenced by the NC seasonality. They are more predominant in winter, while damped in summer. Our results show the importance of NC meanders in creating local net upwelling/downwelling and strengthen the evidence that continuous right-bounded (downwelling favorable) flows can also produce net upwelling inside submarine canyons.

Ahumada-Sempoal, M.-A.; Flexas, M. M.; Bernardello, R.; Bahamon, N.; Cruzado, A.

2013-11-01

357

Grand Canyon: The Hidden Secrets  

NSDL National Science Digital Library

Summertime means vacations for many people, and for many of these sojourning to the American Southwest, this may mean a trip to the brilliance that is the Grand Canyon in northern Arizona. The people at National Geographic certainly know this area quite well, as they have sponsored a number of research expeditions there over the past century or so. Designed as a way to publicize the film that the organization plays at their canyon visitor center, this site contains a number of helpful features for those persons who may be visiting the canyon. First, visitors will want to look at the interactive map of the South Rim offered here. The map allows visitors to learn about selected features of the area, such as the famous bald eagles, the various outlooks, and the plants indigenous to the region. The site also includes a section for young people, a number of free screensavers and wallpapers, along with a travel guide to visiting the Grand Canyon.

358

Canyon waste dump case study  

SciTech Connect

This data packet contains the Canyonville Canyon Waste Dump results of the various physical environmental sampling. Core samples were taken from the on site waste material. Vertical grab samples were made from these borings. The waste samples were screened fro volatile organic compounds (VOC) and logged for lithology. Soil samples were also tested for VOC. Composite sediment samples were taken using a coring device known as a clam gun. No surface water was available for testing from the intermittent Canyon Wash. The hydrogeology of the Canyon Waste Dump was inferred from lithologic logs and hydraulic data from the five monitoring wells located along the canyon floor. Groundwater was monitored through five wells. The soil vapor and air screening techniques used were adaptations of the EPA ERT and NIOSH methodologies. 4 figs., 9 tabs.

Land, M.D.; Brothers, R.R. (Tennessee Univ., Knoxville, TN (United States)); McGinn, C.W. (Oak Ridge National Lab., TN (United States))

1991-01-01

359

Habitat characterization of deep-water coral reefs in La Gaviera Canyon (Avilés Canyon System, Cantabrian Sea)  

NASA Astrophysics Data System (ADS)

Surveys conducted at the complex Avilés Canyon System (southern Bay of Biscay) in order to identify vulnerable habitats and biological communities revealed the presence of noteworthy deep-water coral reefs in one of the tributaries of the system (La Gaviera Canyon). The aim of the present study is to determine why this deep-sea canyon provides suitable environmental conditions for corals to grow. This hanging canyon is characterized by an irregular U-shaped floor with two narrow differentiated flanks. Sand ripples and rocky outcrops structured in diverse W-E directed steps are observed on the canyon floor, suggesting intense hydrodynamic activity. Accordingly, high-frequency near-bottom current and thermal structure profiles showed that there occur strong shifts in currents/hydrography behaving as front-like features at each tidal cycle. These involve the sudden increase of along-axis velocities to over 50 cm/s and vertical velocities of over 5 cm/s in each tidal cycle associated with the passage of sharp thermal fronts and thermal inversions suggesting overturning. A year-long near-bottom current record showed events with near-bottom velocities well over 1 m/s lasting for several days. Three cold-water coral settings were distinguished: a dense coral reef located on stepped rocky bottoms of the eastern and western flanks, carbonate mounds (20-30 m high) located on the canyon floor, and a cluster of shallower water dead coral framework at the head sector of the canyon. Video and still images from a towed sled and ROV verified the presence of dropstones and rippled sand sheets surrounding the mounds and revealed changes in the coral population (alive or dead; total or patchy coverage) in coral reef and carbonate mound areas. The dominant species of the reef are Lophelia pertusa and Madrepora oculata, which considerably increase the habitat?s complexity and biodiversity in relation to other facies described in the canyon. The presence of living cold-water reefs is directly related to a high-energy environment at depths between 700 and 1200 m in the levels between the lower bound of Eastern North Atlantic Central Water (ENACW) and the core of Mediterranean Water (MW). Such level matches the water density range ??=27.35-27.65 kg m-3 which has been identified as limits for cold-water coral distribution in the North Atlantic.

Sánchez, Francisco; González-Pola, Cesar; Druet, María; García-Alegre, Ana; Acosta, Juan; Cristobo, Javier; Parra, Santiago; Ríos, Pilar; Altuna, Álvaro; Gómez-Ballesteros, María; Muñoz-Recio, Araceli; Rivera, Jesus; del Río, Guillermo Díaz

2014-08-01

360

Hawaiian submarine manganese-iron oxide crusts - A dating tool?  

USGS Publications Warehouse

Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae landslide southwest of Oahu has yielded samples with the greatest manganese-iron oxide crusts (9.5 mm thick) and therefore apparently represents the oldest submarine material yet found in the study area. The submarine volcanic field 100 km southwest of Oahu is apparently younger than the Waianae landslide. ?? 2004 Geological Society of America.

Moore, J.G.; Clague, D.A.

2004-01-01

361

Implications for the Removal of Invasive Species in Canyon de Chelly National Monument  

Technology Transfer Automated Retrieval System (TEKTRAN)

As part of a study to investigate the causes of channel narrowing and incision in Canyon de Chelly National Monument, the effects of Tamarisk and Russian-olive on streambank stability were evaluated. Root tensile strengths and distributions in streambanks were measured and used in combination in a r...

