Tide Channel Research Articles

Contribution of Ground Penetrating Radar in the study of an amazon tide channel, influenced by macro tide

This article shows the Ground Penetrating Radar (GPR) experiment applied in the Urumajó tidal channel (Augusto Côrrea, Pará, Brazil) that flows into the Caeté river estuary (Atlantic Ocean). This tidal channel has a length of 50 km (source - mouth, near Augusto Côrrea city) and a hydrographic basin of 544 km2. The GPR geophysical tool allowed extracting information under the depth of the channel bed in the various 2-D profiles. In the central part of the tidal channel, sediment accumulations were identified probably due to the influence of the tide. The results show that with the 200 and 400 MHz frequency antennas, the GPR is able to obtain records (radargrams) of the channel bed, over 7,5 m deep. During the rainy season, the tidal channel is covered by sand (30%) and mud (70%), however, in the dry season the muddy granulometric class (72%) increases a little and the sand (28%) decreases, sediments sludge predominated on the banks of the channel and increased upstream. The silting up of the tidal channel is a consequence of several activities carried out on the banks of the channel (livestock, agriculture, housing, ports, etc), resulting in deforestation.

Sedimentary and reservoir architectures of MB1-2 sub-member of Middle Cretaceous Mishrif Formation of Halfaya Oilfield in Iraq

Based on comprehensive analysis of core, cast thin section, logging and seismic data, the sedimentary and reservoir architectures of the MB1-2 sub-member of Mishrif Formation in Halfaya Oilfield, Iraq, are studied. The MB1-2 sub-member of Mishrif Formation has three types of microfacies, lagoon, bioclastic shoal, and tidal channel, and facies architecture controlled by sequence stratigraphy. In the 4th-order sequence, the lagoon facies aggradated vertically, and the bioclastic shoals in lenticular shape embed in the background of lagoon, the end of the sequence is incised by the “meandering river” shape tide channel, which represents the depositional discontinuity. Three types of reservoirs including tidal channel grainstone to packstone reservoirs, bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed. The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies, whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary. The reservoir sections occur mainly in the 4th sequence highstand systems tract (HST) and are separated by barriers formed in the transgressive systems tract (TST). Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir, which showed the characteristics of “attic type” architecture. The results of this study can guide the development of similar reservoirs in the Middle East.

Bedforms controlled by residual current vortices in a subtropical estuarine tidal channel

The objective of the present work was to analyze the bottom morphology, the genesis of the bedforms, and the patterns of current and sediment transport of the internal portion of the south mouth in Paranaguá Bay, Paraná - Brazil. This region was used as a laboratory field to study the geomorphology of a dune field on a tide channel, with features of flood delta in the inner portion and ebb delta in the direction of the continental shelf. A sediment hydrodynamic model was used to calculate the direction and magnitude of the sediment transport and the residual current flows. A map of apparent roughness was used in the numerical model, obtained through the soundings of a sidescan sonar (Starfish Sonar) and estimated from the classification of the dune field, so it is possible to obtain simulations with higher correspondence with reality. It was observed two vortices of residual circulations near the shores of Pontal do Sul and Ilha do Mel, with directions towards the continental shelf. The residual circulation vortex is responsible for the triangular shape of the large dunes near the Pontal do Sul margin. In the flood, the sediment material is conducted inward forming small ripples and accumulating sediment material on large dunes. During the ebb, these ripples are supposedly destroyed and attached to the large dunes or to the water column. On the other hand, the bedforms of Saco do Limoeiro are formed due to the effects of the tide when entering the mouth and the confinement of the water mass in the region until the next moment of padding.

Comparable short-term morphodynamics of three estuarine–coastal systems in the southwest coastal region of England, UK

Here, we describe and compare the changes in low tide channel position and the morphology of the three estuaries in southwest England from an analysis of contemporary (2008–2016) topographic surveys. The Hayle, Gannel, and Camel estuaries and their adjacent open-coast shorelines were subject of various studies in the past principally in terms of mining impacts on estuarine sediments and sedimentation, but no regional synthesis of the contemporary behaviour has yet been attempted. Light Detection and Ranging (LiDAR) data for the north coast of Cornwall are analysed for planform morphological changes of the systems. At the annual scale, intertidal bars and sandwaves migrate across the foreshore and into the inlet region, where flood-oriented and wave-forced movement is evident. This is evidenced at all the estuarine systems considered here. However, the steep upstream slope of the Hayle is almost devoid of bedforms, while the shallower upstream slope of the Gannel comprises similar scaled bedforms to the whole flood delta, and the megaripples of Camel flood delta are smaller on the backslope. Over the short-term covered by the LiDAR data considered here, there was no significant storm surges, and a relatively consistent wave climate. The occurrence of strong onshore wave conditions are possibly the drivers of contemporary behaviour, and with the inner estuary intertidal currents, for the movements of sediments within the estuarine environment, thereby causing the re-organisation of sediments and the shifting of channel position.

Stratification and loading of fecal indicator bacteria (FIB) in a tidally muted urban salt marsh.

Stratification and loading of fecal indicator bacteria (FIB) were assessed in the main tidal channel of the Ballona Wetlands, an urban salt marsh receiving muted tidal flows, to (1) determine FIB concentration versus loading within the water column at differing tidal flows, (2) identify associations of FIB with other water quality parameters, and (3) compare wetland FIB concentrations to the adjacent estuary. Sampling was conducted four times during spring-tide events; samples were analyzed for FIB and turbidity (NTU) four times over a tidal cycle at pre-allocated depths, depending on the water level. Additional water quality parameters measured included temperature, salinity, oxygen, and pH. Loadings were calculated by integrating the stratified FIB concentrations with water column cross-sectional volumes corresponding to each depth. Enterococci and Escherichia coli were stratified both by concentration and loading, although these variables portrayed different patterns over a tidal cycle. Greatest concentrations occurred in surface to mid-strata levels, during flood tides when contaminated water flowed in from the estuary, and during ebb flows when sediments were suspended. Loading was greatest during flood flows and diminished during low tide periods. FIB concentrations within the estuary often were significantly greater than those within the wetland tide channel, supporting previous studies that the wetlands act as a sink for FIB. For public health water quality monitoring, these results indicate that more accurate estimates of FIB concentrations would be obtained by sampling a number of points within a water column rather than relying only on single surface samples.

Influence of Reclamation on Hydrodynamic Environment in Bohai Bay

The SWAN model was used to simulate the effect of the coastline change caused by the reclamations on the wave fields in Bohai Bay. The numerical results in the year of 2000 had been compared with that of 2010 to study the influence of the sea reclamations on the wind waves in Caofeidian area. The results show that the significant wave height has a declining trend due to the reclamation and decreased in value of 0.1 to 0.4m in 2010. The magnitude of the decrease of the significant wave height in winter is larger than that in summer. The significant variations of wave fields are occurred in the harbor basin and tide channel.

Paleoecology of the ordovician reef-shoal depositional system in the Yijianfang outcrop of the Bachu area, West Tarim Basin

The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang (一间房) outcrop of the Bachu (巴楚) uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system: an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies (a reef base, a reef core, and fore-reef breccias); the organic shoal is formed from five types of genetic facies (tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals). The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The calathium, archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while well-preserved girvanella and nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals.

Optically Stimulated Luminescence to Date Coastal Dunes and a Possible Tsunami Layer on the Kavak Delta (Saros Gulf, NW Turkey)

Optically stimulated luminescence (OSL) dating was used to determine the timing of initial dune formation and reconstruct the evolution of coastal dunes that developed on the Kavak Delta, Saros Gulf, Turkey. Along a 500-m-long representative transect, dune sands were extracted from foredune, semistable (grey) dune, stable (dark) dune and dune-swamp boundary defined by a scarp 50-75 cm high. The data obtained showed that dune drift initiated 670 years ago. A pumice layer 15-20-cm-thick interbedded with marine clay and sand showed an OSL age of 340 years coinciding with underlying dune sand. XRF analysis showed that pumices were of similar composition to those erupted by plinian activity of Thera (Santorini) in 1628 BC. On the basis of OSL ages, these deposits, which are widely distributed on the western Anatolian coasts of Turkey, might have presumably transported landward along tide channels on the delta during a tsunami event that occurred in 1672 near Bozcaada and Kos islands according to tsunami history of the Aegean Sea.

Bio-foam enhances larval retention in a free-spawning marine tunicate.

Here we report a mechanism that reduces dispersal of early developing stages and larvae in a free-spawning intertidal and shallow subtidal tunicate, Pyura praeputialis (Heller 1878), in the Bay of Antofagasta, Chile. The spawning of gametes by the tunicate into the naturally turbulent aerated seawater decreases their surface tension and induces the formation of a bio-foam. Water collected from foamy intertidal pools and tide channels showed a high concentration of P. praeputialis early developing stages and tadpole larvae in the foam. Because gametes are synchronically spawned for external fertilization and larvae settle near adults, our results suggest that this bio-foam increases fertilization success and effective settlement of their short-lived larvae in the vicinity of the adults spawning the gametes. This mechanism reinforces published evidence suggesting that local retention of intertidal and inshore marine invertebrate larvae may be more common than previously thought, offering, for instance, new perspectives for the design and networking of marine protected and management areas.

Contrasting geomorphic response to structural control: The Loughros estuaries, northwest Ireland

Sediment-rich estuaries typically exhibit considerable dynamicity, with channel shifts and shoreline erosion/deposition occurring over timescales of years to decades. Contemporary behaviour is usually attributed to the immediate effect of short-term events (such as storms), longer-term forcing (such as sea-level change) or anthropogenic modifications to system controls (such as wave–tidal–fluvial regime and sediment supply). In this context, geological control is understood to provide an inherited framework within which an estuary will evolve. This paper examines the morphodynamics of two sand-filled, but sediment-limited, mixed-energy estuaries of Loughros Bay in northwest Ireland. Analysis of ebb channel morphometry shows that estuaries can be divided into upper and lower estuary components, which appear to represent a down-valley increasing energy gradient. Examination of historical ebb channel migration reveals three morphodynamic zones delimited by a significant spatial variability in channel mobility that reflects the distribution of specific structural controls along the estuary and their influence on the changing energy gradient. Based upon analysis of low tide channel migration over the last 172 years, three phases of geomorphic response are identified. In Loughros More, the behaviour is characterised by a 19th century phase of steady-state equilibrium; a subsequent period of dynamic response to extrinsic (storm) forcing; and, most recently, adjustment to intrinsically forced changes in structural control. In Loughros Beg, the phases are comparable, but contrast specifically in inlet and ebb-tidal behaviour. This analysis illustrates discontinuities in decadal- to century-scale forcing and morphological response, identified here as complex response. It suggests that the sedimentary evolution of coastal systems that have no appreciable external sediment supply is potentially more strongly determined by local variability in system character than climate or sea-level driven mechanisms.

Relationship between shape and trophic ecology of selected species of Sparids of the Caprolace coastal lagoon (Central Tyrrhenian sea)

The shapes of juveniles of nine species of the family Sparidae (Diplodus annularis, Diplodus puntazzo, Diplodus sargus, Diplodus vulgaris, Lithognathus mormyrus, Pagellus acarne, Sarpa salpa, Sparus aurata, Spondyliosoma cantharus), collected in the tide channel of the Caprolace Lagoon (Central Tyrrhenian Sea—Italy) were studied using geometric morphometry. These species have different ecologies. The trophic ecology of each species, reported as TROPH values, are related to shape. For the first time the relationship between shape and trophic ecology in sparids was studied in a quantitative way giving an ecomorphological meaning to the shape differences. Mean shapes of carnivorous, omnivorous and herbivorous fish were extracted, analyzed and found to be unique. Strict herbivores such as Sarpa salpa have a small mouth gap; omnivores such as the four species of the genus Diplodus have a higher body (discoidal) and a caudal peduncle shorter and higher; carnivorous species such as Lithognathus mormyrus, possess a relatively larger head region, a larger mouth gap, a longer body and a caudal peduncle longer and narrower.

