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Geosciences, Volume 8, Issue 6 (June 2018)

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Cover Story (view full-size image) Shrubby microbial structures known as dendrolites are common in the rock record but rare in modern [...] Read more.
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Open AccessArticle A Numerical 1.5D Method for the Rapid Simulation of Geophysical Resistivity Measurements
Geosciences 2018, 8(6), 225; https://doi.org/10.3390/geosciences8060225
Received: 15 May 2018 / Revised: 9 June 2018 / Accepted: 14 June 2018 / Published: 20 June 2018
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Abstract
In some geological formations, borehole resistivity measurements can be simulated using a sequence of 1D models. By considering a 1D layered media, we can reduce the dimensionality of the problem from 3D to 1.5D via a Hankel transform. The resulting formulation is often
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In some geological formations, borehole resistivity measurements can be simulated using a sequence of 1D models. By considering a 1D layered media, we can reduce the dimensionality of the problem from 3D to 1.5D via a Hankel transform. The resulting formulation is often solved via a semi-analytic method, mainly due to its high performance. However, semi-analytic methods have important limitations such as, for example, their inability to model piecewise linear variations on the resistivity. Herein, we develop a multi-scale finite element method (FEM) to solve the secondary field formulation. This numerical scheme overcomes the limitations of semi-analytic methods while still delivering high performance. We illustrate the performance of the method with numerical synthetic examples based on two symmetric logging-while-drilling (LWD) induction devices operating at 2 MHz and 500 KHz, respectively. Full article
(This article belongs to the Special Issue Petroleum Engineering Applications: Borehole Simulations)
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Open AccessArticle Room for Rivers: Risk Reduction by Enhancing the Flood Conveyance Capacity of The Netherlands’ Large Rivers
Geosciences 2018, 8(6), 224; https://doi.org/10.3390/geosciences8060224
Received: 20 May 2018 / Revised: 12 June 2018 / Accepted: 15 June 2018 / Published: 20 June 2018
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Abstract
The Netherlands has just finished implementing the Room for the Rivers program along the Rhine and Meuse Rivers in response to increasing river discharges. Recently, making more room for the river is, however, being challenged for future application because the flood defenses are
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The Netherlands has just finished implementing the Room for the Rivers program along the Rhine and Meuse Rivers in response to increasing river discharges. Recently, making more room for the river is, however, being challenged for future application because the flood defenses are assessed to be too weak and will need reinforcement anyway. To be able to decide on the most desirable policy for the remainder of the century, we require knowledge of all benefits and costs of individual interventions and strategic alternatives for flood mitigation. In this paper, we quantify some benefits of making more room for the rivers. We recognize and quantify two risk-reducing effects and provide results of analyses for the Rhine and Meuse Rivers in The Netherlands. Making room for rivers was originally advocated because it (1) reduces the consequences of flooding, as well as (2) reduces the probability of failure of the embankments. We have now quantified these effects allowing translation into risk reduction proper. Moreover, larger floodplain surface area may influence the relationship between discharge and flood level, which implies that rivers with widened floodplains are less sensitive to uncertainties about future river discharges. This does not reduce risk proper, but makes the river system more robust, as we shall argue in the discussion where we present risk reduction and robustness as complementary perspectives for assessing strategic alternatives for flood risk management. Full article
(This article belongs to the Special Issue Integrated Risk Analysis and Management of Floods)
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Open AccessArticle Non-Mineralized Fossil Wood
Geosciences 2018, 8(6), 223; https://doi.org/10.3390/geosciences8060223
Received: 25 May 2018 / Revised: 11 June 2018 / Accepted: 11 June 2018 / Published: 18 June 2018
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Abstract
Under conditions where buried wood is protected from microbial degradation and exposure to oxygen or harsh chemical environments, the tissues may remain unmineralized. If the original organic matter is present in relatively unaltered form, wood is considered to be mummified. Exposure to high
