Onshore sandbar migration at Tairua Beach (New Zealand): Numerical simulations and field measurements

We observed the onshore migration (3.5 m/day) of a nearshore sandbar at Tairua Beach, New Zealand during 4 days of low-energy wave conditions. The morphological observations, together with concurrent measurements of waves and suspended sediment concentrations, were used to test a coupled, wave-averaged, cross-shore model. Because of the coarse bed material and the relatively low-energy conditions, the contribution of the suspended transport to the total transport was predicted and observed to be negligible. The model predicted the bar to move onshore because of the feedback between near-bed wave skewness, bedload, and the sandbar under weakly to non-breaking conditions at high tide. The predicted bathymetric evolution contrasts, however, with the observations that the bar migrated onshore predominantly at low tide. Also, the model flattened the bar, while in the observations the sandbar retained its steep landward-facing flank. A comparison between available observations and numerical simulations suggests that onshore propagating surf zone bores in very shallow water (< 0.25 m) may have been responsible for most of the observed bar behaviour. These processes are missing from the applied model and, given that the observed conditions can be considered typical of very shallow sandbars, highlight a priority for further field study and model development. The possibility that the excess water transported by the bores across the bar was channelled alongshore to near-by rip-channels further implies that traditional cross-shore measures to judge the applicability of a cross-shore morphodynamic model may be misleading.     

The influence of 70 and 120 kHz tonal signals on the behavior of harbor porpoises (Phocoena phocoena) in a floating pen

Two harbor porpoises in a floating pen were subjected to five pure tone underwater signals of 70 or 120kHz with different signal durations, amplitudes and duty cycles (% of time sound is produced). Some signals were continuous, others were intermittent (duty cycles varied between 8% and 100%). The effect of each signal was judged by comparing the animals' surfacing locations and number of surfacings (i.e. number of respirations) during test periods with those during baseline periods. In all cases, both porpoises moved away from the sound source, but the effect of the signals on respiration rates was negligible. Pulsed 70kHz signals with a source level (SL) of 137dB had a similar effect as a continuous 70kHz signal with an SL of 148dB (re 1muPa, rms). Also, a pulsed 70kHz signal with an SL of 147dB had a much stronger deterring effect than a continuous 70kHz signal with a similar SL. For pulsed 70kHz signals (2s pulse duration, 4s pulse interval, SL 147dB re 1muPa, rms), the avoidance threshold sound pressure level (SPL), in the context of the present study, was estimated to be around 130dB (re 1muPa, rms) for porpoise 064 and around 124dB (re 1muPa, rms) for porpoise 047. This study shows that ultrasonic pingers (70kHz) can deter harbor porpoises. Such ultrasonic pingers have the advantage that they do not have a "dinner bell" effect on pinnipeds, and probably have no, or less, effect on other marine fauna, which are often sensitive to low frequency sounds.     

A spatiotemporal calculus for reasoning about land-use trajectories

Earth observation images are a powerful source of data about changes in our planet. Given the magnitude of global environmental changes taking place, it is important that Earth Science researchers have access to spatiotemporal reasoning tools. One area of particular interest is land-use change. Using data obtained from images, researchers would like to express abstractions such as ‘land abandonment’, ‘forest regrowth’, and ‘agricultural intensification’. These abstractions are specific types of land-use trajectories, defined as multi-year paths from one land cover into another. Given this need, this paper introduces a spatiotemporal calculus for reasoning about land-use trajectories. Using Allen’s interval logic as a basis, we introduce new predicates that express cases of recurrence, conversion and evolution in land-use change. The proposed predicates are sufficient and necessary to express different kinds of land-use trajectories. Users can build expressions that describe how humans modify Earth’s terrestrial surface. In this way, scientists can better understand the environmental and economic effects of land-use change.     

Shock deformation confirms the impact origin for the Cerro do Jarau,Rio Grande do Sul,Brazil, structure

Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30^o12′S and 56^o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks.     

