Late Ordovician sand-wave complexes on Anticosti Island, Quebec: a marine tidal embayment?

1987 ◽  
Vol 24 (9) ◽  
pp. 1821-1832 ◽  
Author(s):  
D. G. F. Long ◽  
Paul Copper
Keyword(s):  
Local Community ◽  
Late Ordovician ◽  
Sand Wave ◽  
Sand Waves ◽  
The North ◽  
Sand Ridges ◽  
Tidal Embayment ◽  
Tidal Modification ◽  
Global Sea Level ◽  
Anticosti Island

Laterally discontinuous, mixed carbonate–siliciclastic sandstones in the upper Vaureal and lower Ellis Bay formations of Anticosti Island were deposited on an equatorial carbonate ramp with a slope of less than 1°. The 10–18 m thick sandstones are interpreted as subaqueous sand-wave complexes analogous to detached parts of modern shoreface-connected sand ridges. These record storm-enhanced, tidal modification of a northerly derived shoal retreat massif that may have formed in response to recovery from global sea-level lowstands in the Late Ordovician (Ashgill: late Rawtheyan – Hirnantian). The sand-wave complexes formed within a tidal embayment that was confined by the Precambrian Shield to the north and northwest by rising tectonic highlands of the Humber Zone in Newfoundland to the east, and by active tectonic highlands in the Quebec Appalachians (Gaspésie) to the south. Paleocurrent distributions, parallel to the western margins of the Strait of Belle Isle, suggest that the north end of the embayment was closed in Late Ordovician time. Low-diversity faunas within the sand units consist mostly of sowerbyellid, strophomenid, and rhynchonellid brachiopods, bivalves, gastropods, large aulacerid stromatoporoids, and large, domed favositid corals. These "sandy fades" faunas belong to communities significantly different from those found in the laterally interfingering and overlying carbonates and shales, suggesting that the sand waves played an important role in local community modification.

Study of sand wave migration over five years as observed in two windfarm development areas, and the implications for building on moving substrates in the North Sea

2014 ◽  
Vol 105 (4) ◽  
pp. 241-249 ◽  
Author(s):  
Ken P. Games ◽  
David I. Gordon
Keyword(s):  
Case Studies ◽  
Large Scale ◽  
Oil And Gas ◽  
Sand Wave ◽  
Sand Waves ◽  
Migration Rates ◽  
The North ◽  
The North Sea ◽  
Wave Migration ◽  
The Impact

ABSTRACTSand waves are well known indicators of a mobile seabed. What do we expect of these features in terms of migration rates and seabed scour? We discuss these effects on seabed structures, both for the Oil and Gas and the Windfarm Industries, and consider how these impact on turbines and buried cables. Two case studies are presented. The first concerns a windfarm with a five-year gap between the planning survey and a subsequent cable route and environmental assessment survey. This revealed large-scale movements of sand waves, with the displacement of an isolated feature of 155 m in five years. Secondly, another windfarm development involved a re-survey, again over a five-year period, but after the turbines had been installed. This showed movements of sand waves of ∼50 m in five years. Observations of the scour effects on the turbines are discussed. Both sites revealed the presence of barchans. Whilst these have been extensively studied on land, there are few examples of how they behave in the marine environment. The two case studies presented show that mass transport is potentially much greater than expected and that this has implications for choosing turbine locations, the effect of scour, and the impact these sediment movements are likely to have on power cables.

Evolution and extinction of the North American Hiscobeccus brachiopod Fauna during the Late Ordovician

2001 ◽  
Vol 38 (2) ◽  
pp. 143-151 ◽  
Author(s):  
Jisuo Jin
Keyword(s):  
North American ◽  
Narrow Range ◽  
Late Ordovician ◽  
Ocean Temperature ◽  
Carbonate Platforms ◽  
Cool Water ◽  
The North ◽  
Brachiopod Fauna ◽  
Global Sea Level ◽  
Continental Glaciation

