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The contributions of UNCLOS dispute settlement bodies to the development of the law of the seaNguyen, Lan Ngoc January 2019 (has links)
This thesis seeks to systematically examine the contributions made by the dispute settlement bodies established under the United Nations Convention on the Law of the Sea (UNCLOS) to the development of the law of the sea. The two main research questions to be answered are: (i) what kind of contribution have UNCLOS dispute settlement bodies made to the development of the law of the sea? and (ii) what are the factors that impact the performance of UNCLOS dispute settlement bodies in developing the law of the sea? To that end, Chapter 1 provides a working definition for the concept of 'judicial development of international law' in order to establish a framework for an assessment of the contributions of UNCLOS tribunals. Based on this working definition, Chapters 2, 3 and 4 examine the significance of UNCLOS tribunals' decisions in the development of three main areas of the law of the sea, respectively the law on fisheries, the law on the outer continental shelf and the law on marine environmental protection. Based on the findings of these chapters, Chapter 5 analyses the factors that help explain the contributions of UNCLOS tribunals to the law of the sea as identified in the preceding chapters. These factors include: (i) the jurisdictional scope of UNCLOS tribunals, (ii) the institutional design of UNCLOS, (iii) the interpretative method employed by UNCLOS tribunals in deciding their cases and (iv) the perception that UNCLOS tribunals hold regarding their roles. Chapter 6 concludes by taking stock of the contribution of UNCLOS tribunal in these areas and offering some final observations on the role of UNCLOS tribunals in the development of the law of the sea.
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The Effects of Sediment Properties on Barrier Island Morphology and Processes: A Numerical Modeling ExperimentKime, Brittany 20 December 2018 (has links)
Barrier island restoration and nourishment is necessary for sustaining coastal systems worldwide. In the Mississippi River Delta Plain, the lack of sediment supply, relative sea level rise, and reworking of abandoned delta lobes promote rapid disintegration of barriers, which can contribute to mainland storm impacts. Barrier island restorations that utilize higher quality sediments (Outer Continental Shelf- OCS) are expected to exhibit higher resiliency, withstanding coastal erosion, event-induced erosion, and ongoing transgression when compared to barriers nourished using lower quality nearshore (NS) sands. Additionally, use of OCS sediments increases sediment supply by adding material to the system supporting increased barrier longevity by maintaining a subaerial footprint longer compared to NS sediments. We used the Delft3D modeling suite to study barrier geomorphic trajectories nourished using OCS/NS sands, compared with control simulations with no nourishment. Resulting morphologies from 18 simulations with forcing that included annualized forcing, storms, and SLR are evaluated and compared.
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Changes in the structure of demersal fish communities of the South Eastern Australian Ccontinental Shelf from 1915 to 1961Klaer, Neil L, n/a January 2006 (has links)
Haul-by-haul steam trawler catch and effort data for 1918�23, 1937�43 and 1952�57,
which covers a large portion of the history of steam trawling in the Australian South
East Fishery, were examined in detail for the first time. There were 64,371 haul records
in total. The catch-rate for all retained catch combined shows a strong decline overall,
with a brief recovery during World War II, probably due to increased retention of
previously discarded species. The fishing fleet moved to more distant fishing grounds
and deeper waters as the catch-rate declined. The catch-rates of the main commercial
species followed a similar pattern in a number of regions within the fishery. The catchrate
of the primary target species � tiger flathead (Neoplatycephalus richardsoni) �
dropped considerably from the early, very high, catch-rates. Chinaman leatherjacket
(Nelusetta ayraudi) and latchet (Pterygotrigla polyommata) � species that were
apparently abundant in the early years of the fishery � virtually disappeared from
catches in later years. The appearance of greater catches of jackass morwong
(Nemadactylus macropterus), redfish (Centroberyx affinis), and shark/skate during the
war and afterwards was probably due to increased retention of catches of these species.
The disappearance of certain species from the catch may be due to high fishing pressure
alone, or to a combination of fishing pressure, changes in the shelf habitat possibly
caused by the trawl gear, and environmental fluctuations.
