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An intertidal sandstone reef, named barra de Las Canteras, protects the western coast of Las Palmas de Gran Canaria city (Canary Islands, Spain). The beach-reef system of Las Canteras constitutes one of the most valuable coastal geomorphological sites in the archipelago. Stratigraphic studies have identified the formation of the reef in the Last Interglacial (MIS 5e) in a coastal sedimentary paleo-environment. The rock structure is highly exposed to the Atlantic swell and consists mainly of a sandstone beachrock with a medium resistance to erosional processes. However, the historical and current erosion rates and the original extent of the reef are not known to date. This paper explores the geomorphological structure of the reef by combining a topo-bathymetric analysis (obtained by differential GPS, multibeam echosounder and hyperspectral sensor) and the analysis of geomorphological features on high-resolution images, obtained with a hyperspectral camera mounted on a UAV. The results provide a comprehensive, high-resolution image of the subaerial and submerged morphology of the reef. The structure reflects the distribution of erosional fronts and the existence of collapsing submarine blockfields and nearshore, uneroded, remnant reliefs. Detailed analysis of these features allows to estimate the probable original extent of the sandstone reef and to relate the erosional retreat processes to the sea-level dynamics during the Holocene. [ABSTRACT FROM AUTHOR]

Biomineralization is a generic term used to indicate biological‐mediated mineral formation. In carbonate mineralization, nucleation of crystals can be: (1) controlled directly by the organisms, like in the skeletal formation of most metazoans; (2) induced by microbial communities, by indirect precipitation mediated by their metabolic activities; or (3) influenced by organic matter decay, with mineral precipitation on specific non‐living organic cell surfaces. Recognition of these products is a direct marker of biological activity in time and space and is a key element in the study of the biological evolution and of its interactions with the geological processes. In this paper, primary carbonate cements from the Anisian microbial build‐up of the ‘Monte Facito’ Formation (Basilicata region, Southern Italy) have been studied from a geobiological point of view. Optical microscopy, UV‐epifluorescence and micro‐Raman spectroscopy have been applied to investigate the organic mediation on their precipitation. The cements formed in microcavities or on grain substrates, and often show a microstromatolite‐like pattern of growth. They are composed of alternations of cloudy organic and whitish inorganic bands that point to a double phase of mineralization. In the first phase, a biologically induced/influenced biomineralization is confirmed by the presence of organic matter strictly connected with the cloudy bands. This phase is followed by a pure abiotic mineralization that leads to the formation of whitish bands. This process repeated cyclically, ending at the complete filling of the microcavities or because of changes in the chemical conditions of the microsystem, for example, due to burial processes. This model of mineralization is similar to that proposed for primary cements forming in recent beach rocks. The Monte Facito Formation cements could be considered as the product of unconventional biomineralization, and the understanding of their growth process could provide an innovative tool in the research of biological signatures in the fossil record. The term unconventional is here utilized to discriminate this type of biomineralizations from those related to well‐known biotic mineralization processes, like those involved in skeletons and microbialites growth, which can be considered as conventional biomineralizations. [ABSTRACT FROM AUTHOR]

Coastal sand dune sediments with associated intraformational aeolianite, palaeosols and beachrock are found throughout much of the southern African coast, and have important roles as both Quaternary environmental archives and in recording the interplay of sediment supply, coastal processes and sea-level change. This paper examines the stratigraphy and palaeoenvironmental significance of coastal sand dunes and associated sediments, using examples mainly from South Africa but also with reference to the sandy coasts of Namibia and southern Mozambique. Based on morphological, sedimentary and dating evidence reported in the diverse literature, the stratigraphic relationship of coastal sand dune sediments to Marine Isotope Stages (MIS) is summarized, and a chronostratigraphic diagram for the period MIS 6 to 1 along the South African coast is used to identify spatially coherent sedimentary units that correspond to different regional climatic and sea-level phases. This framework provides a stratigraphic context to better examine the relationship between coastal sand dunes and external forcing during the late Quaternary in southern Africa, and to guide future field studies. [ABSTRACT FROM AUTHOR]

The selected effect account is regarded by many as one of the most attractive accounts of function. This account assumes that the function of a trait is what it has been selected for. Recently, it has been generalized by Justin Garson to include cases in which selection is understood as a simple sorting process, i.e., a selection process between entities that do not reproduce. However, once extended, this generalized selected effect account seems to ascribe functions to entities for which it looks unintuitive to do so. For instance, the hardness of rocks on a beach being differentially eroded by waves would be ascribed the function of resisting erosion. Garson provides one central argument why, despite appearance, one should not ascribe functions in cases of such sorting processes. In this paper, I start by presenting his argument, which hinges on whether a collection of entities form a population. I find it wanting. I argue instead that some selection processes are evolutionarily more or less interesting and that when a selection process is regarded as evolutionarily uninteresting, it will yield an uninteresting form of function rather than a reason for withholding the concept of function altogether. [ABSTRACT FROM AUTHOR]