362

Sedimentologic and tectonic factors controlling growth and dimensions of submarine fans  

SciTech Connect

The morphology, development, composition, and structure of submarine fans reflect five controlling factors. Grain-size distribution - sandy debris results in radial fans, whereas mud-dominated debris promotes elongate fans. Eustacy - during high sea-level stands, fan growth is curtailed as sediment, especially coarse sediment, is trapped in paralic settings, whereas during low stands, fan growth is accelerated owing to direct access of sediment to canyon heads and the flushing of debris from shelf areas. Basin architecture - confined or unconfined. Penecontemporaneous tectonics from seismic triggering to migrating source terranes. Postdepositional tectonics that bias or alter lithofacies preservation - bias in sediment subduction results in the preferential loss of distal facies.

Howell, D.G.

1984-04-01

363

On sonobuoy placement for submarine tracking  

NASA Astrophysics Data System (ADS)

This paper addresses the problem of detecting and tracking an unknown number of submarines in a body of water using a known number of moving sonobuoys. Indeed, we suppose there are N submarines collectively maneuvering as a weakly interacting stochastic dynamical system, where N is a random number, and we need to detect and track these submarines using M moving sonobuoys. These sonobuoys can only detect the superposition of all submarines through corrupted and delayed sonobuoy samples of the noise emitted from the collection of submarines. The signals from the sonobuoys are transmitted to a central base to analyze, where it is required to estimated how many submarines there are as well as their locations, headings, and velocities. The delays induced by the propagation of the submarine noise through the water mean that novel historical filtering methods need to be developed. We summarize these developments within and give initial results on a simplified example.

Kouritzin, Michael A.; Ballantyne, David J.; Kim, Hyukjoon; Hu, Yaozhong

2005-05-01

364

Digital Transmission over Submarine Cables  

Microsoft Academic Search

The problems of transoceanic transmission of large volumes of information have been raised increasingly over the past few years. Lately, the need for transoceanic digital communications has been of interest. This paper discusses the significance of these trends and examines the technical prospects for handling large volumes of digital traffic using submarine cables. Concentrating on transatlantic traffic, an argument is

W. Litchman

1965-01-01

365

The Dangeard and Explorer canyons, South Western Approaches UK: Geology, sedimentology and newly discovered cold-water coral mini-mounds  

NASA Astrophysics Data System (ADS)

The Celtic Margin is a complex area in terms of sedimentary dynamics and evolution, with a number of submarine canyons dissecting the continental slope and outer continental shelf. The complex terrain and diverse range of sea-bed sediments play a part in submarine canyons being described as areas of high habitat heterogeneity. This study has concentrated on the heads of two canyons: Dangeard (also known as Dangaard) and Explorer (first named here) located in UK territorial waters, in water depths between 138 and 1165 m. Multibeam echosounder, 2D reflection seismic and photographic ground-truthing data have been combined to map the sea-bed geomorphology, sedimentary features and canyon megafauna of these canyons. In addition, two previously unknown provinces of cold-water coral (CWC) mini-mounds were discovered on the interfluves of the Dangeard and Explorer canyons. The study area comprises a dendritic network of gullies feeding into the canyon thalwegs. Amphitheatre rims, where slope angles are commonly in excess of 20°, occur along the margins and heads of both canyons and are interpreted as drainage basins indicative of retrogressive mass-wasting in a shelfward direction. The CWC mini-mounds occur in water depths between 250 m and 410 m, with more than 400 mounds identified. They are up to 3 m in height and 50-150 m in diameter with no sub-surface expression, suggesting these mounds are, in geological terms, relatively young and possibly Holocene in age. Biological analyses revealed that the mounds form a habitat for ophiuroids and Munida associated with Lophelia pertusa coral rubble, suggesting these mini-mounds are not present-day living features.

Stewart, Heather A.; Davies, Jaime S.; Guinan, Janine; Howell, Kerry L.

2014-06-01

366

Snake Hells Canyon Subbasin Management Plan  

E-print Network

Snake Hells Canyon Subbasin Management Plan May 2004 Prepared for the Northwest Power and Conservation Council Subbasin Team Leader Nez Perce Tribe Watershed Division Written by Ecovista #12;Snake...............................................................................8 4 VISION FOR THE SNAKE HELLS CANYON SUBBASIN

367

30. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONNECTICUT. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

30. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONNECTICUT. 2 JUNE 1930. SUBMARINE TRAINING TANK - STEELWORK 98% COMPLETE; BRICKWORK 95% COMPLETE, PIPING 10% IN PLACE. LOOKING NORTH. CONTRACT NO. Y-1539-ELEVATOR, SUBMARINE ESCAPE TANK.' - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

368

The design and installation of a subsurface trimoor over Scripps and Lajolla canyons  

SciTech Connect

As subsea suspended cable structure technology develops, suspended cable structures are becoming a practical means of supporting oceanographic instrumentation systems. A cable structure is presented that suspends a data collection system into a 2,500-ft (760 m) wide submarine canyon. Extensive computer simulations were used to estimate mooring line tensions, anchor loads, and the ability of the structure to hold the payload in the required location. The effects of mooring angle, line size, oceanic environment, and vessel attachment to the structure are discussed. The installation and the capability to fine-tune the final configuration are also discussed.

McAllister, T.P.; Wilson, J.V.

1983-01-01

369

Geology Fieldnotes: Grand Canyon National Park, Arizona  

NSDL National Science Digital Library

Visitors can access park geology information, photographs, related links, visitor information, multimedia resources, and resources for teaching geology with National Park examples. The park geology section discusses the Grand Canyon's geologic history, structural geology, and features a question-and-answer section about the canyon. The history of the canyon as a park and environmental issues surrounding it are also discussed. A geologic cross section of the canyon showing the various rock layers is included.

370

34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION OF BLISTERS IN 1959, LOOKING SOUTHEAST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

371

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2011-07-01

372

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2012-07-01

373

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2013-07-01

374

32 CFR 707.7 - Submarine identification light.  

...2014-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2014-07-01

375

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 2010-07-01 false Submarine identification light. 707.7 Section...ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a distinctive...

