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1.
  • Bozkurt, S., et al. (författare)
  • Peat as a potential analogue for the long-term evolution in landfills
  • 2001
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 53:02-jan, s. 95-147
  • Forskningsöversikt (refereegranskat)abstract
    • A survey of the existing studies on peat and its decomposition processes is presented with the aim to characterise the long-term behaviour of peat accumulating systems. The chemical and physical characteristics of peat together with its accumulation and decay processes have been analysed. Peat is an acidic mixture of dead and decomposed. mainly vegetable, matter formed in boggy areas; it is the youngest and least altered component of the combustible rocks and is characterised by the lowest content of fixed carbon and the highest content of volatile constituents. Peat is formed by degeneration processes under exclusion of atmospheric oxygen by the action of water; the speed of formation depends upon the climatic and environmental conditions. In most peatlands two layers can be characterised: the aerobic acrotelm and the anaerobic catotelm, their relative importance being controlled mainly by the position of the water table. In the acrotelm the aerobic processes are responsible for the loss of up to 90% of the original mass, Degeneration in the acidic and anaerobic catotelm is still imperfectly characterised even though the catotelm is the real site of peat accumulation. Most of the recent literature considers peat as composed of easily degradable compounds, e.g. polysaccharides. and recalcitrant matter (lignin and complex aromatics). The lone-term destiny of peat has not been sufficiently characterised: although in a large majority of cases it seems probable that peat decomposes completely (even though slowly) provided that it is given a sufficiently long residence rime in the catotelm, some cases can still be interpreted as examples of simple accumulation. The rates of influx of oxygen and hence the degradation of organic matter into both saturated and partially saturated peat have been estimated. The depletion rate is about 4500 g m(-1) year(-1) for partially saturated peat. The average depletion rate of the peat for this case will then be such that it will take on the order of 5 to 50 years to degrade half of the organics in a 10 cm partially saturated layer. For the water-saturated case the depletion rate varies between 8 and 12 g m(-2) year(-1), which is considerably lower than in the partially saturated region. The models used to analyse the field and laboratory data on generation, diffusion and emission of methane and carbon dioxide indicate that laboratory data and field observations agree reasonably well. It is suggested that peat-accumulating ecosystems may be valuable natural analogues for the study of the long-term destiny of industrial and municipal solid wastes. Accurate studies of active mires together with an ad hoc review of the existing literature give valuable insights in this problem. Peatlands might then be considered as organic waste deposition experiments lasting up to several thousands years.
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2.
  • Ledin, Maria (författare)
  • Accumulation of metals by microorganisms : processes and importance for soil systems
  • 2000
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 51:1-4, s. 1-31
  • Tidskriftsartikel (refereegranskat)abstract
    • Metal accumulation by solid substances can counteract metal mobilization in the environment if the solid substance is immobile. Microorganisms have a high surface area-to-volume ratio because of their small size and therefore provide a large contact area that can interact with metals in the surrounding environment. Microbial metal accumulation has received much attention in the last years due to the potential use of microorganisms for cleaning metal-polluted water. However, considerably less attention has been paid to the role of microorganisms for metal mobility in soil even though the same processes may occur there. Therefore, this paper highlights this area. The different accumulation processes that microorganisms perform are analyzed and their potential significance in soil systems is discussed. Different kinds of mechanisms can be involved in the accumulation of metals by microorganisms, e.g. adsorption, precipitation, complexation and active transport into the cell. Physicochemical parameters like pH and ionic composition, as well as biological factors are of importance for the magnitude of accumulation. Often large amounts of metals can be accumulated with varying specificity, and microorganisms may provide nucleation sites for mineral formation. Several studies of microbial metal accumulation have been made with different methods and aims. Most of these studies concern single-component systems with one organism at a time. Data from accumulation experiments with pure cultures of microorganisms have been used to model the overall metal retention in soil. A further development is experimental model systems using various solid soil components in salt medium. Microbial metal accumulation is difficult to study in situ, but some experimental methods have been applied as tools for studying real soil systems, e.g. litter bags buried in soil containing microorganisms, a method where discs with microorganisms have been put onto agar plates with soil extracts, and comparison of sterilized and non-sterilized soils or soils with or without nutrient amendment. Different aspects of microbial metal accumulation are emphasized with the different methods applied. Single-component systems have the advantage of providing excellent information of the metal binding properties of microorganisms but cannot directly be applied to metal behavior in the heterogenous systems that real soils constitute. Studies focused on the behavior of metals in real soils can, in contrast, provide information on the overall metal distribution but less insight into the processes involved. Obviously, a combination of approaches is needed to describe metal distribution and mobility in polluted soil such as areas around mines. Different kinds of multi-component systems as well as modelling may bridge the gap between these two types of studies. Several experimental methods, complementary to each other and designed to allow for comparison, may emphasize different aspects of metal accumulation and should therefore be considered. To summarize, there are studies that indicate that microorganisms may also accumulate metals in soil and that the amounts may be considerable. However, much work remains to be done, with the focus of microorganisms in soil. It is also important to put microbial metal accumulation in relation to other microbial processes in soil, which can influence metal mobility, to determine the overall influence of soil microorganisms on metal mobility, and to be able to quantify these processes.
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3.
  • Abbott, Benjamin, et al. (författare)
  • Using multi-tracer inference to move beyond single-catchment ecohydrology
  • 2016
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 160, s. 19-42
  • Tidskriftsartikel (refereegranskat)abstract
    • Protecting or restoring aquatic ecosystems in the face of growing anthropogenic pressures requires an understanding of hydrological and biogeochemical functioning across multiple spatial and temporal scales. Recent technological and methodological advances have vastly increased the number and diversity of hydrological, biogeochemical, and ecological tracers available, providing potentially powerful tools to improve understanding of fundamental problems in ecohydrology, notably: 1. Identifying spatially explicit flowpaths, 2. Quantifying water residence time, and 3. Quantifying and localizing biogeochemical transformation. In this review, we synthesize the history of hydrological and biogeochemical theory, summarize modem tracer methods, and discuss how improved understanding of flowpath, residence time, and biogeochemical transformation can help ecohydrology move beyond description of site-specific heterogeneity. We focus on using multiple tracers with contrasting characteristics (crossing proxies) to infer ecosystem functioning across multiple scales. Specifically, we present how crossed proxies could test recent ecohydrological theory, combining the concepts of hotspots and hot moments with the Damkohler number in what we call the HotDam framework.
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4.
  • Akam, Sajjad A., et al. (författare)
  • Methane-derived authigenic carbonates – A case for a globally relevant marine carbonate factory
  • 2023
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 243
  • Tidskriftsartikel (refereegranskat)abstract
    • Precipitation of methane-derived authigenic carbonates (MDAC) is an integral part of marine methane production and consumption, but MDAC's relative significance to the global marine carbon cycle is not well understood. Here we provide a synthesis and perspective to highlight MDAC from a global marine carbon biogeochemistry viewpoint. MDAC formation is a result and archive of carbon‑sulfur (C S) coupling in the shallow sulfatic zone and carbon‑silicon (C Si) coupling in deeper methanic sediments. MDAC constitute a carbon sequestration of 3.93 Tmol C yr−1 (range 2.34–5.8 Tmol C yr−1) in the modern ocean and are the third-largest carbon burial mechanism in marine sediments. This burial compares to 29% (11–57%) organic carbon and 10% (6–23%) skeletal carbonate carbon burial along continental margins. MDAC formation is also an important sink for benthic alkalinity and, thereby, a potential contributor to bottom water acidification. Our understanding of the impact of MDAC on global biogeochemical cycles has evolved over the past five decades from what was traditionally considered a passive carbon sequestration mechanism in a seep-oasis setting to what is now considered a dynamic carbonate factory expanding from deep sediments to bottom waters—a factory that has been operational since the Precambrian. We present a strong case for the need to improve regional scale quantification of MDAC accumulation rates and associated carbonate biogeochemical parameters, leading to their incorporation in present and paleo‑carbon budgets in the next phase of MDAC exploration.
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5.
  • Bagherbandi, Mohammad, et al. (författare)
  • A new Fennoscandian crustal thickness model based on CRUST1.0 and a gravimetric-isostatic approach
  • 2015
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 145, s. 132-145
  • Forskningsöversikt (refereegranskat)abstract
    • In this paper a new gravimetric-isostatic crustal thickness model (VMM14_FEN) is estimated for Fennoscandia. The main motivation is to investigate the relations between geological and geophysical properties, the Moho depth and crust-mantle density contrast at the crust-mantle discontinuity. For this purpose the Bouguer gravity disturbance data is corrected in two main ways namely for the gravitational contributions of mass density variation due to the different layers of the Earth's crust such as ice and sediments, as well as for the gravitational contribution from deeper masses below the crust. This second correction (for non-isostatic effects) is necessary because in general the crust is not in complete isostatic equilibrium and the observed gravity data are not only generated by the topographic/isostatic masses but also from those in the deep Earth interior. The correction for non-isostatic effects is mainly attributed to unmodeled mantle and core boundary density heterogeneities. These corrections are determined using the recent seismic crustal thickness model CRUST1.0. We compare our modeling results with previous studies in the area and test the fitness. The comparison with the external Moho model EuCRUST-07 shows a 3.3. km RMS agreement for the Moho depth in Fennoscandia. We also illustrate how the above corrections improve the Moho depth estimation. Finally, the signatures of geological structures and isostatic equilibrium are studied using VMM14_FEN, showing how main geological unit structures attribute in isostatic balance by affecting the Moho geometry. The main geological features are also discussed in the context of the complete and incomplete isostatic equilibrium. 
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6.
  • Bagherbandi, Mohammad, et al. (författare)
  • Improving gravimetric-isostatic models of crustal depth by correcting for non-isostatic effects and using CRUST2.0
  • 2013
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 117, s. 29-39
  • Tidskriftsartikel (refereegranskat)abstract
    • The principle of isostasy is important in different fields of geosciences. Using an isostatic hypothesis for estimating the crustal thickness suffers from the more or less incomplete isostatic model and that the observed gravity anomaly is not only generated by the topographic/isostatic signal but also by non-isostatic effects (NIEs). In most applications of isostatic models the NIEs are disregarded. In this paper, we study how some isostatic models related with Vening Meinez's isostatic hypothesis can be improved by considering the NIE. The isostatic gravity anomaly needs a correction for the NIEs, which varies from as much as 494 mGal to -308 mGal. The result shows that by adding this correction the global crustal thickness estimate improves about 50% with respect to the global model CRUST2.0, i.e. the root mean square differences of the crustal thickness of the best Vening Meinesz type and CRUST2.0 models are 6.9 and 3.2 km before and after improvement, respectively. As a result, a new global model of crustal thickness using Vening Meinesz and CRUST2.0 models is generated. A comparison with an independent African crustal depth model shows an improvement of the new model by 6.8 km vs. CRUST2.0 (i.e. rms differences of 3.0 and 9.8 km, respectively). A comparison between oceanic lithosphere age and the NIEs is discussed in this study, too. One application of this study can be to improve crustal depth in areas where CRUST2.0 data are sparse and bad and to densify the resolution vs. the CRUST2.0 model. Other applications can be used to infer the viscosity of the mantle from the NIEs signal to study various locations around the Earth for understanding complete, over- and under-compensations of the topography.
