Shallow Water Conditions Research Articles

Origin and Evolution of Eocene Rock Salts in Pakistan and Implications for Paleoclimate Studies: Insights From Chemistry and Cl Stable Isotopes

The Kohat Basin (KB) lies on the Himalayan Foothills and is of scientific importance as it directly recorded the closure of the Tethys Sea and the Himalayan collision between India, Asia, and a number of other small plates. During the Eocene, after the collision between the Indian and Eurasian plates terminated the Tethys Sea, thick-bedded marine evaporite sequences developed in the KB. In this study, we combined mineralogy, geochemistry, fluid inclusion and chlorine stable isotope compositions to discuss the origin and evolution of the KB Eocene halite deposits with the ultimate objective of defining the paleoclimate that was prevailing in Asia during the Eocene. Our results showed that halite samples were SO42− rich (225–370.103 ppm) and Br− poor (<3 ppm). Cl−, B+, Mg2+, K+, SO42− and very low Br concentrations as well as the (Br/Cl) ratios indicated that halite resulted of a mixture of solutions with variable compositions and that dissolution, recrystallization and a progressive decrease in dolomitization were the mechanisms leading to the formation of these evaporites. A Br/Cl vs Cl plot revealed that the end members involved were: seawater (sw), saline waters and/or freshwaters. The recrystallization process prevented identifying the primary structures and primary fluid-inclusions. Most of Cl isotope compositions (−0.54‰<δ37Cl < 0.83‰) were within the usual range (0 ± 0.5‰) associated to seawater as the initial source for the halite. The higher isotope compositions (δ37Cl ≥ 0.83‰) comforted the hypothesis of the genesis by mixing of solutions of different origins as well as the involvement of recrystallization. Based on our results, we are proposing the following to explain the regional paleoclimate sequence: 1) shallow water conditions; 2) halite precipitation induced by evaporation, 3) unstable paleoclimatic conditions that resulted in the morphing from an evaporite basin into a terrestrial foreland basin. All these events were controlled by regional tectonic and linked to both the overall uplift times of the NW Indian Craton and the Eocene thermal maximum one during the Eocene-Oligocene period.

Age, microfacies and sedimentary environments of the Sirenia-bearing deposits of the Qom Formation in Central Iran

Sea cows are exceptional fossil vertebrates recently discovered in the deposits of the Qom Formation. Yet, the Sirenia-bearing limestones are still poorly understood in terms of detail paleoenvironmental and micropaleontological investigations. In order to distinguish the temporal and paleoenvironmental context of the Sirenia (sea cow) bearing deposits of the Qom Formation in central Iran, three stratigraphic sections were studied in Hamedan (Ivak and Shirinsu) and Isfahan (Chahriseh) provinces. A total number of 47 thin sections were studied for micropaleontology, biozonation and carbonate microfacies analysis, as well as sedimentary environment recounstruction. Biostratigraphical investigations suggest that the Sirenia-bearing deposits are Aquitanian/Burdigalian in age, which implies restriction of sea cows remains to the Lower Miocene. We recognized nine microfacies (n=8 correspond to carbonate; n=1 correspond to siliciclastic) in the study areas. They are systematically grouped into two microfacies settings, representing inner and middle ramp environments. This is based on the facies associations and the distribution of skeletal components and rock textures. The Sirenia-bearing limestone consists of peloid/algae bearing wackstone/packstone/floatstone. A carbonate (inner) ramp system under shallow water conditions is interpreted as the habitats of the Sirenian mammals during the Aquitanian/Burdigalian in Central Iran. This paleoenvironmental setting could be utilized for further exploration of Qom Formation deposits for discovering sea cows.

A Janus compatible software-defined underwater acoustic multiple-input multiple-output modem

This article describes the implementation of a multiple-input multiple-output acoustic communication link in shallow water conditions to enable a software-defined acoustic modem with a maximum transmission rate of 20 kbps in a 5-kHz bandwidth. The reliability improvement of a low-complexity Alamouti space–time block code is evaluated to improve the diversity in a high-rate transmission mode using single carrier modulation, as well as in a low-rate transmission mode relying on continuous-phase frequency-shift keying. Using measurements in realistic subsea conditions, the effect of the spatial channel correlation is demonstrated. It is found that for the space–time block code/continuous-phase frequency-shift keying, the spatial diversity is significantly degraded due to the high spatial correlation. In contrast, for the high-mode transmission rate, space–time block code with single carrier modulation offers a bit error rate improvement by a factor over hundred, in comparison to a single transmit element, demonstrating that the multiple-input multiple-output optimal code depends on the software-defined acoustic modem transmission mode.