2010-07-01

376

UNCORRECTEDPROOF Hydrogeology and geochemistry of near-shore submarine  

E-print Network

UNCORRECTEDPROOF Hydrogeology and geochemistry of near-shore submarine groundwater discharge rates based on tidal signal and hydraulic gradient analysis indicate a fresh submarine groundwater discharge in this high rainfall region. Ã? 2007 Published by Elsevier Ltd. Keywords: submarine groundwater

377

Submarines, spacecraft and exhaled breath.  

PubMed

Foreword The International Association of Breath Research (IABR) meetings are an eclectic gathering of researchers in the medical, environmental and instrumentation fields; our focus is on human health as assessed by the measurement and interpretation of trace chemicals in human exhaled breath. What may have escaped our notice is a complementary field of research that explores the creation and maintenance of artificial atmospheres practised by the submarine air monitoring and air purification (SAMAP) community. SAMAP is comprised of manufacturers, researchers and medical professionals dealing with the engineering and instrumentation to support human life in submarines and spacecraft (including shuttlecraft and manned rockets, high-altitude aircraft, and the International Space Station (ISS)). Here, the immediate concerns are short-term survival and long-term health in fairly confined environments where one cannot simply 'open the window' for fresh air. As such, one of the main concerns is air monitoring and the main sources of contamination are CO(2) and other constituents of human exhaled breath. Since the inaugural meeting in 1994 in Adelaide, Australia, SAMAP meetings have been held every two or three years alternating between the North American and European continents. The meetings are organized by Dr Wally Mazurek (a member of IABR) of the Defense Systems Technology Organization (DSTO) of Australia, and individual meetings are co-hosted by the navies of the countries in which they are held. An overriding focus at SAMAP is life support (oxygen availability and carbon dioxide removal). Certainly, other air constituents are also important; for example, the closed environment of a submarine or the ISS can build up contaminants from consumer products, cooking, refrigeration, accidental fires, propulsion and atmosphere maintenance. However, the most immediate concern is sustaining human metabolism: removing exhaled CO(2) and replacing metabolized O(2). Another important concern is a suite of products from chemical reactions among oxidizing compounds with biological chemicals such as amines, thiols and carbonyls. SAMAP Meeting We (Armin and Joachim) attended the 2011 SAMAP conference in Taranto, Italy (10-14 October), which occurred just a few weeks after the IABR meeting in Parma, Italy (11-15 September 2011). It was held at the Officers' Club of the Taranto Naval Base under the patronage of the Italian navy; the local host was Lucio Ricciardi of the University of Insubria, Varese, Italy. At the 2011 SAMAP meeting, the theme was air-independent propulsion (AIP), meaning the capability of recharging the main batteries of the submarine without the need to surface. Only a few navies (e.g. US, UK, France, Russia, China) have historically had this capability using nuclear-powered submarines that can function underwater for extended periods of time (months). Most navies operate submarines with conventional diesel-electric propulsion, wherein diesel-powered generators charge battery banks which then drive an electric motor connected to the propeller. The batteries are charged while the boat is on the surface or during snorkelling, when the boat is submerged a few meters below the surface and a snorkel tube is extended to the surface. The period between battery charges can vary from several hours to one or two days depending on the power requirements and the nature of the mission. The process is necessary for breathing air revitalization (flushing out accumulated contaminants) and for the operation of the diesel engines. However, during this period the submarine is vulnerable to detection. Since the 1940s there have been various attempts to develop a power generation system that is independent of external air (AIP). To this end hydrogen peroxide was initially used and later liquid oxygen (LOX). Currently, most AIP submarines use fuel cell technology (LOX and hydrogen) to supplement the conventional diesel-electric system in order to extend the underwater endurance to 2-3 weeks. These propulsion engineering changes also reduce per

Pleil, Joachim D; Hansel, Armin

2012-03-01

378

Russian nuclear-powered submarine decommissioning  

SciTech Connect

Russia is facing technical, economic and organizational difficulties in dismantling its oversized and unsafe fleet of nuclear powered submarines. The inability of Russia to deal effectively with the submarine decommissioning crisis increases the risk of environmental disaster and may hamper the implementation of the START I and START II treaties. This paper discusses the nuclear fleet support infrastructure, the problems of submarine decommissioning, and recommends international cooperation in addressing these problems.

Bukharin, O. [Princeton Univ., NJ (United States); Handler, J. [Greenpeace International`s Disarmament Campaign, Washington, DC (United States)

1995-11-01

379

Saga is largest commercial submarine ever  

SciTech Connect

The long-range autonomous submarine, Saga, went nuclear last year with an agreement between the French and two Canadian companies. The agreement to convert the prototype from Swedish Stirling closed-cycle combustion engines to a nuclear power supply will make Saga the first non-defense nuclear submarine. With an external hull displacement of 500 tons, Saga will be the largest commercial submarine ever built.

Not Available

1985-05-01

380

Tsunami Modeling from Submarine Landslides  

NSDL National Science Digital Library

This paper describes a kinematic model that computes tsunamis generated from submarine landslides. The model is based on bathymetric (ocean floor modeling) data and historical tsunami data. The papers' main focus is the application of the model to the 1741 Oshima-Oshima Tsunami in Japan and landslide events around the Hawaiian Islands. This paper was presented at the U.S. National Tsunami Hazard Mitigation Program Review and International Tsunami Symposium in Seattle, Washington on August 10, 2001.

