Deep-water sediment transport patterns and basin floor topography in early rift basins: Plio-Pleistocene syn-rift of the Corinth Rift,Greece     

Martin Muravchik  Gijs A. Henstra  Gauti T. Eliassen  Rob L. Gawthorpe  Mike Leeder  Haralambos Kranis  Emmanuel Skourtsos  Julian Andrews 《Basin Research》2020,32(5):1184-1212

Our current understanding on sedimentary deep-water environments is mainly built of information obtained from tectonic settings such as passive margins and foreland basins. More observations from extensional settings are particularly needed in order to better constrain the role of active tectonics in controlling sediment pathways, depositional style and stratigraphic stacking patterns. This study focuses on the evolution of a Plio-Pleistocene deep-water sedimentary system (Rethi-Dendro Formation) and its relation to structural activity in the Amphithea fault block in the Corinth Rift, Greece. The Corinth Rift is an active extensional basin in the early stages of rift evolution, providing perfect opportunities for the study of early deep-water syn-rift deposits that are usually eroded from the rift shoulders due to erosion in mature basins like the Red Sea, North Sea and the Atlantic rifted margin. The depocentre is located at the exit of a structurally controlled sediment fairway, approximately 15 km from its main sediment source and 12 km basinwards from the basin margin coastline. Fieldwork, augmented by digital outcrop techniques (LiDAR and photogrammetry) and clast-count compositional analysis allowed identification of 16 stratigraphic units that are grouped into six types of depositional elements: A—mudstone-dominated sheets, B—conglomerate-dominated lobes, C—conglomerate channel belts and sandstone sheets, D—sandstone channel belts, E—sandstone-dominated broad shallow lobes, F—sandstone-dominated sheets with broad shallow channels. The formation represents an axial system sourced by a hinterland-fed Mavro delta, with minor contributions from a transverse system of conglomerate-dominated lobes sourced from intrabasinal highs. The results of clast compositional analysis enable precise attribution for the different sediment sources to the deep-water system and their link to other stratigraphic units in the area. Structures in the Amphithea fault block played a major role in controlling the location and orientation of sedimentary systems by modifying basin-floor gradients due to a combination of hangingwall tilt, displacement of faults internal to the depocentre and folding on top of blind growing faults. Fault activity also promoted large-scale subaqueous landslides and eventual uplift of the whole fault block.  相似文献   

A COMPARISON OF EASTERN AND WESTERN HONG KONG PHYTOPLANKTON FROM WEEKLY SAMPLES (1997-1999)     

唐森铭 《中国海洋湖沼学报》2002,(1)

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Denudation,vertical crustal movements and sedimentary basin infill     

Dr. Mike R. Leeder 《International Journal of Earth Sciences》1991,80(2):441-458

Denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass. Recent empirical results from a wide range of sources are presented on the rates of these processes. Denudation alone can cause non-tectonic (isostatic) surface uplift of the right magnitude predicted by theory. A case is made, following Ahnert, for a single linear relationship (although with much scatter) between denudation rate and mean drainage basin relief for large basins. Some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation. Application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one-dimensionality and neglect of suspended and washload contributions. Basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland, but problems arise in the apportionment of the various hinterland fluxes that occur in »real-world« three dimensional basins. Sediment yields in smaller half-graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields. Examples are given from extensional basins in the Western USA and Greece. The »length« of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed (through the fractal form of Hack's Law) and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands.