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7.
  • Baker, Paul A., et al. (författare)
  • The emerging field of geogenomics : Constraining geological problems with genetic data
  • 2014
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 135, s. 38-47
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of a genomics-derived discipline within geology is timely, as a result of major advances in acquiring and processing geologically relevant genetic data. This paper articulates the emerging field of geogenomics, which involves the use of large-scale genetic data to constrain geological hypotheses. The paper introduces geogenomics and discusses how hypotheses can be addressed through collaboration between geologists and evolutionary biologists. As an example, geogenomic methods are applied to evaluate competing hypotheses regarding the timing of the Andean uplift, the closure of the Isthmus of Panama, the onset of trans-Amazon drainage, and Quaternary climate variation in the Neotropics.
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8.
  • Berglund, Örjan (författare)
  • Digital mapping of peatlands - A critical review
  • 2019
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 196
  • Forskningsöversikt (refereegranskat)abstract
    • Peatlands offer a series of ecosystem services including carbon storage, biomass production, and climate regulation. Climate change and rapid land use change are degrading peatlands, liberating their stored carbon (C) into the atmosphere. To conserve peatlands and help in realising the Paris Agreement, we need to understand their extent, status, and C stocks. However, current peatland knowledge is vague estimates of global peatland extent ranges from 1 to 4.6 million km(2), and C stock estimates vary between 113 and 612 Pg (or billion tonne C). This uncertainty mostly stems from the coarse spatial scale of global soil maps. In addition, most global peatland estimates are based on rough country inventories and reports that use outdated data. This review shows that digital mapping using field observations combined with remotely-sensed images and statistical models is an avenue to more accurately map peatlands and decrease this knowledge gap. We describe peat mapping experiences from 12 countries or regions and review 90 recent studies on peatland mapping. We found that interest in mapping peat information derived from satellite imageries and other digital mapping technologies is growing. Many studies have delineated peat extent using land cover from remote sensing, ecology, and environmental field studies, but rarely perform validation, and calculating the uncertainty of prediction is rare. This paper then reviews various proximal and remote sensing techniques that can be used to map peatlands. These include geophysical measurements (electromagnetic induction, resistivity measurement, and gamma radiometrics), radar sensing (SRTM, SAR), and optical images (Visible and Infrared). Peatland is better mapped when using more than one covariate, such as optical and radar products using nonlinear machine learning algorithms. The proliferation of satellite data available in an open-access format, availability of machine learning algorithms in an open-source computing environment, and high-performance computing facilities could enhance the way peatlands are mapped. Digital soil mapping allows us to map peat in a cost-effective, objective, and accurate manner. Securing peatlands for the future, and abating their contribution to atmospheric C levels, means digitally mapping them now.
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9.
  • Bertrand, Sebastien, et al. (författare)
  • Inorganic geochemistry of lake sediments : a review of analytical techniques and guidelines for data interpretation
  • 2024
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 249
  • Forskningsöversikt (refereegranskat)abstract
    • Inorganic geochemistry is a powerful tool in paleolimnology. It has become one of the most commonly used techniques to analyze lake sediments, particularly due to the development and increasing availability of XRF core scanners during the last two decades. It allows for the reconstruction of the continuous processes that occur in lakes and their watersheds, and it is ideally suited to identify event deposits. How earth surface processes and limnological conditions are recorded in the inorganic geochemical composition of lake sediments is, however, relatively complex. Here, we review the main techniques used for the inorganic geochemical analysis of lake sediments and we offer guidance on sample preparation and instrument selection. We then summarize the best practices to process and interpret bulk inorganic geochemical data. In particular, we emphasize that log-ratio transformation is critical for the rigorous statistical analysis of geochemical datasets, whether they are obtained by XRF core scanning or more traditional techniques. In addition, we show that accurately interpreting inorganic geochemical data requires a sound understanding of the main components of the sediment (organic matter, biogenic silica, carbonates, lithogenic particles) and mineral assemblages. Finally, we provide a series of examples illustrating the potential and limits of inorganic geochemistry in paleolimnology. Although the examples presented in this paper focus on lake and fjord sediments, the principles presented here also apply to other sedimentary environments.
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10.
  • Betts, Marissa, J., et al. (författare)
  • Early Cambrian chronostratigraphy and geochronology of South Australia
  • 2018
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 185, s. 498-543
  • Tidskriftsartikel (refereegranskat)abstract
    • The most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio- and geo-events. Here we present the first regional, high-resolution shelly fossil biostratigraphy integrated with δ13C chemostratigraphy (and corresponding δ18O data) from the traditional lower Cambrian (Terreneuvian and provisional Cambrian Series 2) of South Australia. The global ZHUCE, SHICE, positive excursions II and III and the CARE are captured in lower Cambrian successions from the Arrowie and Stansbury basins. The South Australian shelly fossil biostratigraphy has a consistent relationship with the δ13C results, bolstering interpretation, identification and correlation of the excursions. Positive excursion II straddles the boundary between the Kulparina rostrata and Micrina etheridgei zones, and the CARE straddles the boundary between the M. etheridgei and Dailyatia odyssei zones, peaking in the lower parts of the latter zone. New CA-TIMS zircon dates from the upper Hawker Group and Billy Creek Formation provide geochronologic calibration points for the upper D. odyssei Zone and corresponding chemostratigraphic curve, embedding the lower Cambrian successions from South Australia into a global chronostratigraphic context. This multi-proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower Cambrian successions from South Australia (part of East Gondwana) with coeval terranes on other Cambrian palaeocontinents, including South and North China, Siberia, Laurentia, Avalonia and West Gondwana.
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11.
  • Bohm, Katja, et al. (författare)
  • The provenance of late Cenozoic East Asian Red Clay : Tectonic-metamorphic history of potential source regions and a novel combined zircon-rutile approach
  • 2022
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 225
  • Tidskriftsartikel (refereegranskat)abstract
    • Constraining the provenance of aeolian mineral dust is critical in understanding past climate changes, atmospheric dust activity, circulation, and sediment generation. On the Chinese Loess Plateau (CLP), use of detrital zircon U-Pb age data as source tracers for the dust has seen a huge growth and lead to breakthroughs in understanding dust provenance. However, significant ambiguities remain especially regarding the provenance of the aeolian Neogene Red Clay (RC). To address this, here we review the state of the art of understanding of Neogene RC provenance, with a focus on single-grain analyses, and introduce detrital rutile geochemistry as a tool to complement zircon U-Pb dating. Furthermore, to better utilise the link between the detrital minerals and their primary origin, we compile primary source region geologic background and single-grain data relevant for use of geochronological and metamorphic provenance proxy minerals. We discuss four major tectonic divisions in northern China and southern Mongolia: North China Craton (NCC), Tarim Craton (TC), Central China Orogen (CCO), parts of the Central Asian Orogenic Belt (CAOB), and briefly summarize the Tibetan-Himalayan orogen. Many of these regions have been tectonically active during the same time periods in the Earth's history, and our analysis demonstrates how use of zircon age data alone has limitations in differentiating between a number of key potential dust sources to the CLP. Addition of a metamorphic source tracer such as rutile allows some of these possible source areas to be distinguished. For example, the proximal northern NCC regions that show high−/ultrahigh-temperature metamorphic conditions can potentially be diagnostic of a northerly source component to CLP dust. Our combined zircon-rutile data analysis of ca. 4 Ma Nihewan RC in northern CLP verifies the utility of the novel rutile provenance proxy in sourcing CLP sediments. The zircon and rutile data suggest similar dust provenance: the dominant sources are proximal areas on the NCC, while contributions from the dry areas in parts of the CAOB, central deserts, and the Yellow River are also likely. Our results also hint at a minor source component deriving from distal western source regions in the TC, and/or in the central parts of the CCO, but rutile data from potential secondary source areas are needed to verify this possibility. We also conclude that multi-proxy single-grain provenance analyses are needed for more reliable provenance analyses.
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12.
  • Brown, D., et al. (författare)
  • Arc-continent collision in the Southern Urals
  • 2006
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 79:3-4, s. 261-287
  • Tidskriftsartikel (refereegranskat)abstract
    • The Southern Urals of Russia contain what is arguably one of the best-preserved examples of an arc–continent collision in anyPaleozoic orogen. The arc–continent collision history recorded in the rocks of the Southern Urals began in the Early Devonian withthe onset of intra-oceanic subduction and the formation of the Magnitogorsk Arc and ended with its collision with the margin ofBaltica during the Late Devonian. The Baltica margin consisted of a basement that was composed predominantly of rocks ofArchean and Proterozoic age that, by the time of arc–continent collision, was overlain by Cambrian, Ordovician, Silurian, andDevonian sediments interpreted to have been deposited in rift-related grabens on the continental slope and rise, and on the shallowmarine platform. The Magnitogorsk Arc consists of Early to Late Devonian island arc volcanic rocks and overlying volcaniclasticsediments. Arc–continent collision led to the development of an accretionary complex that includes shallowly and deeplysubducted continental margin rocks, ophiolite fragments, and sediments that were deposited in a foreland-basin setting. Thegeochemistry of the Magnitogorsk Arc volcanic rocks, the structure of the arc–continent collision accretionary complex and theforearc, the high-pressure rocks beneath and along the suture zone, the mafic and ultramafic ophiolitic material, and the syn-tectonic sediments show that the Paleozoic tectonic processes recorded in the Southern Urals can be favorably compared with thosein currently active settings such as the west Pacific.© 2006 Elsevier B.V. All rights reserved.
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13.
  • Brown, D., et al. (författare)
  • Mountain building processes during continent-continent collision in the Uralides
  • 2008
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 89:3-4, s. 177-195
  • Tidskriftsartikel (refereegranskat)abstract
    • Since the early 1990's the Paleozoic Uralide Orogen of Russia has been the target of a significant research initiative as part of EUROPROBE and GEODE, both European Science Foundation programmes. One of the main objectives of these research programmes was the determination of the tectonic processes that went into the formation of the orogen. In this review paper we focus on the Late Paleozoic continent-continent collision that took place between Laurussia and Kazakhstania. Research in the Uralides was concentrated around two deep seismic profiles crossing the orogen. These were accompanied by geological, geophysical, geochronological, geochemical, and low-temperature thermochronological studies. The seismic profiles demonstrate that the Uralides has an overall bivergent structural architecture, but with significantly different reflectivity characteristics from one tectonic zone to another. The integration of other types of data sets with the seismic data allows us to interpret what tectonic processes where responsible for the formation of the structural architecture, and when they were active. On the basis of these data, we suggest that the changes in the crustal-scale structural architecture indicate that there was significant partitioning of tectonothermal conditions and deformation from zone to zone across major fault systems, and between the lower and upper crust. Also, a number of the structural features revealed in the bivergent architecture of the orogen formed either in the Neoproterozoic or in the Paleozoic, prior to continent-continent collision. From the end of continent-continent collision to the present, low-temperature thermochronology suggests that the evolution of the Uralides has been dominated by erosion and slow exhumation. Despite some evidence for more recent topographic uplift, it has so far proven difficult to quantify it.