Evidence for sea-level change during and around Marine Isotope Stage (MIS) 5e (ca. 125 ka) in southern Africa derives from a wide variety of geomorphic and sedimentological sea-level indicators, supported in the past 2 decades by absolute chronological control, particularly on littoral deposits, some of which have a quantifiable relationship to former sea level. In addition to these proxies, data provided by both terrestrial (dune sediments and archaeological remains) and marine (lagoonal and nearshore littoral sediments) limiting points provide broad constraints on sea level. Here, we review publications describing such data points. Using the framework of the World Atlas of Last Interglacial Shorelines, we insert in a standardized database (10.5281/zenodo.4459297, Cooper and Green, 2020) all the elements available to assess former palaeo-relative sea level (palaeo-RSL) and the chronological constraints associated with them (including uncertainties). Overall, we reviewed 71 studies, from which we extracted 39 sea-level indicators and 26 limiting points. As far as age attribution is concerned, early analysis of molluscs and whole-rock beachrock samples using U series allowed dating of several sea-level indicators during the 1980s, but the more widespread application of optically stimulated luminescence (OSL) dating since 2004 has yielded many more (and more accurate) sea-level indicators from several sites. This has helped resolve the nature and timing of MIS 5e shorelines and has the potential to further elucidate the apparent presence of two or more sea-level peaks at several South African sites during this interval. The standardized sea-level database presented in this paper is the first of its kind for this region. Future research should be directed to improve the stratigraphic description of last interglacial shorelines and to obtain better dating, high-accuracy elevation measurements with better palaeo-RSL interpretation. [ABSTRACT FROM AUTHOR]

Different parent rocks, climate, and relief control the provenance of beach sands on the coast of Mexico. This is the first paper to address the provenance problem of beach sands in south‐eastern Mexico considering a homogeneous climate and relative similarity in parental rocks but different relief. Two coastal areas are confined in this study: (a) the Western Gulf of Tehuantepec (WGT) and (b) the Eastern Gulf of Tehuantepec (EGT). The WGT beach sands are probably controlled by the denudation of orthogneisses, Eocene–Miocene basaltic–andesites–dacites–rhyolites from the Volcanic Belt of the Sierra Madre del Sur (VBSMS), and granites to diorites from the Coastal Plutonic Belt (CPB). The rocks exposed in the EGT are represented by orthogneisses and tonalite, granodiorite, and gabbro suites from the Palaeozoic–Mesozoic Chiapas Coastal Plutonic Belt (CHCPB). Quaternary andesites and dacites from the Tacaná Volcano are located in the eastern coastal area. The Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration (PIA) values indicate that the less weathered beach sands are in the WGT compared to the EGT coastal area. Plagioclase transport is preserved in a narrow coastal plain that contributes to a lower a weathering rate compared to the EGT sands deposited in a wider coastal plain. Geochemical analyses show that the WGT and EGT beach sands are admixtures of felsic, intermediate, metamorphic, and volcanic sources in their sands composition. Relief seems to play a major role in the composition of beach sand in both coastlines, since parental rocks are mostly similar in composition and climate remains homogeneous along the coast. [ABSTRACT FROM AUTHOR]

The loess caves developed on Chinese loess plateau are not only a typical phenomenon of soil and water loss, but also a special kind of geological hazard. Many loess dilapidations, collapses and medium to small-sized landslides are related to the loess caves. To understand the characteristics and the geo-disasters induced by loess caves, the loess caves developed on Chinese loess plateau were rigorously investigated. Based on a long-term field surveys on about 800 fixed points in Gansu, Ningxia and northern Shaanxi, the classifications and characterization of loess caves in Chinese loess plateau are discussed in detail. Moreover, the regionally developmental regularity hierarchical development regularity of loess cave and its characteristics are studied in this paper, which show that the density of loess caves on the northwestern loess plateau is higher than that in the southeastern loess plateau than that in the southeast in China. And the main control factors affecting the development of loess caves are analyzed. Interestingly, the development of the caves is related to the loess layer, land characteristics, geologic structure (including the joints and the fracture system), micro topography, hydro-geological factors and climatic conditions. [ABSTRACT FROM AUTHOR]

This paper investigates the potential of using a novel Hermite polynomial neural network to model shoreline realignment along an urban beach fronted by a highly irregular beachrock reef. Modeling takes place on the basis of a number of input variables related to reef morphology and wave forcing, whereas the output variable is time series of shoreline position that have been recorded in high spatio-temporal resolution using a coastal video monitoring system. The main network functionality is the generation of Hermite truncated polynomial series of linear combinations of the input variables, and output is calculated as the weighted sum of these truncated series. It is shown that the proposed network can approximate any continuous function defined on a compact set of the multidimensional Euclidean space to arbitrary accuracy. The network is optimized in terms of a modified artificial bee colony method. For comparative reasons, three more related neural networks have been tested that have been optimized by employing different swarm intelligence-based algorithms. Comparison between the four networks has been carried out by standard performance criteria and detailed parametric statistical analysis. Main results of the study are: (a) polynomial orders 3 and 4 are able to effectively handle reasonably well the high nonlinear effects imposed by the presence of the reef; (b) the statistical analysis indicates that the proposed network outperforms the other networks tested; and (c) model efficiency improves noticeably when beach sections behind reef inlets and/or particular wide sections of the reef that introduce high shoreline variability are not considered. [ABSTRACT FROM AUTHOR]

