Shallow Sea Research Articles

Influence of inter-river water diversion on estuary pollution control: A case study of Liaodong Bay

Long-term mass transport processes in offshore seas are controlled by seasonal residual currents. The Euler residual mass transport velocity field was calculated form seasonal residual current patterns in shallow sea area, comparing with polluted water changes in typical years. The following conclusions were made: closed local large loops of the Euler residual mass transport led to polluted waters in the northeast Liaodong Bay, and the bay's optimal physical self-purification occurred in winter (Euler residual mass transport diffuses polluted water masses) and spring (overall self-purification capacity of the bay plays a role after winter). The central waters were clean while pollutants were discharged into near-shore waters, leading to perennial pollution in some near-shore waters. Pollution in Liaodong Bay could be alleviated or eliminated via diversion of water from the Daliaohe River (flowing into the northeast corner of Liaodong Bay and carrying > 65% of the total amount of pollutants discharged into the top of the bay) into the Liaohe River and Daling River. The percentage of inorganic nitrogen carried by 10% of the flux of the Daliaohe River was 5.70% of that discharged into Liaodong Bay. If 10% of the flux of the Daliaohe River was discharged into the Daling River, the annual total environmental carrying capacity of inorganic nitrogen increased 4.48%. Many bays in the world have adjacent river flows, such as Gulf of Mexico, Gulf of Guinea, and Bay of Bengal. Based on the Euler residual mass transport field, the water transfer between adjacent rivers could make better use of the Euler residual mass transport capacity to mitigate the water pollution of the estuaries.

Source identification and risk assessment of trace metals in surface sediment of China Sea by combining APCA-MLR receptor model and lead isotope analysis

This study aimed to investigate the distribution, pollution, risk and sources of trace metals in sediments along China Sea. Clear spatial variations were found for Cr, Mn, Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, and Pb, whereas As did not show spatial variation. East China Sea (ECS) contained the highest concentrations of Mn, Co, Ni, Cu, Zn, South China Sea (SCS) shallow sea contained the highest concentrations of Zn, Se, Mo, Ag, Cd, and Pb, whereas coral reefs contained the lowest concentrations of trace metals. Spatial variations could be explained by economic development characteristics along China Sea. As, Se and Cd exhibited low to moderate pollution in China Sea sediment, yet pollution for Cu, Zn, Ni, and Ag appeared in some regions. Sediment in ECS had moderate ecological risks and other regions at low ecological risks. The absolute principle component score-multiple linear regression (APCS-MLR) and Pb stable isotope indicated that 43–74% of trace metals (Ni, Cu, Zn, As, Se, Cd, and Pb) were derived from anthropogenic sources like traffic emission, agricultural activities, industrial source. No pollution and ecological risk were observed in coral reefs, yet 39–71% (Pb) was derived from anthropogenic activities such as motor vessels.

Rock Mineralogy Analysis of Airbenakat Formation to Map the Characteristics of the Reservoir Rocks in each Depositional Environment

The Airbenakat Formation is a sandstone reservoir which is one of the oil reservoirs located in Sumatra and is part of the South Sumatra Basin. The mineral composition of the sandstone reservoir in the Airbenakat Formation consists of quartz minerals as rock grains, clay as matrix and is often identified as cement, while carbonate as rock cement. Based on lithofacies observations, the depositional environment of the Airbenakat Formation consists of: Volcanic Alluvial Fan, Lake, Braid Bar, Braided Channel, Braid Deltaic Environment, Mud Flat, Tidal Sand Bar, Tidal Environment, Shallow Sea, and Deep Sea. This research was conducted on 2 (two) oil fields, namely MRP dan TPN which have different depositional environments but are included in the Airbenakat Formation as part of the South Sumatra Basin.The analyzes used in this study include X-Ray Diffraction (XRD) analysis, petrography, and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM/EDX). Analysis of the mineralogical content of the Airbenakat Formation will assist to determine the performance of chemical injections such as injection of anionic surfactant. The anionic surfactant used for chemical injection in Airbenakat Formations will be optimal if the content of smectite and calcite minerals can be ascertained. The presence of smectite and calcite minerals will affect the results of anionic surfactant injection. This research shows the results of anionic surfactant injection on the presence of smectite and carbonate in the injected core.