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14.
  • Carracedo, Juan Carlos, et al. (författare)
  • The 2011-2012 submarine eruption off El Hierro, Canary Islands : New lessons in oceanic island growth and volcanic crisis management
  • 2015
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 150, s. 168-200
  • Tidskriftsartikel (refereegranskat)abstract
    • Forty years after the eruption of the Teneguía volcano on La Palma, 1971, the last volcanic event in the Canary Islands, a submarine eruption took place in 2011 off-shore El Hierro, the smallest and youngest island of the archipelago. In this paper, we review the periods of seismic unrest leading up to the 2011–2012 El Hierro eruption, the timeline of eruptive events, the erupted products, the wider societal impacts, and the insights garnered for our understanding of ocean island growth mechanisms and hazard management. Seismic precursors allowed early detection of magmatic activity and prediction of the approximate location of the eruption. White coloured “floating stones” (“xeno-pumice”) were described within the first few days of the events, the origin of which were hotly debated because of their potential implications for the character of the eruption. Due to epistemic uncertainty derived from delayed flow of scientific information and equivocal interpretations of the “floating stones”, the El Hierro 2011–2012 events were characterised by cautious civil protection measures, which greatly impacted on the residents' lives and on the island's economy. We therefore summarise the scientific lessons learned from this most recent Canary Island eruption and discuss how emergency managers might cope with similar situations of uncertainty during future eruptive events in the region.
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15.
  • Chandler, Benjamin M. P., et al. (författare)
  • Glacial geomorphological mapping : A review of approaches and frameworks for best practice
  • 2018
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 185, s. 806-846
  • Forskningsöversikt (refereegranskat)abstract
    • Geomorphological mapping is a well-established method for examining earth surface processes and landscape evolution in a range of environmental contexts. In glacial research, it provides crucial data for a wide range of process-oriented studies and palaeoglaciological reconstructions; in the latter case providing an essential geomorphological framework for establishing glacial chronologies. In recent decades, there have been significant developments in remote sensing and Geographical Information Systems (GIS), with a plethora of high quality remotely-sensed datasets now (often freely) available. Most recently, the emergence of unmanned aerial vehicle (UAV) technology has allowed sub-decimetre scale aerial images and Digital Elevation Models (DEMs) to be obtained. Traditional field mapping methods still have an important role in glacial geomorphology, particularly in cirque glacier, valley glacier and icefield/ice-cap outlet settings. Field mapping is also used in ice sheet settings, but often takes the form of necessarily highly-selective ground-truthing of remote mapping. Given the increasing abundance of datasets and methods available for mapping, effective approaches are necessary to enable assimilation of data and ensure robustness. This paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available, with a focus on their applicability in particular glacial settings. We distinguish two overarching 'work streams' that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes: (i) mapping of ice sheet geomorphological imprints using a combined remote sensing approach, with some field checking (where feasible); and (ii) mapping of alpine and plateau-style ice mass (cirque glacier, valley glacier, icefield and ice-cap) geomorphological imprints using remote sensing and considerable field mapping. Key challenges to accurate and robust geomorphological mapping are highlighted, often necessitating compromises and pragmatic solutions. The importance of combining multiple datasets and/or mapping approaches is emphasised, akin to multi-proxy approaches used in many Earth Science disciplines. Based on our review, we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment, comparison, and integration of geomorphological data. These will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions. Finally, we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and/or sedimentological evidence, and that such data should ideally be collected as part of a holistic assessment of the overall glacier system.
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16.
  • Christoffersson, Anders, et al. (författare)
  • Seismic tomographic mapping of the Earth's interior : back to basics revisiting the ACH inversion
  • 2011
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 106:3-4, s. 293-306
  • Forskningsöversikt (refereegranskat)abstract
    • It is now more than 35 years since our original work on seismic tomography commenced in June 1974 upon Keiiti Aki's arrival at Kjeller near Oslo. It was published by Aki et al. (1977) and has found wide-spread applications in numerous studies of the Earth's interior from crust to core and in addition triggered many theoretical ones as well. In those times, computer technologies were rather crude and this hampered our tomographic research. In particular, we were somewhat unhappy about both our Generalized Inverse (GI) and the Stochastic Inverse (SI) solutions because of the former being too bumpy and the latter involving vertical smoothing. These problems remain in evidence also in recent studies as will be demonstrated in this review work. We start with re-examining the ACH-original work and then introduce Gauss-Markov (GM) filtering offsetting the defects of both the generalized and stochastic inverses. We highlight the relative merits of our novel inversion method by real tests on the original Norsar P-residuals and the corresponding 5 layered lithosphere model using synthetic velocity anomalies. Then we repeated the original inversion experiment adding the GM solution. The outcome was that the original SI solution was useless; GI too bumpy while the GM solution was appealing both computationally and in the context of geotectonic interpretation. We found that alternative inversion procedures like those forwarded by Backus and Gilbert (1968) and by Pijpers and Thompson (1992), the latter for helioseismology, were not applicable. The reason is that our unknowns are relative velocity anomalies within separate model layers and thus violate basic assumptions in the mentioned procedures. We also discuss source and structure parameter separation and the recent 'double difference' approach in tomography based on local earthquake data.
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17.
  • Davies, Neil S., et al. (författare)
  • Evolutionary synchrony of Earth's biosphere and sedimentary-stratigraphic record
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 201
  • Forskningsöversikt (refereegranskat)abstract
    • The landscapes and seascapes of Earth's surface provide the theatre for life, but to what extent did the actors build the stage? The role of life in the long-term shaping of the planetary surface needs to be understood to ascertain whether Earth is singular among known rocky planets, and to frame predictions of future changes to the biosphere. Modern geomorphic observations and modelling have made strides in this respect, but an underutilized lens through which to interrogate these questions resides in the most complete tangible record of our planetary history: the sedimentary-stratigraphic record (SSR). The characteristics of the SSR have been frequently explained with reference to changes in boundary conditions such as relative sea level, climate, and tectonics. Yet despite the fact that the long-term accrual of the SSR was contemporaneous with the evolution of almost all domains of life on Earth, causal explanations related to biological activity have often been overlooked, particularly within siliciclastic strata. This paper explores evidence for the ways in which organisms have influenced the SSR throughout Earth history and emphasizes that further investigation can help lead towards a mechanistic understanding of how the planetary surface has co-evolved with life. The practicality of discerning life signatures in the SSR is discussed by: 1) distinguishing biologically-dependent versus biologically-influenced sedimentary signatures; 2) emphasizing the importance of determining relative time-length scales of processes and demonstrating how different focal lengths of observation (individual geological outcrops and the complete SSR) can reveal different insights; and 3) promoting an awareness of issues of equifinality and underdetermination that may hinder the recognition of life signatures. Multiple instances of life signatures and their historic range within the SSR are reviewed, with examples covering siliciclastic, biogenic and chemogenic strata, and trigger organisms from across the spectrum of Earth's extant and ancient life. With this novel perspective, the SSR is recognised as a dynamic archive that expands and complements the fossil and geochemical records that it hosts, rather than simply being a passive repository for them. The SSR is shown to be both the record and the result of long-term evolutionary synchrony between life and planetary surface processes.
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18.
  • Fenn, Kaja, et al. (författare)
  • The provenance of Danubian loess
  • 2022
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 226, s. 103920-
  • Tidskriftsartikel (refereegranskat)abstract
    • With one of the largest watersheds in Europe, draining complex geological terrains within the Alps, Bohemian Massif, Carpathians, Dinarides, and the Balkan Mountains, the Danube River valley has long been linked to the formation of thick loess deposits, particularly within the Middle and Lower Danube basins. However, uncertainty over the provenance of loess-palaeosol sequences along the Danube impacts our understanding of sediment generation mechanisms and hinders interpretation of paleoenvironmental proxies preserved in loess. To date, most of the studies investigating loess provenance in Europe have not attempted a standardised characterisation and synthesis of loess deposits with potential source rocks. Further, despite clear links identified between loess and rivers in Asia and Europe, detrital zircons have not yet been used systematically to investigate the relationship between loess and the fluvial sediments of the Danube and its tributaries. Finally, in European loess research, provenance fingerprinting has often been conducted using indirect approaches or bulk sample geochemical analyses, which have been shown to have a limited application in well mixed sedimentary bodies such as loess.This provenance study of loess along the Danube River integrates existing zircon U-Pb ages and Hf datasets for loess, rivers, and bedrock, with new loess zircon U-Pb and Hf results from loess sequences in Croatia, Serbia and Bulgaria. The results show that all surrounding mountain belts (i.e. the Alps, Bohemian Massif, Carpathians, Dinarides Alps, and Balkan Mountains) contribute primary sediment to loess deposits in the Danube valley via its modern tributary network. Critically sedimentary sources remain relatively homogenous along the river, with no apparent major change in source with tributary confluence, further highlighting the role of fluvial transport in homogenising sediment prior to final aeolian deposition. Whilst some small site variations can be observed, they are likely explained by contributions restricted to very local rock outcrops. Moreover, geomorphological results support floodplain sediments as the proximal sediment source and suggest that short-distance aeolian transport dominates sediment delivery to loess sequences, challenging distant sources hypotheses such as major Saharan sources. The identification of sediment sourced from lower elevation regions such as the Bohemian Massif, Dinarides, and Balkans, which did not support ice-caps, suggests that the role of glacial action in silt-size sediment production has been previously exaggerated. Therefore, the glacial and desert loess division inadequately separates and describes sediment generation processes. This research supports and furthers previous work, which suggests “mountain sourced and transported by-rivers” as a more appropriate term for the particles forming loess, at least in the Danube basin.
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19.
  • Foulger, Gillian R., et al. (författare)
  • A new paradigm for the North Atlantic Realm
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 206
  • Forskningsöversikt (övrigt vetenskapligt/konstnärligt)
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20.