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Zusammenfassung Denudation und vertikale Krustenbewegungen sind verbunden durch das isostatische Gesetz über den Erhalt der lithosphärischen Masse. Neuerliche empirische Ergebnisse aus einem weiten Quellenbereich werden im Verhältnis zu diesen Prozessen präsentiert. Denudation allein, kann nicht tektonisch bedingte (isostatische) Oberflächenhebungen hervorrufen, die in der richtigen Größenordnung liegen, wie sie auch theoretisch ermittelt wurden. Es wird in Anlehnung an Ahnert ein Fall geschaffen, in der eine einfach lineare Beziehung (obgleich mit vielen Streuungen) zwischen der Denudationsrate und dem durchschnittlichen Abflußbeckenrelief für große Becken vorliegt. Einige neue Ermittlungen der Denudationszeitkonstanten wurden vernachlässigt, um tektonische und isostatische Begriffe einzufügen, welche sich der Verringerung des Reliefs durch Denudation widersetzen. Die Anwendung des Verbreitungstransportmodells zum Bestimmen der Sedimentationsrate sind streng begrenzt durch die ihm innewohnende Eindimensionalität, und der Vernachlässigung der Schwebe- und Schwämmfrachtbeteiligung. Bekkenfüllungssequenzen können benutzt werden um vergangene Sedimenttransferkoeffizienten aus dem Hinterland festzulegen; aber es treten auch Probleme bei der Verteilung der verschiedenen Hinterlandeinträge auf, die bei einem realen dreidimensionalen Becken vorhanden sind. Sedimenteinträge in kleineren Halbgräben und Growth-fold Becken müssen die Größe des Abflußbeckens widerspiegeln, sowie die komplexen lokalen Steuerungen auf die Sedimenteinträge. Beispiele von Dehnungsbecken aus dem Westen der USA und Griechenlands werden angesprochen. Die Länge des tektonischen Reliefs in verkippten Blöcken und Growth-Folds wird die Fläche des entwickelten Abflußbeckens kontrollieren (durch die fraktale Form des Gesetzes von Hack), und daher die Ablagerungsmenge von Sedimentbecken in der Nähe von tektonischen Hochlagen.

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Résumé L'érosion et les mouvements crustaux verticaux sont liés par l'équation isostatique de conservation de la masse lithosphérique. Des résultats empiriques récents provenant d'un large éventail de sources sont présentés en relation avec ces processus. L'érosion seule peut être la cause d'une montée non tectonique (isostatique) dont l'ampleur est prévue exactement par la théorie. Un cas est présenté, d'après Ahnert, qui montre, pour de grands bassins, une relation linéaire simple (mais avec une forte dispersion des points) entre le taux de dénudation et le relief moyen de l'aire de drainage. Certaines déterminations récentes des constantes de temps de dénudation ont omis de tenir compte des termes tectonique et isostatique qui s'opposent à la destruction du relief par érosion. L'utilisation de modèles de transport diffus en vue de déterminer le taux d'accumulation des sédiments est sévèrement limitée par le caractère unidimensionnel de tels modèles et par le fait qu'il ne tiennent pas compte de la fraction en suspension. Les séquences de comblement d'un bassin sédimentaire peuvent être utilisées pour déterminer les anciens cfficients de transfert à partir de l'hinterland; mais des difficultés surgissent à propos de la répartition des différents flux en provenance de l'hinterland dans le cas réel d'un bassin à 3 dimensions. Les apports sédimentaires dans les bassins de demi-graben et de »growth-fold« doivent traduire la grandeur des aires de drainage et les facteurs locaux complexes qui régissent ces apports. Des exemples sont présentés, relatifs à des bassins d'extension de l'ouest des USA et de Grèce. La »longueur« des reliefs tectoniques en relation avec les blocs basculés et les »growth-folds« déterminent, par la forme fractale de la loi de Hack, la surface des aires de drainage ainsi engendrées et, en conséquence, l'importance des dépôts dans les bassins sédimentaires voisins des reliefs tectoniques.

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Brine-pool deposition for the Zn–Pb–Cu massive sulphide deposits of the Bathurst mining camp, New Brunswick, Canada. II. Ocean anoxia during mineralisation     