Catch-rates in weight per haul per species were standardised to annual indices of
abundance using a log-linear model. Standardised annual index trends for flathead,
latchet and leatherjacket indicate a strong to severe decline over the period covered by
the data. All species showed seasonal patterns, but the peak season varied depending on
the species. The distribution of standardised catch-rate by area also differed greatly by
species, and no single area showed consistent differences across all species. Day trawls
caught more flathead, redfish and latchet, while night trawls caught more morwong and
leatherjacket. Moon phase had less influence on catch-rates than the other factors
examined. Correlation of annual index trends with a number of annual mean
environmental factors was examined and no strong correlations were found.
Annual catches of the major commercial trawl species on the SE Australian shelf were
estimated from recorded total trawl catches, catch species composition from subsamples
and estimates of the rate of discarding. These annual catches, standardised
indices of abundance and biological population parameters were used in single-species
stock reduction models to estimate absolute biomass trends. Biological population
parameters and the biomass estimates were used to calculate management reference
point fishing mortality rates F0.1, Fspr30 and Fmsy. Results showed that simple plausible
population models can be constructed that account for catches over the long period of
time from 1915 to 1961.
Simple mass-balance ecosystem models were built for the demersal community of the
SE Australian shelf for 1915 and 1961 using the Ecopath software. Model inputs were
consistent with a more comprehensive SE marine ecosystem model in development by
CSIRO. The models demonstrate that biomass estimates produced by the single species
stock reduction models can be consistently integrated into simple plausible massbalance
ecosystem models.
Modern stock assessments for the main commercial species in this fishery today mostly
used data collected since about 1985. Abundance indices and total catch estimates from
this study have been used in the most recent assessments for tiger flathead and
morwong, allowing construction of the exploitation history for these species spanning
almost 100 years. Use of the historical information has increased confidence in the
estimates of the modern stock assessments � particularly management reference points,
and has allowed us to quantify changes in fish abundance that have simply been
documented anecdotally in the past.
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Processes and architectures of deltas in shelf-break and ramp platforms : examples from the Eocene of West Spitsbergen (Norway), the Pliocene paleo-Orinoco Delta (SE Trinidad), and the Cretaceous Western Interior Seaway (S. Wyoming & NE Utah)Uroza, Carlos Alberto, 1966- 08 October 2012 (has links)
This research investigates different scenarios of deltaic deposition, both in shelfbreak and ramp settings. I address four ancient cases with particular characteristics: 1) A shelf-margin case from the Eocene Battfjellet Formation, West Spitsbergen, Norway, in which deltas were able to migrate to the shelf-edge during rising and sea-level highstand conditions despite the low-supply character of the system (low progradation/aggradation rates compared to analogous margins), with consequent sand starvation on the slope and deeper areas of the basin. The delta system was overall wave-dominated, with restricted tide-influence at the mouth of the distributaries and more accentuated tide-influence during the transgressive transit of the deltas; 2) A shelf-margin case from the Pliocene paleo-Orinoco Delta System, Mayaro Formation, SE-Trinidad, in which high rates of sediment supply from the paleo-Orinoco River and exceptionally high subsidence rates due to growth-faulting, produced a spectacular stacking of sandstones on the outer shelf and shelf-edge areas, but with apparently limited sand delivery into deeper waters. The delta system was overall storm-wave dominated, with fluvial-influence in the lower segment of the system and some tide-influence in association with the fluvial-influence; 3) A case from a shallow-water ramp, Campanian Rock Springs Formation (Western Interior Seaway), in which deltas accumulated along relatively straight, north-south oriented shorelines highly impacted by wave-storm processes. Tide-influence was limited to the mouth of the distributaries, and fluvial deposits mostly developed within the coastal-plain areas; and 4) A case from the same ramp setting as (3) but in an outer-ramp site, Campanian Haystack Mountains Formation, in which a lowering in sea-level translated the delta system tens of kilometers eastwards into the basin. As a consequence of a shallower and narrower seaway, southerly-oriented tidal currents were enhanced and subsequently skewed or re-aligned the delta system to the south. The key contributions of this research concern (1) the feasibility of shelf-margin accretion during rising and highstand of sea level, (2) the critical importance of shelf width and sediment supply (and not only sea-level behavior) to bring deltas to the shelfedge, and (3) the possible tendency for tides enhancement in the distal reaches of shallow seaway ramps, caused by narrowing of the seaway and fault-topography enhancement during falling sea level. / text