  • Foulger, Gillian R., et al. (författare)
  • The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 206
  • Forskningsöversikt (refereegranskat)abstract
    • The breakup of Laurasia to form the Northeast Atlantic Realm disintegrated an inhomogeneous collage of cratons sutured by cross-cutting orogens. Volcanic rifted margins formed that are underlain by magma-inflated, extended continental crust. North of the Greenland-Iceland-Faroe Ridge a new rift–the Aegir Ridge–propagated south along the Caledonian suture. South of the Greenland-Iceland-Faroe Ridge the proto-Reykjanes Ridge propagated north through the North Atlantic Craton along an axis displaced ~150 km to the west of the rift to the north. Both propagators stalled where the confluence of the Nagssugtoqidian and Caledonian orogens formed an ~300-km-wide transverse barrier. Thereafter, the ~150 × 300-km block of continental crust between the rift tips–the Iceland Microcontinent–extended in a distributed, unstable manner along multiple axes of extension. These axes repeatedly migrated or jumped laterally with shearing occurring between them in diffuse transfer zones. This style of deformation continues to the present day in Iceland. It is the surface expression of underlying magma-assisted stretching of ductile continental crust that has flowed from the Iceland Microplate and flanking continental areas to form the lower crust of the Greenland-Iceland-Faroe Ridge. Icelandic-type crust which underlies the Greenland-Iceland-Faroe Ridge is thus not anomalously thick oceanic crust as is often assumed. Upper Icelandic-type crust comprises magma flows and dykes. Lower Icelandic-type crust comprises magma-inflated continental mid- and lower crust. Contemporary magma production in Iceland, equivalent to oceanic layers 2–3, corresponds to Icelandic-type upper crust plus intrusions in the lower crust, and has a total thickness of only 10–15 km. This is much less than the total maximum thickness of 42 km for Icelandic-type crust measured seismically in Iceland. The feasibility of the structure we propose is confirmed by numerical modeling that shows extension of the continental crust can continue for many tens of millions of years by lower-crustal ductile flow. A composition of Icelandic-type lower crust that is largely continental can account for multiple seismic observations along with gravity, bathymetric, topographic, petrological and geochemical data that are inconsistent with a gabbroic composition for Icelandic-type lower crust. It also offers a solution to difficulties in numerical models for melt-production by downward-revising the amount of melt needed. Unstable tectonics on the Greenland-Iceland-Faroe Ridge can account for long-term tectonic disequilibrium on the adjacent rifted margins, the southerly migrating rift propagators that build diachronous chevron ridges of thick crust about the Reykjanes Ridge, and the tectonic decoupling of the oceans to the north and south. A model of complex, discontinuous continental breakup influenced by crustal inhomogeneity that distributes continental material in growing oceans fits other regions including the Davis Strait, the South Atlantic and the West Indian Ocean.
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21.
  • Gernigon, Laurent, et al. (författare)
  • Crustal fragmentation, magmatism, and the diachronous opening of the Norwegian-Greenland Sea
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 206
  • Forskningsöversikt (refereegranskat)abstract
    • The Norwegian-Greenland Sea (NGS) in the NE Atlantic comprises diverse tectonic regimes and structural features including sub-oceanic basins of different ages, microcontinents and conjugate volcanic passive margins, between the Greenland-Iceland-Faroe Ridge in the south and the Arctic Ocean in the north. We summarize the tectonic evolution of the area and highlight the complexity of the conjugate volcanic and rifted margins up to lithospheric rupture in the NGS. The highly magmatic breakup in the NGS was diachronous and initiated as isolated and segmented seafloor spreading centres. The early seafloor spreading system, initiating in the Early Eocene, gradually developed into atypical propagating systems with subsequent breakup(s) following a step-by-step thinning and rupture of the lithosphere. Newly-formed spreading axes propagated initially towards local Euler poles, died out, migrated or jumped laterally, changed their propagating orientation or eventually bifurcated. With the Palaeocene onset of volcanic rifting, breakup-related intrusions may have localized deformation and guided the final axis of breakup along distal regions already affected by pre-magmatic Late Cretaceous-Palaeocene and older extensional phases. The final line of lithospheric breakup may have been controlled by highly oblique extension, associated plate shearing and/or melt intrusions before and during Seaward Dipping Reflectors (SDRs) formation. The Inner SDRs and accompanying volcanics formed preferentially either on thick continental ribbons and/or moderately thinned continental crust. The segmented and diachronic evolution of the NGS spreading activity is also reflected by a time delay of 1–2 Myrs expected between the emplacement of the SDRs imaged at the Møre and Vøring margins. This complex evolution was followed by several prominent changes in spreading kinematics, the first occurring in the Middle Eocene at 47 Ma–magnetic chron C21r. Inheritance and magmatism likely influenced the complex rift reorganization resulting in the final dislocation of the Jan Mayen Microplate Complex from Greenland, in the Late Oligocene/Early Miocene.
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22.
  • Glodny, Johannes, et al. (författare)
  • The Cycladic Blueschist Unit of the Hellenic subduction orogen : Protracted high-pressure metamorphism, decompression and reimbrication of a diachronous nappe stack
  • 2022
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 224
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss the assembly and tectonochronology of the Cycladic Blueschist Unit (CBU) in the central Aegean Sea region, Greece, as a composite, subduction-related, high-pressure (blueschist to eclogite facies) stack of nappes. Our work is based on a review of geochronologic data from the Cycladic islands of Tinos, Syros and Sifnos. In addition, we present a large set of 34 new, internally consistent Rb-Sr multimineral isochron age data from these islands that can be linked to distinct metamorphic stages and episodes of ductile deformation. The reviewed and new ages provide remarkably similar results indicating that the age data and their interpretation is robust. We find that three distinct, significantly diachronous, CBU high-pressure nappes were sequentially accreted between ~55 and ~30 Ma, with a fourth ~24-22 Ma old high-pressure belt, the Basal Unit, below the CBU. Each CBU nappe was exhumed soon after its high-pressure imprint and experienced greenschist-facies overprinting with partial metamorphic reworking ~10 Ma after high-pressure accretion. At the time the structurally higher high-pressure nappe was exhumed, an underlying nappe was accreted and metamorphosed at high-pressure conditions. Our work suggests that the high-pressure nappes were considerably exhumed as rather coherent units during sustained lithospheric shortening in a subduction channel by return flow. The early Oligocene underthrusting of the External Hellenides to the south of the Cyclades, and tectonically below the CBU, is interpreted to have reduced the taper of the Hellenic subduction wedge, which caused significant shortening across the Cyclades region and an important phase of out-of-sequence thrusting that emplaced the non-high-pressure upper units above the CBU. Our analysis shows that this shortening event also caused significant reimbrication within the CBU along the recently discovered Trans Cycladic Thrust.
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23.
  • Greenwood, Sarah L., et al. (författare)
  • Theoretical, contemporary observational and palaeo-perspectives on ice sheet hydrology : Processes and products
  • 2016
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 155, s. 1-27
  • Tidskriftsartikel (refereegranskat)abstract
    • Meltwater drainage through ice sheets has recently been a key focus of glaciological research due to its influence on the dynamics of ice sheets in a warming climate. However, the processes, topologies and products of ice sheet hydrology are some of the least understood components of both past and modem ice sheets. This is to some extent a result of a disconnect between the fields of theoretical, contemporary observational and palaeo-glaciology that each approach ice sheet hydrology from a different perspective and with different research objectives. With an increasing realisation of the potential of using the past to inform on the future of contemporary ice sheets, bridging the gaps in the understanding of ice sheet hydrology has become paramount. Here, we review the current state of knowledge about ice sheet hydrology from the perspectives of theoretical, observational and palaeo-glaciology. We then explore and discuss some of the key questions in understanding and interpretation between these research fields, including: 1) disagreement between the palaeo-record, glaciological theory and contemporary observations in the operational extent of channelised subglacial drainage and the topology of drainage systems; 2) uncertainty over the magnitude and frequency of drainage events associated with geomorphic activity; and 3) contrasts in scale between the three fields of research, both in a spatial and temporal context The main concluding points are that modem observations, modelling experiments and inferences from the palaeo-record indicate that drainage topologies may comprise a multiplicity of forms in an amalgam of drainage modes occurring in different contexts and at different scales. Drainage under high pressure appears to dominate at ice sheet scale and might in some cases be considered efficient; the sustainability of a particular drainage mode is governed primarily by the stability of discharge. To gain better understanding of meltwater drainage under thick ice, determining what drainage topologies are reached under high pressure conditions is of primary importance. Our review attests that the interconnectivity between research sub-disciplines in progressing the field is essential, both in interpreting the palaeo-record and in developing physical understanding of glacial hydrological processes and systems.
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24.
  • Hallinger, Martin (författare)
  • Methods for measuring arctic and alpine shrub growth: A review
  • 2015
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 140, s. 1-13
  • Forskningsöversikt (refereegranskat)abstract
    • Shrubs have increased in abundance and dominance in arctic and alpine regions in recent decades. This often dramatic change, likely due to climate warming, has the potential to alter both the structure and function of tundra ecosystems. The analysis of shrub growth is improving our understanding of tundra vegetation dynamics and environmental changes. However, dendrochronological methods developed for trees, need to be adapted for the morphology and growth eccentricity of shrubs. Here, we review current and developing methods to measure radial and axial growth, estimate age, and assess growth dynamics in relation to environmental variables. Recent advances in sampling methods, analysis and applications have improved our ability to investigate growth and recruitment dynamics of shrubs. However, to extrapolate findings to the biome scale, future dendroecological work will require improved approaches that better address variation in growth within parts of the plant, among individuals within populations and between species. (C) 2014 Elsevier B.V. All rights reserved.
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25.
  • Hansman, Reuben J., et al. (författare)
  • Structural architecture and Late Cretaceous exhumation history of the Saih Hatat Dome (Oman), a review based on existing data and semi-restorable cross-sections
  • 2021
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 217
  • Forskningsöversikt (refereegranskat)abstract
    • The Saih Hatat Dome in the Al Hajar Mountains provides an outstanding opportunity to study subduction/exhumation processes coeval with obduction of the Semail Ophiolite. The exceptionally good outcrop conditions offer a unique opportunity to constrain the geometry of this subduction/obduction complex. In this review, the metamorphic, structural, and tectonic evolution of the Oman high-pressure complex in the Saih Hatat Dome is discussed. New structural cross-sections are developed and are used to interpret a geometrically feasible tectonic model for the Saih Hatat Dome. Our review highlights the importance of two major tectonic boundaries: (1) The As Sheik Shear Zone which separates the high pressure rocks of the As Sifah Unit (1.7–2.3 GPa and 510–550 °C) from the overlying Hulw Unit (1.0–1.2 GPa and 250–300 °C), and was active at ~79–76 Ma; and (2) the Upper Plate–Lower Plate Discontinuity, which forms a major surface in the landscape and developed by ~76–74 Ma, cutting through structures of the HP rocks in the lower plate (footwall). This discontinuity is associated with a pronounced strain gradient, notably in its upper plate (hanging wall), and separates rocks that have markedly different deformation geometry. The Upper Plate–Lower Plate Discontinuity initiated with a modest dip angle, making it a neutral structure in terms of crustal shortening vs extension. As a result, there is no discernable break in P-T conditions across it. The upper plate is dominated by the Saih Hatat Fold Nappe, forming between ~76 and 70 Ma. Subsequently, the upper plate has been dissected by a number of NNE-dipping thrusts at ~70–66 Ma, followed by normal faults at <~66 Ma. Our review and tectonic model indicate that the Oman high-pressure rocks were exhumed in a contractional tectonic setting that was possibly driven by forced return flow assisted by buoyancy forces. During this exhumation, when the rocks reached the greenschist-facies middle crust the Upper Plate–Lower Plate Discontinuity formed, as a shallow, south-dipping backthrust. Final exhumation of the high-P rocks was achieved by late normal faults after ~66 Ma.
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26.