Beachrocks represent a significant paleo-environmental proxy because they can record both the vertical and the horizontal evolution of the shoreline. They have often been used to assess Holocene shoreline evolution and crustally induced Relative Sea-Level (RSL) changes in the Mediterranean Sea. In this paper, we used submerged beachrocks from Paros and Naxos Islands (Aegean Sea, Greece) to reconstruct the shoreline modification and provide new insights on the RSL evolution in central Cyclades. Paros and Naxos Islands are of great importance in terms of archaeological evidence of coastal occupation. However, the evolution of their coastlines was seldom explored. In this study, we coupled detailed underwater surveys, analysis of aerial photogrammetry, microstratigraphic analysis and luminescence dating to study beachrock outcrops found down to about 6 m below the present sea-level. We, then, spatially and chronologically constrained some major palaeogeographical changes of a number of coastal sectors of the two islands. Furthermore, the multiple analyses of beachrocks, sediment coring and archaeological data suggested that RSL rose by at least 3.8 m in the last 4.0 ka and that RSL variation in the last 2.0 ka did not exceed 2 m with respect to the present mean sea level. [ABSTRACT FROM AUTHOR]

Sedimentological, geochemical, and X-ray diffraction (XRD) analyses in addition to the determination of biogenic fraction components (BFC) were performed in mollusk shells from carbonate beach samples collected on the northern coast of the Yucatan Peninsula, Mexico. The most abundant components of the BFC were bivalves and gastropods shells, ranging from 88.1 to 99.2 % and from 0.1 to 6.0 %, respectively, followed by minor percentages of foraminifera, coral fragments, bryozoa, oolites, spicules, and ostracods. A combination of major element, trace element, and XRD techniques were performed to show how the Mg/Ca and Mg/Sr ratios determine the possibility of a recrystallization process in bivalves and gastropods, which may be attributed to early diagenetic mechanisms caused by groundwater flows, subaerial exposure, high evaporation rates, and neomorphism. The rare earth element analyses gave the average anomalies for the following ratios (Pr/Yb) ratio > 1, (Eu/Eu*) and (Ce/Ce*) < 1, suggesting little incorporation of sea water in the BFC of the shells from the Yucatan beach sands. This is also supported by the flat pattern trends of bivalves and gastropods based on the normalized patterns of light rare earth element compared to heavy rare earth element concentrations. This paper is also a contribution to the methodology of analysis of carbonate sands, i.e., whole bulk composition isolation into their main biogenic components and the accumulation of major, trace, and rare earth elements deposited into their shells, initially under subaquatic marine conditions and currently exposed to subaerial coastal influences based on the allochthonous character of the shells. [ABSTRACT FROM AUTHOR]

Understanding ancient climate changes is hampered by the inability to disentangle trends in continental ice volume from records of relative sea-level change. As a unique coastal deposit in tropical and subtropical regions, beachrock has been proved to be reliable for constraining the glacial meltwater signal and thus the total volume of land-based ice in Quaternary. However, beachrock is rarely recognized in the fossil record due to (a) the two-dimensional distribution of beach deposits, as opposed, for example, to extended platform sediments, and (b) the fact that specific environmental conditions are required in order to lithify sediments directly on the beach. By combining the stratigraphic architecture with petrography of characteristic carbonate cements, we demonstrate the first known occurrence of Ordovician beachrock in the Tarim Block, northwestern China. According to biostratigraphic data, a middle Katian (Upper Ordovician) palaeokarst surface is capped by carbonate conglomerate beachrock and this is suggesting a significant relative sea-level rise in late Katian. The beachrock can be correlated with widespread subaerial exposure surfaces and a pronounced stratigraphic gap within the Katian in northwestern Tarim. We suggest that the beachrock ‘fingerprinted’ a strong melt-water pulse in high latitudes after a short-lived Katian glaciation, which has not received much attention in scientific papers so far. [ABSTRACT FROM AUTHOR]

