Characteristics and context of high-energy, tidally modulated, barred shoreface deposits: Kimmeridgian–Tithonian sandstones, Weald Basin, southern U.K. and northern France

ABSTRACT The influence of tides on the sedimentology of wave-dominated shorefaces has been emphasized in recent studies of modern shorelines and related facies models, but few ancient examples have been reported to date. Herein, we use a case study from the stratigraphic record to develop a revised facies model and predictive spatio-temporal framework for high-energy, tidally modulated, wave-dominated, barred shorefaces. Kimmeridgian–Tithonian shallow-marine sandstones in the Weald Basin (southern England and northern France) occur as a series of laterally extensive tongues that are 5–24 m thick. Each tongue coarsens upward in its lower part and fines upward in its upper part. The lower part of each upward-coarsening succession consists of variably stacked, hummocky cross-stratified, very fine- to fine-grained sandstone beds and mudstone interbeds that are moderately to intensely bioturbated by a mixed Skolithos and Cruziana Ichnofacies. This lower part of the succession is interpreted to record deposition on the subtidal lower shoreface, between effective storm wave base and fairweather wave base. The upper part of each upward-coarsening succession comprises cross-bedded, medium- to coarse-grained sandstones that are pervasively intercalated with mudstone-draped, wave-rippled surfaces (including interference ripples) which mantle the erosional bases of trough cross-sets. Bioturbation is patchy, and constitutes a low-diversity Skolithos Ichnofacies. Cross-bedded sandstones are arranged into cosets superimposed on steeply dipping (up to 10°) clinoforms that dip offshore and alongshore, and extend through the succession. These deposits are interpreted to record shallow subtidal and intertidal bars on the upper shoreface, which likely contained laterally migrating rip channels or formed part of a spit. The lower, upward-coarsening part of each sandstone tongue represents an upward-shallowing, regressive shoreface succession in which the internal bedding of upper-shoreface sandstones was modulated by tidal changes in water depth. The upper, upward-fining part of each sandstone tongue typically comprises an erosionally based bioclastic lag overlain by subtidal lower-shoreface deposits, and constitutes an upward-deepening succession developed during transgression. Regressive–transgressive sandstone tongues fringe the northeastern margin of the basin, which was exposed to an energetic wave climate driven by westerly and southwesterly winds with a fetch of 200–600 km. The high tidal range interpreted from the shoreface sandstone tongues is attributed to resonant amplification in a broad (150–200 km), shallow (18–33 m) embayment as the tidal wave propagated from the Tethys Ocean into the adjacent intracratonic Laurasian Seaway, of which the Weald Basin was a part.

Karakteristik Hidrooseanografi di Perairan Pesisir Kabupaten agam

The research objectives to explore the characteristic of hydrooceanography in coastal of Agam Regency. The observations parameters included physical aspecs such as bathymetric, tide, wave, water current, Transparancy, and temperature; and so chemical aspecs such as pH, salinity, dissolved oxygen, and COD. Hydrooseanographic characteristics on Agam Regency coastal described the bathymetry was shallow to deep , high wave, high tidal range, water currents dependent on season, and water quality were in good criteria to life support of aquatic biota. Key words: Hydrooceanography, wave, tidal, water quality

THE MORPHODYNAMICS OF A MIXED SEDIMENT EMBAYMENT IN A HIGH TIDAL RANGE ENVIRONMENT

As anthropogenic use of the coastal zone diversifies, for example marine energy extraction, the coastal environments of interest to coastal engineers and managers is becoming more varied. Increasingly, the morphodynamics of geomorphologically complex, mixed sediment and geologically constrained beaches are important. Even in areas where erosion and inundation risk is low, understanding of changes to morphodynamics is important to inform ecological studies for environmental impact assessments.

Carbon stocks of mangroves and salt marshes of the Amazon region, Brazil

In addition to the largest existing expanse of tropical forests, the Brazilian Amazon has among the largest area of mangroves in the world. While recognized as important global carbon sinks that, when disturbed, are significant sources of greenhouse gases, no studies have quantified the carbon stocks of these vast mangrove forests. In this paper, we quantified total ecosystem carbon stocks of mangroves and salt marshes east of the mouth of the Amazon River, Brazil. Mean ecosystem carbon stocks of the salt marshes were 257 Mg C ha −1 while those of mangroves ranged from 361 to 746 Mg C ha −1 . Although aboveground mass was high relative to many other mangrove forests (145 Mg C ha −1 ), soil carbon stocks were relatively low (340 Mg C ha −1 ). Low soil carbon stocks may be related to coarse textured soils coupled with a high tidal range. Nevertheless, the carbon stocks of the Amazon mangroves were over twice those of upland evergreen forests and almost 10-fold those of tropical dry forests.