  • Hao, Qian, et al. (författare)
  • Organic blue carbon sequestration in vegetated coastal wetlands: Processes and influencing factors
  • 2024
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 255, s. 104853-104853
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal wetlands play a vital role in carbon (C) sequestration, named ‘blue carbon’. The review aims to disentangle the processes and influencing factors, including elevated atmospheric CO2, global climate warming, sea level rise and anthropogenic activities. Firstly, we provided an overview of C processes, including input, output, and deposition, in coastal wetlands. We then summarized the impacts of different factors on C processes by modifying soil physicochemical properties, plant growth, vegetation type, and microbial community composition. Vegetation composition was a major contributor to C inputs, and C outputs was mainly controlled by microbial decomposition. Increased atmospheric CO2 concentration and associated climate warming often enhanced vegetation growth, while climate warming also promoted soil C decomposition. As a result, C storage could increase under mild warming conditions in the short-term, but decrease in the long-term as the severity of warming intensifies. Elevated salinity, caused by sea level rise, can be harmful to plant growth and inhibit organic C decomposition because of the reduced biomass and the weakened metabolic capacity of microorganisms. Most of human activities, such as reclamation, can lead to less C input and more C output, resulting in decreased C storage in coastal wetlands. Additionally, we also illustrate various coastal wetland restoration methods aimed at enhancing C sequestration, including legal frameworks, scientific theories, vegetation management, hydrological restoration, and other relevant constructions. Vegetation management could benefit plant growth and enhance C input effectively, and hydrological restoration can maintain the harmonious development of coastal wetland ecosystems. Other constructions, including breakwater, spillway, and dredged material, could protect coastal wetlands, especially facing sea level rise. This review offers valuable theoretical support and scientific references for the sustainable development and management of coastal wetlands in a changing climate.
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27.
  • He, Minhui, et al. (författare)
  • Recent advances in dendroclimatology in China
  • 2019
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 194, s. 521-535
  • Forskningsöversikt (refereegranskat)abstract
    • Considerable progress has been made in dendroclimatological research in China during the period 2000-2017, including a significant increase in the spatial coverage of tree-ring chronologies developed for paleoclimatic research. New tree-ring sampling sites have been established across the Tibetan Plateau, as well as the north-eastern and sub-tropical eastern parts of China. Most of the studies use coniferous trees, although different plant functional types (e.g., broadleaf species and shrubs) have also been increasingly investigated. Tree-ring chronologies longer than 600 years, however, are mostly found on the Tibetan Plateau, with the longest one extending back to 2637 BCE (before Common Era). Most tree-ring records in the eastern parts of China are < 400 years long. Tree-ring width is the most commonly studied parameter, although stable isotope ratios and wood density data have also been obtained for specific sites. Stable oxygen isotope data frequently shares a common hydroclimate signal, whereas the climate or environmental signals remain inconsistent for the few available stable carbon isotope records. In general, tree-ring width-based temperature reconstructions originate from higher elevation sites (i.e., treeline) compared to hydroclimate reconstructions. Precipitation or drought reconstructions are mainly obtained from regions with an annual precipitation of < 800 mm. Most of the tree-ring reconstructions are based on individual site or local-scale chronologies, although a limited number of regional-scale and field reconstructions have been produced. The most prominent identified characteristics of the recent advances in dendroclimatological research for China have manifested in aspects such as an expanded network of sampling sites, improved climate reconstruction methodology, and improved uncertainty estimations in the latter. Furthermore, the traditional statistical-based tree growth climate relationships have been supplemented by monitoring and modeling approaches. Based on the progress from 2000 to 2017, and on the research potential of the country in this field, we expect additional widening of the dendroclimatological investigations in China during the coming years.
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28.
  • Ivarsson, Magnus, et al. (författare)
  • The fossil record of igneous rock
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 210, s. 1-20
  • Tidskriftsartikel (refereegranskat)abstract
    • A growing awareness of life in deep igneous crust expands our appreciation for life's distribution in the upper geosphere through time and space, and extends the known inhabitable realm of Earth and possibly beyond. For most of life's history, until plants colonized land in the Ordovician, the deep biosphere was the largest reservoir of living biomass. This suggests that deep crustal habitats played an important role in the evolution and development of the biosphere. Paradoxically, the paleo-perspective of deep life has been largely neglected in the exploration of the deep biosphere as well as in paleontology as a whole. Here, we review the collective understanding of the fossil record in igneous crust with the aim to highlight a rising research field with great potential for substantial findings and progress in the near future. We include new results that emphasize the importance of direct or indirect dating of fossils and introduction of new techniques into the field. Currently, an incoherent record of morphological fossils- and chemofossils stretching from present to ~2.4 Ga implies the presence of an abundant and rich, yet largely unexplored, fossil record. Further investigations of deep paleo-environments will most certainly result in substantial insights into the distribution and development of biospheres throughout life's history, the early evolution of prokaryotes and eukaryotes, and Earth's early biogeochemical cycles. We emphasize the fossil record of igneous rock to give it the same status as the fossil record in sedimentary rocks, and to implement fossil investigations as standard procedures in future international drilling campaigns.
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29.
  • Japsen, Peter, et al. (författare)
  • Episodes of post-Caledonian burial and exhumation in Greenland and Fennoscandia
  • 2024
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 248
  • Forskningsöversikt (refereegranskat)abstract
    • The forces that drive uplift of the continental lithosphere outside collision zones are a topic of considerable dispute. Here we review our studies of the post-Caledonian development of Greenland, Fennoscandia and adjacent regions based on apatite fission-track analysis (AFTA) and stratigraphic landscape analysis (SLA). AFTA defines episodes of cooling (exhumation) while SLA provides a relative denudation chronology. Integrating these results with the geological record can produce a coherent history of both positive and negative vertical crustal movements. Our studies reveal a history involving multiple regional episodes of burial and exhumation, leading to a) formation of peneplains graded to sea level, b) formation of distinct unconformities in sedimentary successions, and c) deposition of thick siliciclastic wedges in basins adjacent to the uplifting landmasses. Exhumation episodes which began in late Carboniferous, Middle Triassic and Middle Jurassic affected the entire study area (with some time variations). These episodes correlate with rifting episodes during the break-up of Pangea, attributed to accumulation of mantle heat beneath the supercontinent. Mid-Cretaceous exhumation affected wide parts of the study area and coincided with the inversion of the Sorgenfrei-Tornquist Zone in southern Scandinavia. This may be linked with changes in the relative motion between the European and African plates in the earliest Late Cretaceous. Maastrichtian exhumation affected wide areas around Greenland, probably reflecting doming above the rising Iceland Plume upon its arrival in the upper mantle, prior to the mid-Paleocene impact at the base of the lithosphere. The mid-Paleocene impact of the plume under Greenland contributed to the onset of sea-floor spreading west of Greenland. This represents the onset of the Eurekan Orogeny which affected wide areas around northern Greenland. End-Eocene exhumation interrupted the Eocene regime of subsidence following earliest Eocene break-up in the North-East Atlantic, coincided with a minimum rate of sea-floor spreading in the North-East Atlantic, possibly related to changes in the motion of Africa relative to Europe. Early Miocene exhumation affected only Fennoscandia and is attributed to intraplate stress transmitted across the Eurasian plate. Late Miocene uplift initiated the formation of Greenland's coastal mountains but did not affect Fennoscandia. This episode correlates with changes in the absolute motion of the North American Plate. Pliocene uplift – amplified by the isostatic response to erosion – raised all margins in the region with maximum elevations reached in coastal areas close to Iceland. This suggests support from the Iceland Plume due to outward-flowing asthenosphere extending beneath the conjugate margins of the North-East Atlantic. We use these observations to argue that these episodes reflect both lithospheric and sub-lithospheric forces, related either to changes in the motion of the plates caused by far-field stress induced by events outside the study area, or driven by movements within the mantle directly within the study area. Geodynamic modelling is required to obtain further insights into the properties of the Earth that allow recurrent episodes of uplift and subsidence of the continents.
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30.
  • Jiang, Qiang, et al. (författare)
  • An appraisal of the ages of Phanerozoic large igneous provinces
  • 2023
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 237
  • Tidskriftsartikel (refereegranskat)abstract
    • Large igneous provinces (LIPs) are the products of exceptional magmatic events that played important roles in tectonic plate reorganizations, environmental crises, energy resource formation and ore genesis. Studying the ages of LIPs has been crucial for constraining the duration of these magmatic events and deciphering their temporal relationship with associated geological events. There have been a significant number of radio-isotopic dating analyses (e.g., Ar-40/Ar-39, U-Pb) conducted for LIPs, especially in the past decade. These dating results have often been directly accepted and propagated into the literature for geological interpretations, regardless of their reliability and precision. This review compiles all published Ar-40/Ar-39 and U-Pb age determinations for the eighteen Phanerozoic large igneous provinces and critically evaluates each for their statistical robustness and precision. The compiled and filtered age data are easily accessible in an online database (https://shorturl. at/kIQT5) that will be regularly maintained by the authors. Using a filtered dataset of reliable and precise ages, which accounts for similar to 30% of all the originally published ages, we discuss the duration of large igneous provinces and compare their relative timing with mass extinctions and global environmental crises. We find that the filtered datasets indeed provide robust evidence for a short duration of a few million years for some LIPs (i.e., Emeishan LIP, Siberian Traps, Central Atlantic magmatic province, Karoo LIP, Ferrar LIP, Parana-Etendeka LIP, Deccan Traps, and Columbia River basalt group). However, evidence for the claimed short-lived, or long-lived and pulsed magmatism for some LIPs is insufficient (e.g., Yakutsk-Vilyui LIP, Kerguelen LIP, Caribbean LIP, High Arctic LIP, North Atlantic igneous province) and more robust geochronology data are needed to constrain their duration and tempo. The filtered data also strengthen the synchronicity between the peak magmatic phase of most LIPs and their associated environmental crises. Clear correlations are identified between the severity of environmental perturbations and LIPs' magma flux rates and likely their accompanied volatile degassing rates, indicating that LIP-induced rapid and intense volatile degassing may have been an important mechanism for a LIP to trigger the deterioration of the environment and even mass extinction.
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31.
  • Johansson, Åke (författare)
  • Comment on Li et al. (2023): A dynamic 2000—540 Ma Earth history: From cratonic amalgamation to the age of supercontinent cycle
  • 2023
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 241, s. 1-3
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • The paper “A dynamic 2000—540 Ma Earth history: From cratonic amalgamation to the age of supercontinentcycle” that was recently published in Earth-Science Reviews by Li et al. (2023) is an impressive piece of work, putting together data for the Proterozoic supercontinent cycle into a coherent model including both maps and animations. Nevertheless, as they write themselves, there will no doubt be room for improvements of their model, some of which I hope to contribute with in this comment from my Baltica perspective, in particular when it comes to the relations between Baltica, Amazonia and West Africa.
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32.