The earliest rhynchonellid brachiopods were small-shelled and preferred cool-water conditions in both siliciclastic and carbonate environments. Relatively large shells of Rhynchotrema evolved in mid-Caradoc time and rapidly became widespread in Laurentia. Hiscobeccus probably evolved from Rhynchotrema during the late Caradoc by developing a large, globular, strongly lamellose shell. The earliest form of Hiscobeccus shows transitional characteristics between Rhynchotrema and typical Hiscobeccus, most notably in its nonglobular shell that is wrinkled by growth lamellae only on the anterior two thirds of the shell. By early Ashgill time, Hiscobeccus became widespread in North American inland basins, although it remained common in marginal carbonate platforms and basins. During the Ashgill, Hiscobeccus, Lepidocyclus, and Hypsiptycha represented a distinct North American fauna, characterized by large, globular, and completely wrinkled shells. These morphological features were adaptations to the shallow, well-circulated, epicontinental, tropical seas with a soft muddy substrate. The gigantism exhibited by the Hiscobeccus Fauna is also shown by orthid and strophomenid brachiopods, gastropods, nautiloids, and trilobites. Extinction of the Hiscobeccus Fauna was probably related to its narrow range of environmental tolerance, especially during the Gondwana continental glaciation, which brought a major global sea-level drawdown and lowered ocean temperature. The cool-water Rostricellula and Rhynchotrema were uncommon in inland seas during the Ashgill and were represented by several opportunistic species in the Anticosti Basin during the Hirnantian and Llandovery, and most of these preferred siliciclastic-rich or deep-water shelf carbonate environments.

scholarly journals A CLASSIFICATION METHOD FOR THE PRESENCE OF TIDAL SAND WAVES AND MAINTENANCE DREDGING DESIGN

2018 ◽  
pp. 48
Author(s):  
Rick De Koning ◽  
Jaap van Thiel De Vries ◽  
Bas Borsje
Keyword(s):  
Large Scale ◽  
Tidal Flow ◽  
Narrow Channel ◽  
Sand Wave ◽  
Maintenance Strategies ◽  
Sand Waves ◽  
Recirculating Flow ◽  
The North ◽  
Tidal Sand ◽  
And Migration

The study into sand wave dynamics in South Channel commenced after large dune forms were observed in monitoring campaigns following the channel deepening project of the Port of Melbourne. The project involved deepening of the harbor berths and channels, but more importantly, it involved the deepening of South Channel in Port Phillip Bay. South Channel, the main shipping channel, crosses the bay over ≈20km. The growth of bedforms at various locations in South Channel now threatens to impede marine traffic. The dimensions and migration rate of the bedforms in the channel are remarkable, especially in the harsh flow conditions in the narrow channel. Therefore, the bedforms in South Channel cannot be given an obvious classification. In this paper it is shown that the bedforms in South Channel can be classified as a tidal sand wave type with a method that requires only insight in water depth, tidal flow velocity and grain size. Tidal sand waves are large-scale bedforms generated by recirculating flow cells that drive sediment to the top of a crest and are commonly observed on shallow coastal seas such as the North Sea. The bedform concern in the channel illustrates the necessity of an evaluation of the present, and alternative, channel maintenance strategies. A numerical model in Delft3D software is applied, along with a probabilistic calculation that combines insights from the simulations and survey data, to assess different maintenance strategies.

scholarly journals Modelling the Past and Future Evolution of Tidal Sand Waves

2021 ◽  
Vol 9 (10) ◽  
pp. 1071
Author(s):  
Janneke Krabbendam ◽  
Abdel Nnafie ◽  
Huib de Swart ◽  
Bas Borsje ◽  
Luitze Perk
Keyword(s):  
Vertical Direction ◽  
Skill Score ◽  
The Other ◽  
Sand Wave ◽  
Sand Waves ◽  
Future Evolution ◽  
The North ◽  
Skill Scores ◽  
The North Sea ◽  
Tidal Sand

This study focuses on the hindcasting and forecasting of observed offshore tidal sand waves by using a state-of-the-art numerical morphodynamic model. The sand waves, having heights of several meters, evolve on timescales of years. Following earlier work, the model has a 2DV configuration (one horizontal and one vertical direction). First, the skill of the model is assessed by performing hindcasts at four transects in the North Sea where sand wave data are available of multiple surveys that are at least 10 years apart. The first transect is used for calibration and this calibrated model is applied to the other three transects. It is found that the calibrated model performs well: the Brier Skill Score is ’excellent’ at the first two transects and ’good’ at the last two. The root mean square error of calculated bed levels is smaller than the uncertainty in the measurements, except at the last transect, where the M2 is more elliptical than at the other three transects. The calibrated model is subsequently used to make forecasts of the sand waves along the two transects with the best skill scores.

