Sea-state contributions to sea-level variability in the European Seas     

Bonaduce  Antonio  Staneva  Joanna  Grayek  Sebastian  Bidlot  Jean-Raymond  Breivik  Øyvind 《Ocean Dynamics》2020,70(12):1547-1569

Ocean Dynamics - The contribution of sea-state-induced processes to sea-level variability is investigated through ocean-wave coupled simulations. These experiments are performed with a...  相似文献   

Hydrograph separation using tracers and digital filters to quantify runoff components in a semi‐arid mesoscale catchment          下载免费PDF全文

Aline Maraci Lopes Saraiva Okello  Stefan Uhlenbrook  Graham P.W. Jewitt  Ilyas Masih  Edward Sebastian Riddell  Pieter Van der Zaag 《水文研究》2018,32(10):1334-1350

Chemical hydrograph separation using electrical conductivity and digital filters is applied to quantify runoff components in the 1,640 km² semi‐arid Kaap River catchment and its subcatchments in South Africa. A rich data set of weekly to monthly water quality data ranging from 1978 to 2012 (450 to 940 samples per site) was analysed at 4 sampling locations in the catchment. The data were routinely collected by South Africa's national Department of Water and Sanitation, using standard sampling procedures. Chemical hydrograph separation using electrical conductivity (EC) as a tracer was used as reference and a recursive digital filter was then calibrated for the catchment. Results of the two‐component hydrograph separation indicate the dominance of baseflow in the low flow regime, with a contribution of about 90% of total flow; however, during the wet season, baseflow accounts for 50% of total flow. The digital filter parameters were very sensitive and required calibration, using chemical hydrograph separation as a reference. Calibrated baseflow estimates ranged from 40% of total flow at the catchment outlet to 70% in the tributaries. The study demonstrates that routinely monitored water quality data, especially EC, can be used as a meaningful tracer, which could also aid in the calibration of a digital filter method and reduce uncertainty of estimated flow components. This information enhances our understanding of how baseflow is generated and contributed to streamflow throughout the year, which can aid in quantification of environmental flows, as well as to better parameterize hydrological models used for water resources planning and management. Baseflow estimates can also be useful for groundwater and water quality management.  相似文献   

Reconnaissance survey of the Duolun ring structure in Inner Mongolia: Not an impact structure          下载免费PDF全文

Xiaoming Xu  Thomas Kenkmann  Zhiyong Xiao  Sebastian Sturm  Nicolai Metzger  Yu Yang  Daniela Weimer  Hannes Krietsch  Meng‐Hua Zhu 《Meteoritics & planetary science》2017,52(9):1822-1842

The Duolun basin, which is located in Inner Mongolia, China, has been proposed to be an impact structure with an apparent rim diameter of about 70, or even 170 km. The designation as an impact structure was based on its nearly circular topography, consisting of an annular moat that surrounds an inner hummocky region, and the widespread occurrences of various igneous rocks, polymict breccias, and deformed crustal rocks. Critical shock metamorphic evidence is not available to support the impact hypothesis. We conducted two independent reconnaissance field surveys to this area and studied the lithology both within and outside of the ring structure. We collected samples from all lithologies that might contain evidence of shock metamorphism as suggested by their locations, especially those sharing similar appearances with impact breccias, suevites, impact melt rocks, and shatter cones. Field investigation, together with thin‐section examination, discovered that the suspected impact melt rocks are actually Early Cretaceous and Late Jurassic lava flows and pyroclastic deposits of rhyolitic to trachytic compositions, and the interpreted impact glass is typical volcanic glass. Petrographic analyses of all the samples reveal no indications for shock metamorphic overprint. All these lines of evidence suggest that the Duolun basin was not formed through impact cratering. The structural deformation and spatial distribution pattern of the igneous rocks suggest that the Duolun basin is most likely a Jurassic–Cretaceous complex rhyolite caldera system that has been partly filled with sediments forming an annular basin, followed by resurgent doming of the central area.  相似文献   

Characterization of the Rapanui mass-transport deposit and the basal shear zone: Mount Messenger Formation,Taranaki Basin,New Zealand     

Sebastian Cardona  Lesli J. Wood  Brandon Dugan  Zane Jobe  Lorna J. Strachan 《Sedimentology》2020,67(4):2111-2148