Satake, Kenji; National Oceanic and Atmospheric Administration (NOAA)

381

Attributes and origins of ancient submarine slides and filled embayments: Examples from the Gulf Coast basin  

SciTech Connect

Large submarine slides and associated shelf margin embayments represent an intermediate member in the continuum of unstable shelf margin features. On seismic profiles, they may resemble submarine canyons, but are different in their size, morphology, origin, and hydrocarbon exploration potential. Two large Neogene submarine slides, located in the northwestern Gulf Coast Basin, formed on the upper slope and flanks of prominent shelf-margin deltas. The basal detachment surface of each slide is a structural discontinuity that may be misinterpreted as an erosional unconformity and misidentified as a stratigraphic boundary separating depositional sequences. Regional stratigraphic correlations indicate that both slides were initiated after the continental platform was flooded. The condensed sections deposited during the rise in relative sea level contain the basal detachment surfaces. The relationships between the slides and sea level fluctuations are uncertain. The shelf-margin embayments created by the slides apparently were partly excavated during periods of lowered relative sea level and were filled during sea level rise and highstand. Eventually the preslide morphology of the shelf margin was restored by coalsced prograding deltas. Submarine slides exhibit landward dipping, wavy, mounded, and chaotic seismic reflection that are manifestations of slump blocks and other mass transport material. Composition of these internally derived slide deposits depends on th composition of the pre-existing shelf margin. Embayment fill above the slide consists mostly of externally derived mudstones and sandstones deposited by various disorganized slope processes, as well as more organized submarine channel-level systems. Thickest slope sandstones, which are potential hydrocarbon reservoirs, commonly occur above the basal slide mudstones where seismic reflections change from chaotic patterns to overlying wavy or subhorizontal reflections. 46 refs., 10 figs., 1 tab.

Morton, R.A. (Univ. of Texas, Austin (United States))

1993-06-01

382

ewly discovered at the bottom of the Hudson Canyon, the largest submarine canyon off the eastern United States, is  

E-print Network

United States, is a series of pits venting methane gas into the waters around the continental shelf-swimming underwater vehicle Eagle Ray (above) allowed scientists to map the contours of the pits that were venting, a "smart" technology that is capable of

Garfunkel, Eric

383

Tubes at Glen Canyon Dam  

USGS Multimedia Gallery

The river outlet tubes at Glen Canyon Dam on the Colorado River in Arizona. At noon Monday, Nov. 19, U.S. Interior Secretary Ken Salazar will open the dam's river outlet tubes, releasing controlled flows larger than the usual 8,000-25,000 cubic feet per second that flows through the turbines of...

384

Amplification of bedrock canyon incision by wind  

NASA Astrophysics Data System (ADS)

Bedrock canyons etch much of the surface of Earth and Mars, and commonly inform interpretations of long-term hydrologic or tectonic changes within these landscapes. However, many bedrock canyons (particularly on Mars) exist in arid environments where wind abrasion can dramatically alter surface morphology. Although it is hypothesized that wind carves or modifies bedrock canyons on Mars, the interplay of wind and fluvial processes in shaping canyon landscapes is, to our knowledge, unexplored. Consequently, here we exploit a natural experiment along the 4.09 Ma Puripicar ignimbrite, situated on the western slope of the Andes in the Atacama Desert and subject to significant erosion from both wind and rivers. The Puripicar exhibits a series of bedrock gorges nested behind a broad north-south escarpment whose southern half is protected from wind by a large topographic barrier. This shielding provides a natural control to examine the effects of wind abrasion on canyon morphology and in particular knickpoint retreat. Our results show that for a given drainage area, knickpoints in wind-affected canyons have incised an order of magnitude farther upstream than wind-protected canyons. In addition, wind-affected canyons are wider and have more streamlined aspect ratios for a given drainage area than wind-protected canyons. Aeolian abrasion appears to result in knickpoints with average slopes half those of shielded canyons (0.2 and 0.4, respectively). Lastly, although the magnitude of knickpoint retreat is larger in wind-affected canyons, the scaling exponent between knickpoint retreat and drainage area is virtually identical for wind-affected canyons (0.56, R = 0.71) and wind-protected canyons (0.60, R = 0.80). Taken together, our results suggest that fluvial incision and wind abrasion are coupled processes in this landscape: convergent canyons funnel wind towards knickpoints, thereby leading to enhanced aeolian abrasion rates at knickpoints. We speculate that the apparent drainage area dependence of knickpoint retreat in wind-affected canyons reflects the fact that larger rivers create wider canyon mouths. Larger canyons mouths, in turn, increase wind convergence and drive higher aeolian abrasion rates at the heads of larger canyons. This study is the first to demonstrate knickpoint retreat via wind abrasion, and highlights that even in landscapes where large river gorges are present, wind may still exert a dominant control on canyon morphology.

Perkins, J. P.; Finnegan, N. J.; de Silva, S. L.

2013-12-01

385

The role of upper-regime flow bedforms in the morphodynamics of submarine channels  

NASA Astrophysics Data System (ADS)

Advances in acoustic imaging of submarine canyons and channels have provided accurate renderings of seafloor geomorphology. Still, a fundamental understanding of channel inception, evolution, sediment transport, and the nature of the currents traversing these channels remains elusive. Here, we review a mosaic of geomorphology, shallow stratigraphy, and morphodynamics of channelized deep-water depositional systems of tectonically active slopes offshore of California, USA. These systems are imaged in high-resolution multi-beam sonar bathymetry (dominant frequency ~200 kHz) and seismic-reflection (2-16 kHz) data. From north to south, the Monterey East, Lucia Chica, and San Mateo channelized deep-water depositional systems show a breadth of geomorphology and stratigraphic architecture, including channel reaches of varying sinuosity, levees, terraces within channels, and crescent-shaped bedforms, especially in the thalwegs of incipient channel elements. Morphodynamic numerical modeling is combined with interpretations of seafloor and shallow subsurface stratigraphic imagery to demonstrate that the crescent-shaped bedforms common to channel thalwegs are likely to be cyclic steps. We propose that net-erosional and net-depositional cyclic steps play a fundamental role in the formation, filling, and maintenance phases of submarine channels in continental margins with high gradient, locally rugose bathymetry. These margins include passive-margin slopes subjected to gravity-driven tectonic deformation. In such settings, high gradients support the development of densimetric Froude-supercritical turbidity currents, and abrupt slope breaks can promote hydraulic jumps and the spontaneous evolution of an erodible seabed into cyclic steps. This morphodynamic investigation of turbidity currents and the seafloor has the potential to enhance prediction of the locations, stratigraphic evolution, and architecture of submarine canyon-channel systems.