  • Kjær, Kurt H., et al. (författare)
  • Glacier response to the Little Ice Age during the Neoglacial cooling in Greenland
  • 2022
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 227
  • Tidskriftsartikel (refereegranskat)abstract
    • In the Northern Hemisphere, an insolation driven Early to Middle Holocene Thermal Maximum was followed by a Neoglacial cooling that culminated during the Little Ice Age (LIA). Here, we review the glacier response to this Neoglacial cooling in Greenland. Changes in the ice margins of outlet glaciers from the Greenland Ice Sheet as well as local glaciers and ice caps are synthesized Greenland-wide. In addition, we compare temperature reconstructions from ice cores, elevation changes of the ice sheet across Greenland and oceanographic reconstructions from marine sediment cores over the past 5,000 years. The data are derived from a comprehensive review of the literature supplemented with unpublished reports. Our review provides a synthesis of the sensitivity of the Greenland ice margins and their variability, which is critical to understanding how Neoglacial glacier activity was interrupted by the current anthropogenic warming. We have reconstructed three distinct periods of glacier expansion from our compilation: two older Neoglacial advances at 2,500 – 1,700 yrs. BP (Before Present = 1950 CE, Common Era) and 1,250 – 950 yrs. BP; followed by a general advance during the younger Neoglacial between 700-50 yrs. BP, which represents the LIA. There is still insufficient data to outline the detailed spatio-temporal relationships between these periods of glacier expansion. Many glaciers advanced early in the Neoglacial and persisted in close proximity to their present-day position until the end of the LIA. Thus, the LIA response to Northern Hemisphere cooling must be seen within the wider context of the entire Neoglacial period of the past 5,000 years. Ice expansion appears to be closely linked to changes in ice sheet elevation, accumulation, and temperature as well as surface-water cooling in the surrounding oceans. At least for the two youngest Neoglacial advances, volcanic forcing triggering a sea-ice /ocean feedback, could explain their initiation. There are probably several LIA glacier fluctuations since the first culmination close to 1250 CE (Common Era) and available data suggests ice culminations in the 1400s, early to mid-1700s and early to mid-1800s CE. The last LIA maxima lasted until the present deglaciation commenced around 50 yrs. BP (1900 CE). The constraints provided here on the timing and magnitude of LIA glacier fluctuations delivers a more realistic background validation for modelling future ice sheet stability.
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33.
  • Landing, Ed, et al. (författare)
  • Cambrian Evolutionary Radiation : Context, correlation, and chronostratigraphy-Overcoming deficiencies of the first appearance datum (FAD) concept
  • 2013
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 123, s. 133-172
  • Tidskriftsartikel (refereegranskat)abstract
    • Use of the first appearance datum (FAD) of a fossil to define a global chronostratigraphic unit's base can lead to intractable correlation and stability problems. FADs are diachronous-they reflect species' evolutionary history, dispersal, biofacies, preservation, collection, and taxonomy. The Cambrian Evolutionary Radiation is characterised by diachronous FADs, biofacies controls, and provincialism of taxa and ecological communities that confound a stable Lower Cambrian chronostratigraphy. Cambrian series and stage definitions require greater attention to assemblage zone successions and non-biostratigraphic, particularly carbon isotope, correlation techniques such as those that define the Ediacaran System base. A redefined, basal Cambrian Trichophycus pedum Assemblage Zone lies above the highest Ediacaran-type biotas (vendobionts, putative metazoans, and calcareous problematica such as Cloudina) and the basal Asteridium tornatumComasphaeridium velvetum Zone (acritarchs). This definition and the likely close correspondence of evolutionary origin and local FAD of T. pedum preserves the Fortune Head, Newfoundland, GSSP of the Cambrian base and allows the presence of sub-Cambrian, branched ichnofossils. The sub-Tommotian-equivalent base of Stage 2 (a suggested "Laolinian Stage") should be defined by the l'/L4/ZHUCE delta C-13 positive peak, bracketed by the lower ranges of Watsonella crosbyi and Aldanella attleborensis (molluscs) and the Skiagia omata-Fimbrioglomerella membranacea Zone (acritarchs). The W. crosbyi and A. attleborensis FADs cannot define a Stage 2 base as they are diachronous even in the Newfoundland "type" W. crosbyi Zone. The Series 2 base cannot be based on a species' FAD owing to the provincialism of skeletalised metazoans in the Terreneuvian-Series 2 boundary interval and global heterochrony of the oldest trilobites. A Series 2 and Stage 3 (a suggested "Lenaldanian Series" and "Zhurinslcyan Stage," new) GSSP base is proposed at the Siberian lower Atdabanian delta C-13 IV peak-which correlates into South China, Avalonia, and Morocco and assigns the oldest trilobites to the terminal Terreneuvian Series. 
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34.
  • Li, Furong, et al. (författare)
  • Towards quantification of Holocene anthropogenic land-cover change in temperate China : A review in the light of pollen-based REVEALS reconstructions of regional plant cover
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 203, s. 1-25
  • Forskningsöversikt (refereegranskat)abstract
    • In an attempt to quantify Holocene anthropogenic land-cover change in temperate China, we 1) applied the REVEALS model to estimate plant-cover change using 94 pollen records and relative pollen productivity for 27 plant taxa, 2) reviewed earlier interpretation of pollen studies in terms of climate- and human-induced vegetation change, and 3) reviewed information on past land use from archaeological studies. REVEALS achieved a more realistic reconstruction of plant-cover change than pollen percentages in terms of openland versus woodland. The study suggests successive human-induced changes in vegetation cover. The first signs of human-induced land-cover change (crop cultivation, otherwise specified) are found c. 7 ka BP in the temperate deciduous forest, and S and NE Tibetan Plateau (mainly grazing, possibly crop cultivation), 6.5-6 ka BP in the temperate steppe and temperate desert (grazing, uncertain), and 5.5-5 ka BP in the coniferous-deciduous mixed forest, NE subtropical region, and NW Tibetan Plateau (grazing). Further intensification of anthropogenic land-cover change is indicated 5-4.5 ka BP in the E temperate steppe, and S and NE Tibetan Plateau (grazing, cultivation uncertain), 3.5-3 ka BP in S and NE Tibetan Plateau, W temperate steppe, temperate desert (grazing), and NW Tibetan Plateau (probably grazing), and 2.5-2 ka BP in the temperate deciduous forest, N subtropical region, and temperate desert (grazing). These changes generally agree with increased human activity as documented by archaeological studies. REVEALS reconstructions have a stronger potential than biomization to evaluate scenarios of anthropogenic land-cover change such as HYDE, given they are combined with information from archaeological studies.
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35.
  • Loisel, Julie, et al. (författare)
  • Insights and issues with estimating northern peatland carbon stocks and fluxes since the Last Glacial Maximum
  • 2017
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 165, s. 59-80
  • Forskningsöversikt (refereegranskat)abstract
    • In this review paper, we identify and address key uncertainties related to four local and global controls of Holocene northern peatland carbon stocks and fluxes. First, we provide up-to-date estimates of the current northern peatland area (3.2 M km(2)) and propose a novel approach to reconstruct changes in the northern peatland area over time (Section 2). Second, we review the key methods and models that have been used to quantify total carbon stocks and methane emissions over time at the hemispheric scale, and offer new research directions to improve these calculations (Section 3). Our main proposed improvement relates to allocating different carbon stock and emission values for each of the two dominant vegetation assemblages (sedge and brown moss-dominated vs. Sphagnum-dominated peat). Third, we discuss and quantify the importance of basin heterogeneity in estimating peat volume at the local scale (Section 4.1). We also highlight the importance of age model selection when reconstructing carbon accumulation rates from a peat core (Section 4.2). Lastly, we introduce the role of biogeomorphological agents such as beaver activity in controlling carbon dynamics (Section 5.1) and review the newest research related to permafrost thaw (Section 5.2) and peat fire (Section 5.3) under climate change. Overall, this review summarizes new information from a broad range of peat-carbon studies, provides novel analysis of hemispheric-scale paleo datasets, and proposes new insights on how to translate peat-core data into carbon fluxes. It also identifies critical data gaps and research priorities, and many ways to consider and address them.
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36.
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37.
  • Luo, Qingyong, et al. (författare)
  • Graptolites as fossil geo-thermometers and source material of hydrocarbons: An overview of four decades of progress
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 200
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermal maturity of lower Paleozoic graptolite-bearing marine sediments, which host many hydrocarbon deposits worldwide, has long been difficult to determine due to the absence of wood-derived vitrinite particles for conventional vitrinite reflectance. In 1976, graptolite reflectance was introduced as a new indicator for organic maturity of these deposits and has been used since in many regional studies. The majority of these studies, however, were done on a limited sample set and a limited range of thermal maturity, which resulted in a number of controversial views concerning the usefulness of graptolite reflectance as an alternative paleothermal indicator and its correlation with vitrinite reflectance through various proxies. In this paper, we review previous studies and combine those analyses with new data to assess the physical and chemical characteristics of graptolite periderm with increasing thermal maturity. We conclude that graptolite random reflectance (GRor) is a better parameter for the thermal maturity assessment than graptolite maximum reflectance (GRomax) due to the better quality of available data. Combining published data with results of our study of both natural and heat-treated graptolites and vitrinite, we present a new correlation between GRor and equivalent vitrinite reflectance (EqVRo), as EqVRo = 0.99GRor + 0.08. Chemical composition of graptolite periderm is similar to vitrinite; graptolites are mainly kerogen Type II-III, are gas prone and have a substantial hydrocarbon potential. Lower Paleozoic graptolite-bearing organic-rich sediments are important shale gas source rocks and reservoirs globally and make a significant contribution to worldwide petroleum reserves
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38.
  • Marcé, Rafael, et al. (författare)
  • Emissions from dry inland waters are a blind spot in the global carbon cycle
  • 2019
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 188, s. 240-248
  • Forskningsöversikt (refereegranskat)abstract
    • A large part of the world's inland waters, including streams, rivers, ponds, lakes and reservoirs is subject to occasional, recurrent or even permanent drying. Moreover, the occurrence and intensity of drying events are increasing in many areas of the world because of climate change, water abstraction, and land use alteration. Yet, information on the gaseous carbon (C) fluxes from dry inland waters is scarce, thus precluding a comprehensive assessment of C emissions including all, also intermittently dry, inland waters. Here, we review current knowledge on gaseous C fluxes from lotic (streams and rivers) and lentic (ponds, lakes, and reservoirs) inland waters during dry phases and the response to rewetting, considering controls and sources as well as implications of including 'dry' fluxes for local and global scale estimates. Moreover, knowledge gaps and research needs are discussed. Our conservative estimates indicate that adding emissions from dry inland waters to current global estimates of CO2 emissions from inland waters could result in an increase of 0.22 Pg C year(-1), or similar to 10% of total fluxes. We outline the necessary conceptual understanding to successfully include dry phases in a more complete picture of inland water C emissions and identify potential implications for global C cycle feedbacks.
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39.