Metamorphosed mélange in the eastern Himalayan syntaxis: constraint for the India–Asia collision in the Eocene

Tectonic mélanges are crucial for deciphering collision processes in orogenic belts. This study investigates the nature of the metamorphosed mélange in the Milin area of the eastern Himalayan syntaxis to shed light on the India–Asia collision in the region. The mélange exhibits a ‘block-in-matrix’ fabric in the lower and upper parts and a ‘lenticular-thrust-slices’ fabric in the middle. Quartzite blocks in the lower part are proposed to be Silurian or younger quartz arenites with a Tethyan affinity. Metacherts and amphibolites in the middle and upper parts may have originated from hydrothermal or terrestrial cherts and Nb-enriched basalts in the Asian forearc or syncollisional basin at ∼48–45 Ma. The diverse blocks/slices of the mélange, sourced from both the subducting and overriding plates, are suggested as having formed during Indian plate subduction. The protoliths of the amphibolite–metachert slice (∼45 Ma) in the mélange are distinctly different from the contemporary shallow sea (post-collisional) deposits but similar to the deep-water (initial collisional or pre-collisional) sediments in other parts of the suture zone. This implies that the amphibolite–metachert slice may represent the product of the initial India–Asia collision or even pre-collision and that (hard) collision likely lagged by ∼10 Myr in the eastern Himalaya syntaxis. Supplementary material: Analytical methods, Figures S1–S5 showcasing field occurrences, cathodoluminescence images of zircons, and geochemical characteristics, Table S1 – geochronology data, Table S2 – zircon Lu–Hf isotopic data, and Table S3 – whole-rock major and trace element results are available at https://doi.org/10.6084/m9.figshare.c.6896942 Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Ecosystem indicators: predicting population responses to combined climate and anthropogenic changes in shallow seas

Crowded seas are becoming a pressing management problem with the increased development of offshore renewable energy (ORE) to combat climate change. Marine ecosystems are complex and varied; therefore, we need new tools to help rapidly increase our understanding of how they are likely to change with both climate and anthropogenic changes. This study uses a pragmatic data‐driven Bayesian network approach to capture the patterns of ecosystem complexity and reveal trends of ecosystem drivers (i.e. indicators) important to ecosystem functioning across space and over time. The ecosystem approach assessed physical and biological indicators and their influence on population (abundance/productivity) trends in four regions with contrasting habitats of the North Sea within the last 30 years (1990–2019). What‐if scenarios were conducted to examine species/functional group responses to physical (temperature and stratification) representing climate and large‐scale ORE development effects, as well as anthropogenic (fishing) changes. Clear patterns were revealed, including temporal trends of the dynamic nature of bottom‐up effects driven by physical change versus top‐down effects driven by fishing across trophic levels and habitat types. All four regions are influenced by both effects; however, the dominance of effects was dependent on region: Shetland and Orkney (bottom‐up driven), southern North Sea (top‐down driven). In general, regions with stronger bottom‐up effects showed increasing population trends whereas those with stronger top‐down effects, decreasing trends. Our findings also suggest that some species are much better indicators of either bottom‐up (e.g. zooplankton), top‐down effects (e.g. fish) or both (e.g. grey seal), but the strength of indicator is dependent on habitat type. The habitat‐specific results provide better understanding of what type of ecosystem change they are indicating (physical or biophysical) and therefore indicators that assess both ecosystem status and resilience, ensuring a more strategic and integrated evaluation of trade‐offs for future sustainable management of our shallow seas.

Early corrosion behavior of 35CrMo steel for high-strength bolt in simulated shallow and deep sea environments

Early corrosion behavior of 35CrMo low-alloy steel for high-strength bolt in the simulated shallow seawater and deep-sea environment was studied using mass loss measurement, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Raman spectrometer, X-ray photoelectron spectrometer (XPS) and 3D microscope. The results show that the corrosion of 35CrMo steel initiates mainly at the steel matrix around the inclusions of CaO–MgO–Al2O3, (Ca, Mn)S and their mixed composite. The corrosion rate in the simulated deep-sea environment is lower than that in the shallow seawater, which is declined with immersion time. The corrosion products formed in the two environments are composed of γ-FeOOH, α-FeOOH, Fe3O4 and little Cr(III) oxide or/and hydroxide, but the rust layer produced in the deep-sea environment is thin and uniform. The steel has pits in a shallow dish shape and tends to develop uniform corrosion in the deep-sea environment.