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From rifting to collision : the evolution of the Taiwan Mountain BeltLester, William Ryan 10 October 2013 (has links)
Arc-continent collisions are believed to be an important mechanism for the growth of continents. Taiwan is one of the modern day examples of this process, and as such, it is an ideal natural laboratories to investigate the uncertain behavior of continental crust during collision. The obliquity of collision between the northern South China Sea (SCS) rifted margin and Luzon arc in the Manila trench subduction zone allows for glimpses into different temporal stages of collision at different spatial locations, from the mature mountain-belt in central-northern Taiwan to the 'pre-collision' rifted margin and subduction zone south of Taiwan. Recently acquired seismic reflection and wide-angle seismic refraction data document the crustal-scale structure of the mountain belt through these different stages. These data reveal a wide rifted margin near Taiwan with half-graben rift basins along the continental shelf and a broad distal margin consisting of highly-extended continental crust modified by post-rift magmatism. Magmatic features in the distal margin include sills in the post-rift sediments, intruded crust, and a high-velocity lower crustal layer that likely represents mafic magmatism. Post-rift magmatism may have been induced by thermal erosion of lithospheric mantle following breakup and the onset of seafloor spreading. Geophysical profiles across the early-stage collision offshore southern Taiwan show evidence the thin crust of the distal margin is subducting at the Manila trench and structurally underplating the growing orogenic wedge ahead of the encroaching continental shelf. Subduction of the distal margin may induce a pre-collision flexural response along the continental shelf as suggested by a recently active major rift fault and a geodynamic model of collision. The weak rift faults may be inverted during the subsequent collision with the continental shelf. These findings support a multi-phase collision model where the early growth of the mountain belt is driven in part by underplating of the accretionary prism by crustal blocks from the distal margin. The wedge is subsequently uplift and deformed during a collision with the continental shelf that involves both thin-skinned and thick-skinned structural styles. This model highlights the importance of rifting styles on mountain-building. / text
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Patterns and dynamics of ocean circulation variability on the West Florida shelfLiu, Yonggang 01 June 2006 (has links)
Patterns of variability and the dynamics of the ocean circulation on the West Florida Shelf (WFS) are investigated using multi-year, shelf-wide oceanographic observations from moored Acoustic Doppler Current Profiler (ADCP) arrays,hydrographic cruises, High-Frequency (HF) radars, satellites, and coastal tide gauges.Novel neural network techniques, Self-Organizing Map (SOM) and Growing Hierarchical Self-Organizing Maps (GHSOM), are introduced as feature extraction methods in physical oceanography. The SOM is demystified and demonstrated to be a useful feature extraction method in a series of performance evaluations using artificial data sets comprising known patterns. It is then applied to velocity time series from moored ADCP arrays and to a joint HF-radar and ADCP data set, respectively, to extract patterns of ocean current variability, and it is shown to be a useful technique for extracting dynamically consistent ocean current patterns. The extracted characteristic patte
rns of upwelling/downwelling variability are coherent with the local winds on the synoptic weather time scale, and coherent with both the local winds and thecomplementary Sea Surface Temperature (SST) patterns on the seasonal time scale. Thecurrents are predominantly southeastward during fall-winter and northwestward during summer. The GHSOM is used to describe the SST seasonal variation. As feature extraction methods, both the SOM and the GHSOM have advantages over the conventional Empirical Orthogonal Function method.The circulation dynamics are examined, first through depth-averaged momentum balances at selected locations and then via sea surface height (SSH) estimates across the inner shelf. Dominant dynamics of the shelf circulation are diagnosed and a method is discussed for estimating along-shelf currents from coastal sea level and wind data. Nontidal coastal sea level fluctuations are related to both the offshore SSH and the dynamical responses of the inner shelf to wind and bu
oyancy forcing. The across-shelf distribution of the SSH is estimated from the velocity, hydrography, wind, and coastal sea level data.Subtracting the variability that may be accounted for by inner shelf dynamical responses yields a residual at the 50 m isobath that compares well with satellite altimetry data. This suggests the possibility of calibrating satellite SSH data on the continental shelf.