Mike Solomon   《Ore Geology Reviews》2008,33(3-4):352-360

Current models of massive sulphide ore genesis in the Bathurst mining camp, New Brunswick, involve settling of sulphide particles from a stagnating, low-salinity hydrothermal plume spreading laterally in an anoxic ocean layer with minimal sulphate content. There is fragmentary evidence of ocean anoxia in the form of local fine lamination in the shales that host some of the deposits but the total organic carbon, S, Fe, U/Th, Ni/Co, V/Ni and V/Cr relationships indicate deposition under oxic or dysoxic conditions. Vanadium and Mn values range from oxic to anoxic and sulphate-reducing to non-sulphate reducing but Mn may be anomalously low due to derivation by erosion of acidic volcanic rocks. The somewhat equivocal physical and chemical data, combined with the likely disturbing effects of penecontemporaneous volcanism, considerably weaken the case for an anoxic bottom layer in a static ocean. The presence of barite with ambient seawater ³⁴S values in Brunswick no. 12 ore, and the abundance of sulphate in modern euxinic basin waters, make a sulphate-free layer unlikely, even if anoxic. Sulphate-bearing, low-salinity fluids mixing with seawater would lead to growth of barite-bearing chimneys and baritic rubble mounds, which are not observed. A model involving brine-pool deposition better explains the major features of the Bathurst ores.  相似文献   

Arctic Coastal Dynamics (ACD): an introduction     

Volker Rachold  Feliks E. Are  David E. Atkinson  Georgy Cherkashov  Steven M. Solomon 《Geo-Marine Letters》2005,25(2-3):63-68

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Swimming endurance of haddock (Melanogrammus aeglefinus L.) at prolonged and sustained swimming speeds, and its role in their capture by towed fishing gears     

Breen  Mike; Dyson  Jamie; O'Neill  Finbarr G.; Jones  Emma; Haigh  Michael 《ICES Journal of Marine Science》2004,61(7):1071-1079

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The Southern Antarctic Circumpolar Current Front: physical and biological coupling at South Georgia     

Peter Ward  Mick Whitehouse  Mike Meredith  Eugene Murphy  Rachael Shreeve  Rebecca Korb  Jon Watkins  Sally Thorpe  Rachel Woodd-Walker  Andrew Brierley  Nathan Cunningham  Sharon Grant  Doug Bone 《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(12):139

The coupling of physics and biology was examined along a 160 km long transect running out from the north coast of South Georgia Island and crossing the Southern Antarctic Circumpolar Current Front (SACCF) during late December 2000. Surface and near surface potential TS properties indicated the presence of three water types: a near-shore group of stations characterised by water which became progressively warmer and fresher closer to South Georgia, an offshore grouping in which sea surface temperatures and those at the winter water level were relatively warm (1.8°C and 0.5°C, respectively), and a third in which surface and winter water temperatures were cooler and reflected the presence of the SACCF. The transect bisected the SACCF twice, revealing that it was flowing in opposite directions, north-westward closest to South Georgia and south-eastwards at its furthest point from the island. The innermost limb was a narrow intense feature located just off the shelf break in 2000–3500 m of water and in which rapid surface baroclinic velocities (up to 35 cm s⁻¹) were encountered. Offshore in the outermost limb, shown subsequently to be a mesoscale eddy that had meandered south from the retroflected limb of the SACCF, flow was broader and slower with peak velocities around 20 cm s⁻¹. Chlorophyll a biomass was generally low (<1 mg m⁻³) over much of the transect but increased dramatically in the region of the innermost limb of the SACCF, where a deepening of the surface mixed layer was coincident with a subsurface chlorophyll maximum (7.4 mg m⁻³) and elevated concentrations down to 100 m. The bloom was coincident with depleted nutrient concentrations, particularly silicate, nitrate and phosphate, and although ammonium concentrations were locally depleted the bloom lay within an elevated band (up to 1.5 mmol m⁻³) associated with the frontal jet. Increased zooplankton abundance, higher copepod body carbon mass and egg production rates all showed a strong spatial integrity with the front. The population structure of the copepods Calanoides acutus and Rhincalanus gigas at stations within the front suggested that rather than simply resulting from entrainment and concentration within the jet, increased copepod abundance was the result of development in situ. Estimates of bloom duration, based on silicate and carbon budget calculations, set the likely duration between 82 and 122 d, a figure supported by the development schedule of the two copepod species. Given this timescale, model outputs from FRAM and OCCAM indicated that particles that occurred on the north side of South Georgia in December would have been in the central-southern Scotia Sea 2–3 months earlier, probably in sea ice affected regions.  相似文献   

Pacific subtropical cell variability in coupled climate model simulations of the late 19th–20th century     