Submarine channel-related thin-bedded turbidites are deposited in environments such as external levees, internal levees, depositional terraces and at times of channel abandonment. Thin-bedded turbidites are defined as beds that are less than 10 cm thick, but the described environments can at times contain beds up to 100 cm thick which would be classified as medium- or thick-bedded. This paper addresses examples of these environments from the modern seafloor, outcrop and the subsurface to suggest criteria that assist in the differentiation of levees and terraces from an architectural, sedimentological, ichnological and hydrocarbon reservoir perspective. External levees confine channel belts and are elongate sedimentary deposits that are a product of over-spill of turbidity currents from the channel belt they confine. External levees often have predictable vertical, lateral and downstream changes in thickness and sand content but are commonly modified by collapse of the inner external levee into the channel, by collapse on the outer external levee, by sediment waves, and by interaction of external levees with topographic features such as other channels, other external levees, basin margins or previous slump/slide blocks, which can greatly modify the sand distribution within them. A combination of internal levees, depositional terraces and slide blocks of external levee sediment make up thin-bedded turbidites within channel belts. We differentiate between wedge-shaped internal levees and topographically flat or subdued depositional terraces, whose differing geometries and sand distribution reflect the fact that the flow processes involved in the formation of these deposits are different. The characteristic wedge shape of an internal levee requires sufficient space within the channel belt for the over-spilling current to spread, decelerate and deposit the majority of its silt and sand grade suspended sediment before reaching the bounding topography of the channel belt. In the case of depositional terraces the space available in the channel belt is insufficient for the current to decelerate and deposit the majority of its sediment before reaching the bounding topography of the channel belt, creating confined sheet-like deposits. External levees, internal levees and depositional terraces have distinct sedimentological characteristics such as sand bed thickness trends and sedimentary structures that can be used to distinguish them. Together with sedimentological characteristics, in some systems these thin-bedded turbidite deposits contain distinctive trace fossil assemblages, where channel proximal deposits such as proximal external levees, internal levees and depositional terraces can have much higher ichnodiversity than sand-rich channel axes and more mud-dominated outer external levees. The depositional sites for internal levees and depositional terraces within channel belts can be formed by various processes such as entrenchment, point bar accretion, meander bend cut-off, channel margin failure, or changes in the flow parameters. These processes can result in elevated surfaces within the confines of the channel belt that subsequently become prone to the deposition of over-bank deposits. The development and preservation of levees and terraces is closely related to the evolution of the channel belt as a whole, which is controlled both by allogenic mechanisms (such as sea-level fluctuations, changes in turbidity current size and sediment calibre, and changes in the equilibrium profile of the channel), and by autogenic mechanisms (such as channel avulsion and resulting knick-point migration). Where preserved in the rock record thin-bedded turbidites have been uncommon primary targets for hydrocarbon field development, since most efforts have focused on the channel-fills which have the highest proportion of sand. However, thin-bedded turbidites can contain large amounts of sand, of which individual beds can be very laterally continuous, and hence can make significant secondary reservoir targets. [ABSTRACT FROM AUTHOR]

Powerful typhoons frequently affect eastern Taiwan. On Dabaisha beach on the SW coast of Ludao Island, a small volcanic island lying SE off mainland Taiwan, the presence of numerous beachrock slabs provides evidence of the sediment transport capabilities of high-energy waves generated by these storms. With a well-defined beachrock source from which the slabs were derived, it is easy to differentiate clasts transported in run-up or backwash flow based on their current position relative to the outcrop. In order to estimate the wave-generated flow velocities from the measured beachrock slabs, the hydrodynamic equations for boulder transport by Nandasena et al. (2011) have been rearranged so that they are appropriate for this particular geomorphic setting, where exposed in situ beachrock outcrops liberate clasts which may then be transported either by run-up onto the beach or backwash flow onto adjacent reef platforms. Such settings are common on tropical coastlines with fringing coral reefs and beaches comprising mostly biogenic sediments. In the Dabaisha beach case, the lowest flow velocities required to transport all measured beachrock slabs from their source outcrop to current positions are 2.18–3.16 m/s for run-up and 1.76–3.24 m/s for backwash. With a discussion of advantages and limitations on the use of beachrock clasts for interpreting wave behaviour, this paper presents another proxy for studying high-energy wave events that is highly suitable for certain carbonate-rich coastlines. [ABSTRACT FROM AUTHOR]

Rocas Atoll is a remote place and the only atoll in the southwestern Atlantic Ocean. This study presents new paleo-sea level reconstructions and a new interpretation on former ones. The new data indicate that sea level was higher at the Late-Holocene than it is at present and that the hydrodynamic factors overlap with sea-level changes, precluding more precise paleo-sea level reconstructions. According to previous works, the Rocas Atoll presents one of the most conspicuous paleo-sea level indicators, represented by reef remains. But, in this paper, these supposedly reef remains are reinterpreted as algal-reef boulders detached from the atoll reef-front by high-wave energy events and deposited over the reef rim, where they remain detached or are cemented and, sometimes, mushroom shaped. It is considered that the bigger boulders may have been deposited in their current position by the cumulative effects of past energetic wave events. Furthermore, the use of beachrocks as paleo-sea level indicators in former studies is discussed, leading to the conclusion that they actually indicate beach progradation and lateral accretion resulting from a positive sand budget. Finally, a schematic morphological evolution of the atoll during the Late-Holocene is proposed. At the atoll, leveling with RTK and imagery with laser scanner were collected, and eleven radiocarbon ages were measured by accelerator mass spectrometry (AMS). • New paleo sea-levels were determined and former ones were reinterpreted. • A field of boulders detached from the atoll reef front is described. • Beachrock sedimentary facies are described. • A schematic morphological evolution of the atoll during the Late Holocene is provided. [ABSTRACT FROM AUTHOR]

The present paper supplies biological and lithological evidence for the mechanisms of biochemical cementation in modern beachrocks on the tropical Yongle Atoll, Xiasha Islands in the South China Sea. High-throughput sequencing was used to precisely determine the epilithic microbial community in beachrocks. Microscopic mineralogical examination of sedimentary grains further showed complex processes from rapid carbonate precipitation. The results from 18/16 s rRNA diversity examination indicated that green algae and cyanobacteria only occupied a small proportion of the community, albeit they had considerable amounts. The occurrences of Lyngbya (Family Oscillatoriaceae), Calothrix and Dichothrix (Family Rivulariaceae) with light colour may be related to calcified sheaths coated on the living cells. The short rod-like Mg calcite in Lyngbya sheaths and anhedral to euhedral Mg calcite in Calothrix or Dichothrix sheaths were organominerals mediated most likely by photosynthesis of microorganisms with chloroplasts. Different initial crystal patterns were closely related to different cyanobacterial extracellular polymeric substance (EPS) structures. After cell death, these microcrystals were released into the voids and removed by interstitial water. The carbonate seeds scattered all around the particle surface and then began to enlarge the grain size with the degradation of organic matter. Different paths of crystal growth eventually cemented the intertidal grains abiotically or biotically. This case sheds light on cryptic microbially mediated mineralization in beachrock. Even though chemical processes were considerable in the formation of the beachrocks on the modern reef flat, the pervasive microbial geological processes occurred quietly but effectively. • Epilithic biotic communities in the beachrock were studied by genetic sequencing. • Cyanobacteria filaments Lyngbya , Calothrix and Dichothrix have calcified sheaths. • Magnesium calcite seeds in cyanobacterial EPS are biominerals. • Microbially-mediated carbonates rapidly consolidate the beachrock. [ABSTRACT FROM AUTHOR]

Abstract: A standard assumption in coastal engineering is that the porosity of natural beach sand (non-cohesive) is 40%. However, is this assumption correct for all beach sand? This paper proposes an accurate and simplified method to assess changes in sand porosity after beach nourishment by means of in-situ density surveys through a nuclear densimeter. This novel application has been applied to different beaches in the southwest of Spain according to the tidal range, grain size and beach morphology in several terms. General results show that sand porosities range from 25.6% to 43.4% after beach nourishment works. This research can be considered a support tool in coastal engineering to find shifting sand volumes as a result of sand porosity variability after beach nourishment and later marine influence. [Copyright &y& Elsevier]

Abstract: The present study brings new insights on the small-scale characteristics of relatively distal turbidite deposits (classically defined as depositional lobes or sheets) from the deep-water clastic slope system of the Annot Sandstones (Grès d''Annot), in the Trois Evêchés area. This “seismic scale” outcrop has been studied in detail to characterize sedimentary geometries and facies associations within and between sheet-like sandstone-bodies. In terms of facies, their internal architecture is dominated by numerous erosional features, variable scale cross-bedding and dewatering structures. Facies range from gravelly sandstones to fine-grained sandstones and their spatial distribution inside sandstone-bodies is provided, allowing us to discuss the spatial changes in flow behaviour. A detailed dataset, made of very high-resolution correlations in thick to thin-bedded sheet-like sandstone-bodies, enables to identify five main types of architectural elements, composed of both channelised and unchannelised depositional bodies. Gravelly-filled channel-elements, laterally stacked channel-elements (interpreted as being related to sinuous channel migrations) and wing-like channel-elements constitute the channelised sheet systems whereas tabular sandstones (sheets sensu stricto), prograding and/or dome-shaped units constitute layered sheet systems. Sinuous channels are represented by the association of erosive-based, laterally stacked bedsets and very coarse-grained, low-angle cross-bedded facies. These latter facies are interpreted as the result of flow deconfinement and overbanks above channel margins. The stratigraphic relationships between these architectural elements permit establishing a conceptual model of the distribution and organisation of the components. This distribution scheme is based on the longitudinal differentiation of gravity processes, which are directly linked with architectural element types. This model is composed of proximal confined units where channelization processes, amalgamation and bypass dominate, to more distal and less confined units where compensation, constructive structures and high deposition rates control sedimentary architectures. The Trois Evêchés sub-basin may be considered as a good example of a channelised lobe to unchannelised lobe transitional environment, which explains the lateral and vertical high variability during its infill. The widespread apparition of residual facies, such as cross-stratified sandstones as well as basal lags, suggests significant bypass. The appearance of both channelised and unchannelised units is consistent with this transitional environment. The provided detailed dataset in this paper displays the associated wide range of architectural elements in these settings, and highlights the significant heterogeneities of sand-rich confined turbidite sheet systems. These heterogeneities are under the seismic resolution and may influence fluid migration in sand-rich deep-water reservoirs. [Copyright &y& Elsevier]

This paper discusses the measurement of naturally occurring radioactivity materials (NORM) in beach sand minerals using high resolution gamma spectrometry. In India, the beach sand minerals of economic interest from coastal Kerala, Tamil Nadu and Orissa are enriched with NORM due to the occurrence of monazite deposits and heavy minerals such as zircon, ilmenite, magnetite, garnet, rutile etc. Since many of these ores are rich in Th and other radio elements, certification of radioactivity levels has become mandatory in recent years. The average activity concentrations of Ra in zircon, rutile and garnet were 3,531, 1,134 and 17 Bq kg, respectively. The average activity concentration of Th observed in zircon, rutile and garnet were 618, 454 and 64 Bq kg, respectively. Concentration of Ra, Th, and K in ilmenite ore ranged from 17.6-444 Bq kg, 80.4-1971 Bq kg and ≤5.5-25.0 Bq kg, respectively. [ABSTRACT FROM AUTHOR]

This paper deals with the dry magnetic separation tree analysis on typical beach sand sample containing 12.74 % magnetic minerals. In the present investigation four level magnetic separation tree analysis has been carried out for obtaining more than 96 % total magnetic minerals. The study reveals that the first output of magnetic separation tree analysis of four levels contains 96.79 % magnetic minerals, which accounts to 64.31% ilmenite and 32.48 % garnet minerals. [ABSTRACT FROM AUTHOR]

Abstract: The Lefkada–Preveza coastal zone, NW Greece, is characterised by an active barrier system and related extensive beachrock sequences. Besides the gradual coastal processes of longshore drift and spit evolution, the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system. In this paper, we present the results of detailed multi-proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back-beach positions. Our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary breakdown of the barrier system. Sedimentary findings suggest that one generation of event deposits may be related to the 365AD Crete earthquake and associated tsunami. According to our results, the Lefkada coastal system formed by the interaction of both long-term, gradual and sudden, impulsive littoral geomorphodynamics. Extreme wave events are assumed to have played a significant role in the evolution of the present coastline, acting as recurrent impulsive disturbances of the coastal system. Subsequently, the onset of long-term gradual coastal processes, such as longshore drift, re-established a state of natural coastal balance by re-arranging the coastal sediments. [Copyright &y& Elsevier]

Abstract: This paper focuses on the cement characteristics and optical luminescence age of late Pleistocene–Holocene beachrock, exposed on the southeast shore of freshwater Lake İznik in northwest Turkey, based on field observations, various spectroscopic analyses and optical dating results. The studied beachrock is a poorly-sorted coastal conglomerate composed mostly of gravels derived from surrounding volcanic rocks and marbles as well as quartz and carbonate grains. We identified different types of cements; dominated by micritic envelopes, bladed isopachous aragonite rims, void fills, radial aggregates and meniscus bridges, implying no single origin. Cementation characteristics indicate that marine-like cement micro-fabrics may occur in freshwater lake environments where the lake-water chemistry favors carbonate precipitation. OSL data revealed the existence of older beachrock dating back to 20.2ka, together with younger Holocene-age beachrock of between 5.6 and 2.4ka. This suggests that younger beachrocks have been superimposed on older cemented carbonates through the removal of carbonates by wave motion (splash and spray) during lower lake level conditions. [Copyright &y& Elsevier]

In a 1971 Nature paper (Harrison 1971) entitled “Atlantis Undiscovered — Bimini, Bahamas,” I reported on beachrock, marble, and cement materials lying offshore at shallow depth to the west of North Bimini. I concluded that these materials were too young to reflect a supposed ancient culture. In March 2007, J. Eagle and I cored three exploratory boreholes to 50-ft depths in the Bimini Inlet (Fig. 1). The rocks encountered were far too old to fit with a curve for Holocene sea-level rise in the broader Caribbean (includes the Bahamas). Instead, C-14 and fossil-coral age dating, and stratigraphic information, indicate that a significant disconformity is present beneath the Bimini Islands. A reasonable implication of the missing rocks is that during a period of time covering perhaps 800,000 years — or a minimum of 120,000 years at the least — an ancient land surface in the Bimini area could have been above sea-level during the Pleistocene continental glaciations. This old land surface would have been available for human habitation for upwards of the last 120,000 years, at a minimum. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents, for the first time, detailed geomorphological, sedimentological, geoarchaeological, geophysical and geochemical evidence of a strong tsunami impact on the Bay of Aghios Nikolaos and its environs (NW Greece) during Classical–Hellenistic times. Tsunamigenically dislocated beachrock slabs found on top of the Santa Maura beach ridge complex are closely interrelated to adjacent coarse-grained washover fan deposits encountered in vibracores and detected by earth resistivity measurements. Based on detailed topographic surveys and geomorphometric investigations, it was possible to localize areas of high intensity overflow. Underwater studies revealed that the central and northern parts of the former Plaka beach ridge were completely destroyed by tsunami impact. Loose littoral deposits were flushed into the Bay of Aghios Nikolaos and mega blocks of the underlying beachrock structure were dislocated landwards. Tsunami landfall occurred all along the eastern and northern shores of the bay where deposits, partly weathered and associated to archaeological findings, were found. Runup was estimated to minimum values between 2–3m and 4–6m a.s.l. Crosschecking the results of radiocarbon analyses with archaeological ages from five sites allowed to date the strong tsunami event to the time period between 395calBC and 247calBC. Due to the funnel-like contour of the coastline, the area is extremely sensitive to tsunami events of mid to high magnitude and high frequency. [Copyright &y& Elsevier]