PEMBERDAYAAN MASYARAKAT BERBASIS EDUWISATA BAWAH AIR PADA WILAYAH KELOLA HUKOM ADAT LAOT (WK-HAL) LHOK LAMTEUNGOH SINERGISME DENGAN USK DALAM MENDUKUNG KAMPUS PTNBH

The Laot Lhok Lamteungoh traditional legal management area has marine natural characteristics consisting of shallow sea areas with coral reef ecosystems in several places, one of which is on Tuan Island, and several other points to the west-south in Peukan Bada District, Aceh Besar Regency. Coral reef areas are resources that must be conserved and provide income for the surrounding communities. PKMBP 2023 seeks an integrated program which will ultimately produce prospective entrepreneurs in the marine or maritime services sector, especially underwater tourism from traditional fishing communities. Service activities have been carried out for approximately 6 months June-November 2023 with socialization activities, FGDs, and a number of trainings and product placements in designated locations. The outputs produced in this activity include IPRs in the form of Copyright certificates, artificial reef prints, artificial reef products, mass media publications, and service journal publications. All targets were achieved as planned.

Foraminifera in the Holocene sediments at the shallow sea from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) (0÷60 m of water depth)

The shallow sea (0÷60 m of water depth) from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) belongs to the internal shelf in Central Vietnam. This is quite a good geological structure for the land-sea interaction study, especially during the Holocene. Therefore, it is necessary to study the geological history of the area during the Holocene period. Foraminifera is the subject of geological studies to solve the environmental problems of sedimentary, stratigraphic, and paleogeography. However, at present, the research documents on Foraminifera in the sediments in Vietnam in general as well as in the research area in particular are still very modest. This paper presents research results of Foraminifera fauna in Holocene sediments from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) (0÷60 m of water depth). 93 species, belonging to 48 genera, 28 families and 5 suborders Foraminifera have been identified based on the analysis of 59 available samples. Miliolina Delage et Hérouard, 1896 has 06 families, 18 genera and 40 species; Rotaliina Delage et Hérouard, 1896 has 12 families, 15 genera and 29 species; Textulariina Delage et Hérouard, 1896 has 03 families, 05 genera and 07 species; Lagenina Delage et Hérouard, 1896 has 03 families, 04 genera and 07 species; Globigerinina Delage et Hérouard, 1896 has 04 families, 06 genera and 10 species. The quality of the benthonic Foraminifers is dominant, clearly showing the geological environment of the shallow sea near shore, where the hydrodynamic regime is high and the salt concentration is not stable.

Optimizing Seagrass Detection in Lampung Selatan: Leveraging Machine Learning Algorithms and Sentinel-2A Imagery

Seagrass beds are one of the coastal ecosystems that play an important role in maintaining the stability of blue carbon. However, high community activities threaten the existence of seagrass beds themselves. South Lampung Regency is one of the areas with considerable seagrass potential but the availability of distribution and density data is still minimal. This research aims to identify and map seagrass density as a first step for seagrass management. The data used in this research is Sentinel 2A multispectral image. Machine learning-based classification methods used are random forest (RF) and support vector machine (SVM) because these algorithms have a good ability to distinguish objects based on their features. This study uses a 2-level classification scheme, where level 1 consists of land, shallow sea, and deep-sea classes. Level 2 is the shallow marine bottom benthic habitat class. The type of seagrass found in this area is Enhalus acoroides. Based on the results of the analysis, low, medium, and high-density classes were obtained with an area of low around 20.12 ha, medium around 34.67 ha and high around 320.12ha with a total area of 374.91ha. RF has a higher overall accuracy of 88.00% while SVM accuracy is 84.00% so it can be concluded that Sentinel 2A images can be used to detect seagrass meadows.

Phase Invariants of Vector–Scalar Fields Excited in the Shallow Sea by Multipole Sources

Phase Invariants of Vector–Scalar Fields Excited in the Shallow Sea by Multipole Sources

Application of the use of local natural materials as cement treated base materials

The use of local natural materials as alternative materials in road construction could save construction costs, especially for Maluku Province. One of the local natural materials in Maluku Province is Limestone in Kelan Village and Kaliobar Village. Therefore, this study aims to see how far the use of limestone to be applied as a cement treated base material. Before being applied, the limestone is tested first in the laboratory. After the limestone was applied as a cement treated base (CTB) material, compaction and compressive strength tests were carried out. The number of CTB compressive strength test specimens was 26 samples from STA 4+100 to STA 8+900. The limestone on Larat Island is unique in that it contains the composition CaCO3 (Calcium Carbonate), which is the result of shallow sea sedimentation. The potential of limestone in the work location area has not been utilized optimally to improve the economic level of the community. The test results show that the compressive strength values obtained are still within the interval range, namely between 25 - 40 gr/cm2. Therefore, it can be concluded that the CTB mixture material at this location meets the requirements to be used as a foundation layer for road pavement using local natural materials.