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Observational and Numerical Modeling Studies of Turbulence on the Texas-Louisiana Continental ShelfZhang, Zheng 16 December 2013 (has links)
Turbulent dynamics at two sites (C and D) in a hypoxic zone on the Texas- Louisiana continental shelf were studied by investigating turbulence quantities i.e. turbulence kinetic energy (TKE), dissipation rate of TKE (E), Reynolds stress (τ ), dissipation rate of temperature variance (χ), eddy diffusivity of temperature (ν't), and eddy diffusivity of density (ν'p). Numerical models were also applied to test their capability of simulating these turbulence quantities.
At site D, TKE, E, and τ were calculated from velocity measurements in the bot- tom boundary layer (BBL), using the Kolmogorov’s -5/3 law in the inertial subrange of energy spectra of vertical velocity fluctuations in each burst measurement. Four second-moment turbulence closure models were applied for turbulence simulations, and modeled turbulence quantities were found to be consistent with those observed. It was found from inter-model comparisons that models with the stability functions of Schumann and Gerz predicted higher values of turbulence quantities than those of Cheng in the mid layer, which might be due to that the former stability functions are not sensitive to buoyancy.
At site C, χ, E, v’t, and ν’p were calculated from profile measurements throughout the water column, and showed high turbulence level in the surface boundary layer and BBL, as well as in the mid layer where shear stress was induced by advected non-local water above a hypoxic layer. The relatively high dissolved oxygen in the non-local water resulted in upward and downward turbulent oxygen fluxes, and the bottom hypoxia will deform due to turbulence in 7.11 days. Two of the four models in the study at site D were implemented, and results showed that turbulence energy resulting from the non-local water was not well reproduced. We attribute this to the lack of high-resolution velocity measurements for simulations. Model results agreed with observations only for χ and E simulated from the model with the stability function of Cheng in the BBL. Discrepancies between model and observational results lead to the following conclusions: 1) the stability functions of Schumann and Gerz are too simple to represent the turbulent dynamics in stratified mid layers; 2) detailed velocity profiles measurements are required for models to accurately predict turbulence quantities. Missing such observations would result in underestimation,
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Sedimentology, coral reef zonation, and late Pleistocene coastline models of the Sodwana Bay continental shelf, Northern ZululandRamsay, Peter John. January 1991 (has links)
This geostrophic current-controlled Zululand/Natal shelf displays a unique assemblage of interesting
physical, sedimentological and biological phenomena. The shelf in this area is extremely narrow
compared to the global average of 75km, and is characterised by submarine canyons, coral reefs, and
steep gradients on the continental slope. A shelf break occurs 2.1km to 4.1km offshore and the shelf
can be divided into a northern region and a southern region based on the presence or absence of a
defined shelf break. The southern shelf has a poorly-defined shelf break whilst the northern shelf has
a well-defined break at -65m. The poor definition of the shelf break on the southern shelf can possibly
be attributed to the presence of giant, climbing sand dunes offshore of Jesser Point at depths of -37m
to -60m. The northern shelf has a series of coast-parallel oriented patch coral reefs which have
colonised carbonate-cemented, coastal-facies sequences.
The northern shelf can be divided into three distinct zones: inner-, mid-, and outer-shelf zones. The
inner-shelf is defined as the area landward of the general coral reef trend, with depths varying from
0m to -I5m and having an average gradient of 1.1. The mid-shelf is defined by the general coral reef
trend, varying from -9m over the shallow central axis of the reefs to -35m along the deep reef-front
environments. The outer-shelf is seaward of the coral reefs and occurs at a depth range of -35m to -
65m. Gradients vary from 1° in the south to 2.5° in the northern part of the study area, and are steep
compared to world average shelf gradient of 0.116°.