On the use of logistic regression for stellar classification

We are totally immersed in the Big Data era and reliable algorithms and methods for data classification are instrumental for astronomical research. Random Forest and Support Vector Machines algorithms have become popular over the last few years and they are widely used for different stellar classification problems. In this article, we explore an alternative supervised classification method scarcely exploited in astronomy, Logistic Regression, that has been applied successfully in other scientific areas, particularly biostatistics. We have applied this method in order to derive membership probabilities for potential T Tauri star candidates from ultraviolet-infrared colour-colour diagrams.     

Adsorption of cobalt by using inorganic components of sediment samples from water bodies

The adsorption of cobalt ions was evaluated using sediment samples from water bodies to investigate the adsorption properties of sediment and the behavior of these natural materials in the presence of nuclear and industrial waste.The two sediments(S1 and S2)were treated to eliminate humic and fulvic acids and then they were characterized by several techniques.The minerals found in both the sediments(X-ray diffraction)were quartz and albite;plus,goethite and muscovite in S1,and kaolinite and montmorillonite in S2.Point of zero charge(PZC)of S1 and S2 was 6.00 and 5.22,respectively.The specific area of S1(63.3 m²/g)is higher than S2(1.5 m²/g).Adsorption kinetics data for S1 and S2 were best fitted to the pseudo second-order model.The removal efficiency of S1 for cobalt was 96%with an adsorption capacity(qe)of 0.93 mg/g,and for S2 was 45%with a qeof 0.40 mg/g.The experimental data of the adsorption isotherms were adjusted to Langmuir and Freundlich models for S1 and S2,respectively.The thermodynamic parameters(enthalpy,entropy,and Gibb’s free energy)indicated that the adsorption processes were endothermic,spontaneous,and chemisorption mechanism.The results show that the adsorption capacities of the sediments depend on their composition.These water sediments have important adsorption properties for cobalt,and they can be used in the treatment of nuclear and industrial aqueous wastes.     

Stratigraphic signatures of translation of thrust-sheet top basins over low-angle detachment faults

Abstract Low‐angle detachment faults and thrust‐sheet top basins are common features in foreland basins. However, in stratigraphic analysis their influence on sequence architecture is commonly neglected. Usually, only eustatic sea level and changing flexural subsidence are accounted for, and when deformation is considered, the emphasis is on the generation of local thrust‐flank unconformities. This study analyses the effects of detachment angle and repetitive detachment activation on stratigraphic stacking patterns in a large thrust‐sheet top basin by applying a three‐dimensional numerical model. Model experiments show that displacement over low‐angle faults (2–6°) at moderate rates (～5.0 m kyr^?1) results in a vertical uplift component sufficient to counteract the background flexural subsidence rate. Consequently, the basin‐wide accommodation space is reduced, fluvio‐deltaic systems carried by the thrust‐sheet prograde and part of the sediment supply is spilled over towards adjacent basins. The intensity of the forced regression and the interconnectedness of fluvial sheet sandstones increases with the dip angle of the detachment fault or rate of displacement. In addition, the delta plain is susceptible to the formation of incised valleys during eustatic falls because these events are less compensated by regional flexural subsidence, than they would be in the absence of fault displacement.     

Tectonic significance of the present relief of the Betic Cordillera

Tortonian calcarenites of the Betic Cordillera were deposited in coastal or very shallow marine environments and represent an ideal marker for estimating vertical movements from the late Miocene to the Present. A map showing the heights at which these Tortonian marine rocks are situated has a clear correlation with the present relief, indicating that today's relief has been formed since the Tortonian. There is also a good correlation between present relief and the Bouguer anomaly distribution in the Betic Cordillera, as well as with crustal thickness. Likewise, the present relief is directly related to the geodynamic setting of a horizontal N–S to NNW–SSE compression and an almost perpendicular extension, along with isostatic readjustment, existing in the Betic Cordillera from the Tortonian. As a result of these regional stresses, faults and folds have produced notable vertical movements. The highest rates of uplift of the Betic Cordillera coincide with large antiforms, in particular those of the Sierra Nevada and the Sierra Filabres. Several subsiding sectors also exist (for example, the Granada Basin or the Guadalquivir Basin). The foreland Guadalquivir Basin has a complex history because the uplift in its eastern sector and subsidence in the western sector coexisted during the late Tortonian. Today the whole Betic Cordillera is characterized by differential regional uplift, even in the aforementioned subsiding sectors.