Katian (Late Ordovician) conodonts on the northwestern margin of the North China Craton

2021 ◽  
pp. 1-22
Author(s):  
Zhihua Yang ◽  
Xiuchun Jing ◽  
Hongrui Zhou ◽  
Xunlian Wang ◽  
Hui Ren ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Late Ordovician ◽  
Carbonate Platforms ◽  
Upper Ordovician ◽  
The North ◽  
Low Latitudes ◽  
Northwestern Margin ◽  
Conodont Fauna ◽  
Stratigraphic Range

Abstract Upper Ordovician strata exposed from the Baiyanhuashan section is the most representative Late Ordovician unit in the northwestern margin of the North China Craton (NCC). In total, 1,215 conodont specimens were obtained from 24 samples through the Wulanhudong and Baiyanhuashan formations at the Baiyanhuashan section. Thirty-six species belonging to 17 genera, including Tasmanognathus coronatus new species, are present. Based on this material, three conodont biozones—the Belodina confluens Biozone, the Yaoxianognathus neimengguensis Biozone, and the Yaoxianognathus yaoxianensis Biozone—have been documented, suggesting that the Baiyanhuashan conodont fauna has a stratigraphic range spanning the early to middle Katian. The Baiyanhuashan conodont fauna includes species both endemic to North China and widespread in tropical zones, allowing a reassessment of the previous correlations of the Katian conodont zonal successions proposed for North China with those established for shallow-water carbonate platforms at low latitudes. UUID: http://zoobank.org/7cedbd4a-4f7a-4be6-912f-a27fd041b586

Participation trends according to relative age across youth UK Rugby League

2017 ◽  
Vol 12 (3) ◽  
pp. 339-343 ◽  
Author(s):  
Stephen P Cobley ◽  
Kevin Till
Keyword(s):  
Local Community ◽  
Sports Participation ◽  
Rugby League ◽  
Age Effects ◽  
Relative Age ◽  
The North

Relative age effects in sports participation highlight the presence of a significant social and developmental inequality. To assess its prevalence, patterning, and size, this study examined participation trends of youth (ages 7–21 years) Rugby League players registered to local community clubs across the North of England ( N = 23,943). Results showed that irrespective of relative age, participation growth occurred from U8 to U12s age categories. However, from U13 to U19s, participation became differentiated with the relatively younger showing earlier and progressively lowering participation proportions (e.g. Q4s – U13–U17 = 24–17%) and were up to 50% less likely to participate (i.e. Q4 vs. Q1 – U15–U16 OR = 0.48 and 0.50). Findings highlight the substantial earlier loss of participation for the relatively younger across youth ages. Player development systems containing inherent selection and differentiation during adolescence are presented as one key process affecting the decision to participate in youth Rugby League.

scholarly journals Study on hydraulic resistance of erodible bed at the Chiyoda experimental flume

2014 ◽  
Vol 39 ◽  
pp. 81-87
Author(s):  
T. Kakinuma ◽  
T. Inoue ◽  
R. Akahori ◽  
A. Takeda
Keyword(s):  
Large Scale ◽  
Flow Distribution ◽  
Longitudinal Survey ◽  
Sand Wave ◽  
Vertical Flow ◽  
Sand Waves ◽  
Wave Development ◽  
Logarithmic Distribution ◽  
Steady Flow Condition ◽  
Experimental Flume

Abstract. The authors made erodible bed experiments under steady flow condition at the Chiyoda Experimental Flume, a large-scale facility constructed on the floodplain of the Tokachi River, and observed sand waves on the bed of the flume. In this study, the characteristics of the sand waves are examined along the longitudinal survey lines and confirmed to be dunes. Next, the authors estimated Manning's roughness coefficients from the observed hydraulic values and assumed that the rise of the coefficients attributed to the sand wave development. Finally, vertical flow distribution on the sand waves are examined, and observed velocity distribution on the crest of waves found to be explained by the logarithmic distribution theory.

scholarly journals Processes controlling the dynamics of compound sand waves in the North Sea, Netherlands

2005 ◽  
Vol 110 (F4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Thaiënne A. G. P. van Dijk ◽  
Maarten G. Kleinhans
Keyword(s):  
North Sea ◽  
Sand Waves ◽  
The North ◽  
The North Sea

Investigating microplastic behaviour in a well-mixed estuary

2021 ◽  
Author(s):  
Nia Jones ◽  
Simon Neill ◽  
Peter Robins ◽  
Matthew Lewis
Keyword(s):  
Type System ◽  
Water Quality Monitoring ◽  
Irish Sea ◽  
Human Populations ◽  
Natural Ecosystems ◽  
Future Projections ◽  
Catchment Population ◽  
The North ◽  
Direct Exposure ◽  
Tidal Embayment