Four submarine canyons occur in the study area and are classified as mature- or youthful-phase
canyons depending on the degree to which they breach the shelf. The origin of these canyons is not
related to the position of modern river mouths but can probably be linked to palaeo-outlets of the
Pongola and Mkuze River systems. It is suggested that the canyons are mass-wasting features which
were exploited by palaeo-drainage during regressions. The youthful-phase canyons appear to be mass-wasting features associated with an unstable, rapidly-deposited, progradational late Pliocene sequence
and a steep upper continental slope. The mature-phase canyons were probably initiated by mass-wasting
but have advanced shoreward, breaching the shelf, due to their link with the palaeo-outlets
of the Pongola and Mkuze Rivers during late Pleistocene regressions.
Evidence of modem canyon growth has been noted on numerous SCUBA diving surveys carried out
on the canyon heads. These take the form of minor wall slumps and small-scale debris flows. The
canyons are also supplied with large quantities of sand in the form of large-scale shelf subaqueous
dunes generated and transported by the Agulhas Current. As these bedforms meet the canyons the
sediment cascades down the canyon thalweg and causes erosion and downcutting of the canyon walls
and floor thereby increasing the canyon dimensions.
Late Pleistocene beachrock and aeolianite outcrops with or without an Indo-Pacific coral reef veneer
are the dominant consolidated lithology on the shelf. These submerged, coast-parallel, carbonate cemented,
coastal facies extend semi-continuously from -5m to -95m, and delineate late Pleistocene
palaeocoastline events. The rock fabric of these high primary porosity lithologies shows grains floating
in a carbonate cement with occasional point-contacts. Grains are mostly quartz (80-90%), minor K-feldspar
and plagioclase (5-10%), and various lithic fragments. The rocks contain conspicuous organic
grains including foraminifera, bivalve, echinoid, bryozoan, red algal, and occasional sponge spicule
fragments; these commonly display replacement fabrics or iron-stained rims. The dominant
sedimentary structures found in these sandstone outcrops include high-angle planar cross-bedding and
primary depositional dip bedding. Palaeocurrent directions sngest a palaeoenvironment dominated
by a combination of longitudinal and transverse dunes with wind directions similar to those observed
forming the modem dune systems. Erosional features evident on the submerged beachrocks and
aeolianites include gullies trending in two different directions and sea-level planation surfaces with or
without the presence of potholes.
The unconsolidated sediment on the shelf is either shelf sand, composed mainly of terrigenous quartz
grains; or bioclastic sediment which is partially derived from biogenic sources.
The quartzose sand from the inner-shelf is generally fine-grained, moderately- to well-sorted, and
coarsely- to near symmetrically-skewed. Carbonate content is low, and varies between 4-13%.
Quartzose sand from the outer-shelf is fine-grained, moderately- to well-sorted, and coarsely- to very
coarsely-skewed. The inner-shelf quartzose sand is better sorted than the outer-shelf sand due to
increased reworking of this sediment by the high-energy swell regime. Sediment from the shallower
areas of the outer-shelf (< -50m) is better sorted than sediment from depths of greater than -50m.
Generally wave-reworking of quartzose shelf sand from the Sodwana Bay shelf results in greater
sediment maturity than that observed from geostrophic current effects or a combination of geostrophic
and wave-reworking. This sediment was derived by reworking of aeolian and beach sediments,
deposited on the shelf during the period leading up to the Last Glacial Maximum (15 000 - 18 000
years B.P.) when sea-level was -130m, during the Holocene (Flandrian) transgression.
Bioclastic sediment on the Sodwana Bay shelf is defined as having a CaC03 content of greater than
20% and is a mixture of biogeoically-derived debris and quartzose sand. The distribution of bioclastic
sediment in the study area is widespread, with reef-derived and outer-shelf-derived populations being
evident. This sediment consists of skeletal detritus originating from the mechanical and biological
destruction of carbonate-secreting organisms such as molluscs, foraminifera, alcyonaria, scleractinia,
cirripedia, echinodermata, bryozoa, porifera. The reef-derived bioclastic population is confined to
depths less than -40m in close proximity to reef areas, whereas the shelf-derived bioclastic population
occurs at depths greater than -40m and is derived from carbonate-producing organisms on deep water
reefs and soft-substrate environments on the shelf.