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Under conditions where buried wood is protected from microbial degradation and exposure to oxygen or harsh chemical environments, the tissues may remain unmineralized. If the original organic matter is present in relatively unaltered form, wood is considered to be mummified. Exposure to high temperatures, whether from wild fires or pyroclastic flows, may cause wood to be converted to charcoal. Coalification occurs when plant matter undergoes gradual metamorphosis, producing bituminous alteration products. Examples of all three types of non-mineralized wood are common in the geologic record. This report describes some of the most notable occurrences, reviews past research and introduces data from several localities in North America. Full article
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Open AccessArticle Potential Indicator Value of Subfossil Gastropods in Assessing the Ecological Health of the Middle and Lower Reaches of the Yangtze River Floodplain System (China)
Geosciences 2018, 8(6), 222; https://doi.org/10.3390/geosciences8060222
Received: 20 April 2018 / Revised: 12 June 2018 / Accepted: 15 June 2018 / Published: 17 June 2018
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Abstract
The lakes across China’s middle and lower reaches of the Yangtze River system have a long history of sustaining human pressures. These aquatic resources have been exploited for fisheries and irrigation over millennia at a magnitude of scales, with the result that many
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The lakes across China’s middle and lower reaches of the Yangtze River system have a long history of sustaining human pressures. These aquatic resources have been exploited for fisheries and irrigation over millennia at a magnitude of scales, with the result that many lakes have lost their ecological integrity. The consequences of these changes in the ecosystem health of lakes are not fully understood; therefore, a long-term investigation is urgently needed. Gastropods (aquatic snails) are powerful bio-indicators that link primary producers, herbivores, and detritivores associated with macrophytes and grazers of periphyton and higher-level consumers. They are sensitive to abrupt environmental change such as eutrophication, dehydration, flooding, and proliferation of toxicity in floodplain lake systems. The use of the remains of gastropod shells (subfossils) preserved in the sedimentary archives of the floodplain lakes of the middle and lower reaches of the Yangtze River system holds high significance, as their potential in environmental change has not been studied in detail in the past. Here, we aim to test the hypothesis that modern and sub-fossil gastropods in the sediments of the middle and lower reaches of the Yangtze River floodplains systems have significant value as bioindicators, as they have the ability to reveal health-gradients of lake-ecosystem change in the region. Full article
(This article belongs to the Special Issue New Theoretical and Applied Advances in Paleolimnology)
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Open AccessFeature PaperArticle Extending INSPIRE to the Internet of Things through SensorThings API
Geosciences 2018, 8(6), 221; https://doi.org/10.3390/geosciences8060221
Received: 30 April 2018 / Revised: 5 June 2018 / Accepted: 12 June 2018 / Published: 16 June 2018
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Abstract
Spatial Data Infrastructures (SDI) established during the past two decades “unlocked” heterogeneous geospatial datasets. The European Union INSPIRE Directive laid down the foundation of a pan-European SDI where thousands of public sector data providers make their data, including sensor observations, available for cross-border
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Spatial Data Infrastructures (SDI) established during the past two decades “unlocked” heterogeneous geospatial datasets. The European Union INSPIRE Directive laid down the foundation of a pan-European SDI where thousands of public sector data providers make their data, including sensor observations, available for cross-border and cross-domain reuse. At the same time, SDIs should inevitably adopt new technology and standards to remain fit for purpose and address in the best possible way the needs of different stakeholders (government, businesses and citizens). Some of the recurring technical requirements raised by SDI stakeholders include: (i) the need for adoption of RESTful architectures; together with (ii) alternative (to GML) data encodings, such as JavaScript Object Notation (JSON) and binary exchange formats; and (iii) adoption of asynchronous publish–subscribe-based messaging protocols. The newly established OGC standard SensorThings API is particularly interesting to investigate for INSPIRE, as it addresses together all three topics. In this manuscript, we provide our synthesised perspective on the necessary steps for the OGC SensorThings API standard to be considered as a solution that meets the legal obligations stemming out of the INSPIRE Directive. We share our perspective on what should be done concerning: (i) data encoding; and (ii) the use of SensorThings API as a download service. Full article