Covault, Jacob A.; Kostic, Svetlana; Fildani, Andrea

2014-05-01

386

Stress release, joints, and instability on submarine slopes  

SciTech Connect

Mass movements related to gradual stress release within a sediment section may be quantitatively important on submarine slopes, particularly when such stress release involves joint sets. The sequence of events that promotes this phenomenon has been established by numerous terrestrial studies. The process involves: mass wasting or erosion to remove vertical stress (overburden) or lateral stress (such as through canyon cutting); consequent elastic rebound of the unloaded section; and opening of existing joints and/or formation of new joint sets. The presence of joints, which constitute planes of weakness within the sediment section, controls and reduces the stability of the affected slope; that is, the stability of the slope may no longer be dependent on the inherent strength of the sediments. The results of this process have been observed on the continental slope off the Mid-Atlantic coast of the United States. There, exposed Tertiary sediments have a well-developed joint pattern that has been observed in sidescan-sonar images, from submersible operations, and in a piston core. The measured preconsolidation stress on an Eocene core sample suggests that more than 100 m (330 ft) of overburden may have been removed from parts of the area. Intact Eocene blocks, which represent apparent failure along joint planes, have fallen from canyon walls on the lower slope and moved onto the upper rise. It is suggested that this process has the potential to operate on most deeply eroded surfaces and that exhumed (overconsolidated) sediments do not necessarily represent stable conditions despite their typical high shear strengths.

Booth, J.S.; Robb, J.M.

1984-04-01

387

Research on Submarine Maneuverability of Flooded Compartment  

Microsoft Academic Search

The paper establishes the emergency recovery maneuver motion model. According to the characteristic of hydrodynamics coefficients on flooded submarine, attaining hydrodynamics coefficients of different angle of attack by limited ship model hydrodynamics experiment of large angle of attack. A sensitivity index is introduced to evaluate submarine's controllability. The experiment results are regressed to two kinds of hydrodynamic coefficients for big

Liu Hui; Pu Jinyun; Jin Tao

2009-01-01

388

THE SUBMARINE REVIEW FIXED SONAR SYSTEMS  

E-print Network

is the detection of submerged vessels approaching our shores. Since World War I, sonar has been used with varying sonar hydrophones, developed during World War I, could detect submarines from several miles away degrees of success to detect submarines. By the end of World War II, it was considered the premier sensor

389

Reactivity Accident of Nuclear Submarine near Vladivostok  

Microsoft Academic Search

After the collapse of the Soviet Union and consequently the termination of the Cold War and the disarmament agreements, many nuclear warheads are in a queue for dismantling. As a result, substantial number of nuclear submarines equipped with ballistic missiles will be also withdrawn from service. However, Russian nuclear submarines have suffered from reactivity accidents five times. In the paper,

Makoto TAKANO; Vanya ROMANOVA; Hiromi YAMAZAWA; Yuri SIVINTSEV; Keith COMPTON; Vladimir NOVIKOV; Frank PARKER

2001-01-01

390

Submarine landslide geomorphology, US continental slope  

Microsoft Academic Search

The morphometric analysis of submarine landslides in four distinctly different tectonic environments on the continental slopes of Oregon, central California, Texas, and New Jersey provides useful insight into submarine process, including sediment transport mechanisms and slope stability. Using Geographic Information System (GIS) software, we identify landslides from multibeam bathymetric and GLORIA sidescan surveys based solely on surficial morphology and reflectivity.

B. g. Mcadoo; L. f. Pratson; D. l. Orange

2000-01-01

391

Submarine landslide flows simulation through centrifuge modelling  

E-print Network

SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING by Chang Shin GUE A dissertation submitted for the degree of Doctor of Philosophy at the University of Cambridge Churchill College January... “Continuous effort – not strength or intelligence – is the key to unlocking our potential” - Winston Churchill ABSTRACT SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING Chang Shin GUE Landslides occur both onshore...

Gue, Chang Shin

2012-05-08

392

Mineral resources of the Coal Canyon, Spruce Canyon, and Flume Canyon Wilderness Study Areas, Grand county, Utah  

SciTech Connect

This paper reports on the Coal Canyon, Spruce Canyon, and Flume Canyon Wilderness Study Areas in the Book and Roan Cliffs in Grand Country, Utah, approximately 12 miles west of the Colorado state line. The wilderness study areas consist of a series of deep, stair-step-sided canyons and high ridges eroded into the flatlying sedimentary rocks of the Book Cliffs. Demonstrated coal reserves totaling 22,060,800 short tons and demonstrated subeconomic coal resources totaling 39,180,000 short tons are in the Coal Canyon Wilderness Study Area. Also, inferred subeconomic coal resources totaling 143,954,000 short tons are within the Coal Canyon Wilderness Study Area. No known deposits of industrial minerals are in any of the study area. All three of the wilderness study areas have a high resource potential for undiscovered deposits of coal and for undiscovered oil and gas.

Dickerson, R.P.; Gaccetta, J.D.; Kulik, D.M.; Kreidler, T.J.

