Mesozoic extension in the Basque–Cantabrian basin (N Spain): Contributions from AMS and brittle mesostructures     

Ruth Soto  Antonio M. Casas-Sainz  Juan J. Villalaín  Beln Oliva-Urcia 《Tectonophysics》2007,445(3-4):373-394

In this work we analyse and check the results of anisotropy of magnetic susceptibility (AMS) by means of a comparison with palaeostress orientations obtained from the analysis of brittle mesostructures in the Cabuérniga Cretaceous basin, located in the western end of the Basque–Cantabrian basin, North Spain. The AMS data refer to 23 sites including Triassic red beds, Jurassic and Lower Cretaceous limestones, sandstones and shales. These deposits are weakly deformed, and represent the syn-rift sequence linked to basins formed during the Mesozoic and later inverted during the Pyrenean compression. The observed magnetic fabrics are typical of early stages of deformation, and show oblate, triaxial and prolate magnetic ellipsoids. The magnetic fabric seems to be related to a tectonic overprint of an original, compaction, sedimentary fabric. Most sites display a NE–SW magnetic lineation that is interpreted to represent the stretching direction of the Early Cretaceous extensional stage of the basin, without recording of the Tertiary compressional events, except for sites with compression-related cleavage.Brittle mesostructures include normal faults, calcite and quartz tension gashes and joints, related to the extensional stage. The results obtained from joints and tension gashes show a dominant N–S to NE–SW, and secondary NW–SE, extension direction. Paleostresses obtained from fault analysis (Right Dihedra and stress inversion methods) indicate NW–SE to E–W, and N–S extension direction. The results obtained from brittle mesostructures show a complex pattern resulting from the superposition of several tectonic processes during the Mesozoic, linked to the tectonic activity related to the opening of the Bay of Biscay during the Early Cretaceous. This work shows the potential in using AMS analysis in inverted basins to unravel its previous extensional history when the magnetic fabric is not expected to be modified by subsequent deformational events. Brittle mesostructure analysis seems to be more sensitive to far-field stress conditions and record longer time spans, whereas AMS records deformation on the near distance, during shorter intervals of time.  相似文献   

The IGEX Campaign     

Ruth Neilan 《GPS Solutions》1998,2(2):68-68

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Grain-size trends, basin subsidence and sediment supply in the Campanian Castlegate Sandstone and equivalent conglomerates of central Utah   总被引：2，自引：1，他引：1  

Ruth A. J. Robinson  & Rudy L. Slingerl 《Basin Research》1998,10(1):109-127

Reconstructions of grain-size trends in alluvial deposits can be used to understand the dominant controls on stratal architecture in a foreland basin. Different initial values of sediment supply, tectonic subsidence and base-level rise are investigated to constrain their influence on stratal geometry using the observed grain-size trends as a proxy of the goodness of fit of the numerical results to the observed data. Detailed measurements of grain-size trends, palaeocurrent indicators, facies and thickness trends, channel geometries and palynological analyses were compiled for the middle Campanian Castlegate Sandstone of the Book Cliffs and its conglomerate units in the Gunnison and Wasatch plateaus of central Utah. They define the initial conditions for a numerical study of the interactions between large-scale foreland basin and small-scale sediment transport processes. From previous studies, the proximal foreland deposits are interpreted as recording a middle Campanian thrusting event along the Sevier orogenic belt, while the stratal architecture in the Book Cliffs region is interpreted to be controlled by eustatic fluctuation with local tectonic influence. Model results of stratal geometry, using a subsidence curve with a maximum rate of ≈45 m Myr^?1 for the northern Wasatch Plateau region predict the observed grain-size trends through the northern Book Cliffs. A subsidence curve with a maximum rate of ≈30 m Myr^?1 in the Gunnison–Wasatch Plateaus best reproduces the observed grain-size trends in the southern transect through the southern Wasatch Plateau. Eustasy is commonly cited as controlling Castlegate deposition east of the Book Cliffs region. A eustatic rise of 45 m Myr^?1 produces grain-size patterns that are similar to the observed, but a rate of eustatic rise based on Haq et al. (1988) will not produce the observed stratal architecture or grain-size trends. Tectonic subsidence alone, or a combined rate of tectonic subsidence and a Haq et al. (1988) eustatic rise, can explain the stratal and grain-size variations in the proximal and downstream regions.  相似文献   

Lead and copper in the waters of Raritan and Lower New York Bays     

Ruth Waldhauer  Albert Matte  Robert E Tucker 《Marine pollution bulletin》1978,9(2):38-42

A survey of waters adjacent to this heavily urbanized and industrialized region showed concentrations of copper, 65 μg l.^?1 to be the highest reported to date for estuarine waters, and lead up to 13.9 μg l.^?1 Correlations between distributions of dissolved and total metal concentration in the water column, hydrography, and metal in the sediment were related to benthic studies in this area. Laboratory studies are cited which show the potential for adverse effects on marine animals at these metal concentrations.  相似文献   