Large-scale subaqueous dunes form in the unconsolidated sediment on the outer-shelf due to the
Agulhas flow acting as a sediment conveyor. These dunes are a common feature on the Sodwana Bay
shelf occurring as two distinct fields at depths of -35m to -70m, the major sediment transport direction
being towards the south. The two dune fields, the inner- and outer subaqueous dune fields, are
physically divided by Late Pleistocene beachrock and aeolianites ledges. A bedform hierarchy has been
recognised. The larger, outer dune field appears to have originated as a system of climbing bedforms
with three generations of bedforms being superimposed to form a giant bedform, while the inner dune
field has a less complex construction. The largest bedforms are those of the outer dune field off Jesser
Point, being up to 12 m high, 4 km long and 1.2 km wide. A major slip face, with a slope of 8° is
present.
Bedload parting zones exist where the bedform migration direction changes from south to north.
Three bedload parting zones occur in the study area at depths of -60m, -47m and -45m; two in the
inner dune field and one in the outer dune field. These zones are invariably located at the southern
limits of large clockwise eddy systems. Such eddies appear to be the result of topographically induced
vorticity changes in the geostrophic flow and/or the response to atmospheric forcing caused by coastal
low-pressure system moving up the coastline.
It has been demonstrated that the inner subaqueous dune sediment conveyor is not active all the time
but only during periods . of increased current strength when the Agulhas Current meanders inshore.
The smaller bedforms in the outer dune field undergo continuous transport due to the current velocity
on the shelf edge outer dune field being higher than the velocity experienced on the inner dune field.
The very large 2·D dune which forms the outer dune field is probably not active at present: this is
inferred due to the shallow angle of the mega-crest lee slope (8°).
The very large Sodwana Bay subaqueous dune fields may be compared with the very large,
reconstructed, subaqueous dunes which occur in Lower Permian sediments of the Vryheid Formation,
northern Natal. These Permian dunes are represented, in section, as a fine- to medium-grained distal
facies sandstone with giant crossbeds. These large-scale bedforms are unidirectional, but rare
directionally-reversed, climbing bedforms do occur, this directional reversal may be related to bedload
parting zones. On the evidence presented in this thesis, it is proposed that these Permian subaqueous
dunes may be ancient analogues of the modem subaqueous dune field on the Sodwana Bay shelf.
Positive-relief hummocks and negative-relief swale structures are fairly common in the fine-grained,
quartzose shelf sand at depths of -30m to -60m. These appear to be transitional bedforms related to
the reworking by storms of medium 2-D subaqueous dunes. These hummocky structures may be the
modem equivalent of hummocky cross-stratification noted in the geological record, and if so, they are
probably the first to have ever been observed underwater.
The occurrences of ladderback ripples on the Sodwana Bay shelf at depths of -4m to -17m, suggest that
subtidal ladderback ripples may be more common than previously thought. Ladderback ripples are
common features of tidal flats and beaches where they form by late-stage emergence run-off during
the ebb tide. They are generally considered diagnostic of clastic intertidal environments. The mode
of formation on the Sodwana Bay shelf is different from the classic late-stage emergence run-off model
of intertidal occurrences, being a subtidal setting. Subaqueous observations indicate that ladderback
ripples are not environment-specific, and that additional evidence of emergence is therefore necessary
to support an intertidal setting in the rock record: ladderback ripples alone are insufficient to prove
an intertidal environment.