1990-01-01

393

Carbonate apron models: Alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration  

USGS Publications Warehouse

Sediment gravity flow deposition along the deep-water flanks of carbonate platforms typically does not produce submarine fans. Rather, wedge-shaped carbonate aprons develop parallel to the adjacent shelf/slope break. The major difference between submarine fans and carbonate aprons is a point source with channelized sedimentation on fans, versus a line source with sheet-flow sedimentation on aprons. Two types of carbonate aprons may develop. Along relatively gentle (< 4??) platform-margin slopes, aprons form immediately adjacent to the shallow-water platform and are referred to as carbonate slope aprons. Along relatively steep (4-15??) platform margin slopes, redeposited limestones accumulate in a base-of-slope setting, by-passing an upper slope via a multitude of small submarine canyons, and are referred to as carbonate base-of-slope aprons. Both apron types are further subdivided into inner and outer facies belts. Inner apron sediments consist of thick, mud-supported conglomerates and megabreccias (Facies F) as well as thick, coarse-grained turbidites (Facies A) interbedded with subordinate amounts of fine-grained, peri-platform ooze (Facies G). Outer apron sediments consist of thinner, grain-supported conglomerates and turbidites (Facies A) as well as classical turbidites (Facies C) with recognizable Bouma divisions, interbedded with approximately equal proportions of peri-platform ooze (Facies G). Seaward, aprons grade laterally into basinal facies of thin, base-cut-out carbonate turbidites (Facies D) that are subordinate to peri-platform oozes (Facies G). Carbonate base-of-slope aprons grade shelfward into an upper slope facies of fine-grained peri-platform ooze (Facies G) cut by numerous small canyons that are filled with coarse debris, as well as intraformational truncation surfaces which result from submarine sliding. In contrast, slope aprons grade shelfward immediately into shoal-water, platform-margin facies without an intervening by-pass slope. The two carbonate apron models presented here offer alternatives to the submarine-fan model for paleoenvironmental analysis and hydrocarbon exploration for mass-transported carbonate facies. ?? 1986.

Mullins, H.T.; Cook, H.E.

1986-01-01

394

Mineral resources of the Fish Creek Canyon, Road Canyon, and Mule Canyon Wilderness Study Areas, San Juan County, Utah  

Microsoft Academic Search

This book reports the Fish Creek Canyon (UT-060-204), Road Canyon(UT-060-201), and Mule Canyon (UT-060-205B) Wilderness Study Areas, which comprise 40,160 acres, 52,420 acres, and 5,990 acres, respectively, studied for their mineral endowment. A search of federal, state, and county records showed no current or previous mining-claim activity. No mineral resources were identified during field examination of the study areas. Sandstone

D. J. Bove; D. R. Shawe; G. K. Lee; W. F. Hanna; R. E. Jeske

1989-01-01

395

Modes of development of slope canyons and their relation to channel and levee features on the Ebro sediment apron, off-shore northeastern Spain  

USGS Publications Warehouse

Six submarine slope canyons in an area of the northwestern Mediterranean, offshore from the Ebro River and Delta, were surveyed with bathymetric swathmapping (SeaBeam) and mid-range side-looking sonar (SeaMARC I). All of the canyons have slightly winding paths with concave-upwards gradients that are relatively steep shallower than 1,200 m. Two major types of canyons are identified on the basis of their morphologic character at the base of the slope; Type-I canyons lead to an unchannelled base-of-slope deposit and Type-II canyons are continuous with channel-levee systems that cross the rise. Four Type-I canyons were surveyed in the area. Two of these are broad, U-shaped, steep (average gradients of 1:14), do not indent the shelf, and terminate downslope at debris-flow deposits. These two canyons, the most northern in the area, have rounded heads with extensive gullies separated by knife-edge ridges. Relief of the canyon walls is about equal on both sides of the canyons, although the right-hand walls (looking downslope) are generally steeper. The other two Type-I canyons in the area are similar in that they do not indent the shelf, but they are much smaller and shallower and coalesce before terminating in the base-of-slope region. The two Type-II canyons that feed leveed-channels are U-shaped with flatter floors, longer profiles and gentler gradients than Type-I canyons. They are closer to the Valencia Valley and have relatively small cross-sectional areas. We propose a four-stage evolutionary sequence to explain the development of the canyons observed in this section on the prograding Ebro margin. During the initial stage, slumping and erosion on the slope creates a network of small gullies. During the next stage, headward growth of one (or more) gully leads to a major indentation of the shelf. This is the critical factor for developing a channel that will incise the slope and provide a major conduit for moving sediment to the basin. Stage 3 is characterized by the development of a continuous channel accompanied by levee growth across the lobe. In the final stage, the channel-levee system becomes inactive either through destruction by mass wasting, infilling of the channel, or loss of the major sediment source. ?? 1987.

O'Connell, S.; Ryan, William B. F.; Normark, W.R.

1987-01-01

396

32. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONN. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

32. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONN. OCTOBER 3, 1932. COMPLETION OF ERECTION OF STEELWORK FOR ELEVATOR. LOOKING NORTH. CONTRACT NO. Y-1539-ELEVATOR, SUBMARINE ESCAPE TANK.' - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

397

29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT POINT JUST ABOVE THE SUBMARINE SECTION AT THE 110-FOOT LEVEL 1929-1930 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

398

78 FR 7810 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2013-02-04

399

76 FR 24516 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2011-05-02

400

77 FR 9265 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2012-02-16

401

77 FR 43117 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2012-07-23

402

78 FR 21415 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2013-04-10

403

77 FR 22801 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY: Bureau of Reclamation...The Glen Canyon Dam Adaptive Management Work Group (AMWG) makes recommendations to...advisory committee, the AMWG, a technical work group, a Grand Canyon Monitoring and...