Organic chemical characterization of sediment-trap particulates from San Nicolas,Santa Barbara,Santa Monica and San Pedro Basins,California     

P.T. Crisp  S. Brenner  M.I. Venkatesan  E. Ruth  I.R. Kaplan 《Geochimica et cosmochimica acta》1979,43(11):1791-1801

Particulate matter was collected during September–October, 1977, in particle traps suspended 30–60 m above the floor of San Nicolas, Santa Barbara, Santa Monica and San Pedro Basins, off the coast of southern California. The trap particulates were analyzed for C₁₅–C₃₅ hydrocarbons using gas chromatography (GC) and GC-mass spectrometry. Kerogens and humic acids were characterized by H/C, N/C, δ¹³C, δ¹⁵N and δ³⁴S ratios, and by electron-spin resonance. Hydrocarbons arising from fresh and weathered petroleum, marine autochthonous and terrestrial sources were identified. The rates of petroleum deposition during the collection period followed the order: San Nicolas Basin < Santa Barbara Basin ~ Santa Monica Basin < San Pedro Basin, with the largest amount of weathered petroleum being deposited in San Pedro Basin. The rates of petroleum deposition are correlated more strongly with human activities such as shipping, and the discharge of municipal and industrial wastes, than with natural submarine oil seepage. Analyses of kerogens and humic acids indicate that the majority of the organic matter in the trap particulates is of marine origin. The water column overlying Santa Barbara Basin appears to have the highest marine productivity of the four basins studied.  相似文献   

THE VISUAL EFFECTS OF GEOMETRIC RELATIONSHIPS ON THREE-DIMENSIONAL MAPS     

Paul V. Crawford  Ruth A. Marks 《The Professional geographer》1973,25(3):233-238

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Report of an excursion to Tilburstow Hill and Nutfield,Surrey: Saturday,June 26th, 1915     

A. Hubert Cox 《Proceedings of the Geologists' Association. Geologists' Association》1915,26(5):324-326

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SOCIAL THEORY AND THE FUTURE OF URBAN GEOGRAPHY*     

Ruth Fincher 《The Professional geographer》1987,39(1):9-12

Three themes that seem likely to be influential in the near future have recently characterized the work of geographers using social theories as the basis of their explanations of urban phenomena. They are (1) the debates about structure and human agency. (2) the claims of feminists about the analytical significance of the social construction of gender roles, and (3) the demand that we now use our social theories more actively to explain experienced reality. In continuing our use of social theory in urban geography, we must prevent its marginalization as one specific substantive topic; the alternative epistemologies of this type of work can guide new interpretations of every substantive issue in urban geography.  相似文献   

Drought tolerant maize for farmer adaptation to drought in sub-Saharan Africa: Determinants of adoption in eastern and southern Africa   总被引：2，自引：1，他引：1  

Monica Fisher  Tsedeke Abate  Rodney W. Lunduka  Woinishet Asnake  Yoseph Alemayehu  Ruth B. Madulu 《Climatic change》2015,133(2):283-299

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Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework     

T. M. Lenton  R. Marsh  A. R. Price  D. J. Lunt  Y. Aksenov  J. D. Annan  T. Cooper-Chadwick  S. J. Cox  N. R. Edwards  S. Goswami  J. C. Hargreaves  P. P. Harris  Z. Jiao  V. N. Livina  A. J. Payne  I. C. Rutt  J. G. Shepherd  P. J. Valdes  G. Williams  M. S. Williamson  A. Yool 《Climate Dynamics》2007,29(6):591-613

We have used the Grid ENabled Integrated Earth system modelling (GENIE) framework to undertake a systematic search for bi-stability of the ocean thermohaline circulation (THC) for different surface grids and resolutions of 3-D ocean (GOLDSTEIN) under a 3-D dynamical atmosphere model (IGCM). A total of 407,000 years were simulated over a three month period using Grid computing. We find bi-stability of the THC despite significant, quasi-periodic variability in its strength driven by variability in the dynamical atmosphere. The position and width of the hysteresis loop depends on the choice of surface grid (longitude-latitude or equal area), but is less sensitive to changes in ocean resolution. For the same ocean resolution, the region of bi-stability is broader with the IGCM than with a simple energy-moisture balance atmosphere model (EMBM). Feedbacks involving both ocean and atmospheric dynamics are found to promote THC bi-stability. THC switch-off leads to increased import of freshwater at the southern boundary of the Atlantic associated with meridional overturning circulation. This is counteracted by decreased freshwater import associated with gyre and diffusive transports. However, these are localised such that the density gradient between North and South is reduced tending to maintain the THC off state. THC switch-off can also generate net atmospheric freshwater input to the Atlantic that tends to maintain the off state. The ocean feedbacks are present in all resolutions, across most of the bi-stable region, whereas the atmosphere feedback is strongest in the longitude–latitude grid and around the transition where the THC off state is disappearing. Here the net oceanic freshwater import due to the overturning mode weakens, promoting THC switch-on, but the atmosphere counteracts this by increasing net freshwater input. This increases the extent of THC bi-stability in this version of the model. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献