The coral patch reefs of the northern Natal coast are unique, being the most southerly reefs in Africa,
and totally unspoilt. The Zululand reefs are formed by a thin veneer of Indo-Pacific type corals which
have colonised submerged, late Pleistocene beachrocks and aeolianites. Two-Mile Reef at Sodwana Bay
has been used to develop a physiograpbic and biological zoning model for Zululand coral reefs, which
has been applied to other reefs in the region. Eight distinct zones can be recognised and differentiated
on the basis of physiographic and biological characteristics. The reef fauna is dominated by an
abundance of alcyonarian (soft) corals, which constitute 60-70% of the total coral fauna. The Two-Mile
Reef zoning model has been successfully applied to larger reefs such as Red Sands Reef, and smaller
patch reefs (Four-Mile and Seven-Mile Reefs) in the same general area.
In this thesis extensive use has been made of Hutton's uniformitarian principles. Hutton's doctrine
is particularly relevant to the study of depositional processes and relict shorelines. Coastal processes
and weather patterns during the late Pleistocene were broadly similar to modem conditions enabling
direct comparisons to be made. A computer-aided facies analysis model has been developed based on
textural statistics and compositional features of carbonate-cemented coastal sandstones. Many
attempts have been made to distinguish different ancient sedimentary depositional environments, most
workers in this field having little success. The new method of facies reconstruction is based on:
(1) underwater observations of sedimentary structures and general reef morphology;
(2) a petrographic study of the reef-base enabling flve facies: aeolianite, backbeach,
forebeach, swash, and welded bar facies to be recognised, which control the
geomorphology of Two-Mile Reef;
(3) cluster and discriminant analysis comparing graphic settling statistics of acid-leached
reef-base samples with those of modem unconsolidated dune/beach environments.
The results of this analysis demonstrated that the beachrocks and aeolianites on the shelf formed
during a regression and that late Pleistocene coastal facies are similar to modem northern Zululand
coastal environments, which have been differentiated into aeolian, backbeach, forebeach, swash, &
welded bar.
A late Pleistocene and Holocene history of the shelf shows that during the late Pleistocene, post
Eemian regressions resulted in deposition and cementation of coast-parallel beachrocks and
aeolianites, which define a series of four distinct palaeocoastline episodes with possible ages between
117 000 and 22 000 years B.P. The beachrock/aeolianites formed on the shelf during stillstands and
slow regressions, and the gaps between these strandline episodes represent periods of accelerated sealevel
regression or a minor transgressive phase which hindered deposition and cementation. The
formation of these lithologies generated a considerable sediment sink in the nearshore zone. This
reduced sediment supply and grain transport in the littoral zone during the Holocene, and probably
enhanced landward movement of the shoreline during the Flandrian transgression.
Prior to the Last Glacial Maximum, the beachrock/aeolianite sedimentary sequence was emergent and
blanketed by shifting aeolian sands. The Pongola River, which flowed into Lake Sibaya, reworked the
unconsolidated sediments on the shelf, and exploited the route of least resistance: along White Sands
and Wright Canyon axes. The erosion resulting from fluvial denudation in Wright Canyon has caused
this canyon to erode some of the beachrock/aeolianite outcrops which form palaeocoastline episode 2
and entrench the canyon to a deeper level; this eroded the shelf to a distance of 2km offshore.
During the Flandrian transgression the unconsolidated sediment cover was eroded, exposing and
submerging the beachrock/aeolianite sequence. Flandrian stillstands caused erosional features such
as wave-planed terraces, potholes, and gullies to be incised into beachrock and aeolianite outcrops;
these are seen at present depths of -47m, -32m, .26m, -22m, -17m to -15m, and -12m. High energy
sediment transfers, in an onshore direction, resulted in the deposition of sand bars across the outlet
of Lake Slbaya's estuary and the development of a 130m + coastal dune barrier on a pre-existlng,
remnant Plelstocene dune stub. Sea-level stabilised at its present level 7 000-6 000 years B.P. and coral
reef growth on the beachrock/aeolianite outcrops probably started at 5 000 years B.P. A minimum age
for the formation of the northern Zululand coral reefs has been established at 3780 ± 60 years B.P.