Advanced Sensor For Monitoring Buoy System Marine Environments

Monitoring of marine ecosystems is essential to identify the parameters of condition. Ongoing advances utilized in senor innovation have been controlled by observing rapid and ease electronic circuits, novel sign handling techniques and imaginative advances in assembling advances. The information got from the sensors used to screen the advancement of numerical models with which to foresee the conduct of states of the water, the ocean bed and the living creatures inhabiting it. Potential field of digital signal preparing includes new methodologies for the improvement of sensor properties. In this paper proposed method are Multi-sensor buoy systems. The chance of use in beach front shallow-water marine conditions, appropriate measurements for arrangement and steadiness of the sensor framework in a moving domain like the ocean bed, and absolute independence of intensity flexibly and information recording .The buoy system has successfully performed remote monitoring of temperature and marine pressure (SBE 41CP sensor), temperature(MCP9700 sensor), atmospheric pressure (YOUNG 61302L sensor), Wind speed (DNA802sensor), and Wind direction (DNA821 sensor). Wind display and signal conditioning (meteorological translator 05603C interface). Measurement values or a decision than usually used threshold base algorithms. The watched future advancement patterns are: the scaling down of sensors and segments, the inescapable utilization of multi-sensor frameworks and the expanding significance of radio remote and self-governing sensors.

Wave overtopping at vertical and battered smooth impermeable structures

Coastal structures play a major role in protecting people and property given the increasing threat of climate-change-induced flooding. Hence, an accurate prediction of wave overtopping for each structure is required to protect both people and properties on the structure's lee side. In this study, a formula set is developed for predicting the mean wave overtopping rate for vertical and slightly battered smooth impermeable structures. The formula set is derived using available datasets of small-scale laboratory experiments and further validated using large-scale laboratory and prototype tests and field measurements. The developed formula set for vertical structures is simple, physically sound, and contains consistent functional forms for deep and shallow water conditions, making it unique among other existing formulas. More importantly, its performance based on several accuracy metrics, is superior to existing prediction methods, including over a wide range of environmental conditions and structural characteristics. Correction factors are proposed for applications to slightly battered structures, as well as obliquely attacking waves. Finally, the formula for probabilistic design is also suggested to account for safety margins in practical applications.

Experimental investigation of the entrapped air on the hydroelasticity induced by liquid slamming under shallow-water condition

The liquid impact induced by slamming in the membrane-type tank is an important issue for the design of Floating Liquefied Natural Gas (FLNG) facilities. The free surface entrapping air may easily happen under shallow-water condition in the tank, which could result in structural local failure. Studying the effect of entrapped air on slamming load is essential to understand the air-free surface-elastic structure interaction. Thus, a series of experiments are designed and conducted in an elastic rectangular tank under shallow-water condition. The evolution of free surface and the development of entrapped air are analyzed quantitatively. Furthermore, both impact load and structural response are measured and studied in the spatial and temporal distribution under shallow-water condition. The results show that the air cavity plays a cushion role between free surface and elastic wall. Therefore, the impact mode is changed from liquid-direct impact to liquid-indirect impact. The existence of the air cavity leads to a significant reduction of the maximum slamming load and structural response but an increase in the pressure impulse in spatial distribution. It is suggested to consider the effect of the entrapped air on the determination of the slamming load for the design of super-large LNG tanks in the offshore engineering.