A Transformed Coordinate Model to Predict Tide and Surge Along the Head Bay of Bengal- Application to Cyclone of 1991 and 1970

The head Bay of Bengal region is one of the most vulnerable regions for extreme water levels associated with severe tropical cyclones. The shallow nature of the head Bay, presence of a large number of deltas formed by major rivers and high tidal range are responsible for storm surge flooding in the region. Specifically, the rise and fall of tidal phases influence the height, duration, and arrival time of peak surge along the coast. The objective of the present study is to evaluate the tide-surge interaction during the super cyclone of 1991 and 1970. A transformed coordinate model is developed to estimate the possible water levels along the coast of Bangladesh.GANIT J. Bangladesh Math. Soc.Vol. 35 (2015) 7-25

Pseudopataecus carnatobarbatus, a new species of velvetfish (Teleostei: Scorpaeniformes: Aploactinidae) from the Kimberley coast of Western Australia

Pseudopataecus carnatobarbatus, new species, is described from 12 specimens collected on shallow coastal reefs of northernWestern Australia, between the Monte Bello Islands and Adele Island. It is distinguished from its sole congener, P. taenianotusJohnson 2004, by branched (versus simple) tips to most fin rays, last soft dorsal-fin ray joined by membrane more fully toupper caudal-fin ray, spinous dorsal fin more distinctly notched, pelvic fins more robust, anterior face of lower lip smooth (ver-sus profusely covered with cirri), and a narrow quadrangular pit on the forehead, bounded by frontal, supraorbital, ocular andpreocular ridges (versus pit and preocular ridge absent). It also has modally fewer anal-fin rays and modally greater numbers ofgill rakers. Pseudopataecus carnatobarbatus is found in an extremely high tidal range area of Australia, where movement of upto 11 m occurs during spring tides. Specimens were collected in rocky tide pools with coral rubble and thick stands of brownmacroalgae, especially Padina species. The new species has been found in intertidal areas up to only 13 m deep, whereas P. taenianotus has been collected by trawling soft bottom habitats in depths of 20 to 63 m.

Wave and tidal power

This chapter reviews how electricity can be generated from waves and tides. The UK is an excellent example, as the British Isles have rich wave and tidal resources. The technologies for converting wave power into electricity are easily categorized by location type. 1. Shoreline schemes. Shoreline Wave Energy Converters (WECs) are installed permanently on shorelines, from where the electricity is easily transmitted and may even meet local demands. They operate most continuously in locations with a low tidal range. A disadvantage is that less power is available compared to nearshore resources because energy is lost as waves reach the shore. 2. Nearshore schemes. Nearshore WECs are normally floating structures needing seafloor anchoring or inertial reaction points. The advantages over shoreline WECs are that the energy resource is much larger because nearshore WECs can access long-wavelength waves with greater swell, and the tidal range can be much larger. However, the electricity must be transmitted to the shore, thus raising costs. 3. Offshore schemes. Offshore WECs are typically floating structures that usually rely on inertial reaction points. Tidal range effects are insignificant and there is full access to the incident wave energy resource. However, electricity transmission is even more costly. Tidal power technologies fall into two fundamental categories:1. Barrage schemes. In locations with high tidal range a dam is constructed that creates a basin to impound large volumes of water. Water flows in and out of the basin on flood and ebb tides respectively, passing though high efficiency turbines or sluices or both. The power derives from the potential energy difference in water levels either side of the dam. 2. Tidal current turbines. Tidal current turbines (also known as free flow turbines) harness the kinetic energy of water flowing in rivers, estuaries, and oceans. The physical principles are analogous to wind turbines, allowing for the very different density, viscosity, compressibility, and chemistry of water compared to air. Waves are caused by winds, which in the open ocean are often of gale force (speed >14 m/s).

Offshore Tidal Power Generation—A New Approach to Power Conversion of the Oceans' Tides

Offshore tidal power generation (“OTP”) is a new approach to tidal power conversion that resolves the environmental and economic problems of the familiar “tidal barrage” technology. OTP uses a rubble mound impoundment structure and low-head hydroelectric generating equipment situated a mile or more offshore in a high tidal range area. Shallow tidal flats provide the most economical sites. Multi-cell impoundment structures provide higher load factors (about 62%) and have the flexibility to shape the output curve in order to dispatch power in response to demand price signals. The tides are highly predictable and permit tidal power to fit comfortably into existing electricity distribution grids. The author describes a computer simulation program that uses equipment performance characteristics and tidal data to create a detailed simulation of generation output, water flows and storage, and is used for design optimization. The article also contains a history of tidal power and discussion of tidal power's place in the renewables market.