A mid Holocene transgression relating to the Climatic Optimum deposited a + 2m raised beach rock
sequence. This transgression eroded the coastal dune barrier and caused a landward shoreline
translation of approximately 40m. A minor transgression such as this can be used as a model for
coastal erosion which will result from the predicted 1.5m rise in sea-level over the next century. This
rise in sea-level could result in a 30m landward coastline translation of the present coastline, ignoring
the influence that storms and cyclones will have on the coastline configuration. / Thesis (Ph.D.)-University of Natal, Durban, 1991.
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Physical processes along the southern continental shelf and slope of Western AustraliaMohd Akhir, Mohd Fadzil January 2010 (has links)
The circulation along the south coast of Western Australia was examined using field data and numerical modelling. Physical processes in this region, particularly along the continental shelf and slope regions, were poorly understood due to a paucity of field measurements. Data were collected during a research cruise on RV Southern Surveyor (04/2006) during April 2006 consisting of 18 CTD transects from Twilight Cove (126oE) to Cape Leeuwin (115oE) and was augmented by shipborne ADCP data. The field data set provided a detailed understanding of three major current systems: Leeuwin Current (LC), Leeuwin Undercurrent (LU) and Flinders Current (FC). The LC along the south coast exhibits different characteristics when compared to that along the west coast. The LC flows into the colder and lower salinity subantarctic environment of the south coast. This is evident in a strong geopotential gradient off the south-west corner of Australia (Cape Leeuwin) resulting in rapid acceleration of the LC as it reaches a maximum velocity in this region. Numerical modelling studies, using the Regional Ocean Modelling System (ROMS) indicated that wind stress is an important component of the dynamics in this region. This was identified when comparing summer and winter conditions when the winds act in opposite directions, from north-westerly to southeasterly respectively. Along the shelf break and slope, the Flinders Current (FC) interacts with LC. As the dominant current, the FC serves both as a surface and as an undercurrent, transporting sub Antarctic mode water (SAMW). This interconnection the FC and LU can be seen clearly from the salinity, temperature and velocities within the depth range 200-700m postulating a connection between subsurface waters off Tasmania (origin of the Flinders Current) and the tropical Indian Ocean through the Flinders and Leeuwin Undercurrents.
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Summer circulation and water masses along the West Australian coastWoo, Lai Mun January 2005 (has links)
The Gascoyne continental shelf is located along the north-central coastline of Western Australia between latitudes 21° and 28°S. This study presents CTD and ADCP data together with concurrent wind and satellite imagery, to provide a description of the summer surface circulation pattern along the continental margin, and the hydrography present in the upper 1km of ocean, between latitudes 21° and 35°S. It also discusses the outcome of a numerical modelling study that examined the physical factors contributing to a bifurcation event persistently observed in satellite imagery at Point Cloates. The region comprises a complex system of four surface water types and current systems. The Leeuwin Current dominated the surface flow, transporting lower salinity, warmer water poleward along the shelf-break, and causing downwelling. Its signature ‘aged’ from a warm (24.7°C), lower salinity (34.6) water in the north to a cooler (21.9°C), more saline (35.2) water in the south, as a result of 2-4Sv geostrophic inflow of offshore waters. The structure and strength of the current altered with changing bottom topographies. The Ningaloo Current flowed along the northernmost inner coast of the Gascoyne shelf, carrying upwelled water and re-circulated Leeuwin Current water from the south. Bifurcation of the Ningaloo Current was seen south of the coastal promontory at Point Cloates. Numerical modelling demonstrated a combination of southerly winds and coastal and bottom topography off Point Cloates to be responsible for the recirculation, and indicated that the strength of southerly winds affect recirculation. Hypersaline Shark Bay outflow influenced shelf waters at the Bay’s mouth and to the south of the Bay. The Capes Current, a wind-driven current from south of the study region was identified as a cooler, more saline water mass flowing northward. Results of the hydrography study show five different water masses present in the upper-ocean. Their orientations were affected by the geopotential gradient driven Leeuwin Current/Undercurrent system at the continental margin. The Leeuwin Undercurrent was found at the shelf-slope, carrying (>252 μM/L) Subantarctic Mode Water at a depth of 400m
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