Submarine mass-transport deposits are important in many ancient and modern basins. Mass-transport deposits can play a significant role in exploration as reservoir, seal or source units. Although seismic data has advanced the knowledge about these deposits, more outcrop studies are needed to better understand gravity mass flows and predict the properties of their resultant deposits. It is proposed that sufficiently well-exposed outcrops of mass-transport deposits can be divided into three strain-dominant morphodomains: headwall, translational and toe. The outcrops of the Rapanui mass-transport deposit, part of the Lower Mount Messenger Formation in the Taranaki Basin, New Zealand, are exposed along a ca 4 km transect in coastal cliffs that enable the identification of the three morphodomains. The aim of this study is to characterize the stratigraphic and sedimentological nature of the Miocene-age Rapanui mass-transport deposit outcrops and the evolution of its basal shear zone. The basal shear zone of a mass-transport deposit is defined as the stratal zone formed in the interface between the overriding mass flow and the underlying in situ deposits or sea floor. Accordingly, the deformation structures in the Rapanui mass-transport deposit and the basal shear zone were documented in an established spatial framework. Traditional methodologies were used to characterize the sedimentology of the Rapanui mass-transport deposit. Data collected from intrafolial folds, rafted blocks and samples from the Rapanui mass-transport deposit were used to investigate strain and matrix texture evolution, estimate palaeoflow direction, and calculate yield strength and overpressure at time of deposition. Additionally, a one-dimensional numerical model was used to test sedimentation-driven overpressure as probable trigger. This work demonstrates that the basal shear zone, as well as the matrix texture of a mass-transport deposit, can vary spatially as sediments from underlying deposits are entrained during shear-derived mixing. This phenomenon can impact the seal potential of mass-transport deposits and their interaction with fluids in the subsurface.  相似文献   

LakeCC: a tool for efficiently identifying lake basins with application to palaeogeographic reconstructions of North America     

Sebastian Hinck  Evan J. Gowan  Gerrit Lohmann 《第四纪科学杂志》2020,35(3):422-432

Along the margins of continental ice sheets, lakes formed in isostatically depressed basins during glacial retreat. Their shorelines and extent are sensitive to the ice margin and the glacial history of the region. Proglacial lakes, in turn, also impact the glacial isostatic adjustment due to loading, and ice dynamics by posing a marine-like boundary condition at the ice margin. In this study we present a tool that efficiently identifies lake basins and the corresponding maximum water level for a given ice sheet and topography reconstruction. This algorithm, called the LakeCC model, iteratively checks the whole map for a set of increasing water levels and fills isolated basins until they overflow into the ocean. We apply it to the present-day Great Lakes and the results show good agreement (∼1−4%) with measured lake volume and depth. We then apply it to two topography reconstructions of North America between the Last Glacial Maximum and the present. The model successfully reconstructs glacial lakes such as Lake Agassiz, Lake McConnell and the predecessors of the Great Lakes. LakeCC can be used to judge the quality of ice sheet reconstructions. © 2019 The Authors Journal of Quaternary Science Published by John Wiley & Sons Ltd.  相似文献   

Convergence Tests for Transdimensional Markov Chains in Geoscience Imaging     

Somogyvári  Márk  Reich  Sebastian 《Mathematical Geosciences》2020,52(5):651-668

Mathematical Geosciences - Classic inversion methods adjust a model with a predefined number of parameters to the observed data. With transdimensional inversion algorithms such as the...  相似文献   

The potential influence of shallow gas and gas hydrates on sea floor erosion of Rock Garden, an uplifted ridge offshore of New Zealand     

Gareth J. Crutchley  Sebastian Geiger  Ingo A. Pecher  Andrew R. Gorman  Hai Zhu  Stuart A. Henrys 《Geo-Marine Letters》2010,30(3-4):283-303