2012-04-17

404

De-Stabilization of Streambanks by Removal of Invasive Species in Canyon de Chelly National Monument, Arizona  

Technology Transfer Automated Retrieval System (TEKTRAN)

As part of a study to investigate the causes of channel narrowing and incision in Canyon de Chelly National Monument, the effects of Tamarisk and Russian-olive on streambank stability were evaluated. The National Park Service (NPS) is currently engaged in an experimental program to remove the invasi...

405

Sea Ice Properties from Submarine Multi Beam Sonar  

NASA Astrophysics Data System (ADS)

A Konsberg EM 3002 Multibeam (MB) sonar was installed on Royal Navy submarine ‘HMS Tireless' in collaboration with the DAMOCLES project to measure properties of Arctic sea ice in Spring 2007. MB sonar makes successive, parallel, along-track narrow beam soundings comprised of 254 individual ‘pings' spread out perpendicular to the direction of motion of the parent vessel. Reconstructed multiple soundings provide high-resolution descriptions and locations of physical features of interest to mariners, i.e. submerged vessels, bathymetry of continental shelves and navigation hazards. HMS Tireless looked upward with the MB sonar, gathering data on the highly variable Arctic sea ice underside. We present 200 km of MB data, in a region located 350 km off the northern coast of Greenland, where the submarine performed a gridded overlapping survey between 12 and 13 March 2007. This ice topography data includes pressure ridge spacing, frequency and orientation, draft, and we demonstrate its ability to demarcate regions of first-year and multi-year ice.

Toberg, Nicholas; Wagner, Till

2010-05-01

406

Nicolas and Eel submarine fans, California continental borderland  

SciTech Connect

Nicolas and Eel Submarine Fans occur in the San Nicolas basin - an outer basin of the California continental borderland that has a low sedimentation rate. Nicolas Fan lies southeast of San Nicolas Island and the broad San Nicolas Bank. The upper fan is characterized by numerous channels. The midfan region may be divided into three distinct areas: a central midfan and two subfans. The central midfan deposition system is typical of Normark's suprafan. The subfans are essentially flat, sandy lobes. Eel Fan lies west of San Clemente Island and is fed by an erosional valley. Its midfan region may also be characterized as a flat, sandy lobe. Box-core data show that holocene turbidity currents have occurred on the central Nicolas Fan, whereas the subfans and Eel Fan are nearly inactive. The local tectonic regime influences these fans by determining slope trends, creating bathymetric obstacles, controlling canyon location, and triggering mass movements. Sea level changes affect sedimentation patterns of the fans by increasing the mean grain size and the amount of sediment delivered to the fan during lowstands. These changes may, in turn, affect the morphology of the fan. The characteristics of these fans represent variations of the generalized fan models described in the literature. 12 figures, 1 table.

Reynolds, S.; Gorsline, D.S.

1987-04-01

407

Distribution of cold-water corals in the Whittard Canyon, NE Atlantic Ocean  

NASA Astrophysics Data System (ADS)

The deep-sea floor occupies about 60% of the surface of the planet and is covered mainly by fine sediments. Most studies of deep-sea benthic fauna therefore have concentrated on soft sediments with little sampling of hard substrata, such as rocky outcrops in submarine canyons. Here we assess the distribution and abundance of cold-water corals within the Whittard Canyon (NE Atlantic) using video footage from the ROV Isis. Abundances per 100 m of video transect were calculated and mapped using ArcGIS. The data were separated into five substratum types, 'Sediment', 'Mixed Sediment and Rock', 'Sediment Slope', 'Lophelia reef' and 'Lophelia and rock'. Abundance and community structure were compared. A maximum abundance of 855 coral colonies per 100 m of ROV transect were observed with 31 coral types identified. Highest taxon richness was observed along a 'Lophelia reef' area, although a larger richness of Octocorallia was observed away from the 'Lophelia reef' areas. 'Lophelia reef' and 'Lophelia and rock' areas were found to have a different coral community structure from the other substratum types. We suggest this is the result of Lophelia outcompeting other coral types because there is increased coral taxon richness in areas without Lophelia. We also hypothesise that the hydrodynamic regime within the Whittard Canyon results in differences in organic matter input including higher quality food, in comparison with other deep-water environments, leading to changes in the coral communities.

Morris, Kirsty J.; Tyler, Paul A.; Masson, Doug G.; Huvenne, Veerle I. A.; Rogers, Alex D.

2013-08-01

408

Modeling and Understanding Remotely Forced Rip Current Systems at the Nearshore Canyon Experiment (NCEX)  

NASA Astrophysics Data System (ADS)

Evaluation of data collected during the Nearshore Canyon Experiment, has shown that our time-dependent circulation model (OK-Model; Özkan-Haller and Kirby, JGR, 1999), forced using radiation stress gradients derived from spectral wave models, can predict the spatial location of large offshore directed flows (rip currents). The locations of these transient rip currents, which are not controlled by the local nearshore bathymetry, are visible in remote sensing time exposure and variance images due to the advection of foam on the water surface (Eos Trans. AGU, 84(46), Ocean Sci. Meet. Suppl., Abstract OS21I-04, 2003). Further investigation has indicated that optical measurements of circulation patterns coincide with the numerical predictions. With this validation, the numerical models are being used to evaluate the sensitivity of the dynamic rip current system at the NCEX site to changes in wave conditions and nearshore bathymetry. Additionally, the walls of the offshore submarine canyon contain an undulating pattern that may be important in generating small-scale variations in waveheight, thereby driving rip currents where the water surface is at a local minimum, even in regions where the wave height is generally high. Theoretical tests using bottom boundaries with anomalies in intermediate and deep water are being performed to determine the effect these offshore contours can have in dictating nearshore circulation patterns. These results will provide insight regarding the role of patterns along canyon walls in prescribing the spatial location of the rip currents.