Stratigraphic model of a Middle-Late Jurassic carbonate system (Mozduran Ridge, Kopet Dagh area, NE Iran)

Lithostratigraphy and biostratigraphy of Middle to Upper Jurassic carbonate platforms of the Eastern Kopet Dagh (EKD), northeastern Iran were assessed. Up to 3000 m of sedimentological logs located along ten stratigraphic sections were investigated. At least five types of carbonate production systems were identified in the study area: (1) a mud-dominated platform carbonate topped by (2) an off-platform carbonate grain-production system, (3) a grain-reworking system deposited within basinal settings (gravity-driven reworking), (4) mounds built by tubular sponges and corals, and (5) prograding oolitic wedges. The first carbonate production system (Callovian‒early Oxfordian) yields platy and solitary corals, together with stromatactis-like structures. The second carbonate production system is represented by upper Oxfordian off-platform grainstones. These two carbonate production systems comprise the Khaneh Zou Fm. The third system is characterised by oncoids, originating from the carbonate platforms. These oncoids, together with bioclasts, were transported into the Kimmeridgian hemipelagic succession of the Chaman Bid Fm. The last two carbonate production systems are common in the Mozduran Fm. Tithonian tubular sponges-corals mounds, and their related dismantling products constitute a major characteristic system of the Mozduran Fm. Shallowing-upward prograding clinoforms are a second characteristic system of the Mozduran Fm., whereby ooids, generated under shallow-water conditions, were shed downslope to form interbeds within basinal mudstones. Our findings suggest that the combination of 2nd order eustatic sea-level changes with hydrodynamic processes as well as rift-inherited morphologies and climatic changes controlled the development and lateral facies evolution of the Middle to Upper Jurassic carbonate platforms. The description of these carbonate systems and of their morphology, together with stratigraphic interpretations may lead to exploration of complex structural-stratigraphic traps, thereby highlighting new potential hydrocarbon reservoirs in the EKD.

Characteristics and controlling factors of lacustrine source rocks in the Lower Cretaceous, Suhongtu depression, Yin-E basin, Northern China

Lacustrine source rocks are widely distributed in the Mesozoic rift basins of northern China. Two lacustrine rift sub-depressions in the Suhongtu depression, Yin-E Basin, have been subjected to a comprehensive analysis of their source rock potential to further reveal the controlling factors and enrichment mechanisms by constructing models for lacustrine source rocks in different tectonic settings. The Hari sag in the Suhongtu depression has significantly greater sedimentary cover and better hydrocarbon generation conditions when compared to the Babei sag by comprehensive analyses of total organic carbon (TOC), chloroform bitumen “A”, Rock-Eval pyrolysis and δ13CPDB. The results show that source rock deposition was affected by organic productivity, organic matter preservation and sedimentation rates. The TOC and δ13CPDB values indicate that there was higher productivity in the lakes of the Hari sag, and productivity reached a maximum during the deposition of the Yingen Formation. The total reduced sulphur (TRS), Pr/Ph, and gammacerane index values indicate that a relative reducing environment was present in the Hari sag. During deposition of the Bayingebi Formation in the Hari sag, the water was suboxic-anoxic, gradually turning anoxic and finally formed a strongly reducing, high-salinity, stratified water environment during deposition of the Yingen Formation. The Babei sag was suboxic-oxidizing throughout the deposition of the Lower Cretaceous lacustrine mudstones. With more active boundary faults and higher sedimentation rates, the terrigenous organic matter inputs to the Hari sub-depression were higher than those in the Babei sub-depression. These observations permitted the development of a model for the formation mechanism for the effective lacustrine source rocks in the Cretaceous fault basin of the Suhongtu depression. In the Hari sag, during source rock deposition of the K1b and K1s formations, intense and more active faults resulted in high terrigenous organic matter being carried into the lake. However, rapid sedimentation rates caused organic matter dispersed. During source rock deposition of the K1y Formation, the sag entered a transition stage from synrift to post-rift with an intermediate sedimentation rate. More organic matter was continuously transported into the basin with high salinity and a strongly reducing sedimentary environment, which caused enrichment of organic matter. In the Babei sag, due to small-scale rifting structures and shallow water conditions, a relatively low influx of terrigenous organic matter and suboxic to oxidizing conditions were developed. This study have important implications for source rock prediction in other lacustrine rift basins.

Growth and survival dynamics of mesophotic coral juveniles in shallow reefs

As many degrading shallow reefs suffer from recruitment failure, mesophotic coral ecosystems have been suggested as a potential source of coral propagules promoting the recolonization of these reefs. However, whether mesophotic coral populations can repopulate shallower reefs is currently debatable. Here, we compared the response of corals settled on mesophotic (50 m) tiles and transplanted to the shallow reef (10 m), at a Nature Reserve and an unprotected site in the northern Gulf of Eilat/Aqaba, Red Sea. Mortality was substantially higher for the transplanted corals, as compared with their shallow counterparts living on the tiles, with over half of the transplanted juveniles dying 1 yr post-transplantation. Transplanted corals exhibited a 24% higher survivorship at the MPA site. We further explored the survival and growth rates of the 4 most common transplanted coral genera (Cyphastrea, Porites, Psammocora, and Stylophora). An inverse relationship between survival and growth was evident among the transplanted coral genera; Porites and Stylophora demonstrated similar net growth rates to those of their shallow-water counterparts but lower post-transplantation survivorship, while Cyphastrea and Psammocora showed the opposite trend. Although this study demonstrates the reduced plasticity of mesophotic coral juveniles to cope with shallow-water conditions, it nonetheless offers some potential to facilitate shallow-reef recovery.

Multiple factors regulate filtration by invasive mussels: Implications for whole-lake ecosystems

The quagga mussel (Dreissena rostriformis bugensis) is a filter-feeding invasive species that has re-engineered many freshwater ecosystems worldwide. High clearance rates (CRs) and dense populations underpin their ecological impacts. CRs, however, are highly variable, as are environmental factors that regulate them. Despite their widespread distribution in Europe and North America, knowledge of how multiple environmental factors regulate CRs of quagga mussels remains limited. We investigated quagga mussel CRs under varying conditions including water temperature, food availability, habitat depth, flow velocity, and duration of incubation in chambers with both static and flowing water. We found that CR was positively related to water temperature and initial food concentration in static chambers. When coupled with limited food concentration, cold water (7.5 °C), due to a deep-water upwelling event, produced very low CR (~ 10× lower) compared to warmer water (12–24 °C) (0.47 vs. 3.12–5.84 L g−1 DW h−1). Mussels from deeper water (20 m) had CRs that were ~ 3.5× higher than from shallower depths (2–10 m) and CRs were inversely affected by total mussel dry weight. Flow rates from 1 to 22 cm s−1 generated a unimodal pattern of CR with an optimal flow velocity of 6–12 cm s−1 (~ 2× higher than suboptimal CRs). Enhanced flow velocity (22 cm s−1), reflective of storm conditions in shallow waters, significantly increased the closing/reopening activity of mussel valves relative to lower velocities (1–12 cm s−1). Incubation time had a strong negative effect (~ 2–4× reduction) on CRs likely reflecting refiltration in static chambers versus food saturation of mussels in flowing chambers, respectively. Our findings highlight how multiple factors can influence quagga mussel CRs by factors of 2–10. Given widespread habitat heterogeneity in large aquatic ecosystems, whole-lake estimates of mussel impacts should include multiple regulatory factors that affect mussel filtration.

Integrated Geophysical Analyses of Shallow-Water Seismic Imaging With Scholte Wave Inversion: The Northern Adriatic Sea Case Study

The integrated analysis using different seismic wave types in a record is a very efficient approach for a comprehensive characterization of marine sediments, especially in shallow water conditions. The proposed integrated method to analyze seismic data in post-critical conditions consists of: 1) the inversion of Scholte waves to obtain a reliable Vs distribution of the near seafloor; 2) pre-processing of seismic data; 3) construction of the P-wave velocity field by using all available information, including available well data; and 4) the application of the wave equation datuming and post-processing, such as pre-stack time migration. We demonstrate how this approach could be successfully applied on seismic datasets characterized by post-critical conditions and the occurrence of the Scholte waves, which may be exploited to provide fundamental information instead of being only an unwanted effect. The integrated analysis of seismic events can thus help, together with data processing, by providing better seismic imaging, which is a priority for a reliable seismostratigraphic interpretation.

Complex depositional environments on a siliciclastic-carbonate platform with shallow-water turbidites: The Natividade Group, central Brazil