Effect of atmospheric corrections on shallow sea bathymetric mapping using gaofen-2 imagery: a case study in Lingyang Reef, South China Sea

Satellite-derived bathymetry (SDB) with high spatial resolution effectively maps detailed information about shallow sea depths. Properly selecting atmospheric correction (AC) methods is crucial to obtaining precise bathymetric information from satellite data. In this work, three different AC methods (FLAASH, 6S, and DOS) were applied to GaoFen-2 imagery in Lingyang Reef, South China Sea. Water depth retrieval models, such as single-band, multiband, and band ratio models, were established by 470 points of in-situ water depth data and used for evaluating the model performances. Additionally, the optimal model was applied to depth inversion. The results show that the multiband model based on four bands performs well in this study area with R2 =0.736. The choice of AC methods significantly affects SDB, although acceptable results can be derived without these methods. Specifically, the DOS method has the highest inversion accuracy, with a mean relative error and root mean square error of 14.05% and 3.31 m, respectively. Furthermore, the inversion accuracy in various depth ranges may be primarily influenced by suspended sediment concentration and bottom-type uniformity. This study provides a valuable reference for selecting AC approaches and inversion models in high-spatial-resolution SDB in shallow seas.

Influences of hydrodynamics on microbial community assembly and organic carbon composition of resuspended sediments in shallow marginal seas

Hydrodynamic processes play a crucial role in driving the transmission of sediments, likely harboring diverse microbes and heterogeneous organic carbon (OC) in the ocean. Here we conducted continuous micro-erosion experiments on surface sediments retrieved from shallow marginal seas, and analyzed the microbial community structures, OC content, and isotope compositions (δ13C and Δ14C) of resuspended sediments to investigate the effects of hydrodynamics on microbial assembly and OC composition in marginal seas. Our results showed that gene abundance and major microbial compositions in resuspended sediments changed with varying benthic shear stresses, which evolved towards diversification after continuous hydrodynamic erosion. Aerobic bacteria were more likely to be eroded out from sediments under lower shear stresses compared with anaerobic bacteria. Our study provides evidence that hydrodynamic disturbances shape the assembly of microbial communities with different metabolic functions, especially for bacteria, which may spatially influence the microbial-mediated biogeochemical transformation in marginal seas. Isotopic results revealed that more terrestrial OC was resuspended under initial erosion, while more marine OC was eroded out with increasing shear stresses, suggesting that hydrodynamics may control the redistribution of different sourced OC and contribute to the dispersion and degradation of terrestrial OC during transport process. Our findings further suggest that the nature of resuspended OC may influence the assembly of sediment-attached microbes due to their metabolic preference for carbon sources, as evidenced by correlations between OC compositions and microbial diversity and abundance. We thus suggest that hydrodynamic disturbance is an extrinsic physical driver of OC redistribution and microbial reassembly, whereas OC may be an intrinsic factor influencing microbial colonization, helping to interpret the spatial heterogeneity of microbes and OC compositions observed in marginal sea sediments. Our study underscores the significant roles of hydrodynamic-driven sediment resuspension in shaping diverse microbial communities and redistributing OC in aquatic systems, and highlights the importance of this process in biogeochemical cycles and ecological environment evolution in shallow marginal sea systems.

Numerical analysis of dispersion characteristics of underwater gas-oil two-phase leakage process

Fatigue failure, third-party destruction and internal corrosion may easily trigger gas and oil leakage during the operation of submarine multiphase pipelines. In order to analyze the underwater gas-oil plume development and migration law, a 3D model based on coupled Eulerian-Lagrangian numerical approach is proposed. The model is validated by laboratory experiment and the dynamic dispersion process of gas-oil plume in a large scale shallow sea environmental is further explored. Influencing factors such as leak location, leak size and water depth, flow pattern are investigated. The simulated results show that leak location affects the gas-oil plume migration behaviors by influencing the leakage amount. Water depth significantly affects gas-oil migration and the separation of gas plume and oil plume is gradually apparent as water depth increases. This study fills in the gap of ignoring the influence of flow pattern previously and is expected to help build more accurate emergency response guidelines.