Long, J. W.; Özkan-Haller, H. T.; Holman, R. A.

2004-12-01

409

Sediment concentrations, flow conditions, and downstream evolution of two turbidity currents, Monterey Canyon, USA  

NASA Astrophysics Data System (ADS)

The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in the submarine environment has attracted the attention of researchers from different disciplines. Yet not only are field measurements of oceanic turbidity currents a rare achievement, but also the data that have been collected consist mostly of velocity records with very limited or no suspended sediment concentration or grain size distribution data. This work focuses on two turbidity currents measured in Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, primarily controlled by the source of the gravity flows and their interaction with bed material, play a significant role in shaping the characteristics of the turbidity currents as they travel down the canyon. Before the flows reach their normal or quasi-steady state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through a preliminary adjustment stage where they are subject to capacity-driven deposition, and release heavy material in excess. Flows composed of fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm that flow patterns differ between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology.

Xu, J. P.; Sequeiros, Octavio E.; Noble, Marlene A.

2014-07-01

410

Chirp seismic-reflection data from the Baltimore, Washington, and Norfolk Canyons, U.S. mid-Atlantic margin  

USGS Publications Warehouse

A large number of high-resolution geophysical surveys between Cape Hatteras and Georges Bank have been conducted by federal, state, and academic institutions since the turn of the century. A major goal of these surveys is providing a continuous view of bathymetry and shallow stratigraphy at the shelf edge in order to assess levels of geological activity during the current sea level highstand. In 2012, chirp seismic-reflection data was collected by the U.S. Geologial Survey aboard the motor vessel Tiki XIV near three United States mid-Atlantic margin submarine canyons. These data can be used to further our understanding of passive continental margin processes during the Holocene, as well as providing valuable information regarding potential submarine geohazards.

Obelcz, Jeffrey B.; Brothers, Daniel S.; ten Brink, Uri S.; Chaytor, Jason D.; Worley, Charles R.; Moore, Eric M.

2014-01-01

411

NOAA Explorations: Submarine Ring of Fire 2004  

NSDL National Science Digital Library

NOAA's 2004 Submarine Ring of Fire expedition's goals are to examine over a 1,000 km stretch of submarine volcanoes and sea-floor hot springs in the Mariana Island Arc. At this website, users can find general information about the Mariana Arc, the research, and the scientists involved. Educators can find intriguing lesson plans about volcanoes and the chemistry of hydrothermal vents for grades fifth through twelfth. The site presents fascinating materials about seafloor mapping, volcanism, and vent chemistry. Visitors can view amazing satellite images of the overall Mariana Arc Volcanic Chain, its sea floor, and the NW Uracas and Ahyi submarine volcanoes.

412

Narrow Bandwidth Telecommunications.  

ERIC Educational Resources Information Center

The basic principles of narrow bandwidth telecommunications are treated in a manner understandable to the non-engineer. The comparative characteristics of the various narrow bandwidth communications circuits are examined. Currently available graphics transmission and reception equipment are described and their capabilities and limitations…

Kessler, William J.; Wilhelm, Michael J.

413

The submarine river of Port Miou (France), A karstic system inherited from the Messinian deep stage  

NASA Astrophysics Data System (ADS)

The Port Miou system (Cassis, France) is a two kilometers long submarine gallery that extends in the limestone series of Calanques (Marseille, France). The average discharge is between 2 to 5 m3/s but the water is brackish and cannot be used for water supply. In the 1970s, a dam was built to prevent saltwater intrusion in the cave but these experimental attempts did not succeed in getting rid of the residual salinity which remained near 3 g l-1 upstream the dam. The use of helium and later rebreathers by cave divers made possible the exploration of a vertical pit down to 179 m below the sea level. At that depth, the water is still brackish. The cave extends further and deeper but the exploration is limited by the present diving technology. The canyon of Cassidaigne is located a few kilometers south from Port Miou. It cuts the continental shelf where bathymetric studies have shown the presence of dolines. Caves and speleothems have been observed during submarine explorations on the walls of the canyon. This canyon is not connected to a continental valley and it is assumed that it is a pocket valley. Its presence is related to the several lowering stages of the Mediterranean Sea during the Messinian Salinity Crisis. We suggest that during the important drop of sea level of the Mediterranean, the underground river of Port-Miou, flowed several hundreds meters below its current position, and excavated the canyon. At the end of the Messinian crisis, the system was flooded by seawater. The karst water now flows through an upper gallery but the presence of a paleo-drain filled by seawater makes possible a deep marine intrusion into the karst system. Several geomorphologic clues (bathymetry, submarine valley network…) reinforce the fact that the continental shelf near Marseilles is an important karstic network drowned below the sea level. This model is supported by the observation in Port Miou of an important quantity of titanium at the upper surface of the cave sediment, upstream of the dam and at the end of the cave. The presence of heavy metals in the sediments of the Port Miou gallery is explained as resulting from the suction of residues of bauxite treatments, rejected in the nearby Cassidaigne deep-sea canyon at a depth of 300 m bsl. This residual product locally called "red mud" is very rich in titanium. The saline contamination of Port Miou could be carried out by a seawater inflow through a deep karstic conduit connected to the canyon of Cassidaigne. A long term monitoring of the springs, indicates that the system is contaminated by a permanent sweater inflow close to 500 l.s-1. A laboratory model has been realized that simulates perfectly the functioning.

Cavalera, T.; Gilli, E.

2009-04-01

414

Loblolly Pines in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

415

Barrel Cactus in Pine Creek Canyon  

USGS Multimedia Gallery

Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of...

416

Snow-covered Sandstone at Bryce Canyon  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

417

Panorama of Bryce Canyon National Park  

USGS Multimedia Gallery

Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates