Search

Loess deposits are widely spread all over Eastern Europe, extending as far south as the Sea of Azov and the northern Black Sea. For many decades these regions have been noted for series of key sections. However, despite prolonged investigations, a lack of absolute dating and detailed lithological data has left many unresolved problems in the correlation of the regional stratigraphic schemes. In this study, integrated studies were undertaken on the loess-paleosol sequence exposed on the northern coast of the Taman Peninsula, separating the Sea of Azov from the Black Sea. The exposure in the coastal scarp near Cape Pekla was sampled in detail for standard lithological and stratigraphic analyses, and for the first time, detailed data on the sediments lithology and petromagnetic properties were obtained, as well as the first optically stimulated luminescence age estimates. The data lead us to conclude that the formation of continental series exposed in the Pekla section started at the beginning of the Middle Pleistocene. There are five well pronounced buried soil complexes (PS 1–5) exposed in the sequence, covering sedimentation from the Middle Pleistocene to the present day. We attribute two lower paleosols (PS 4 and PS 5) to two main warm intervals of the Middle Pleistocene – MIS 9 and MIS 13, and the Kamenka interglacial paleosol, correlated with MIS 7 from other parts of the Azov loess area, is represented in the Pekla section by a sand layer formed at the time of the marine transgression dated to interval 220–280 ka (MIS 7). The upper soil horizons (PS1, PS2 and PS3) developed between 20 and 220 ka. The Pekla section contains a considerable proportion of sand fraction – presumably, due to active eolian processes that developed in immediate vicinities of sources of the material. The paleosol characteristics and the structure of loess horizons in the Pekla subaerial series differ considerably from the well described loess-paleosol series of the Northern Azov Sea coasts. In all probability, this region of the Taman Peninsula belongs to a specific province located south of the North Azov loess-soil province.

This review serves as an explanatory note to the sketch map of loessoids, i.e. loess and various loess-like deposits. The map is a byproduct of the ongoing project of Quaternary Map of the Russian Federation, scale 1:2,500,000 in GIS-format. The primary information is derived from the standard National Geological Map scale 1:1,000,000 of the last two generations supplemented by literary data. The map polygons present all mappable loessoid units, including thick southern carbonate loess with paleosols, loess-like silts of northern terrains, intercalations of loessic sediments with waterlain facies and icy silts of the Arctic and Subarctic type. The loessoid formations are classified according to their stratigraphic intervals: 1) the radiocarbon dated Upper Pleistocene of northern terrains, 2) the Middle plus Upper Pleistocene of central Russia, 3) the late Lower Pleistocene to Upper Pleistocene series of southern regions and 4) the Lower Pleistocene red clays of the south. The distribution of diverse loessoids is an imprint of: i) the diverse sedimentary environments of the basically arid periglacial zones of the Pleistocene and ii) the modern geographical zonality changing from subtropics to the icy High Arctic and responsible for post-depositional alteration of subaerial dust. Whatever the origin of the primary dust and geographical varieties of the diagenesis, all loessoids share the same fundamental feature – paleosols, whether numerous and expressive or scarce and weak. They underline the climatically driven intermittent process of loessoid formation – basically subaerial and independent of any aqueous agencies.

Within the sediments of the Pyrzyce Ice-dammed Lake (Polish Lowlands), a number of soft-sediment deformation structures (SSDS) in varve series were distinguished. The unique morphology of the ice-dammed lake—the occurrence of level IV overload and the presence of dead ice in the central zone (Lake Miedwie) and the marginal reservoir—had a decisive impact on the formation and nature of sedimentary structures. Dead ice melting and loss of support could be the cause of plastic deformation. The highest intensity deformation in layered sediments of both plastic and rigid types was observed in the marginal (highest) part of the reservoir. Their formation is associated with the melting of rooted lumps of dead ice in sub-aquatic conditions. The exception is deformation resulting from desiccation under subaerial conditions. The genesis of the deformation observed in rhythmically-layered varves is associated with the last stage of functioning and disappearance of the reservoir during the recession of an ice sheet of the Pomeranian phase of the Weichselian glaciation. These studies detail the current state of knowledge on the processes and factors responsible for the formation of soft structures occurring in glaciolimnic basin.

Subaerial physical, chemical and biological weathering processes are significant contributors to mountain landscape development worldwide, and over long time scales. This paper reports on pseudokarst features formed by different subaerial weathering processes on a high-elevation basalt plateau surface in the Maloti–Drakensberg mountains of eastern Lesotho, southern Africa. Different mesoscale landforms identified on this plateau surface include enclosed depressions (containing seasonal pools) that are morphologically similar to karstic solutional features. Such basalt pseudokarst landforms have not been previously described. This study uses field data on depression morphometry, sediments, water chemistry and rock surface hardness to explore the varied subaerial weathering and erosion processes contributing to pseudokarst depression development. Results show that physical, chemical and biological weathering and erosion processes in combination can impact on the basalt land surface in widening and deepening these depressions. An evolutionary model for pseudokarst depression development proposes that different weathering processes in combination within the ‘critical zone’ cause changes in depression morphology, and that there are significant feedbacks between bedrock, weathering, and the development of distinctive micromorphological forms. It is likely that similar pseudokarst landforms from other locations with non-carbonate substrates have been under-reported in the literature.

The sudden eruption of submerged calderas can potentially pose imminent danger to nearby communities. Hence, it is crucial to closely monitor the changes in volatile effluents in these environments. Unlike subaerial volcanoes, underwater volcanic activity is difficult to observe. Wakamiko, a submerged caldera in southern Japan shares a magma source with the active subaerial volcano, Mt. Sakurajima . Following years of inactivity, the volcanic eruptions in Mt. Sakurajima became more frequent in 2009; however, it is undetermined how the neighboring Wakamiko caldera has behaved in relation to this upsurge in activity. In this study, we assess the state of hydrothermal venting inside Wakamiko following recent disturbances in Mt. Sakurajima. Based on gas bubbles, seawater and sediment pore water measurements of samples obtained in 2015, it appears that acidic fluids enriched in 3He continue to be discharged to the seafloor. Excess 3He in the water column shows no apparent change since 2010; however, the helium isotopic ratio of the magmatic source continues to be elevated at ∼7.2 Ra. This ratio for the magmatic component is higher than previously observed in 1986 (∼6 Ra). The difference could be related to changes in the degassing activity as well as the mantle composition of the magmatic source. Using the new data from sediment pore water, we estimate the diffusive fluxes of 3He and 4He through the seafloor at 16.05 atoms cm-2s-1 and 1.52 x 106 atoms cm-2s-1, respectively. We also calculated the vent 3He flux at 3.38 x104 atoms cm-2s-1. With the use of the 3He flux, we calculated the diffusive CO2 flux from Wakamiko at 1.41 x 106 mol yr-1 and the vent flux at 3.72 x 108 mol yr-1. The available data that we have are still limited and a more frequent and longer observation is necessary to deduce the temporal changes in Wakamiko and its relation to the volcanic activity of Mt. Sakurajima.

Sections at Baghuk Mountain, 45 km NNW of Abadeh (Central Iran), have excellent exposures of fossiliferous marine Late Permian to Early Triassic sedimentary successions. Detailed bed-by-bed sampling enables the analysis of microfacies changes of three successive rock units across the Permian–Triassic boundary. The Late Permian Hambast Formation is mainly the result of biogenic carbonate production. Its carbonate microfacies is dominated by biogen-rich and bioturbated nodular limestones, indicating a well-oxygenated aphotic to dysphotic environment. The biogen-dominated carbonate factory in the Permian ceased simultaneously with the main mass extinction pulse, which is marked by a sharp contact between the Hambast-Formation and the overlaying Baghuk Member (= ‘Boundary Clay’). The clay and silt deposits of the Baghuk Member with some carbonate beds show only a few signs of bioturbation or relics of benthic communities. The Early Triassic Claraia Beds are characterised by a partly microbially induced carbonate production, which is indicated by frequent microbialite structures. The depositional environment does not provide evidence of large amplitude changes of sea level or subaerial exposure during the Permian–Triassic boundary interval. The deposition of the Baghuk Mountain sediments took place in a deep shelf environment, most of the time below the storm wave base., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Museum für Naturkunde – Leibniz-Institut für Evolutions- und Biodiversitätsforschung (3498)

Selenium behaves as a chalcophile and moderately volatile element during planetary accretion and magmatic processes on Earth. Together with the geochemically similar S and Te, Se is more volatile than most other moderately volatile elements and thus potentially becomes a new tracer to constrain the mechanism of volatile depletion in the Earth's mantle and other planetary bodies. As previously observed for several volatile elements, stable isotopes of Se are expected to fractionate upon eruptive outgassing of magmas. To understand the degassing behavior of Se and associated isotope fractionation, we report on Se and Te contents and Se isotope compositions (δSe) of submarine glasses across a range of distant ridge depth intervals along the Reykjanes Ridge and subglacial/subaerial basalts on Iceland (51–65°N; N = 22). Selenium (150–399 ng/g) and Te (2.61–14.5 ng/g) contents of the submarine glasses display progressive enrichment along the Reykjanes Ridge towards Iceland. This can be explained either by enhanced mantle melting towards Iceland or by enrichment of Se–Te contents in the mantle source due to the Icelandic plume–Reykjanes Ridge interaction. Both scenarios are equally plausible. The δSe values of submarine Reykjanes Ridge glasses range between −0.20 ± 0.08‰ and −0.08 ± 0.08‰ (on average −0.15 ± 0.07‰; 2SD, N = 15), which are unaffected by the Icelandic plume contribution and remain strictly within the previously reported average for depleted MORBs. These new data combined with literature δSe for depleted MORBs define a highly homogeneous depleted mantle composition δSe = −0.15 ± 0.11‰ (2SD, N = 44). On the other hand, we observed degassing of Se and Te to a variable extent (~40–95%) in submarine Reykjanes glasses at depths shallower than ~250 m and in subaerial/subglacial basalts on Iceland. Degassing-induced Se isotope fractionation shifted δSe of subaerial lavas towards heavier values (by up to ~0.44‰) well outside the range of submarine MORBs. However, when Se outgassing is associated with subglacial eruption, the outer glass rim of basalt preserves the primary/undegassed Se isotopic signature; whereas the pillow interior experiencing further Se loss (~50%) is enriched in heavier isotopes (−0.01 ± 0.12‰) relative to the outer glass rim (−0.22 ± 0.08‰). These observations are complemented by measurements of BHVO-2G from high-temperature heating experiments of the natural Hawaiian basalt BHVO-2, which show evaporation of 40% Se and 85% Te and resulting shift in δSe by ~+0.74‰. Degassing-induced Se isotope fractionation during volcanic eruption may be well explained by a simple Rayleigh distillation model with an empirical fractionation factor α of ~0.9998 (between volcanic gas and silicate melt). The results presented here show that Se isotope and Se–Te systematics can potentially contribute further constraints on degassing of chalcophile and volatile elements during terrestrial volcanism and large-scale planetary processes., We are especially grateful to Jean-Guy Schilling for his initial support and encouragement of the project, and to Katherine A. Kelley for providing us with all the samples. We acknowledge fruitful discussions with Ronny Schoenberg, Jabrane Labidi, and Timon Kurzawa, and lab support from Elmar Reitter and Maria Isabel Varas-Reus. We also thank Frances Jenner, Alex McCoy-West, and an anonymous reviewer for their through reviews and constructive suggestions, and Julie Prytulak for the efficient editorial handling. S. K. acknowledges financial support by the ERC Starting Grant O2RIGIN (636808).

The area around the town of Mangalia in Southern Dobrogea (Romania) hosts a unique karst landscape represented mostly by large collapse dolines. Around one of these collapse dolines, named Obanul Mare, there is a peculiar morphology of hillocks that resemble the tropical labyrinth-cone karst but on a much-reduced scale. This peculiar relief was hypothesized to be residual, resulting from the ceiling collapse of a two-dimensional maze cave. This type of maze caves form when the water table remains stable for long periods of time, allowing groundwater to dissolve the carbonate host rock along all available discontinuities. The Obanul Mare structure contains a 200 m long cave (Movile cave), whereas a few kilometers away we can find Limanu maze cave, whose passages sum up to more than 3,500 m. Because the existence of a former maze cave is difficult to demonstrate, in this study we took an indirect approach to this issue. We hypothesize that if there was a maze cave and its ceiling collapsed, then the inner walls would be left standing as pillars. Subsequent subaerial evolution of these pillars would create slopes that would incline towards the former cave passages. By quantifying the slope aspect from a high-resolution digital surface model, we would be able to identify the direction of the original passages, hence the main hypothetical fracture lines along which those passages formed. By comparing these orientations to those of local fractures (deduced from the nearby valley and doline axes), as well as with the orientations of the Movile Cave passages, we found that they are well correlated. This strengthens the hypothesis that the hillocky terrain is tectonically conditioned and that it might be the result of cave ceiling collapse, bringing more information on the existence of maze caves in the region. La zone autour de la ville de Mangalia dans le sud de la Dobrogea (Roumanie) abrite un paysage karstique unique représenté principalement par de grandes dolines effondrées. Autour de l'une de ces dolines d'effondrement, appelée Obanul Mare, il existe une morphologie particulière de buttes qui ressemble aux karsts à cône labyrinthiques tropicaux, mais à une échelle très réduite. Au sein de ce travail, nous proposons l'hypothèse que ce relief particulier était résiduel, résultant de l'effondrement du plafond d'une grotte labyrinthe bidimensionnelle. Ce type de grottes labyrinthiques se forme lorsque la nappe phréatique reste stable pendant de longues périodes, permettant aux eaux souterraines de dissoudre la roche carbonatée hôte le long de toutes les discontinuités disponibles. La structure Obanul Mare contient une grotte de 200 m de long (grotte Movile), tandis qu'à quelques kilomètres de là se trouve la grotte Limanu, dont les passages totalisent plus de 3 500 m. Parce qu'il est difficile de démontrer l'existence d’une ancienne grotte-labyrinthe, dans cette étude, nous avons adopté une approche indirecte de la question. Nous émettons l'hypothèse que s'il y avait une grotte-labyrinthe et que son plafond s'effondrait, alors les murs intérieurs resteraient debout tels des piliers. Les phases d’érosion subaérienne postérieures de ces piliers créeraient des pentes qui s'inclineraient vers les anciens passages de la grotte. En quantifiant l'aspect de la pente à partir d'un modèle de surface numérique à haute résolution, nous pourrions identifier la direction des passages d'origine, d'où les principales lignes de fracture hypothétiques le long desquelles ces passages se sont formés. En comparant ces orientations à celles des fractures locales (déduites des axes de vallées voisines et dolines), ainsi qu'avec les orientations des passages de Movile Cave, nous avons trouvé qu'elles sont bien corrélées. Cela renforce l'hypothèse selon laquelle le terrain vallonné est conditionné tectoniquement et qu'il pourrait être le résultat de l'effondrement du plafond de la grotte, apportant plus d'informations sur l'existence de grottes labyrinthiques dans la région.

Subaerial landslides falling into a large body of water can generate large impulse waves (tsunamis). The wave generation by subaerial landslides involves sediment, water and air, and thus multi-phase flow models are most suitable for simulating the processes involved. This paper reports a laboratory and numerical study of impulse waves generated by subaerial landslides, with a focus on grain size effects. Four different grain sizes were examined in this study, ranging from fine sand to very coarse sand. A multi-phase flow model was used to perform the numerical simulations of the laboratory experiment. Both measured and simulated results have shown that the speed of the granular front and the height of the impulse wave increase with decreasing grains size. Possible explanations for the effects of grain size on the landslide process and the resulting waves are discussed.

Isla Socorro is an oceanic island located in the Eastern Pacific Ocean, at the junction of the Clarion Fracture Zone and Mathematician Ridge, approximately 600 km west of the Mexican coastline. Very little is known about the submarine portion of the island, but based on the oldest subaerial deposits, it is inferred to be primarily a basaltic shield cone. In this study, the subsurface structure of Isla Socorro was analysed based on an integration of geological and geophysical data. The geophysical data consist of high-resolution airborne magnetic data as well as an integration of terrestrial gravity and high-resolution satellite gravity. The study revealed important information about the composition, structure and origin of the volcanic edifice. The analysis and interpretation of the gravity and magnetic data indicate the existence of extensional systems associated to the principal tectonic structures of the Revillagigedo area. The horizontal gradient and Euler deconvolution of magnetic data reveal the presence of curved features interpreted as caldera structures. A central, vertically extensive body low in both density and magnetic susceptibility was identified through the 2D forward and 3D inverse modelling techniques. This body could represent a high-temperature zone above the Curie point, thus, we propose this body as a remnant magma reservoir and the source of the most recent volcanic activity from subaerial Socorro, and indicates that the possibility of a future large volume eruption from the summit cannot be ruled out.

[Abstract Lacustrine carbonate facies distribution is controlled by multiple environmental parameters including climate, hydrology, and tectonic setting, but few published models address this complexity. In this study, seismic and borehole data, integrated with outcrop logging, correlations, and facies models, are used to create a new tectono‐sedimentary model demonstrating how extensional faults, linked by a relay ramp, control distribution of lacustrine carbonate facies in the Upper Jurassic to Lower Cretaceous Purbeck Limestone Group (Wessex Basin, UK). Accumulation occurred in half‐graben sub‐basins south of two extensional east‐west faults, with widespread subaerial emergence of footwall blocks to the north. The lacustrine limestones of the lowest unit of this Group are characterised by in‐situ microbial mounds within bedded inter‐mound packstones‐grainstones. Mounds occur in three depositional intervals separated by paleosols. The distribution of facies indicates more brackish‐water conditions shoreward to the west, and more hypersaline conditions basinward to the east. The relay ramp hosts extensive microbial carbonate buildups formed in response to carbonate‐rich waters sourced from the northern limestone footwall blocks that fed into extensive shallow‐water areas on the low‐angle relay ramp slope., Depositional model of the Cap Beds of the Purbeck Limestone Group or Dorset showing the facies distribution in the Purbeck lake (modified after Underhill, 2002). ]

The potentially biodeteriogenic, subaerial green alga Trentepohlia umbrina is widely distributed on shaded substrates with northern aspects. This preference for low light was confirmed by a recent survey in Lazio, Italy. However, the same survey revealed an isolated occurrence of extensive growths of T. umbrina-dominated biofilms on surfaces with diverse aspects that ranged from highly exposed to shaded. Prior studies of Trentepohlia photosynthesis have been restricted to single sites, so this multi-aspect site was particularly interesting to understand the photoacclimation potential of Trentepohlia. Photosynthetic pigment concentrations and chlorophyll fluorescence (in situ and ex situ) were used to assess the photosynthetic response to changes in light exposure and humidity. Pigment contents and photoinhibition decreased, while the maximum photosynthetic rate and the level of light that saturated photosynthesis increased with an increasing light exposure duration (ranging from c. 5 to 300 min d–1 of exposure to sunlight). Laboratory tests of relative humidity (RH) on biofilm photosynthesis showed no recorded activity up to 32% RH, only 26% of the maximum activity at 77% RH, and full activity at 92% RH. When T. umbrina was in the desiccated state a lowering of basal of chlorophyll a fluorescence emission and a loss of variable fluorescence occurred. This suppression of fluorescence when cells are desiccated is known to result in photoprotection of reaction centres from continuing high irradiances, as the enhanced thermal dissipation replaces slower and potentially damaging energy transfer to the functional reaction centres. It was concluded that T. umbrina has a much wider environmental range than previously thought, but its growth is very slow and may be overlooked during cultural heritage surveillance, leading to inconspicuous chronic degradation of outdoor stone substrata.

Newly discovered dinosaur footprints from the Lower Cretaceous (Albian) Folkestone Formation (Lower Greensand Group) of Kent in S.E. England can be referred to theropod, ornithopod and possibly ankylosaur dinosaurs. The occurrence of dinosaur footprints, together with fossil wood and oysters in a matrix of well-rounded quartz grains indicates a coastal depositional environment of an extremely shallow depth, perhaps with short periods of subaerial exposure. This is the first record of dinosaur footprints from the Folkestone Formation, and it represents the youngest association of dinosaur footprints from England. The moderately diverse dinosaur ichnoassemblage of theropods, ornithopods, ankylosaurs and previously documented fossils indicate deposition on a sandy beach setting.

The cross-instrumental dating of the Quaternary deposits in the Sambia (Kaliningrad) Peninsula has made it possible to obtain a time series that indicates the formation of a sequence overlapping the Last Glaciation deposits in the Late Holocene under subaerial conditions with active aeolian accumulation starting from 450–400 BP. The earlier established fluvioglacial genesis and Late Glacial age of the surface deposits need to be revised. Greater aeolian activity is presumably related to climate changes during the Little Ice Age. OSL dating of very young (Late Holocene) subaerial deposits demonstrates the reliable results supported by agreement with the radiocarbon analysis data and the stratigraphic position of the dated sequences.

Frequent or consecutive storms impacting coastal areas can result in unexpected or variable impacts. This study evaluates spatiotemporal variability and cumulative impacts on the subaerial beach from four major tropical storms of varying intensity and proximity impacting the study area of Palm Beach County, Florida, during the 2020 Atlantic Basin Hurricane season. Impacts from Hurricanes Isaias, Laura, Sally, and Teddy were measured using Real-Time Kinematic Global Positioning System (RTK GPS) at 14 transects throughout the northern and southern portion of the county. Alongshore morphologic variability resulted from each storm, with some expected patterns of erosion and accretion with a few unexpected impacts. The first three storms caused swash or collision regime impacts on the Sallenger scale. Hurricane Teddy was the fourth storm to impact the study area, causing overwash at numerous locations. Whereas the first two storms of the season caused mostly erosion of the subaerial beach, the southeasterly approach of Hurricane Sally reversed the cumulative volume loss trend in the northern portion of the study area with accretion. Hurricane Teddy was the most distant storm but occurred at the highest tide and produced the largest waves and highest winds. The most variable patterns in erosion and accretion resulted from Hurricane Teddy, which also dominated the overall (or cumulative) volume and contour change. Further study is recommended for a multi-storm season that includes the subaqueous portion of the beach profile to elucidate trends of cross-shore and alongshore drivers of storm-induced morphology change.

Hurricanes are known to play a critical role in reshaping coastlines, particularly on the open ocean coast in cases of overwash, but storm induced seaward-directed flow and responses are often ignored or un-documented. Subaerial evidence for seaward sediment transport (outwash, return-flow) increases our understanding of the impact hurricanes have on coastal and barrier island evolution. Towards this goal we catalog all available National Geodetic Survey Emergency Response Imagery (ERI), the National Oceanic and Atmospheric Administration’s (NOAA) collection of post-hurricane aerial imagery on the U.S East Atlantic and Gulf of Mexico coasts, for visible washout and return flow features. The most recent examples are from the North Core Banks, North Carolina, after Hurricane Dorian (2019), the Carolina coasts after Hurricane Isaias (2020), the Isles Dernieres, Louisiana, after Hurricane Zeta (2020), and the southwest coast of Louisiana, after Hurricanes Laura and Delta (2020); these include erosive scours and channels but also depositional deltas and fans on the shoreface and nearshore. Over the nearly 200 km of coastline analyzed, hundreds of seaward-flow features were identified; the density exceeds 20 per km in some areas. Individual features measure between 5 m and 500 m in both the along- and cross-shore dimensions. The extensive occurrence of these storm-induced return-flow and outwash morphologic features demonstrates that their sediment transport role may be more influential than previously thought. Based on these observations, we advocate for their inclusion in coastal change hazards classification schemes and coastal evolution morphodynamic models and propose an adoption of direction-explicit terms to use when describing return- and seaward-flow features to reduce redundant jargon and distinguish them from more frequently documented landward-flow features.

The studied section is located in the core of the Gara Anticline, about 12 km southeast of Amedi Town. The Baluti Formation is generally composed of grey and green shale, calcareous, dolostone with intercalations of thinly bedded dolostones, dolomitic limestones, and silicified limestones which are occasionally brecciated. The petrographic study shows five main microfacies in the Baluti Formation namely; finely laminated dolomudstone, fossil-barren and lime mudstone, fenestral mudstone/packstone, peloids and ooids wackestone, and lithoclasts (intraclasts) grainstones. The mudstones facies with no fauna and radial-fibrous ooids can point to a protected and low energy environment. Moreover, fenestral structures are reliable criteria for identifying a tidal flat environment. The presence of the lithoclasts (intraclasts) with radial ooids and a few terrestrial fragments may represent a quiet environment, albeit one affected by infrequent storm deposits. As a supplementary to microfacies, the biomarker characterizations were used to deduce the depositional environment of the Baluti Formation. Biomarker parameters show that the Baluti Formation could be deposited in anoxic to suboxic environment, and organic matter input is more likely characterized by land plant organic matter. This study showed that the most likely paleoenvironments for the Baluti Formation were supratidal, intertidal, subtidal, and sand shoals setting. However, the lack and/or very low diversity of skeletal fauna, and the lack of subaerial exposure may indicate that some parts of the formation seem to be deposited in low energy and restricted environment (Lagoon).

High-resolution geochronology is essential for determining the growth rate of volcanoes, which is one of the key factors for establishing the periodicity of volcanic eruptions. However, there are less high-resolution eruptive histories ( > 10 6 years) determined for long-lived submarine arc volcanic complexes than for subaerial complexes, since submarine volcanoes are far more difficult to observe than subaerial ones. In this study, high-resolution geochronology and major-element data are presented for the Milos volcanic field (VF) in the South Aegean Volcanic Arc, Greece. The Milos VF has been active for over 3 Myr , and the first 2 × 10 6 years of its eruptive history occurred in a submarine setting that has been emerged above sea level. The long submarine volcanic history of the Milos VF makes it an excellent natural laboratory to study the growth rate of a long-lived submarine arc volcanic complex. This study reports 21 new high-precision 40 Ar / 39 Ar ages and major-element compositions for 11 volcanic units of the Milos VF. This allows us to divide the Milos volcanic history into at least three periods of different long-term volumetric volcanic output rate ( Qe ). Periods I (submarine, ∼ 3.3–2.13 Ma ) and III (subaerial, 1.48 Ma –present) have a low Qe of 0.9 ± 0.5 × 10 −5 and 0.25 ± 0.05 × 10 −5 km3 yr−1 , respectively. Period II (submarine, 2.13–1.48 Ma ) has a 3–12 times higher Qe of 3.0 ± 1.7 × 10 −5 km3 yr−1 . The Qe of the Milos VF is 2–3 orders of magnitude lower than the average for rhyolitic systems and continental arcs.

Among the great variety of geological relics of Ukraine, one of the most attractive is the Rybalsky Quarry, located in the city of Dnipro, and well known outside Ukraine. First of all, it is famous for the Mandrykivski Layers exposed in one of the ridges of the Quarry back in the 1970s, although there are many other important peculiarities of the geological structure of the Quarry which attract scientists from Ukraine, Germany, France, Netherlands, Russia and other countries. There are full data on the history of discovery and survey of the Mandrykivski Layers from their discovery by Valerian Domger in 1882 to current studies that reveal various aspects of geological structure of the Quarry, the results of study of different groups of fossil fauna, compare them with the fauna of the Paris Upper Eocene basin and other well- known locations. Particularly in the Rybalsky Quarry, thanks to the author`s efforts, the Layers received the status of “layers with geographic name”, as confirmed by the decision of Cenozoic Commission of the National Stratigraphic Committee of Ukraine in 2001. New fragments of the section of subaerial and subaqueous deposits of the Quaternary deposits were found and their composition, structure and complete stratigraphic content were studied. The research allows us to consider it typical for the Middle Prydniprovia. Fluvioglacial and lake-glacial deposits of the Dnipro glaciations in the Quarry exposed for the second time in 25 years, but this is the first time when their genetic origin, position in the section and lithological-facies peculiarities were determined. Thick layer of sands embedded on the roof of the Mandrykivski Layers were identified to the fifth or Hadzhybeiska terrace of the Dnipro, in the upper part of which there were notable siliceous-clayey-ferruginous formations or lateral crust (ferruginous crusts). The studies of the layer of brown-green and red-brown clays in the roof of the Mandrykivski layers allows us to presume their marine origin. In this case, they are underwater weathering crust (terra rossa) developed in the process of halmyrolysis or are the product of dissolution of carbonate silt enriched with detritus of mollusks, corals and other inhabitants of the warm Mandrykivske Sea.

The sequence of sediment accumulation of the first and second terraces of the Tarbagataika River and changes in the stages of incision and filling, as well as sedimentation and soil formation over the last 14 kyr in the river valley were revealed. The dynamics of the sedimentation stages and of the phases of their stabilization and pedogenesis was determined by landscape-climatic changes in the study area. The period of geomorphologic formation of above-floodplain terraces was determined. The floodplain sedimentation regime was changed by the subaerial regime on the second terrace of the Tarbagataika River approximately 8 kyr BP. The accumulation of cover deposits on the first terrace began approximately 3.4 kyr BP. Deposits of the second terrace of the Tarbagataika River were formed during the Late Glacial and the Holocene during the last 14 kyr. They are composed of alluvial sediments that accumulated 14.0–8.0 kyr BP and of cover deposits, which accumulated 8.0–0 kyr BP. The first terrace of the Tarbagataika River of the Holocene age is composed of alluvial deposits, which were accumulated 7.0–3.4 kyr BP, and of deposits of the covering complex, which were formed over the last 3.4 kyr. The phases of intensification of erosion-accumulative processes related to increased water discharge were identified. The main stages of soil formation in the study area were determined. The data we obtained are in good agreement with the previously identified stages of pedogenesis in the Selenga middle mountains and adjacent regions of South-Eastern Siberia and Mongolia.

Massive CO2 and SO2 degassed from large igneous provinces (LIPs) are thought to cause ocean acidification and calcification crisis with a significant loss of calcified marine biota. The ocean acidification caused by the Emeishan LIP event has been proposed as one of the important factors that triggered the end-Guadalupian (Middle Permian) crisis, although the driving mechanism remains unclear. Here we represent a detailed field investigation combined with LA-ICP-MS, SIMS and CA-ID-TIMS zircon geochronology of tuffs from four volcanic sections in the eastern part of the Emeishan LIP. Our new data combined with previous results from this LIP confirm that: (i) the submarine volcanism occurred between ~260.7 Ma and ~ 257.9 Ma, with most basaltic eruptions at ~260.1 Ma to 259.5 Ma; and (ii) explosive tuff eruptions occurred during ~257.9 Ma to ~256.9 Ma in the subaerial environment. We propose a model involving SO2 release from the submarine basaltic eruptions in the Emeishan LIP as the trigger of the end-Guadalupian ocean acidification, due to the high solubility of SO2 in seawater that could produce strongly acidic conditions. The late explosive silicic volcanism in the subaerial setting during Early to Middle Wuchiapingian (Late Permian) might have been a potential strong driver of the global Wuchiapingian cooling event.

Process-physics-based, coupled hydrodynamic–morphodynamic delta models are constructed to understand preserved facies heterogeneities that can influence subsurface fluid flow. Two deltaic systems are compared that differ only in the presence of waves: one river dominated and the other strongly influenced by longshore currents. To understand an entire preserved deltaic succession, the growth of multiple laterally adjacent delta lobes is modeled to define delta axial to marginal facies trends through an entire regressive–transgressive depositional succession. The goal is to refine a facies model for symmetrical wave-dominated deltas (where littoral drift diverges from the delta lobe apex). Because many factors change depositional processes on deltas, the description of the river-dominated example is included to provide a direct reference case from which to define the impact of waves on preserved facies patterns. Both systems display strong facies trends from delta axis to margin that continued into inter-deltaic areas. River-dominated delta regression preserved a dendritic branching of compensationally stacked bodies. Transgression, initiated by sea-level rise, backfilled the main channel and deposited levees and splays on the submerging delta top. Wave-dominated deltas developed dual clinoforms: a shoreface clinoform built as littoral drift carried sediment away from the river month and onshore, and a subaqueous delta-front clinoform composed of sediment accumulated below wave base. Although littoral drift in both directions away from the delta axis stabilized the position of the river at the shoreline, distributary-channel avulsions and lateral migration of river flows across the subaqueous delta top produced heterogeneities in both sets of clinoform deposits. Separation of shoreface and subaqueous delta-front clinoforms across a subaqueous delta top eroded to wave base produced a discontinuity in progradational vertical successions that appeared gradual in some locations but abrupt in others. Littoral drift flows away from adjacent deltas converged in inter-deltaic areas, producing shallow water longshore bars cut by wave-return-flow channels with associated terminal mouth bars. Transgression initiated by sea-level rise initially led to vertical aggradation of wave-reworked sheet sands on the subaqueous delta top and then retreating shoreface barrier sands as the subaerial delta top flooded. Pseudo inter-well flow tests responded to local heterogeneities in the preserved deposits. As expected, abandoned channels in the river-dominated case defined shoreline-perpendicular preferential flow paths and wave-dominated delta deposits are more locally homogeneous, but scenarios for development of more pronounced shore-parallel heterogeneity patterns for wave-influenced deltas are discussed. The results highlight the need to consider the dual clinoform nature of wave-dominated delta deposition for facies prediction and subsurface interpretation.

Bioturbation has long been considered an antagonist of microbialite development and preservation, because metazoan grazing and burrowing destroy benthic microbial communities. However, metazoan bioturbation, in conjunction with microbial accretion, may have had a significant role in the morphogenesis of some columnar microbialites, as suggested by the case study presented and by some Phanerozoic and Upper Proterozoic analogues discussed here. Late Miocene in age, the studied microbial biostrome developed in a western Mediterranean restricted shallow-water platform dominated by grainy sediments and with a notable influence of bioturbation. This study is focused on the complex accretionary history of the columnar microbialite biostrome and on its striking dark grey colour, which is attributed to Mn-oxyhydroxides precipitated during meteoric diagenesis linked to subaerial exposure. The characteristic columnar structure of the microbialite biostrome has features consistent with an accretionary origin of the columns, but also has features suggesting metazoan disruption. Therefore, a new morphogenetic model for columnar microbialites is presented, highlighting the concomitant roles of microbial accretion, bioturbation and grainy sediment infill of the intercolumn space. Whether this model is an exception or a rule, should be tested on other examples of Phanerozoic and Upper Proterozoic columnar microbialites. Nevertheless, this model is a step forward in understanding the complex microbe–metazoan interactions as constructive coexistence rather than just as destructive competition.

Cephaleuros is a subaerial green alga widely distributed in tropical and subtropical regions. In this study, we investigated the taxonomy of Cephaleuros in southern China. Eight morphospecies (C. v...

The harmful effects of ultraviolet (UV) radiation have increased the demand for new sources of UV photoprotectants to develop cosmetic and skin care products. In this study, a filamentous cyanobacterial strain was isolated from the topsoil collected in an arid and exposed region in Chetimari, Niger. On the basis of 16S rDNA sequences, the isolated strain was identified as Pseudanabaena sp. CCNU1. UV-B treatment of Pseudanabaena sp. CCNU1 significantly enhanced the production of active photoprotectants, including UV-absorbing mycosporine-like amino acids (MAAs) and carotenoids. UV-B irradiation mainly induced the production of one MAA, identified as palythine-serine. The palythine-serine content was as high as 16 mg g−1 dry weight after a 4-day UV-B treatment. Eight carotenoids were detected in the methanol extracts of UV-B-treated Pseudanabaena sp. CCNU1: β-carotene, echinenone, canthaxanthin, zeaxanthin, synechoxanthin, and three myxoxanthophyll derivatives. With the exception of β-carotene and echinenone, these carotenoids were positively correlated with the UV-B treatment duration. Thus, Pseudanabaena sp. CCNU1 was identified as a unique organism that produces a considerable abundance of palythine-serine as well as carotenoids to protect against UV-B radiation. Pseudanabaena sp. CCNU1 may be useful as a producer of UV photoprotectants, although the genetic basis of the relevant biosynthetic pathways remains to be precisely characterized in the future.

Barrier coasts, including barrier islands, beach-ridge plains, and associated landforms, can assume a broad spectrum of morphologies over multi-decadal scales that reflect conditions of sediment availability, accommodation, and relative sea-level rise. However, the quantitative thresholds of these controls on barrier-system behavior remain largely unexplored, even as modern sea-level rise and anthropogenic modification of sediment availability increasingly reshape the world's sandy coastlines. In this study, we conceptualize barrier coasts as sediment-partitioning frameworks, distributing sand delivered from the shoreface to the subaqueous and subaerial components of the coastal system. Using an idealized morphodynamic model, we explore thresholds of behavioral and morphologic change over decadal to centennial timescales, simulating barrier evolution within quasi-stratigraphic morphological cross sections. Our results indicate a wide diversity of barrier behaviors can be explained by the balance of fluxes delivered to the beach vs. the dune or backbarrier, including previously understudied forms of transgression that allow the subaerial system to continue accumulating sediment during landward migration. Most importantly, our results show that barrier state transitions between progradation, cross-shore amalgamation, aggradation, and transgression are controlled largely through balances within a narrow range of relative sea-level rise and sediment flux. This suggests that, in the face of rising sea levels, subtle changes in sediment fluxes could result in significant changes in barrier morphology. We also demonstrate that modeled barriers with reduced vertical sediment accommodation are highly sensitive to the magnitude and direction of shoreface fluxes. Therefore, natural barriers with limited sediment accommodation could allow for exploration of the future effects of sea-level rise and changing flux magnitudes over a period of years as opposed to the decades required for similar responses in sediment-rich barrier systems. Finally, because our model creates stratigraphy generated under different input parameters, we propose that it could be used in combination with stratigraphic data to hindcast the sensitivity of existing barriers and infer changes in prehistoric morphology, which we anticipate will provide a baseline to assess the reliability of forward modeling predictions.

The article deals with deposits exposed in sections along the rivers of the Caspian lowland and on the eastern slope of the Ergenei. The conclusion is made about the lagoonal origin of chocolate clays lying on high-capacity subaerial and alluvial–deltaic deposits. The impact of the Caspian Sea level rise on coastal processes is examined. Taking into account the regularities in the behavior of the coastal zone during sea level rise, subaerial deposits with such thickness in the outcrops could not have been preserved during the early Khvalynian transgression from –100 m. Another curve of Caspian Sea level fluctuations is proposed, where there is no deep Atelian regression between the Khazarian and Khvalynian transgressions. It is concluded that the Khazarian transgression was one of the largest in the history of the Caspian Sea. Its level was slightly less than that of the Khvalynian transgression. The rise of the level of the latter began not from –100 m, but from about 5–15 m; i.e., this transgression was in fact an oscillation of the Caspian Sea against its gradual regression after the Khazarian transgression. Sea level oscillations contributed to the formation of lagoonal-transgressive terraces, in which chocolate clays accumulated.

Surface topography (whether subaerial or submarine) is a product of plate tectonic, geological, climate and surface processes. Plate tectonic processes, predominantly operated through earthquake cycle, dominate, at least in the seismically active regions, and are responsible for a significant amount of topography build up. On a shorter time scale, they appear to cause devastation, but on a longer time scale, they lead to the development of diverse landscapes which not only makes them look beautiful but also inhabitable. The topography build-up, due to deformation caused by earthquake processes, depends upon the mechanism of deformation and earthquake occurrence. The earthquake occurrence mechanism is different in the plate boundary regions as compared to that in the plate interior regions. Here in this article, I discuss the nuances of crustal deformation in the interplate and intraplate regions in the context of India and India plate.

Topographic/bathymetric conditions of the continental shelf can significantly influence the long-term growth of river deltas. In particular, these conditions constrain the accommodation space for sedimentation in the deltaic areas. In this study, we use a conceptual geometric model to evaluate the role played by this factor, on the basis of the principle of mass conservation. The Ganges-Brahmaputra, Mekong and Nile deltas are examined as three typical examples, in terms of their different original seabed morphologies. The control variate method is applied to eliminate the effect of the difference in model input variables. The results show that, assuming a constant sediment load, the delta growth rate will decrease with time; a higher value of the original seabed slope leads to a lower shoreline progradation rate for the subaerial delta and a higher growth rate for the subaqueous delta. Thus, the original seabed morphology represented by slope is a critical factor affecting the evolution of Holocene large-river deltas. These results explain the interrelationships between sediment load, deltaic plain area, and the original seabed slopes for the 27 large-river deltas worldwide, located in the middle/low latitudes, with different tectonic backgrounds. In the future, the conceptual geometric model may be combined with sediment dynamic modeling to identify more details of the evolution of these deltas.

On December 22, 2018, a destructive tsunami related to the phenomena caused by the volcanic eruption of Gunung Anak Krakatau (GAK) was generated following a partial collapse of the volcano that caused serious damage and killed more than 400 people. This recent event challenged the traditional understanding of tsunami hazard, warning and response mechanisms and raised the topic of volcanic tsunami hazard. The complex mechanism of this tsunamigenic volcano collapse still needs further investigation as Anak Krakatau is one of the potentially tsunamigenic volcanoes in the world. This study investigates the possible source mechanisms of this phenomenon and their contribution to explaining the observed sea level disturbances by considering the impacts of this destructive event. We configured a flank collapse scenario with a volume of 0.25 km3 as a combination of submarine and subaerial mass movement as the possible source scenarios to the December 22, 2018 Sunda Strait tsunami. A two-layer model is applied to simulate the tsunami generation by these landslides up to 420 s. The tsunami propagation and inundation are then simulated by NAMI DANCE model in GPU environment. The simulation results suggest that this scenario seems capable of generating such a tsunami observed along the coast of Sunda Strait. However, the contribution of the possible submarine mass movements in the close area between GAK and the surrounding islands either to this event or potential tsunami threat in the region is still questionable. We employed a bathymetric dataset through pre- and post-event analyses, which demonstrate submarine slope failures in the southwestern proximity of GAK. Hence, additional two scenarios of elliptical landslide sources on the slopes of bathymetry change area (could be triggered by seismic motion/volcanic eruption) are considered, searching for the possible effects of the tsunami that might be generated by these submarine landslides. The study may also provide some perspective for potential tsunami generation by combined sources and help to elucidate the extent of volcanic tsunami hazard in the region due to potential future eruptions of Gunung Anak Krakatau.

Following more than 25 years of exploration and research since the last regional appraisal, the number of known subaerially exposed volcanoes in the northern Antarctic Peninsula region has more than trebled, from less than 15 to more than 50, and that total must be increased at least three-fold if seamounts in Bransfield Strait are included. Several volcanoes remain unvisited and there are relatively few detailed studies. The region includes Deception Island, the most prolific active volcano in Antarctica, and Mount Haddington, the largest volcano in Antarctica. The tectonic environment of the volcanism is more variable than elsewhere in Antarctica. Most of the volcanism is related to subduction. It includes very young ensialic marginal basin volcanism (Bransfield Strait), back-arc alkaline volcanism (James Ross Island Volcanic Group) and slab-window-related volcanism (seamount offshore of Anvers Island), as well as volcanism of uncertain origin (Anvers and Brabant islands; small volcanic centres on Livingston and Greenwich islands). Only ‘normal’ arc volcanism is not clearly represented, possibly because active subduction virtually ceased at c. 4 Ma. The eruptive environment for the volcanism varied between subglacial, marine and subaerial but a subglacial setting is prominent, particularly in the James Ross Island Volcanic Group.

Borobudur Temple is a historical heritage building located in an open area and made of porous building materials (stone materials). This condition makes the Borobudur Temple susceptible to various problems related to degradation and weathering. Biodeterioration of Borobudur Temple may be caused by activities of living organisms present in the biofilm of stone. Continuous monitoring and evaluation need to be carried out by observing and isolating the growth of micro-organisms, including epilithic microalgae. Therefore, this study aims to isolate and identify epilithic microalgae from the biofilm on Borobudur Temple stones. Epilithic microalgae were isolated to obtain a uni-algae and maintained under culture conditions. The morphological of microalgae were observed using light microscopy, while the 18S rRNA gene sequence determined the molecular identification of microalgae for eukaryotic and 16S rRNA sequence for prokaryotic. A total of nine epilithic microalgae were successfully isolated from the biofilm of Borobudur Temple stones. The isolated were identified as Ankistrodesmus falcatus, Tetraselmis cordiformis, Pseudendoclonium arthropyreniae, Anabaena cylindrica, Nostoc gelatinosum, Oscillatoria limnetica, Messastrum gracile, Stigeoclonium aestivale, and Scenedesmus acuminatus. This is the first study for the identification of microalgae from Borobudur temple stones. The isolates will be collected and will be used as a source for further study.

The sediments of the floodplain of Kamchatka River in its middle course have been studied. Two types of floodplain accumulation environment are distinguished: stable (overgrowth of oxbow lakes distant from the main channel) and dynamic (banks of the central part of the valley, subject to regular flooding). Radiocarbon dating of buried organics was carried out. The oldest peat formed around 3200 14C years (3460 cal BP), during a period of low water flow, which may have been caused by climatic changes. Formation of the floodplain-oxbow alluvium began not later than 3.8 thousand years ago. Changes in hydrological regime and major reorganization of the river channel led to the formation of a new surface, possibly due to seismic processes. The age of that seismic event may be several hundred years older than the beginning of subaerial sedimentation on the high floodplain in the middle course of Kamchatka river.

In the present study, three different types of landslide-generated tsunamis (subaerial, partially submerged and submarine) were investigated through laboratory experiments that used 261 different e...

Marine shales, the most common lithology in the stratigraphic record, represent an archive of long-term changes in sediment production, weathering intensity, and seawater chemistry through Earth history whose potential has been underexploited to date. In this study, we compiled compositional data for 14,531 samples from 268 shale and mud units ranging in age from the early Cryogenian (840 Ma) to the Recent. We examined secular variation in the Al-normalized concentrations of ten elements (Mg, Na, K, Ba, Sr, Y, Th, Rb, Nb, and Zr) selected for (1) their presence in typical X-ray fluorescence (XRF) datasets (thus providing sufficient data), and (2) their lack of redox sensitivity (thus excluding elements whose primary control is aqueous redox conditions). Relationships among the study elements were quantified using principal component analysis (PCA) and cluster analysis (CA), revealing several significant groupings: (1) a subset of “detrital elements” (K, Rb, Th, Nb, Y, and Zr) whose concentrations are primarily controlled by subaerial weathering processes; (2) a subset of “hydrogenous elements” (Mg, Na, and Sr) whose concentrations are significantly influenced by seawater chemistry, and (3) Ba, which is subject to multiple controls. The dominant influence on the detrital elements appears to have been not chemical weathering intensity per se but the ratio of Al-poor silt to Al-rich clay in the particulate weathering flux. Although possibly modulated by factors such as climate and land plant evolution, silt:clay ratios appear most closely linked to tectonism, with higher values associated with major orogenic events. The concentrations of the hydrogenous elements in marine shales were likely related to their seawater inventories, which were modulated at long time scales by rates of submarine hydrothermal alteration. Ba in marine shales may have been significantly influenced by atmospheric pO2 and seawater sulfate levels via their control of barite saturation in seawater. In summary, our findings document significant relationships of marine shale composition to first-order geological controls, suggesting that long-term secular changes in sediment and seawater chemistry can be reconstructed from fine-grained siliciclastic sediments.

Carbonate cave deposits (speleothems) have been used widely for paleoclimate reconstructions; however, few studies have examined the utility of other speleothem-forming minerals for this purpose. Here we demonstrate for the first time that stable isotopes (δ17O, δ18O and δD) of structurally-bound gypsum (CaSO4·2H2O) hydration water (GHW) can be used to infer paleoclimate. Specifically, we used a 63 cm-long gypsum stalactite from Sima Blanca Cave to reconstruct the climate history of SE Spain from ~ 800 BCE to ~ 800 CE. The gypsum stalactite indicates wet conditions in the cave and humid climate from ~ 200 BCE to 100 CE, at the time of the Roman Empire apogee in Hispania. From ~ 100 CE to ~ 600 CE, evaporation in the cave increased in response to regional aridification that peaked at ~ 500–600 CE, roughly coinciding with the transition between the Iberian Roman Humid Period and the Migration Period. Our record agrees with most Mediterranean and Iberian paleoclimate archives, demonstrating that stable isotopes of GHW in subaerial gypsum speleothems are a useful tool for paleoclimate reconstructions.

Debris flows and lahars are dense masses of water and sediment which are common phenomena in mountainous and volcanic regions, respectively. Where these flows debouch into water bodies they can trigger impulse waves (tsunamis) and form subaqueous deposits. Such deposits are important indicators for areas at risk from debris flows, lahars, and tsunamis and form archives of past environmental conditions. Correctly interpreting this archive, however, depends on our understanding of the sedimentology and architecture of the deposits. While subaerial debris-flow deposits have been extensively studied, there is a comparative lack of understanding of the deposits of subaerial debris flows that debouch into a water body. We experimentally investigate the similarities and contrasts between subaerial and subaqueous debris-flow deposits for flows of various magnitudes and compositions initiated in a subaerial environment. We show that flows depositing on a subaqueous plane generally have a deposit area similar to flows forming in a subaerial setting. Deposits forming on a subaqueous plane, however, are typically shorter and wider with similar thickness, as a result of interactions between the flow and the reservoir water body. Both in subaerial and subaqueous environments the deposits form coarse-grained lateral levees and frontal snout margins. However, where the levees are able to laterally confine the subaerial flows leading to deposits with constant to tapering width, the subaqueous deposits widen with distance offshore because of flow fluidization. Moreover, the frontal snout is often very dispersed, a sharp frontal margin is absent, and many isolated particles are deposited in front of the main deposit margin as a result of interactions between the debris flow and the reservoir water body. These results largely agree with observations of subaqueous pyroclastic-flow deposits. The similarity in area of subaerial and subaqueous deposits suggests that we can apply empirical relations based on subaerial flows to estimate the inundation area and flow volume of subaerial–subaqueous flows.

The principal features, geotectonic settings and association with near-surface hydrothermal mineral systems of ancient and present subaerial hot springs, fumaroles and geysers are herein reviewed. Fumaroles and geysers usually occur in volcanic craters and are in most cases, part and parcel of hot spring environments. Subaerial hot springs are characterised by siliceous- and carbonate-rich chemical sediments, such as sinters and travertines, respectively. Sinters are commonly enriched in various metalliferous elements. Hot springs surface discharges are also characterised by pools, which exhibit bright colours due to the presence of microorganisms. Present-day examples discussed in this paper, include the fumaroles and hot springs of the White Island volcano (New Zealand), the world-renowned Yellowstone caldera (USA) and the Afar region of the East African Rift System. The Afar triangle, in the northern part of East African Rift System, provides a good example of hot springs associated with evaporative deposits. The Tuli-Sabi-Lebombo triple junction rifts were formed during the ~ 180 ​Ma Karoo igneous event in southern Africa, of which the Tuli arm is the failed rift (aulacogen), as is the Afar region. The Tuli rift is effectively an unusual, if not unique, tectono-thermal setting, because it comprises Karoo-age hot springs systems and associated vein stockworks and breccias, which includes the Messina Cu deposit as well as currently active hot springs with sinter deposits probably due to post-Karoo uplift. Fumarolic pipes in ignimbrites of the Erongo Volcano-Plutonic Complex in Namibia are discussed. This is followed by an example of banded chert rocks in the Killara Formation of the Palaeoproterozoic Capricorn Orogen (Western Australia), interpreted as hot spring chemical sediments, which also show evidence of “fossil” microbial filaments. The paper ends with a brief overview of possible analogues of hot springs on planet Mars.

Nine species of the diatom genus Luticola D.G.Mann were collected from wet walls and other subaerial habitats from the Western Ghats of India and analysed using light and scanning electron microsco...

A bathymetric survey of Harrison Lake in southwest British Columbia revealed deposits of three large landslides on the lake floor. The blocky and flow-like surface morphology of the deposits suggests rapid emplacement from subaerial sources. The multibeam survey, together with a subbottom acoustic survey, allowed us to estimate deposit volumes of 2.4 Mm3, 1.3 Mm3, and 0.2 Mm3 for the Mount Douglas, Mount Breakenridge, and Silver Mountain landslides, respectively. The large volumes and inferred rapid emplacement of the Mount Douglas and Mount Breakenridge landslides suggest they were tsunamigenic. Because people live along the shoreline of Harrison Lake, our discovery and characterization of these landslide deposits and their tsunami-generating potential form an important foundation for further landslide-tsunami hazard analysis in the region.

As falésias costeiras representam cerca de 80% da linha de costa mundial e se classificam de acordo com a influência marinha em sua base em duas categorias: ativas e inativas. No estado do Ceará, Nordeste do Brasil, as falésias situam-se em maior proporção no litoral leste. Com isso, o objetivo do estudo foi de mapear e quantificar as falésias ativas e inativas da zona costeira costa leste cearense focando na litologia, geologia e geomorfologia de topo e das escarpas, através de imagens de alta resolução de LiDAR (Light Detection and Ranging) e Ortofotos. O resultado do estudo mostra que 40% da linha de costa leste do Ceará são compostas por falésias ativas e/ou inativas, ou seja, 73.83 km de falésia no litoral, totalizando 36.7 km de falésias ativas e 39.64 km de falésias inativas. Apresentando feições como voçorocas bem desenvolvidas nas duas classificações de falésias, identificação de uma erosão remontante e patamares escalonados em uma praia com falésias ativas, relacionados à erosão diferenciada subaérea e neotectônica da região.