Abstract: This paper describes the complex patterns of diagenesis in Holocene beachrock ledges located along both the eastern and northern coasts of the state of Rio Grande do Norte, northeastern Brazil. These beachrocks show highly variable diagenetic processes, fabrics and textures. Carbonate cements are exclusively composed by high-Mg calcite and occur in seven main morphologies: (1) cryptocrystalline coatings; (2) isopachous prismatic rims; (3) equant spar; (4) cryptocrystalline or micritic pore-filling; (5) pseudo-peloidal aggregates; (6) radial aggregates; (7) isolated and randomly oriented clumps of scalenohedral crystals. Other diagenetic features include: (a) carbonate-siliciclastic mixed sediment; (b) infiltrated micrite; (c) authigenic smectitic clay minerals; (d) organic films; (e) chalcedony pore-filling cement; (f) vadose silty internal sediment. The texture and composition of the cements are indicative of precipitation in the active marine phreatic zone. The presence of vadose features and planktonic foraminifers within the infiltrated materials suggest that they were introduced in the backshore sands by muddy waters dislocated from the shelf during storms. A general succession of diagenetic phases can be recognized, comprising the precipitation of authigenic smectite, micritic coatings, radial aggregates, isopachous rims of prismatic crystals or equant spar, cryptocrystalline and pseudo-peloidal pore-filling cements, and vadose infiltration of micritic, carbonate-siliciclastic mixed sediments or silty materials. The absence of organic structures, such as microbial (bacteria or fungi) filaments and bodies within the cements suggests that the mechanism behind beachrock cementation is essentially inorganic, most probably the evaporation of entrapped seawater in response to the dry climatic conditions. [Copyright &y& Elsevier]

This paper addresses the possibilities of the combined use of airborne hyperspectral data and airborne laserscanning data to study sand dynamics on the Belgian backshore and foreshore. In August 2000, August 2001, and October 2002, airborne hyperspectral imagery was acquired with a CASI-2 sensor from the entire Belgian beach at low tide. Hyperspectral images contain a reflectance spectrum for each pixel. The characteristics of this spectrum are influenced by the state, the composition, and the structure of the topsoil of the beach. After radiometric, geometric, and atmospheric correction of the images, a normalization of the spectral signatures was necessary to allow comparison of wet and dry pixels. Consequently, the first derivative of the normalized spectra was taken, followed by a spectral angle mapper algorithm that was used to perform a supervised classification. The beach was classified into eight sand classes. Almost simultaneous with the first two CASI campaigns (in September 2000 and September 2001), a laserscan survey was performed to generate digital terrain models with a mean vertical accuracy of 5 cm. By differencing both digital terrain models, a map with sedimentation and erosion zones could be extracted. The combined interpretation of the erosion/sedimentation map with the classified hyperspectral data yields an appropriate method for studying the processes of sand transport along the Belgian coastline. The method was tried out with success on the Belgian east coast. [ABSTRACT FROM AUTHOR]

Pleistocene raised coastal deposits characterized by locally abundant shells, aragonite-cemented beachrock and associated nearshore deposits border the western Marmara Sea at elevations of 0–50 m. Field observations confirm that these deposits formed during a series of transgressive and regressive events. U/Th dates in 16 in situ shells from four localities show that the peak of the transgressions occurred during the highstands of oxygen isotopic stages 7 and 5, between ∼53 and ∼210 ka. The elevations of these dated deposits can be used to quantify their post-depositional uplift and indicate that the entire western Marmara shelf, including the Strait of C¸anakkale (Dardanelles) has been rising at an average rate of ∼0.40 mm yr−1 since ∼225 ka. The primary cause of uplift is the local compression associated with a restraining bend in the western segment of the North Anatolian Fault. Paleogeographic maps constructed using the average rate of tectonic uplift and detailed topographic and bathymetric maps reveal that prior to glacial oxygen isotopic stage 8 the Marmara Sea was never isolated from the Aegean Sea, even when global sea level was low, because the floor of the Strait of C¸anakkale was too deep early in its uplift history. The dominance of Mytilus edulis in raised coastal terraces dating from the lowstand of glacial oxygen isotopic stage 8 suggests that the degree of communication between the Aegean Sea and Marmara Sea was comparable to that of the present. During the peak of glacial oxygen isotopic stage 6, the floor of the strait was subaerially exposed, isolating the Marmara Sea for the first time in the Pleistocene from the higher salinity Mediterranean water inflow and possibly causing it to become a blackish-water lake. During interglacial isotopic stages 9, 7 and 5, the Strait of C¸anakkale was very wide and deep (∼100–125 m), and there were two subsidiary channels (Bolayır and Eceabat channels), providing additional links between the Aegean Sea the Marmara Sea, further promoting significant water exchange between these basins. The dominance of Ostrea edulis in the raised terraces dating from isotopic stages 5 and 7 confirms an enhanced penetration of the Mediterranean water mass into the Marmara Sea. The history of communication between the Black Sea, fed by central and northern European drainage systems, and the low-latitude Mediterranean Sea is of fundamental importance in understanding the genesis of organic-rich sapropel deposits throughout the region. The results presented in this paper caution against the simple assumption that sea-level change alone controlled the degree of connection across this oceanographic gateway. Instead, the physiography and paleoceanography of the region were controlled both by variations in global sea level and the rate of uplift in an area of active transpression. [Copyright &y& Elsevier]