Model-based optimal action selection for Dyna-Q reverberation suppression cognitive sonar

The Doppler shift of low-speed targets is frequently disturbed by the reverberation Doppler spread clutter under the shallow sea. The clutter is generated by underwater scatterers, which increases the difficulty of Doppler estimation. To solve this problem, a reverberation target resolution function based on the Doppler spread clutter statistical model is proposed in this paper. Through the width of reverberation Doppler clutter, this function adjusts the waveform parameters by determining whether the target is discriminable. In addition, the reverberation Doppler spread clutter is time-spatial varying and affected by grazing angle, waves, wind speed, fish and other effects. Thus, the sonar waveform parameters need to be adjusted constantly. Therefore, this paper combines the cognitive sonar based on reinforcement learning with the reverberation target resolution function to evaluate different waveforms in different environments. Consequently, the sonar can adjust the waveform parameters in real-time and obtain the optimal waveform in different environments. Meanwhile, in this paper, the action selection strategy of Dyna-Q reinforcement learning is optimized, and the model-based maximum action selection Dyna-Q algorithm (Dyna-Q-Max-Action) is proposed. Compared with the traditional Dyna-Q and Q-learning algorithms, the proposed algorithm needs fewer episodes. Finally, numerical simulation verified the effectiveness of the proposed algorithm.

Background Topography Affects the Degree of Three‐Dimensionality of Tidal Sand Waves

AbstractOffshore tidal sand waves on the sandy bed of shallow continental shelf seas are more three‐dimensional (3D) in some places than others, where 3D refers to a pattern that shows variations in three spatial directions. Such sand waves have crestlines that meander, split or merge. The degree of three‐dimensionality seems to vary especially when large‐scale bedforms, such as tidal sand banks, are present underneath the sand waves. Understanding this behavior is important for offshore activities, such as offshore windfarm construction or the maintenance of navigation channels. In this study, the degree of three‐dimensionality of sand waves at five sites in the North Sea is quantified with a new measure. Results show that tidal sand waves on top of tidal sand banks are more two‐dimensional (2D) than those on bank slopes or in open areas. These differences in sand wave pattern are supported by numerical simulations performed with a new long‐term sand wave model. The primary cause of these differences is attributed to the deflection of tidal flow over a sand bank, which causes sand wave crests to be more aligned with the bank at its top than at its slopes. It is subsequently made plausible that the different patterns result from the competition between two known mechanisms. These mechanisms are nonlinear interactions between sand waves themselves (SW‐SW interactions) and nonlinear interactions between sand banks and sand waves (SB‐SW interactions). On bank tops, SB‐SW interactions favor a 2D pattern, while SW‐SW interactions, which elsewhere produce a 3D pattern, are less effective.

The dynamical study and analysis of diverse bright-dark and breathers wave solutions of nonlinear evolution equations and their applications

In this work, we establish novel solitary wave solutions of three nonlinear evolution dynamical models, namely, Boussinesq model, [Formula: see text]-dimensional generalized shallow water wave (SWW) and [Formula: see text]-dimensional Fokas dynamical models by applying two-variable [Formula: see text]- expansion technique. The SWW equations are usually appropriate when the fluid is in a state where the vertical length scale is significantly smaller than the length of horizontal scale. In computer simulations for ocean engineering, Boussinesq-type models are frequently used to represent water waves in harbors and shallow seas. In order to understand the physical processes of waves inside and on the surface of water, the Fokas dynamical model plays a crucial part in wave theory. Analytical solutions in different forms such as solitons, solitary waves, trigonometric, hyperbolic, rational function solutions, breathers-type waves and more wave solutions are devised through using the proposed method. The exact solutions are also presented in graphical form having applications in engineering and other areas of applied sciences. The obtained results show that the given technique is universal and efficient. In addition, this technique can also be applied on lots of other nonlinear dynamical wave models occurring in many scientific real-world application domains, including engineering sciences, mathematics physics, and many more.