Amy Solomon  Dongxiao Zhang 《Ocean Modelling》2006,15(3-4):236

Observational studies of the Pacific basin since the 1950s have demonstrated that a decrease (increase) in tropical Pacific sea surface temperatures (SSTs) is significantly correlated with a spin-up (slow-down) of the Pacific Subtropical Cells (STCs). STCs are shallow wind-driven overturning circulations that provide a pathway by which extratropical atmospheric variability can impact the equatorial Pacific thermocline and, through upwelling in the eastern equatorial Pacific, tropical Pacific SSTs. Recent studies have shown that this observed relationship between SSTs and STCs is absent in coupled climate model simulations of the late 19th–20th centuries. In this paper we investigate what causes this relationship to breakdown and to what extent this limits the models’ ability to simulate observed climate change in the equatorial Pacific since the late 19th century. To provide insight into these questions we first show that the NCAR Community Climate System Model’s simulation of observed climate change since the 1970s has a robust signal in the equatorial Pacific that bears a close resemblance to observations. Strikingly, absent is a robust signal in the equatorial thermocline. Our results suggest that the coupled model may be reproducing the observed local ocean response to changes in forcing but inadequately reproducing the remote STC-forcing of the tropical Pacific due to the underestimate of extratropical winds that force these ocean circulations. These conclusions are found to be valid in five different coupled climate model simulations of the late 19th–20th centuries (CCSM3, GISS EH, GFDL CM2.1, CSIRO-Mk3, and HadCM3).  相似文献   

Reservoir description using dynamic parameterisation selection with a combined stochastic and gradient search     

Lars Kristian Nielsen  Sam Subbey  Mike Christie  Trond Mannseth 《Computational Geosciences》2006,10(3):321-342

There is a correspondence between flow in a reservoir and large scale permeability trends. This correspondence can be derived by constraining reservoir models using observed production data. One of the challenges in deriving the permeability distribution of a field using production data involves determination of the scale of resolution of the permeability. The Adaptive Multiscale Estimation (AME) seeks to overcome the problems related to choosing the resolution of the permeability field by a dynamic parameterisation selection. The standard AME uses a gradient algorithm in solving several optimisation problems with increasing permeability resolution. This paper presents a hybrid algorithm which combines a gradient search and a stochastic algorithm to improve the robustness of the dynamic parameterisation selection. At low dimension, we use the stochastic algorithm to generate several optimised models. We use information from all these produced models to find new optimal refinements, and start out new optimisations with several unequally suggested parameterisations. At higher dimensions we change to a gradient-type optimiser, where the initial solution is chosen from the ensemble of models suggested by the stochastic algorithm. The selection is based on a predefined criterion. We demonstrate the robustness of the hybrid algorithm on sample synthetic cases, which most of them were considered insolvable using the standard AME algorithm.  相似文献   

Groundwater study using remote sensing and geographic information systems (GIS) in the central highlands of Eritrea   总被引：3，自引：1，他引：3  

Semere Solomon  Friedrich Quiel 《Hydrogeology Journal》2006,14(6):1029-1041

Remote sensing, evaluation of digital elevation models (DEM), geographic information systems (GIS) and fieldwork techniques were combined to study the groundwater conditions in Eritrea. Remote sensing data were interpreted to produce lithological and lineament maps. DEM was used for lineament and geomorphologic mapping. Field studies permitted the study of structures and correlated them with lineament interpretations. Hydrogeological setting of springs and wells were investigated in the field, from well logs and pumping test data. All thematic layers were integrated and analysed in a GIS. Results show that groundwater occurrence is controlled by lithology, structures and landforms. Highest yields occur in basaltic rocks and are due to primary and secondary porosities. High yielding wells and springs are often related to large lineaments, lineament intersections and corresponding structural features. In metamorphic and igneous intrusive rocks with rugged landforms, groundwater occurs mainly in drainage channels with valley fill deposits. Zones of very good groundwater potential are characteristic for basaltic layers overlying lateritized crystalline rocks, flat topography with dense lineaments and structurally controlled drainage channels with valley fill deposits. The overall results demonstrate that the use of remote sensing and GIS provide potentially powerful tools to study groundwater resources and design a suitable exploration plan.The online version of the original article can be found at  相似文献