(This article belongs to the Special Issue Geodata Management)
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Open AccessArticle Clay Mineral Suites in Submarine Mud Volcanoes in the Kumano Forearc Basin, Nankai Trough: Constraints on the Origin of Mud Volcano Sediments
Geosciences 2018, 8(6), 220; https://doi.org/10.3390/geosciences8060220
Received: 23 April 2018 / Revised: 9 May 2018 / Accepted: 9 May 2018 / Published: 15 June 2018
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Abstract
Clay mineralogy is an important characteristic of mud volcano sediments. This study determined the clay mineral compositions of sediment from two submarine mud volcanoes in the Kumano forearc basin, Nankai Trough, by X-ray diffraction analysis. Similar compositions dominated by smectite in the two
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Clay mineralogy is an important characteristic of mud volcano sediments. This study determined the clay mineral compositions of sediment from two submarine mud volcanoes in the Kumano forearc basin, Nankai Trough, by X-ray diffraction analysis. Similar compositions dominated by smectite in the two mud volcanoes indicate that the mud volcanoes in the basin are rooted in the same source sequence. These clay mineral compositions differed from those in Pleistocene basin sediment, suggesting that the mud volcano sediment originated beneath the Pleistocene sediment. The illite content in the illite–smectite mixed layer averaged 32% in the mud volcano sediment, which implies that the sediment experienced temperatures above 60 °C that promoted the smectite-to-illite transformation. However, porewater extracted from the mud volcano sediment had Cl concentrations roughly half that of seawater and proportional enrichment in 18O and depletion in D, indicating that dehydration reactions of clay minerals had previously occurred in a deeply buried sedimentary layer. The smectite and illite contents (<60%) in the clay-size fraction rule out in situ smectite dewatering as the cause of the dilution of Cl in porewater. Thus, fluids derived from clay dewatering must have originated from deeper than the source of the mud volcano sediment. Full article
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Open AccessArticle Regional Landslide Potential Mapping in Earthquake-Prone Areas of Kepahiang Regency, Bengkulu Province, Indonesia
Geosciences 2018, 8(6), 219; https://doi.org/10.3390/geosciences8060219
Received: 8 February 2018 / Revised: 17 April 2018 / Accepted: 17 April 2018 / Published: 15 June 2018
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Abstract
Kepahiang regency is an area above the Musi segment of the Sumatran fault system. This condition makes the study area prone to natural disasters such as landslides in the slope area caused by earthquakes due to tectonic plate movement. The objective of this
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Kepahiang regency is an area above the Musi segment of the Sumatran fault system. This condition makes the study area prone to natural disasters such as landslides in the slope area caused by earthquakes due to tectonic plate movement. The objective of this study was to locate potential landslide areas in earthquake-prone areas of Kepahiang regency, Bengkulu province, Indonesia. We performed horizontal to vertical spectral ratio (HVSR) analysis and simple additive weighting (SAW) methods to accomplish the goal. The acquisition of field data involved a broad band seismometer PASI Gemini-2 (triaxial geophone). The microtremor data recorded in the field were then analyzed by the wave spectrum. The results showed that the landslide potential in the study area could be divided into three categories, i.e., low, medium, and high potential. Areas with high potential should be more aware of the threat of landslides, especially in population-dense areas. The greatest threat in the study area is an earthquake along Sumatra’s active fault. An earthquake that occurs in a very steep, landslide-prone area can increase risk and trigger a landslide. Full article
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Open AccessArticle Application of Sensitivity Analysis for Process Model Calibration of Natural Hazards
Geosciences 2018, 8(6), 218; https://doi.org/10.3390/geosciences8060218
Received: 15 May 2018 / Revised: 10 June 2018 / Accepted: 12 June 2018 / Published: 15 June 2018
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Abstract
Sensitivity analysis (SA) describes how varying inputs to a model subsequently varies its outputs. Its inclusion can support the systematic calibration of numerical models to back-calculate intensity properties of past torrent events that would otherwise be difficult or impossible to collect during their
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Sensitivity analysis (SA) describes how varying inputs to a model subsequently varies its outputs. Its inclusion can support the systematic calibration of numerical models to back-calculate intensity properties of past torrent events that would otherwise be difficult or impossible to collect during their occurrence. Sensitivity analysis for model calibration is assessed with the back-calculation of a known torrent event. In particular, FLO-2D, a cell-based numerical model, is used to simulate the 2005 debris flow event that occurred in Brienz, Switzerland. Under 4000 simulations were completed with ranges of physically reasonable parameter values. Model results were compared in 3-dimensions with both sediment deposition extents (x, y) and estimated deposition heights (z) from available post-event images. The comparisons highlighted that more accurate input and validation data, namely the flow behavior of hazardous processes and post-event deposition heights, are required to produce stronger agreements between simulated and observed results. Furthermore, the application of SA for model calibration supports systematic exploration of large parameter spaces characteristic of complex phenomena like natural hazard events. These findings demonstrated how important model input factors can be identified, which provide guidance for future data collection efforts to capture both the rheology and the spatial distribution of hazards more accurately. Full article
(This article belongs to the Section Natural Hazards)
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Open AccessArticle Hybrid GMPEs for Region-Specific PSHA in Southern Italy
Geosciences 2018, 8(6), 217; https://doi.org/10.3390/geosciences8060217
Received: 8 February 2018 / Revised: 6 June 2018 / Accepted: 6 June 2018 / Published: 14 June 2018
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Abstract
This paper describes the main findings of the project HYPSTHER (HYbrid ground motion prediction equations for PSha purposes: the study case of souTHERn Italy; supported by the Italian Institute of Geophysics and Volcanology). The goal of the project is to develop a methodological
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This paper describes the main findings of the project HYPSTHER (HYbrid ground motion prediction equations for PSha purposes: the study case of souTHERn Italy; supported by the Italian Institute of Geophysics and Volcanology). The goal of the project is to develop a methodological approach to retrieve hybrid Ground Motion Prediction Equations (GMPEs) based on integration of recorded and synthetic data. This methodology was applied to the study area of southern Italy, focusing on the southern Calabria and Sicily regions. The target area was chosen due to the expected high seismic hazard levels, despite the low seismic activity in recent decades. In addition, along the coast of the study area, there are many critical infrastructures, such as chemical plants, refineries, and large ports, which strongly increase the risk of technological accidents induced by earthquakes. Through the synthetic data, the predictions of the hybrid GMPEs have been improved under near-field conditions, with respect to empirical models for moderate to large earthquakes. Attenuation at distances greater than 50 km is instead controlled by the empirical data, because attenuation is faster with distance. The aleatory variability of the hybrid models has strong impact on probabilistic seismic hazard assessment, as it is lower than the sigma of the empirical GMPEs. The use of the hybrid GMPEs specific for the study area can produce remarkable reductions in hazard levels for long-return periods, mainly due to changes in median predictions and reduction of the aleatory variability. Full article
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Open AccessFeature PaperArticle Using ArcticDEM to Analyse the Dimensions and Dynamics of Debris-Covered Glaciers in Kamchatka, Russia
Geosciences 2018, 8(6), 216; https://doi.org/10.3390/geosciences8060216
Received: 10 May 2018 / Revised: 7 June 2018 / Accepted: 11 June 2018 / Published: 13 June 2018
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Abstract
On the Kamchatka Peninsula, a number of glaciers are covered by thick volcanic debris, which makes their margins difficult to delineate from satellite imagery. Fortunately, high resolution, multi-temporal digital surface models (DSMs) covering the entire peninsula have recently become freely available (i.e., ArcticDEM).
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On the Kamchatka Peninsula, a number of glaciers are covered by thick volcanic debris, which makes their margins difficult to delineate from satellite imagery. Fortunately, high resolution, multi-temporal digital surface models (DSMs) covering the entire peninsula have recently become freely available (i.e., ArcticDEM). We use these DSMs to analyse the dimensions and dynamics of debris-covered glaciers in the northern Kluchevskoy Volcanic Group, central Kamchatka. This approach demonstrates that between 2012 and 2016, some of the region’s glaciers advanced despite regional and local climate warming. These glacial advances are part of a long-term trend, presumed to reflect the role of extensive supraglacial debris in limiting ice ablation, though there is also evidence for local ice melt due to supraglacial lava/debris flows. Glacier surface velocities during the period 2012–2015 were typically 5–140 m yr−1. Velocities for the major outlets of the region’s central icefield were typically higher than for other extensively debris-covered glaciers globally, likely reflecting the influence of ice supply from the high altitude Ushkovsky caldera. In all, we find ArcticDEM useful for analysing debris-covered glaciers in Kamchatka, providing important information on flow dynamics and terminus change that is difficult to derive from satellite imagery. Full article
(This article belongs to the Special Issue Glacial and Geomorphological Cartography)
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Open AccessArticle Joint and Lineament Patterns across the Midcontinent Indicate Repeated Reactivation of Basement-Involved Faults
Geosciences 2018, 8(6), 215; https://doi.org/10.3390/geosciences8060215
Received: 7 April 2018 / Revised: 30 May 2018 / Accepted: 4 June 2018 / Published: 13 June 2018
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Abstract
Joint networks hosted in successively younger rocks, developing as a result of forced (trishear) folding of a rock mass above a deep-seated fault, can be used to infer the reactivation history of that deep-seated fault. This study aims to use joint networks in
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Joint networks hosted in successively younger rocks, developing as a result of forced (trishear) folding of a rock mass above a deep-seated fault, can be used to infer the reactivation history of that deep-seated fault. This study aims to use joint networks in Pennsylvanian, Permian and Cretaceous rocks to document evidence of reactivation on basement faults during the Paleozoic and Mesozoic of Nebraska and Kansas. The most prominent basement features in southeast Nebraska and northeast Kansas are oriented NE-SW, likely related to the Midcontinent Rift System and Nemaha Uplift, and oriented NW-SE, likely related to fabrics from the Central Plains Orogeny. These features are well defined in the potential fields data. Joint patterns in the study area show an E-W oriented trend, as well as clearly discernable NE-SW and subsidiary N-S and NW-SE trends. The E-W trend is interpreted to be related to far-field stresses from Laramide and Ancestral Rocky Mountain orogenic events, whilst the NE-SW trend is interpreted to be related to subtle reactivation on the Mid-continent rift and related faults, observed in basement data. These movements produced stresses of sufficient magnitude to produce joints in the post-rift rock units, but not sufficient to generate shear fractures. Similarly, the ~N-S and NW-SE joint trends are taken as evidence of subtle reactivation on the Nemaha Uplift and Central Plains Orogeny systems, generating joints by the formation of forced folds. This contribution therefore provides a convincing case study of the value of coupled potential fields and surface feature studies in discerning buried tectonic trends and subtle reactivation thereon. Full article
(This article belongs to the Special Issue Tectonics and Morphodynamics)
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Open AccessArticle Improved Interpretation of Marine Sedimentary Environments Using Multi-Frequency Multibeam Backscatter Data
Geosciences 2018, 8(6), 214; https://doi.org/10.3390/geosciences8060214
Received: 8 May 2018 / Revised: 8 June 2018 / Accepted: 9 June 2018 / Published: 12 June 2018
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Abstract
Backscatter mosaics based on a multi-frequency multibeam echosounder survey in the continental shelf setting of the North Sea were compared. The uncalibrated backscatter data were recorded with frequencies of 200, 400 and 600 kHz. The results showed that the seafloor appears mostly featureless
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Backscatter mosaics based on a multi-frequency multibeam echosounder survey in the continental shelf setting of the North Sea were compared. The uncalibrated backscatter data were recorded with frequencies of 200, 400 and 600 kHz. The results showed that the seafloor appears mostly featureless in acoustic backscatter mosaics derived from 600 kHz data. The same area surveyed with 200 kHz reveals numerous backscatter anomalies with diameters of 10–70 m deviating between −2 dB and +4 dB from the background sediment. Backscatter anomalies were further subdivided based on their frequency-specific texture and were attributed to bioturbation within the sediment and the presence of polychaetes on the seafloor. While low frequencies show the highest overall contrast between different seafloor types, a consideration of all frequencies permits an improved interpretation of subtle seafloor features. Full article