• The Strait of Messina (Sicily, Italy) includes a long-shore beachrock structure. • Beachrock microtidal pools represent a highly biodiverse and variable environment. • Beachrock communities structure allows the insurgence of prey-predator interaction. • Interactions between C. erythropus and P. turbinatus follow a Holling type-III model. The Strait of Messina (Sicily, Italy) attracts the interest of marine ecologists for the presence of a large variety of habitat and mutually-interacting communities. Among them, beachrock formations, despite their wide geographic distribution, which also includes the Mediterranean area, have been poorly investigated from the biotic viewpoint. In this paper, the spatial and seasonal variability of benthic megafauna from the Messina microtidal beachrock is described. Combining in situ collected data (measurements of abiotic parameters and underwater visual census) with theoretical post-processing analyses (analysis of similarity percentages and cluster analysis), we deduced the possibility to model the dynamics observed between the most dominant species, a top snail, Phorcus turbinatus (Born, 1778), and a hermit crab, Clibanarius erythropus (Latreille, 1818), in terms of a prey-predator interaction. These species gave rise to different intriguing dynamical regimes (including periodic oscillations) that were qualitatively captured by a mathematical model focused on the respective trophic chain levels. The identification of all model parameters and the use of numerical simulations complemented the above analysis and allowed to gain more insights into the complex dynamics of these oligotypic communities and on the most relevant factors determining the ecosystem equilibria. [ABSTRACT FROM AUTHOR]

The paper presents the first study of heavy-mineral sand beaches from the Mediterranean coast of Annaba/Algeria. The studied beaches run along the basement outcrops of the Edough massif, which are mainly composed by micaschists, tourmaline-rich quartzo-feldspathic veins, gneisses, skarns and marbles. Sand samples were taken from three localities (Ain Achir, Plage-Militaire and El Nasr). The heavy-mineral fraction comprises between 74 and 91 vol%. The garnets of the beaches are almandine rich and tourmalines vary with respect to their location from schorl to dravite. Tourmaline at Ain Achir and the Plage-Militaire is schorlits, while at El Nasr beach dravite is ubiquitous. The World Shale Average normalised REE of the sands and the basement outcrops reveal: (i) Ain Achir beach: REE pattern of sand and the coastal rocks from the studied beaches reflects a multiple sources; (ii) Plage-Militaire: the sand and the coastal outcrops show similar LREE and a strong enrichment in HREE, suggesting the presence HREE-rich phases found as inclusions in staurolite; (iii) El Nasr: two types of sand patterns are found: one with flat REE pattern similar to the proximal rocks and other one enriched in HREE suggesting a mixed source. [ABSTRACT FROM AUTHOR]

Up until the last ten years, remote sensing data and especially high-resolution satellite data and airphotos were mainly used in shallow water mapping. The evolution and low cost of unmanned aerial vehicles (UAVs) provides a new tool for coastal area monitoring. This paper presents the synergistic use of a small commercial UAV and an unmanned surface vehicle (USV) for beachrock mapping in Syros Island, Greece. RGB images collected with a quadcopter were processed using Structure from Motion (SFM) photogrammetry in order to create digital surface models (DSMs) and orthophotos of the coastline. A beachrock lying in shallow waters was detected and mapped using the UAV derived products. At the same time, a USV equipped with a compact side scan sonar (SSS) and bathymetric sonar system, provided the shape of the beachrock by mosaicking the backscatter strength of the SSS. In order to evaluate the results of the UAV and USV data derivatives, the beachrock perimeter and its depth were also mapped using a differential global navigation satellite system (GNSS) receiver. During the fieldwork, samples from the beachrock were collected and analyzed in the laboratory. The mineralogical composition of the bulk samples was determined by powder X-ray diffraction (XRD). Further petrographic study was also performed by petrographic polarizing microscope, macroscope, and scanning electron microscopy (SEM). Beachrock samples are classified as fine to medium grain sandstones and conglomerates. The mineral compositions of their grains and lithoclasts reflect the bedrocks of Syros Island (mainly metamorphic rocks) while a micritic high-Mg calcite constitutes the cement of these rocks. [ABSTRACT FROM AUTHOR]