The Natividade Group is a Paleo-Mesoproterozoic metasedimentary sequence outcropping in the external zone of the Northern Brasília Belt, western margin of the São Francisco Craton, Brazil. The present study delimited eleven sedimentary rock types grouped into four rock assemblages: i) Sand-Silt-Carbonate; ii) Sand-Conglomerate; iii) Sand, iv) Silt-Clay. A geological map for the region was produced, and six stratigraphic columns were composed. Based on the descriptions of rock types and on lateral variation of rock assemblages, it was possible to establish four depositional environments for the Natividade Group, including mixed platform (siliciclastic-carbonate deposition), internal siliciclastic platform, open-marine siliciclastic platform, and a shallow water turbidite (mass flow slope deposition). The mixed platform was controlled by the basement paleogeography, which allowed the deposition of carbonates in warm, agitated, and clean, shallow water conditions in parallel to deposition in deeper water setting, where thin siliciclastic sediments were deposited. The siliciclastic internal platform consists mostly of quartzite, originating from sandy sediments, probably indicating deposition dominated by bedload currents under shallow water shoreface conditions. The open-marine siliciclastic platform is dominated by fine-grained sediments, indicating deepening water conditions under lower shoreface conditions below the fair-weather wave base. Shallow water turbidite occurs in the southern parts of the study area. The elevated paleorelief in the southeast of the Natividade basin is considered as the provenance area providing suitable slope environments for density flow initiation. The basin was shallower in the southern portion with a predominance of carbonate and gravitational flux deposits and deeper to the north, evidenced by the northward predominance of fine-grained sediments. Finally, the study shows that the Natividade Group was deposited in a basin controlled by thermo-flexural subsidence.

Reconstructing the level of the central Red Sea evaporites at the end of the Miocene

AbstractReconstructing the original depositional level of the Mesozoic and older c‘salt giants’ can reveal if their basins became filled to global sea level, but is complicated by dissolution, diapirism and because the time elapsed is so great. This is less of a problem in the Red Sea, a young rift basin that is transitioning to an ocean basin and where the evaporites away from coastal fringes are less affected by diapirism. In this study, we explore vertical movements of the evaporite surface of the central Red Sea imaged with deep seismic profiling, for the period of time after most evaporite deposition ended at 5.3 Ma (the Miocene‐Pliocene boundary). This boundary is readily mapped across the basin as a prominent reflection in seismic data correlated with stratigraphy at three DSDP sites. We quantify changes in the average elevation of the evaporite surface due to (a) thermal lithospheric subsidence, (b) isostatic loading by Plio‐Pleistocene sediments and water, (c) deflation needed to balance the volume of evaporites overflowing oceanic crust of 5.3 Ma age, (d) loss of halite by dissolution and (e) dynamic topography. Our best estimate of the evaporite level (−132 m air‐loaded or −192 m water‐loaded) lies below the range of estimated global sea level towards the end of the Miocene, suggesting that the basin remained under‐filled. If geological interpretations of shallow water conditions existing at the end of the Miocene (Zeit Formation) are correct, this implies that the water level of the Red Sea declined and was unstable. These calculations illustrate how spreading of evaporites can enhance thermal subsidence to cause rapid development of accommodation space above major evaporite bodies, which in the Red Sea case has remained largely unfilled.

Petroleum source rocks of the Silurian deposits on the Chernov swell (Timan‑Pechora basin)

Silurian source rocks are among the least studied in the Timan-Pechora basin. This is mainly due to their occurrence at great depths (3.0–4.5 km) and the limited penetration of this stratigraphic interval by wells. Another source of information is the outcrops of the Silurian, which are known in the eastern and northeastern parts of the Timan-Pechora basin. The studied section of the Silurian deposits is exposed on the Padimeityvis River, located on the Chernov swell in the northeastern part of the basin. This article is devoted to the study of Silurian source rocks based on the results of lithological, coal petrographic studies and geochemistry of organic matter. The studied section is composed of carbonate and clay-carbonate deposits formed in shallow-water shelf conditions. Most of the section, composed of microcrystalline and microcrystalline with bioclasts limestones, is characterized by low concentrations of organic matter (Corg is generally less than 0.3 %). Elevated Corg contents (up to 1.16 %) are characteristic of clay-carbonate rock varieties, which make up about 20 % of the section. Sediments with increased concentrations of organic matter were formed in isolated and deepened areas of the bottom of the shallow-water basin as a whole. Assessment of the catagenetic transformation based on Rock-Eval pyrolysis data, coal petrographic studies, and conodont color indices showed that organic matter reached the conditions of the middle-end of the main oil generation zone (gradation MC2‑MC3). The obtained geochemical characteristics (Corg, S2, HI), taking into account a certain level of organic matter maturity, indicate that the Silurian source rocks had an average hydrocarbon potential.

A Neogene bristlemouth of the genus Cyclothone (Stomiiformes: Gonostomatidae) from South Korea

ABSTRACT A fossil specimen of bristlemouth fish of the genus Cyclothone is reported for the first time from the marine deposits of the middle Miocene Duho Formation, South Korea, and described as new species Cyclothone duhoensis, sp. nov. This is the second stomiiform fish discovered there. It represents the oldest nominal species of its genus, and the third and southernmost record of fossil bristlemouth from the ancient Eastern Sea (Sea of Japan) basin after the findings in the Sakhalin (Russia) and Honshu (Japan) islands. The new Miocene bristlemouth is very similar to the Recent congeners. Nevertheless, it can be separated from them by the presence of more than 15 photophores in the AC series, of which at least four photophores are behind the anal-fin base, and by a peculiar upper jaw dentition. The biological features of the Recent bristlemouths along with this unique finding hint at shallow-water conditions during the Duho Formation sedimentation.

In situ Photosynthetic Activities and Associated Biogeochemical Changes in Three Tropical Seagrass Species

Tropical seagrasses, experience considerable spatio-temporal changes in light and other biogeochemical conditions and adopt species-specific acclimatization strategies. Variation in photo-acclimatory responses of three tropical seagrass species (Cymodocea serrulata, Thalassia hemprichii and Enhalus acoroides) were studied by measuring photosynthetic electron transport rates (ETR) using Pulse Amplitude Modulated (PAM) fluorometry technique. Quantitative values of ETR and rates of photosynthetic O2 evolution (net O2 exchange corrected for dark respiration) were compared to establish species-specific relationships in these shallow water conditions. The apparent average molar ratio of O2 evolution to ETR for Cymodocea serrulata, Thalassia hemprichii and Enhalus acoroides were estimated as 0.23, 0.19 and 0.20, respectively. The highest photosynthetic activity (ETRmax) varied significantly among the three studied species in the decreasing order as: E. acoroides (59.27); T. hemprichii (54.06) and C. serrulata (46.72). The effective quantum yield (Y) of PS II (Photosystem II), one of the most useful indicators of stress conditions for seagrass, was observed to be significantly higher for E. acoroides compared to the other two species. Variability of Y in the ambient conditions are explained by the difference in water temperature and pCO2 for the three seagrass species. This study is useful in predicting the photo-acclimation strategies to any change in light availability and subsequent biogeochemical changes at the bottom surface, by these shallow water tropical seagrass species.

Distributed Propulsion Systems for Shallow Draft Vessels

The aim of this study was to investigate the impact of distributed propulsion systems used on inland and coastal navigation in shallow water. Five layouts were assessed by computational fluid dynamics (CFD) simulation. The hull/propulsion layout cases have been analyzed for discrete flow speed values in the range 0–6 m/s. All cases have been examined under restricted draft conditions in shallow water with a minimum of 0.3 m under keel clearance (UKC) and under unrestricted draft conditions in deep water. The results show that distributed propulsion consisting of 6 or 8 (in some cases, even more) units produces noticeable higher thrust effects in shallow water than the traditional layout. Under restricted conditions, the thrust increase between two distributed layouts with different numbers of propulsors is higher, in contrast to deep water, where differences in performance are not so significant.

Theoretical and experimental investigations of wave field around vessel in shallow water

Un-running vessel at the shallow-water road anchorage is under exposure to waves that come at arbitrary angle from the high sea. 3D waves from deep-sea area become practically 2D when entering shallow water. While mean periods are kept, waves become shorter and their crests become higher and sharpener than for deep-water ones. As a result of diffraction of waves that come from the deep-water sea at the vessel, a transformation zone appears where waves become 3D again. Dimensions of the waves’ transformation zone, character and height of waves in this zone specify safety of auxiliary crafts, e.g. tugboats, bunker vessels, pilot and road crafts, oil garbage collectors and boom crafts. In the complex 3D waves the trajectory of auxiliary vessel’s movement has to be safe, vessel’s motions have to be moderate. Besides waves’ height is one of the parameters that are used for forecast of movement of spilled oil. Last years the biggest part examination of waves’ problems was devoted to estimation of waves’ impact onto stationary or floating shelf facilities. For validity estimation, waves’ characteristics defined due to different theories, are compared with experimental ones. But characteristics of the waves around shelf facilities are hardly able to be compared to same ones of waves around bodies with vessel-type shape. At the experiments with vessels’ models, waves’ impact onto vessel was examined, but not the transformation of the waves themselves. So, comparing of waves area’s characteristics defined by both theoretical experimental ways is an actual problem. Aim of the paper is verification of results of wave area investigation; wave area is located around a vessel that is exposed of arbitrary angle waves at shallow water conditions. Description of experimental investigations of transformed waves in the towing tank is done; transformation zone appears around vessel’s model while running waves diffract on it. Distribution of waves’ amplitudes at the designated points was fixed by the special designed and manufactured unit. Experimental data is compared with computation results both of linear and non-linear theories. It was assumed that experimental results and theoretical data satisfactory meet each other; also that non-linear computations define the maximal values of waves’ amplitudes at all cases.

Bivalves from the Innviertel Group of Allerding in the North Alpine Foreland Basin (lower Miocene, Upper Austria)

During the Ottnangian (Burdigalian, early Miocene), the North Alpine Foreland Basin operated as a sea-way connecting the Central Paratethys Sea with the Rhône Basin in the Western Mediterranean. Within this short time window, an intensive faunal exchange between the two paleo-biogeographic units occurred, which is reflected in macrofossil assemblages. The extraordinarily rich fossil record of the study site, Allerding, located in the westernmost Central Paratethys, provides valuable insights into the composition and origins of the bivalve fauna colonizing the marine gateway. The site documents the early Ottnangian marine transgression over deeply weathered crystalline basement, grading from fossil bearing shallow water clay and sand into the open marine "Schlier" facies of the Ottnang Formation. Despite considerable taphonomic overprint including aragonite leaching and mechanical abrasion of bivalve shells under turbulent shallow-water conditions, a total of 46 species are recorded, including two new species (Lima allerdingensis n. sp. and Astarte danningeri n. sp.). The dominance of suspension feeders, and the presence of several deposit feeders and chemosymbiotic taxa point to well diversified inshore settings, including low intertidal mudflats, as well as seagrass meadows. An abundance of primary and secondary hardgrounds is reflected in the high number of cementing and byssate species, as well as in the occurrence of species drilling actively into hard substrate. Finally, the dominance of active burrowers suggests a patchwork of habitats, where sandy and muddy soft bottoms occur interspersed. Biostratigraphic analysis constrains the deposits to the early to middle Ottnangian, based on the presence of the index species Flexopecten davidi and the concurrence of several taxa, which have their last or first occurrences within this interval. These are predominantly taxa persisting into the Badenian, therefore allowing for a straightforward differentiation between late Eggenburgian and early Ottnangian assemblages. While a few Central Paratethys endemics reflect a continued semi-isolated position of the area, the majority of the newly arriving species are shared with the Mediterranean and NE Atlantic, documenting the establishment of a faunal migration route via the North Alpine Foreland Basin. In the present study the lectotypes of Nucula mayeri Hörnes, 1865, Saccella subfragilis (Hörnes, 1875) and Lucinoma wolfi (Hoernes, 1875) are designated.

Experimental study on nonlinear sloshing frequency in shallow water tanks under the effects of excitation amplitude and dispersion parameter

Sloshing of liquid in partially filled tanks under high excitation amplitude is always a complicated phenomenon for shallow water condition. This complication arises due to nonlinear behaviour of liquid free-surface motion when the excitation amplitude is sufficiently large. Due to nonlinearity, the sloshing resonant frequency also gets affected and so the performance of several devices developed based on linear sloshing concept is disturbed. One widely studied and used such device is Tuned Liquid Damper (TLD). In the present study, a series of experiments has been conducted to investigate the nonlinear shallow water sloshing in detail. Experimental tests were carried out for tanks of different base-aspect ratios (length to width of tank), different water-depths, wide range of excitation amplitudes and frequencies. Nonlinear characteristics such as frequency jump-phenomenon, shift in resonant frequency, super-harmonic resonance, responses at higher harmonics and fractional harmonics of forcing frequency have been reported. It has been found that the resonant frequency is sensitive to the excitation amplitude and dispersion parameter (ratio of water-depth to tank-length). For a tank of large aspect-ratio under high excitation amplitude, it is also found that the resonance frequency increases about 45% in comparison to the linear sloshing frequency.