  • Marchant, Rob, et al. (författare)
  • Drivers and trajectories of land cover change in East Africa : Human and environmental interactions from 6000 years ago to present
  • 2018
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 178, s. 322-378
  • Tidskriftsartikel (refereegranskat)abstract
    • East African landscapes today are the result of the cumulative effects of climate and land-use change over millennial timescales. In this review, we compile archaeological and palaeoenvironmental data from East Africa to document land-cover change, and environmental, subsistence and land-use transitions, over the past 6000 years. Throughout East Africa there have been a series of relatively rapid and high-magnitude environmental shifts characterised by changing hydrological budgets during the mid- to late Holocene. For example, pronounced environmental shifts that manifested as a marked change in the rainfall amount or seasonality and subsequent hydrological budget throughout East Africa occurred around 4000, 800 and 300 radiocarbon years before present (yr BP). The past 6000 years have also seen numerous shifts in human interactions with East African ecologies. From the mid-Holocene, land use has both diversified and increased exponentially, this has been associated with the arrival of new subsistence systems, crops, migrants and technologies, all giving rise to a sequence of significant phases of land-cover change. The first large-scale human influences began to occur around 4000 yr BP, associated with the introduction of domesticated livestock and the expansion of pastoral communities. The first widespread and intensive forest clearances were associated with the arrival of iron-using early farming communities around 2500 yr BP, particularly in productive and easily-cleared mid-altitudinal areas. Extensive and pervasive land-cover change has been associated with population growth, immigration and movement of people. The expansion of trading routes between the interior and the coast, starting around 1300 years ago and intensifying in the eighteenth and nineteenth centuries CE, was one such process. These caravan routes possibly acted as conduits for spreading New World crops such as maize (Zea mays), tobacco (Nicotiana spp.) and tomatoes (Solanum lycopersicum), although the processes and timings of their introductions remains poorly documented. The introduction of southeast Asian domesticates, especially banana (Musa spp.), rice (Oryza spp.), taro (Colocasia esculenta), and chicken (Gallus gallus), via transoceanic biological transfers around and across the Indian Ocean, from at least around 1300 yr BP, and potentially significantly earlier, also had profound social and ecological consequences across parts of the region. Through an interdisciplinary synthesis of information and metadatasets, we explore the different drivers and directions of changes in land-cover, and the associated environmental histories and interactions with various cultures, technologies, and subsistence strategies through time and across space in East Africa. This review suggests topics for targeted future research that focus on areas and/or time periods where our understanding of the interactions between people, the environment and land-cover change are most contentious and/or poorly resolved. The review also offers a perspective on how knowledge of regional land-use change can be used to inform and provide perspectives on contemporary issues such as climate and ecosystem change models, conservation strategies, and the achievement of nature-based solutions for development purposes.
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40.
  • Markovic, Slobodan B., et al. (författare)
  • Danube loess stratigraphy - Towards a pan-European loess stratigraphic model
  • 2015
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 148, s. 228-258
  • Tidskriftsartikel (refereegranskat)abstract
    • The Danube River drainage basin is the second largest river catchment in Europe and contains a significant and extensive region of thick loess deposits that preserve a record of a wide variety of recent and past environments. Indeed, the Danube River and tributaries may themselves be responsible for the transportation of large volumes of silt that ultimately drive loess formation in the middle and lower reaches of this large catchment However, this vast loess province lacks a unified stratigraphic scheme. European loess research started in the late 17th century in the Danube Basin with the work of Count Luigi Ferdinand Marsigli. Since that time numerous investigations provided the basis for the pioneering stratigraphic framework proposed initially by Kukla (1970, 1977) in his correlations of loess with deep-sea sediments. Loess-palaeosol sequences in the middle and lower reaches of the Danube River basin were a key part of this framework and contain some of the longest and most complete continental climate records in Europe, covering more than the last million years. However, the very size of the Danube loess belt and the large number of countries it covers presents a major limiting factor in developing a unified approach that enables continental scale analysis of the deposits. Local loess-palaeosol stratigraphic schemes have been defined separately in different countries and the difficulties in correlating such schemes, which often change significantly with advances in age-dating, have limited the number of basin-wide studies. A unified basin-wide stratigraphic model would greatly alleviate these difficulties and facilitate research into the wider significance of these loess records. Therefore we review the existing stratigraphic schemes and define a new Danube Basin wide loess stratigraphy based around a synthetic type section of the Mosorin and Stari Slankamen sites in Serbia. We present a detailed comparison with the sedimentological and palaeoclimatic records preserved in sediments of the Chinese Loess Plateau, with the oxygen isotope records from deep-sea sediments, and with classic European Pleistocene stratigraphic subdivisions. The hierarchy of Danubian stratigraphic units is determined by climatically controlled environmental shifts, in a similar way to the Chinese loess stratigraphic scheme. A new unified Danube loess stratigraphic model has a number of advantages, including preventing confusion resulting from the use of multiple national schemes, a more transparent basis, and the potential to set Pleistocene palaeoenvironmental changes recorded in the Danube catchment area into a global context. The use of a very simple labelling system based on the well-established Chinese loess scheme facilitates interpretation of palaeoenvironmental information reported from the Danube Basin loess sites in a wider more accessible context that can be readily correlated world-wide. This stratigraphic approach also provides, for the first time, an appropriate framework for the development of an integrated, pan-European and potentially pan-Eurasian loess stratigraphic scheme.
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41.
  • Mays, Chris, 1983-, et al. (författare)
  • Permian–Triassic non-marine algae of Gondwana—distributions, natural affinities and ecological implications
  • 2021
  • Ingår i: Earth-Science Reviews. - Amsterdam : Elsevier. - 0012-8252 .- 1872-6828. ; 212, s. 1-29
  • Tidskriftsartikel (refereegranskat)abstract
    • The abundance, diversity and extinction of non-marine algae are controlled by changes in the physical and chemical environment and community structure of continental ecosystems. We review a range of non-marine algae commonly found within the Permian and Triassic strata of Gondwana and highlight and discuss the non-marine algal abundance anomalies recorded in the immediate aftermath of the end-Permian extinction interval (EPE; 252 Ma). We further review and contrast the marine and continental algal records of the global biotic crises within the Permian–Triassic interval. Specifically, we provide a case study of 17 species (in 13 genera) from the succession spanning the EPE in the Sydney Basin, eastern Australia. The affinities and ecological implications of these fossil-genera are summarised, and their global Permian–Triassic palaeogeographic and stratigraphic distributions are collated. Most of these fossil taxa have close extant algal relatives that are most common in freshwater, brackish or terrestrial conditions, and all have recognizable affinities to groups known to produce chemically stable biopolymers that favour their preservation over long geological intervals. However, these compounds (e.g., sporopollenin and algaenan) are not universal, so the fossil record is sparse for most algal groups, which hinders our understanding of their evolutionary histories. Owing partly to the high preservational potential of Zygnematophyceae, a clade of freshwater charophyte algae and sister group to land plants, this group has a particularly diverse and abundant Permian–Triassic fossil record in Gondwana. Finally, we review and contrast the marine and continental algal records of the global biotic crises within the Permian–Triassic interval. In continental settings, Permian algal assemblages were broadly uniform across most of southern and eastern Gondwana until the EPE; here, we propose the Peltacystia Microalgal Province to collectively describe these distinct and prolonged freshwater algal assemblages. In the immediate aftermath of the EPE, relative increases in non-marine algae have been consistently recorded, but the distributions of prominent taxa of Permian freshwater algae became severely contracted across Gondwana by the Early Triassic. We highlight the paucity of quantitative, high-resolution fossil evidence for this key group of primary producers during all biotic crises of the Permian and Triassic periods. This review provides a solid platform for further work interpreting abundance and diversity changes in non-marine algae across this pivotal interval in evolutionary history.
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42.
  • Meurer, Katharina, et al. (författare)
  • Tillage intensity affects total SOC stocks in boreo-temperate regions only in the topsoil - A systematic review using an ESM approach
  • 2018
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 177, s. 613-622
  • Forskningsöversikt (refereegranskat)abstract
    • Shifting from high intensity (HT) to intermediate intensity (IT) or no tillage (NT) practices has been credited as being a promising agricultural management option towards climate change mitigation due to carbon (C) sequestration in the soil. The consequences of conversion from HT to mainly NT on soil organic carbon (SOC) have been subject to a number of meta-analyses revealing either a positive or non-significant effect. In this study, we used the equivalent soil mass (ESM) approach to evaluate SOC stock changes following the conversion from HT to IT and NT considering studies compiled within a systematic review. In order to maximize the use of available evidence, we used different substitution methods for imputing missing information on the variance of both SOC and bulk density (pb). Based on a total of 101 long-term field trials ( > 10 years), the positive effect of IT and NT compared to HT was found to be limited to the topsoil (0-30 cm depth). Estimated SOC stock increases for this particular depth ranged from 3.22 +/- 1.48 to 3.50 +/- 1.60 (HT vs. IT) and 4.19 +/- 1.82 to 4.23 +/- 1.92 Mg ha(-1) (HT vs. NT). Calculating stocks based on fixed depth layers and without consideration of the equivalent soil mass, respectively, resulted in an overestimation of the increase with 15 (HT vs. IT) and 47% (HT vs. NT and IT vs. NT). Due to shallow sampling depth, HT vs. IT and IT vs. NT comparisons were limited to 0-30 cm depth, but the effect of HT to NT conversion could also be determined for 0-60 cm. The results indicate that the NT sequestration potential is overvalued when neglecting deeper depths, since the SOC storage capacity was reduced to < 0.10 Mg ha(-1) yr(-1). No linear relation between relative SOC stock changes and climate, soil, and cropping systems was found.
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43.
  • Möller, Per, et al. (författare)
  • Glacial history and palaeo-environmental change of southern Taimyr Peninsula, Arctic Russia, during the Middle and Late Pleistocene
  • 2019
  • Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 196
  • Forskningsöversikt (refereegranskat)abstract
    • We here reconstruct a glacial and climate history of arctic NW Siberia for the last similar to 600,000 years, based on the stratigraphy and chronology of 35 studied river sections on the southern Taimyr Peninsula. From this strati graphic mosaic we have identified four glacial events, marked by tills/glaciotectonics, which are intercalated with mainly marine sediments deposited in proglacial settings during transitions from glacial conditions into subsequent interglacials/interstadials. The traces of early shelf-based Kara Sea Ice Sheet (KSIS) glaciations in marine isotope stages (MIS) 12-14 and 8 are sparsely preserved, but these ice advances are suggested to have terminated far south into the central Siberian uplands, as also was the case with the younger Taz glaciation (MIS 6). The inception phase of the latter glaciation was complex, with ice advancing into a proglacial marine basin both from the south (Putorana - Anabar uplands) and the north. The deglaciation leading into the Karginsky interglacial (MIS 5e) was marked by the development of the southerrunost ice-marginal zones (IMZs) on the Taimyr lowlands - the Urdakh and Sampesa IMZs. The most recent (late Pleistocene) glacial cycle is recorded by three successively smaller KSIS advances from the Kara Sea shelf onto Taimyr, of which only the first, during Early Zyryanka (MIS 5d), reached south of the Byrranga Mountains, with its maximum extent marked by the Jangoda - Syntabul - Severokokorsky IMZ. Retreat of the ice margin during MIS 5c-b was accompanied by deposition of glaciomarine sediment in the proglacial basin and deposition of large successions of delta sediments in the foothills of the Byrranga Motmtains, reaching a >= 100 m above present sea level. The region north of the Byrranga Mountains was subjected to two subsequent KSIS glaciations, during MIS 4 and MIS 2, while the area south of the Byrranga Mountains transitioned to a terrestrial environment from the Middle into the Lower Zyryanka, as evidenced by deposition of fluvial, aeolian and ice-complex (Yedoma) sediments.