<p>Rivers and estuaries act as conduits of microplastic transport, linking terrestrial and marine environments: however, it is unclear to what extent estuaries act as sources or sinks for marine plastic waste. In densely populated catchments, microplastic pollution could impact human populations and natural ecosystems including through industry, domestic activities or direct exposure. An investigation into the physical behaviour of microplastic within estuarine systems will allow for a greater understanding of plastic retention and exportation to coastal and offshore environments. A high resolution 3D model (Delft D-Flow FM) of the Conwy Estuary (UK) is under development, with current and future projections of microplastic concentrations used to determine local exposure levels, residence times and temporal variability.</p><p>The Conwy Estuary (UK) is a well-mixed macro-tidal, embayment type system connecting the Conwy catchment to the North Wales coast and Irish Sea – where waters are used for leisure and aquaculture. Microplastics derived from the catchment population, industry and agriculture are thought to flow into the estuary primarily from the Conwy river network. Because of this, this study will incorporate in-situ samples of microplastic concentrations in river water to be able to predict microplastic levels in the estuary with greater accuracy. Plastic dispersal simulations through particle tracking and water quality monitoring will be undertaken using known concentrations and future projections of microplastic.</p><p>The results of the model validation as well as application to plastic dispersal simulations will be presented.</p>

scholarly journals Origin of the Late Ordovician Lepidocyclus brachiopod fauna in North America and its biogeographic significance

1992 ◽  
Vol 6 ◽  
pp. 149-149
Author(s):  
Jisuo Jin
Keyword(s):  
North America ◽  
Sea Level ◽  
North American ◽  
Plate Tectonics ◽  
Late Ordovician ◽  
Sea Level Changes ◽  
Stepping Stones ◽  
Shell Size ◽  
Larval Stages ◽  
The North

Three rhynchonellid brachiopod genera, Hiscobeccus, Lepidocyclus, and Hypsiptycha, are the most diagnostic elements of the Lepidocyclus fauna of North America in Late Ordovician time. These are characterized by relatively large, strongly biconvex to globular shells with coarse imbricating growth lamellae and, internally, with septiform cardinal processes in brachial valves. Among the three genera, Hiscobeccus appears the earliest, now known from rocks of late Trentonian-Edenian age in the Canadian Rocky Mountains and Mackenzie Mountains. Morphologically, Hiscobeccus is distinguished from the other two genera by its open delthyrium in the pedicle valve. Early forms of Hiscobeccus show close morphological similarity to Rhynchotrema in their non-globular biconvex shells covered by strong growth lamellae only in the anterior portions. It has been suggested that Hiscobeccus evolved from the Rhynchotrema wisconsinense stock through increase in shell size, globosity, and strength of growth lamellae. Earliest species of Rhynchotrema has been documented convincingly from rocks of early Trentonian age, and the derivation of Hiscobeccus most likely took place during the mid-Trentonian. Lepidocyclus and Hypsiptycha evolved from either Rhynchotrema or Hiscobeccus by developing a pair of deltidial plates covering the delthyrium.Rhynchotrema and other rhynchonellids that evolved before mid-Trentonian time are common to the North American (Laurentian) and the Siberia-Kazakhstan paleocontinents. In contrast, Hiscobeccus, Lepidocyclus, and Hypsiptycha that evolved after the mid-Trentonian are virtually restricted to Laurentia. Therefore, Rhynchotrema marked the last successful intercontinental migration of rhynchonellids during their Llandeilian-Caradocian cosmopolitanism. The pronounced provincialism of the North American Lepidocyclus fauna may have been caused by a number of factors. Facies control is not likely the explanation because these rhynchonellids occur in nearly all the inland and marginal platform seas of Laurentia and commonly are found together in the same types of rocks. Plate tectonics and sea-level changes are considered major causes. The Ordovician rhynchonellids lived in shallow marine (intertidal-subtidal) environments and were incapable of crossing vast, deep oceanic barriers because of their sedentary mode of life and short-lived motile larval stages. The widening of the ocean between North America and Siberia, coupled with high sea-level stand, may have created a sufficiently wide oceanic barrier to interrupt faunal mixing between the two paleocontinents by late Trentonian time. Moreover, the rise in sea level would have resulted in the disappearance of island faunas, which could have served as stepping stones for intercontinental migration of shallow-water benthic faunas during low sea-level stand.

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