Random matrix theory for description of sound scattering on background internal waves in a shallow sea

The problem of propagation of low-frequency sound in a shallow waveguide with random hydrological inhomogeneity caused by background internal waves is considered. A new approach to statistical modeling of acoustic fields, based on the application of the random matrix theory and previously successfully used for deep-water acoustic waveguides, is used to the case of shallow-water waveguides. In this approach, sound scattering on random inhomogeneity is described using an ensemble of random propagator matrices which describe the transformation of the acoustic field in the space of normal waveguide modes. A study of the effect of sound “escaping” from a waveguide was carried out. The term “escaping” here means energy transfer to modes with stronger attenuation due to scattering on internal waves. A model of an underwater sound channel with an axis at a depth of about 45 meters is considered. It is shown that the first few modes propagating inside the water column are very little subject to losses due to the “escaping”. The strongest impact of the leakage scattering is experienced by the middle group of modes capable of reaching the sea surface. It is revealed as significant increasing of losses as compared to a horizontally homogeneous waveguide. On the other hand, the existence of linear mode combinations for which loss enhancement is practically absent has been revealed. These linear combinations correspond to the eigenfunctions of an inhomogeneous waveguide. Statistical analysis of propagator eigenfunctions indicates on qualitative differences of mechanisms of scattering for frequencies of 100 and 500 Hz.

Nitrogen and oxygen isotopic profiles and redox structure across the Chinese Altay reveal the source rocks of granites, core of the Central Asian Orogenic Belt

Two rock series in the Chinese Altay (CA) were identified. The protoliths of the overlying series are fine sandstone and siltstone that consist of quartz and clay but contain little feldspar. The underlying series includes biotite–plagioclase gneiss and amphibolite entrained by the CA granite, migmatitic granite and the Early-Devonian Kangbutiebao Fm. as the uncovered, latest-formed southwestern margin. The CA granites include oligoclase microcline granite and biotite plagioclase granite that exhibit extensive K-Na-metasomatism of plagioclase porphyroclast. The two series both have high positive εNd-εHf values but are NO isotopically distinguishable. This study employed NO isotopes to trace source rocks of the CA granites and to explore devolatilization from metamorphism, migmatization to partial melting.The overlying series yielded much higher N content (20.2–484 ppm; average: 87.3 ± 99.0 ppm; 1σ; n = 36), δ15N (−3–19‰; average: 5.8 ± 4.3‰; n = 36) and δ18O (6.9–15.6‰; average: 13.6 ± 3.05‰; n = 29) than the underlying series that yielded N (9.9–71.1 ppm; average: 32 ± 17.1 ppm; n = 22), δ15N (−7.3–8.1‰; average: 1.1 ± 4.7‰; n = 22) and δ18O (4.5–12.1‰; average: 8.8 ± 1.9‰; n = 22). The protoliths of the overlying series were accumulated on oxic shallow sea in the CA and, hence, recorded high δ15N, whereas the protoliths of the underlying series extended to anoxic deep-ocean and experienced high-temperature seawater reaction, which resulted in low δ18O and δ15N values of the protoliths of the underlying series. The CA granites yielded much lower N content, δ15N and δ18O than the overlying series but have values overlapping those of the underlying series with a marginal increase in δ18O. The δ15N values tend to increase with decreasing element normalized-N contents from the underlying series to the CA granites, suggesting that migmatization and partial melting of the underlying series have caused 15N/14N fractionation. Quantitative modeling demonstrates that NH3 devolatilization of the underlying series at 550 to 750 °C can fit the underlying series and the CA granites, whereas 15N/14N fractionation trajectories of the overlying series miss the CA granites. These results suggest that the CA granites have been derived from the underlying series. Most data of the underlying series and the CA granites can be modeled by Rayleigh distillation suggesting escape of degassed NH3 from essentially solid-state protolith/source rock from metamorphism to migmatization. Partial conversion to N2 or N2O caused 15N-enrichment in the two series at the leading edge of the overlying series, the eastern CA. The magma derived from the underlying series mixed with magma stemming from the metasomatized mantle with contribution from country rock-derived fluid result in high δ15N of the Qinggeli granodiorite and microdioritic enclaves.

Random Matrix Theory for Sound Propagation in a Shallow-Water Acoustic Waveguide with Sea Bottom Roughness

The problem of sound propagation in a shallow sea with a rough sea bottom is considered. A random matrix approach for studying sound scattering by the water–bottom interface inhomogeneities is developed. This approach is based on the construction of a statistical ensemble of the propagator matrices that describe the evolution of the wavefield in the basis of normal modes. A formula for the coupling term corresponding to inter-mode transitions due to scattering by the sea bottom is derived. The Weisskopf–Wigner approximation is utilized for the coupling between waterborne and sediment modes. A model of a waveguide with the bottom roughness described by the stochastic Ornstein–Uhlenbeck process is considered as an example. Range dependencies of mode energies, modal cross coherences and scintillation indices are computed using Monte Carlo simulations. It is shown that decreasing the roughness correlation length enhances mode coupling and facilitates sound scattering.