Regional erosion of the Rock Garden ridge top, a bathymetric high within New Zealand’s Hikurangi Subduction Margin, is likely associated with its gas hydrate system. Seismic data reveal gas pockets that appear partially trapped beneath the shallow base of gas hydrate stability. Steady-state fluid flow simulations, conducted on detailed two-dimensional geological models, reveal that anomalous fluid pressure can develop close to the sea floor in response to lower-permeability hydrate-bearing sediments and underlying gas pockets. Transient simulations indicate that large-scale cycling of fluid overpressure may occur on time scales of a few to tens of years. We predict intense regions of hydro-fracturing to preferentially develop beneath the ridge top rather than beneath the flanks, due to more pronounced overpressure generation and gas migration through hydrate-bearing sediments. Results suggest that sediment weakening and erosion of the ridge top by hydro-fracturing could be owed to fluid dynamics of the shallow gas hydrate system.  相似文献   

Water intrusions and particle signatures in the Black Sea: a Biogeochemical-Argo float investigation     

Emil Vassilev Stanev  Sebastian Grayek  Hervé Claustre  Chaterine  Schmechtig  Antoine Poteau 《Ocean Dynamics》2017,67(9):1119-1136

Continuous observations during 3 years with a vertical resolution of 1 dbar from two Bio-Argo floats in the Black Sea that were equipped with oxygen optodes, chlorophyll fluorometers, and backscattering sensors are analyzed. The particle backscattering coefficient, b _bp provides a proxy for the concentration of suspended particles. The observations clearly identify thermal and b _bp intrusions down to ~700–800 m in the Bosporus inflow area. In this area, b _bp is more than five times larger than elsewhere, which could indicate bacterial abundance and possible biological involvement in the precipitation of Mn-containing particles. The b _bp anomalies become much shallower than the temperature anomalies with increasing distance to the east of the strait. Their maxima are located between the onset of the suboxic zone and the upper part of the anoxic layer. Unlike well-known intrusions that are caused by inflow, open ocean intrusions are shallower and often characterized by multiple layers of backscatter maxima with thicknesses of only 15–20 m. The ratio between backscattering coefficients measured at two wavelengths, which gives a proxy for particle size, shows that the relative amount of larger size particles in the anoxic layer increases with depth. The particle concentrations and their size distribution display different vertical variability, which indicates the complex transformation of biological matter. The lower concentration of particles and lower chlorophyll-a during the extremely warm 2016 reveals an overall positive correlation between the two properties. The trends in the particle backscattering coefficient in the suboxic zone during 2013–2016 could indirectly reveal a biogeochemical response to temperature changes.  相似文献   

Reaction of a polar gravel-spit system to atmospheric warming and glacier retreat as reflected by morphology and internal sediment geometries (South Shetland Islands,Antarctica)     

Pablo Heredia Barión  Sebastian Lindhorst  Ilona Schutter  Ulrike Falk  Gerhard Kuhn 《地球表面变化过程与地形》2019,44(5):1148-1162

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Thermo‐mechanical interaction of a large impact melt sheet with adjacent target rock,Sudbury impact structure,Canada     

Paul L. Gllner  Torben Wüstemann  Lisa Bendschneider  Sebastian Reimers  Martin D. Clark  Lisa Gibson  Peter C. Lightfoot  Ulrich Riller 《Meteoritics & planetary science》2019,54(6):1228-1245

The 1.85 Ga Sudbury Igneous Complex (SIC) and its thermal aureole are unique on Earth with regard to unraveling the effects of a large impact melt sheet on adjacent target rocks. Notably, the formation of Footwall Breccia, lining the basal SIC, remains controversial and has been attributed to impact, cratering, and postcratering processes. Based on detailed field mapping and microstructural analysis of thermal aureole rocks, we identified three distinct zones characterized by static recrystallization, incipient melting, and crystallization textures. The temperature gradient in the thermal aureole increases toward the SIC and culminates in a zone of partial melting, which correlates spatially with the Footwall Breccia. We therefore conclude that assimilation of target rock into initially superheated impact melt and simultaneous deformation after cratering strongly contributed to breccia formation. Estimated melt fractions of the Footwall Breccia amount to 80 vol% and attest to an extreme loss in mechanical strength and, thus, high mobility of the Breccia during assimilation. Transport of highly mobile Footwall Breccia material into the overlying Sublayer Norite of the SIC and vice versa can be attributed to Raleigh–Taylor instability of both units, long‐term crater modification caused by viscous relaxation of crust underlying the Sudbury impact structure, or both.  相似文献