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44.
  • Olierook, Hugo K.H., et al. (författare)
  • Age of the Barremian–Aptian boundary and onset of the Cretaceous Normal Superchron
  • 2019
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 197
  • Tidskriftsartikel (refereegranskat)abstract
    • The age assigned to the boundary of the Barremian and Aptian stages remains one of the most poorly constrained post-Pangean stratigraphic boundaries. The lack of a Global Boundary Stratotype Section and Point (GSSP) for the stage boundary has hampered efforts to calibrate the absolute age of the Cretaceous period in the geological time scale. The current definition of the Barremian–Aptian boundary also approximates the onset of magnetic polarity chron M0r; the end of this chron denotes the start of the Cretaceous Normal polarity Superchron that is of fundamental importance for plate reconstructions. Currently, there is up to 5% discrepancy in the age estimates of the Barremian–Aptian boundary (ca. 126–121 Ma) and the start of the Cretaceous Normal Superchron. Here, we review available geochronological information from the late Barremian and early Aptian stages collected from the Pacific Ocean, China, California, the Ontong Java Nui large igneous province and the High Arctic large igneous province. By utilizing only robust geochronological data including U-Pb and recalibrated 40Ar/39Ar ages from sites with magnetic polarity information and/or paleontological constraints, we calculate a best estimate of between 123.8 and 121.8 Ma for the Barremian–Aptian boundary and the onset of chron M0r at 2σ confidence. Using estimates of the duration of chron M0r (0.49 ± 0.10 Myr, 2σ), we conservatively compute the start of the Cretaceous Normal Superchron to between 123.4 and 121.2 Ma (2σ). Using an age of 83.07 ± 0.15 Ma (2σ) for the end of the Cretaceous Normal Superchron, the duration of the superchron is also constrained to between 38.0 and 40.5 Myr (2σ). These age ranges for the Barremian–Aptian boundary, the onset of the Cretaceous Normal Superchron and the duration of the superchron currently provide the best estimates until a GSSP is formally ratified.
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45.
  • O'Sullivan, Gary, et al. (författare)
  • The trace element composition of apatite and its application to detrital provenance studies
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 201
  • Tidskriftsartikel (refereegranskat)abstract
    • Apatite's ubiquity in crystalline rocks, variable trace element contents (particularly with regard to the REE, actinides and Sr), and amenability to various datingtechniques based on the decay of the radioisotopes U and Th, permit specific provenance determinations. In this study, we first present a comprehensive descriptionof the trace element behaviour of apatite in various kinds of bedrocks (igneous rocks from felsic through to ultramafic compositions, metamorphic rocks from low tohigh grades and of diverse protolith composition, and authigenic apatite) in which we explain why apatite is so highly diverse in terms of its trace elementcomposition. Next, we present a synthesis of bedrock apatite trace-element compositional data from previous work, assembling a library of apatite compositions thatincludes the most abundant apatite-bearing lithologies in the Earth's crust, and many other less abundant rock types. Compositional statistics, classification, and amachine learning classifier are then applied to this dataset to generate biplots that can be used to determine the broad source lithology of detrital apatite, withmisclassification averaging 15%. This methodology is tested in three case studies to demonstrate its utility. In these examples, detrital apatite can be convincinglylinked to different lithology types, and combined apatite trace-element and UePb data can determine the terranes from which individual apatites were likely derived.The addition of apatite trace-element information therefore enables the determination of the source lithology, making the extraction of novel information and morespecific provenance determinations possible, and opening up new avenues in source-to-sink modelling.
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46.
  • Peace, Alexander L., et al. (författare)
  • A review of Pangaea dispersal and Large Igneous Provinces : In search of a causative mechanism
  • 2020
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 206
  • Forskningsöversikt (refereegranskat)abstract
    • The breakup of Pangaea was accompanied by extensive, episodic, magmatic activity. Several Large Igneous Provinces (LIPs) formed, such as the Central Atlantic Magmatic Province (CAMP) and the North Atlantic Igneous Province (NAIP). Here, we review the chronology of Pangaea breakup and related large-scale magmatism. We review the Triassic formation of the Central Atlantic Ocean, the breakup between East and West Gondwana in the Middle Jurassic, the Early Cretaceous opening of the South Atlantic, the Cretaceous separation of India from Antarctica, and finally the formation of the North Atlantic in the Mesozoic-Cenozoic. We demonstrate that throughout the dispersal of Pangaea, major volcanism typically occurs distal from the locus of rift initiation and initial oceanic crust accretion. There is no location where extension propagates away from a newly formed LIP. Instead, LIPs are coincident with major lithosphere-scale shear movements, aborted rifts and splinters of continental crust rifted far out into the oceanic domain. These observations suggest that a fundamental reappraisal of the causes and consequences of breakup-related LIPs is in order.
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47.
  • Qvarnström, Martin, et al. (författare)
  • Vertebrate coprolites (fossil faeces) : An underexplored Konservat-Lagerstatte
  • 2016
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 162, s. 44-57
  • Forskningsöversikt (refereegranskat)abstract
    • Fossilized soft tissues of animals (e.g. muscles, hair and feathers) are valuable sources of palaeobiological information, but a poor preservation potential makes them undesirably scarce in the fossil record. The aim of this review is to summarize main findings, current progress and the analytical constraints of detecting fossilized soft tissues in coprolites from, mainly, freshwater and terrestrial carnivorous vertebrates. We conclude that soft-tissue inclusions in coprolites are sources of two important lines of information: the fossils can be put in a direct palaeoecological context, and characters of extinct taxa are more likely preserved in the phosphate-rich taphonomic microenvironment of coprolites than elsewhere. As a result, it is possible to unravel the deep-time origins of host-parasite relations, to understand ancient trophic food webs and detect new soft-tissue characters of different animal groups. Examples of the latter include muscle tissues from a tyrannosaurid prey, tapeworm eggs (including a developing embryo) in a Permian shark coprolite, as well as hair from multituberculates and, probably, from stem-mammals (Therapsids). Additionally, the use of coprolites in an archaeological context is briefly reviewed with focus on key aspects that may become implemented in studies of pre-Quaternary specimens as well. In summary, there is a wide range of information that can be extracted from coprolites, which has not yet been fully explored in palaeontological studies.
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48.
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49.
  • Ring, Uwe, et al. (författare)
  • The importance of tangential motion in the Central Alps : Kinematic analysis and Rb-Sr dating of mylonitic rocks from the Pennine nappes in the eastern Central Alps
  • 2021
  • Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 218
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss the important role of tangential stretching in the Central Alps highlighting that the Alps are a truly three-dimensional orogen. A review of pressure-temperature (P-T) conditions allows us to define three major breaks in metamorphic pressure (P-breaks) across the nappe pile. We constrain the kinematics of mylonites associated with these P-breaks and report eight new RbSr multi-mineral isochrons that define the age of the mylonites. Kinematic data and RbSr geochronology indicate that the timing of top-SE normal shearing in the Avers-Turba mylonite zone (≥45–34 Ma; P-break1) and in a zone of distributed top-E normal shearing (>35–30 Ma) above the (ultra)high-P Adula nappe of the distal, thinned European margin (P-breaks 2 and 3). The ages from both sets of mylonite are grading into each other at about 35–34 Ma. All ages appear to postdate high-P metamorphism in the Pennine nappes but are, in part, coeval with and predate (ultra)high-P metamorphism in the underlying Adula nappe of the distal European (Helvetic) margin. The oldest RbSr age of 42.3 ± 2.5 Ma (2σ uncertainties) dates the waning stage of mylonitization and indicates that the Avers-Turba mylonite zone started to operate ≥45 Ma, and predated the exhumation of the Adula nappe by ~10 Ma. We suggest that the motion in the Avers-Turba mylonite zone overlapped with backfolding of the Schams nappe in an extrusion wedge. When this process started, the Adula nappe was still being underthrust/underplated. The ages for distributed top-E normal shearing are contemporaneous with thrusting of the Adula nappe on top of distinctly lower-P Helvetic nappes. When the Adula nappe was being thrust onto non-high-P nappes the necessary reduction of its overburden was largely accomplished by distributed top-E normal faulting above the Adula nappe, and possibly still ongoing top-SE normal shearing. We discuss that major normal shearing occurred during lithospheric shortening. Our data indicate considerable tangential (out-of-plane) movements during overall top-N/NW thrust propagation in the Central Alps and have implications for current tectonic models of the Alps.
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50.
  • Ring, Uwe, et al. (författare)
  • The Samail subduction zone dilemma : Geochronology of high-pressure rocks from the Saih Hatat window, Oman, reveals juxtaposition of two subduction zones with contrasting thermal histories
  • 2024
  • Ingår i: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 250
  • Forskningsöversikt (refereegranskat)abstract
    • The Samail Ophiolite in the Oman Mountains formed at a Cretaceous subduction zone that was part of a wider Neo-Tethys plate-boundary system. The original configuration and evolution of this plate-boundary system is hidden in a structurally and metamorphically complex nappe stack below the Samail Ophiolite. Previous work provided evidence for high-temperature metamorphism high in the nappe pile (in the metamorphic sole of the Samail Ophiolite), and high-pressure metamorphism in the deepest part of the nappe pile (Saih Hatat window), possibly reflecting a downward younging, progressive accretion history at the Samail subduction zone. However, there is evidence that the two subduction-related metamorphic events are disparate, but temporally overlapping during the mid-Cretaceous. We present the first geochronologic dataset across the entire high-pressure nappe stack below the Samail Ophiolite, and the shear zones between the high-pressure nappes. Our 22 new Rb-Sr multimineral isochron ages from the Saih Hatat window, along with independent new field mapping and kinematic reconstructions, constrain the timing and geometry of tectonometamorphic events. Our work indicates the existence of a highpressure metamorphic event in the nappes below the ophiolite that was synchronous with the hightemperature conditions in the metamorphic sole. We argue that the thermal conditions of these synchronous metamorphic events can only be explained through the existence of two Cretaceous subduction zones/segments that underwent distinctly different thermal histories during subduction infancy. We infer that these two subduction zones initially formed at two perpendicular subduction segments at the Arabian margin and subsequently rotated relative to each other and, as a consequence, their records became juxtaposed: (1) The hightemperature metamorphic sole and the Samail Ophiolite both formed above the structurally higher, outboard, 'hot' and rotating Samail subduction zone and, (2) the high-pressure nappes developed within the structurally lower, inboard, 'cold' Ruwi subduction zone. We conclude that the formation and evolution of both subduction zones were likely controlled by the density structure of the mafic-rock-rich Arabian rifted margin and outermost Arabian Platform, and the subsequent arrival of the buoyant, largely mafic-rock-free, full-thickness Arabian lithosphere, which eventually halted subduction at the southern margin of Neo-Tethys.
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