(This article belongs to the Special Issue Geological Seafloor Mapping)
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Open AccessArticle A Mathematics Inspired Notation of Scales in the Climate System
Geosciences 2018, 8(6), 213; https://doi.org/10.3390/geosciences8060213
Received: 13 April 2018 / Revised: 5 June 2018 / Accepted: 7 June 2018 / Published: 11 June 2018
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Abstract
Conducting integrated climate research with involvement of such diverse disciplines as mathematics, meteorology, oceanography, economics, geology, biology, social, and communication sciences poses great challenges to the underlying nomenclature and methodology. In this article, we give a definition of the notion of scales, which
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Conducting integrated climate research with involvement of such diverse disciplines as mathematics, meteorology, oceanography, economics, geology, biology, social, and communication sciences poses great challenges to the underlying nomenclature and methodology. In this article, we give a definition of the notion of scales, which is a central term in the geosciences, but not so familiar to social sciences or economics. We start with defining agents, involved in a specific subject of study, determined by their attributes or states. We move on to understand processes and phenomena as maps and subsets of image sets. With this and the introduction of metrics, we can measure sizes of phenomena and processes and finally define scales. Several examples illustrate our definition. An attempt is made to motivate a notion of scale interaction. This concept has proved useful in an interdisciplinary teaching project. Full article
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Open AccessFeature PaperArticle Living Dendrolitic Microbial Mats in Hamelin Pool, Shark Bay, Western Australia
Geosciences 2018, 8(6), 212; https://doi.org/10.3390/geosciences8060212
Received: 24 April 2018 / Revised: 18 May 2018 / Accepted: 5 June 2018 / Published: 11 June 2018
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Abstract
Hamelin Pool, Shark Bay, Western Australia, is home to the largest and most diverse assemblage of living marine stromatolites, with shapes and sizes comparable to ancient structures. A recent field-intensive program revealed seasonally ephemeral occurrences of modern dendrolitic microbial mats forming in intertidal,
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Hamelin Pool, Shark Bay, Western Australia, is home to the largest and most diverse assemblage of living marine stromatolites, with shapes and sizes comparable to ancient structures. A recent field-intensive program revealed seasonally ephemeral occurrences of modern dendrolitic microbial mats forming in intertidal, low energy settings. Dominated by filamentous cyanobacteria, dendrolitic microbial mats are formed when filaments provide a supporting framework as a result of gliding mobility, to build a shrubby morphology. Dendrolites, known throughout the rock record, refer to macroscopic microbialites with mesostuctures composed of unlaminated arborescent structures called shrubs. In these modern examples, thick filaments of Lyngbya aestuarii form the “trunk” of the bush, with finer filaments of Lyngbya fragilis, Phormidium sp. and Schizothrix sp. forming the “branches” These biologically-influenced dendrolitic structures provide insight into the complex interplay of microbial communities and the environment, broadening our understanding of shrub and dendrolite formation throughout the rock record. Full article
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Open AccessArticle Ancient Microbial Activity in Deep Hydraulically Conductive Fracture Zones within the Forsmark Target Area for Geological Nuclear Waste Disposal, Sweden
Geosciences 2018, 8(6), 211; https://doi.org/10.3390/geosciences8060211
Received: 24 April 2018 / Revised: 4 June 2018 / Accepted: 7 June 2018 / Published: 11 June 2018
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Abstract
Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and
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Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and lifeforms in this vast realm, for example, regarding the spatiotemporal extent and variability of the different processes in the crust. Here, we present a study that set out to detect signs of ancient microbial life in the Forsmark area—the target area for deep geological nuclear waste disposal in Sweden. Stable isotope compositions were determined with high spatial resolution analyses within mineral coatings, and mineralized remains of putative microorganisms were studied in several deep water-conducting fracture zones (down to 663 m depth), from which hydrochemical and gas data exist. Large isotopic variabilities of δ13Ccalcite (−36.2 to +20.2‰ V-PDB) and δ34Spyrite (−11.7 to +37.8‰ V-CDT) disclose discrete periods of methanogenesis, and potentially, anaerobic oxidation of methane and related microbial sulfate reduction at several depth intervals. Dominant calcite–water disequilibrium of δ18O and 87Sr/86Sr precludes abundant recent precipitation. Instead, the mineral coatings largely reflect an ancient archive of episodic microbial processes in the fracture system, which, according to our microscale Rb–Sr dating of co-genetic adularia and calcite, date back to the mid-Paleozoic. Potential Quaternary precipitation exists mainly at ~400 m depth in one of the boreholes, where mineral–water compositions corresponded. Full article
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