Actuopalaeontological trackway experiments withIguana on intertidal flat carbonates of the Arabian Gulf — a comparison to fossilRhynchosauroides tracks of Triassic carbonate tidal flat megatracksites in the European Germanic Basin

In the recent carbonate tidal flats of the lower to upper intertidal zone of the Khor Al Qirqishan Bay western of Abu Dhabi at the southern Arabian Gulf actuopaleontological trackway experiments with the lizardIguana were made. The different moving activities such as basking, slow walk or running over dry to wet biolaminate surfaces and swimming or walking activities through ponds and tide channels have left a variety of quadruped track preservations.Iguana has produced trackways on nearly dry microbial mats of the upper intertidal only with claw marks. On slightly wet substrates detailed imprints of the subdigital lamellae were produced, while in wet mud a medium impressed imprint type without subdigital structures was typical. On very wet mud scratch marks were left by the long claws combined with medium impressed imprints. In about 25 cm deep intertidal channels or pondsIguana began to swim and touched the ground. In less deep water the lacertid left swimming and subaquatic walk scratch marks. In slow move the tail produced a more or less straight deep impression and the pes was printed behind the manus. By running activities the pelvic girdle was uplifted, the tail did not touch the ground and the pes was printed besides the manus. Astonishing is the identical track preservation of the fossil European Triassic trackways on biolaminates. The experiment results are very similar to the fossil record with the very abundant Lower to Middle Triassic track genusRhynchosauroides in the southern margin of the Germanic Basin with its ancient carbonate tidal flat megatracksites. With the study of the recent lower or upper intertidal environments in the Arabian Gulf fossil footprints can be positioned in the palaeoenvironments of the old tidal flats, tidal ponds or channels. Also the biolaminate consistence of the fossil Middle Triassic carbonate tidal flats and moving activity zones of the most possible trackmakerMacrocnemus, a fossil Middle Triassic prolacertilian of Europe, can be reconstructed. These old reptiles must have lived primary in the carbonate tidal flats, especially searching for food in the lower intertidal, where they left the highest density of their trackways in the entire surrounding Germanic Basin coastline about 240 Mio. years ago under the same subtropical arid conditions as in the recent Ana logon, the southern Arabian Gulf.

Diurnal and Tidal Variation in the Abundance of the Fish Fauna of a Temperate Tidal Mudflat

Mud and sand intertidal flats are a dominant feature of many estuaries and harbours, and may comprize a significant component of the total estuarine habitat available to fish. Information on what fish utilize such habitats, and when, is sparse. Small fish usage of a medium sized tidal flat (∼1 by 1km) in Manukau Harbour, New Zealand has been quantified. Fish assemblages were sampled with respect to tide (high, low) and diurnal (night, day) phases, using beach seine and outrigger trawl (a form of push net). Catches were dominated by fish smaller than 100mm, and included juveniles of larger species, and adults of smaller species. For beach seine, low tide samples had substantially higher species diversity and abundance than high tide samples. In addition, low tide night samples had greater species diversity and abundance than low tide day samples. High tide samples varied little between day and night.Data from the outrigger trawl, a novel method able to sample across the full tidal flats, showed that most fish species occurred across the full extent of the tidal flat at high tide. This indicates that fish move 1000m or more per tidal cycle between the deep, low tide channels and the shoreward margin of the tidal flat. The fish assemblage was not concentrated along the tideline. Species that were expected to be less mobile (a goby and a triplefin), declined in abundance with increasing distance from the low tide channel. Overall, no particular tidal zone was more important than any other. Most species were present over both day and night periods, although catch rates were higher at night for many species. The degree to which gear avoidance may have contributed to this is not known.

Dolomite in Modern Carbonate Sediments, Southern Florida: ABSTRACT

The western margin of Florida Bay contains extensive shallow-water banks of unconsolidated, fine carbonate mud. The banks are separated by narrow tide channels and rest on hard Pleistocene bedrock. The banks attain a maximum thickness of about 4½ feet. Radiocarbon dates show that they have been formed in the past 4,000 years. The carbonate mud is composed principally of aragonite, with lesser proportions of dolomite and both high- and low-magnesium calcite. The proportion of dolomite varies, ranging up to about 5 per cent by weight of the total carbonate. Other constituents are quartz and opaline sponge spicules, but these rarely form more than 1 or 2 per cent. Dolomite crystals are euhedral rhombohedrons varying in size from less than 1 micron to approximately 60 microns. They commonly have dark internal rhombohedrons that appear to be intergrowths of dolomite and organic materials. Complex clusters of interpenetrating rhombohedrons are present, but are rare. The occurrence of interpenetrating rhombohedrons and intergrowtbs of organic and carbonate material suggests that dolomite has been formed in situ in Florida Bay; however, radiocarbon dating shows that the dolomite is older than 35,000 years and must be detrital. End_of_Article - Last_Page 281------------