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  • Articles  (143)
  • Geosciences  (143)
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  • Articles  (143)
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  • 1
    Electronic Resource
    Electronic Resource
    INTERNAL STRUCTURE OF WAVE-FORMED RIPPLE MARKS IN THE NEARSHORE ZONE (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 11 (1968), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Wave-formed ripple marks in the nearshore zones of the Baltic Sea (tideless) and North Sea (tidal) exhibit a unidirectional internal lamination identical to that of current ripples. This holds true whether the ripples are symmetrical or asymmetrical. In most cases wave-formed ripple laminae dip toward shore and can thereby provide a shoreline direction indicator when found in ancient sediments. The sediment transport direction, however, may be other than in the foreset laminae dip direction, and cross-lamination as a sediment transport direction indicator should be used with caution.Ripple height, wave length and the orientation of the ripple internal structure are dependent upon both the orbital diameter and the velocity of the positive component of oscillation of the waves forming them. The thickness of the individual laminae making up ripples is highly dependent upon sediment grain size; the role hydrodynamics plays is problematic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1968.tb00857.x
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  • 2
    Electronic Resource
    Electronic Resource
    Grossular activity-composition relationships in ternary garnets determined by reversed displaced-equilibrium experiments (1989)
    Springer
    Contributions to mineralogy and petrology 103 (1989), S. 423-433 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Activity-composition relationships of Ca3Al2Si3O12 (grs) in ternary Ca-Mg-Fe garnets of various compositions have been determined by reversed displaced equilibrium experiments at 1000° C and 900° C and pressures of 8 to 17 kbar. The mixing of grs in garnet is nearly ideal at 30 mol% grs, with positive deviations from ideality at lower grs contents. Models of garnet mixing currently in the literature do not predict this trend. Analysis of the present reversals, in conjunction with a garnet mixing model based solely on calorimetry measurements on the binary joins, indicates that a ternary interaction constant for a ternary asymmetric Margules model (Wohl 1953) cannot be constrained. Apparently, some aspects of the garnet binary joins are still not well-known. An alternative asymmetric empirical model, based on analysis of pseudobinary joins of constant Mg/Mg + Fe(Mg #), reproduces the data well and is able to predict grs activity coefficients for garnets with grs contents between 3 and 40 mol% and Mg numbers between 0 and 0.60. The grossular activity coefficient,γ grs, is given by: $$RT\ln \gamma _{grs} = (1 - X_{grs} )^2 [W_{Ca} + 2X_{grs} (W_{FM} - W_{Ca} )]$$ where: $$\begin{gathered} W_{Ca} (J) = - 2060 + 3.57 \times 10^4 (Mg\# ) - 4.95 \times 10^4 (Mg\# )^2 \hfill \\ W_{FM} (J) = 3390 - 3.71 \times 10^4 (Mg\# ) + 6.49 \times 10^4 (Mg\# )^2 \hfill \\ \end{gathered} $$ These expressions are valid only over the composition range investigated. The formulation cannot be used to extract Fe and Mg activity coefficients. There appears to be no temperature or pressure dependence of theW-parameters over theP-T range investigated. The improved definition of the grossular activity coefficient which results from the present work contributes to an improved formulation of the garnet-Al2SiO5-quartz-plagioclase (GASP) geobarometer and other phase equilibria relevant to metamorphic petrology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01041750
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  • 3
    Electronic Resource
    Electronic Resource
    Aragonite crystallization from strained calcite at reduced pressures and its bearing on aragonite in low-grade metamorphism (1969)
    Springer
    Contributions to mineralogy and petrology 22 (1969), S. 335-348 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Aragonite, the dense form of CaCO3, grew hydrothermally at 100–300° C and dry at 300–400° C at very low pressures from calcite strained by grinding. Nearly complete inversion to aragonite occurred in some runs with Ca-Mg chloride solutions at 0–2.4 kb and 100–200° C on strained calcite having a (10¯14) reflection with a half-width of 0.48° 2 Θ Cu Kα. A little aragonite grew dry at one atm. from the ground calcite at 300–400° C in a few hrs. Simultaneous shear during recrystallization of calcite in a rotating squeezer resulted in significant aragonite at 300–400° C several kb. below the stability field. No inversion occurred in any ground calcite when previously annealed in CO2 at 500° C for a few hrs. Thermochemical data show that at least 200 cal/mole of strain energy can be produced in calcite by mild deformation. This much stored energy would lower the pressure requirements of aragonite, relative to the strained calcite by more than 3 kb, and our observation that aragonite growth was faster than strain recovery of calcite indicates that aragonite can grow in nature at reduced pressures from strained calcite. Some experiments were also carried out on highly magnesian calcites with the thought that aragonite might also form at the expense of this metastable material. No aragonite was produced, but the possibility that this mechanism could be operative in nature cannot be discounted. The microtexture of aragonitic deformed marbles from NW Washington (prehnite-pumpellyite facies rocks, courtesy of J. A. Vance) as well as electron probe microanalysis of these rocks indicates that aragonite selectively replaced highly strained calcite. The calcite-aragonite transition is thus a questionable indicator of high-pressure in certain metamorphic rocks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00400128
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  • 4
    Electronic Resource
    Electronic Resource
    Stability of the scapolite meionite (3CaAl2Si2O2 · CaCO3) at high pressures and storage of CO2 in the deep crust (1975)
    Springer
    Contributions to mineralogy and petrology 49 (1975), S. 49-62 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The stability field of the end-member scapolite meionite was determined in piston-cylinder apparatus. Meionite has very high thermal stability at high pressures, exceeding 1500° C at 20 kbar. Below 6 kbar and 1270 ° C scapolite breakdown is subsolidus, to an-orthite + gehlenite + wollastonite + CO2, with a slope of 20 bars/degree. An extrapolation of existing thermodynamic data for CO2 permits calculation of ΔG F o =-2384.5 kcal/mol for meionite at 1270 ° C, very close to the value for 3 anorthite + calcite. Above 1270 ° C, scapolite begins to melt to An+Geh+Liq+CO2, and as pressure increases the melting curve steepens, the Geh and An being progressively replaced by Liq+corundum with Al in 6-coordination. At pressures 〉25kbar dp/dt becomes negative, corundum is the only crystalline product, and CO2 bubbles disappear from the quenched glass, indicating a solubility of CO2 under these conditions of about 5 wt. percent in the liquid. The subsolidus breakdown of meionite at high pressures to grossularite + kyanite + quartz + calcite nearly coincides with the upper pressure limits of anorthite. Thus scapolite is essentially limited to crustal rocks. In view of its great thermal stability, meionite can play a role as a primary mineral in deep-seated basic or intermediate magmatic processes. It is also likely that CO2 coming from the earth's interior will be captured by reaction with plagioclase and clinopyroxene. Scapolite has been noted in basic granulite inclusions from basaltic pipes in three continents. It seems probable that scapolite acts as a major storage site for CO2 in the deep crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371078
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  • 5
    Electronic Resource
    Electronic Resource
    The compositions of coexisting pyroxenes and garnet in the system CaO-MgO-Al2O3-SiO2 at 900°–1,100°C and high pressures (1981)
    Springer
    Contributions to mineralogy and petrology 75 (1981), S. 291-300 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The compositions of coexisting orthopyroxene, clinopyroxene and garnet in the CaO-MgO-Al2O3-SiO2 system are fixed at any givenP andT. Reversed hydrothermal experiments over theP/T range 15–40 kb/900°–l,100° C indicate that the garnet composition is nearly constant at Py86Gr14; the Alcontent and Ca/Ca+Mg values of the pyroxenes vary significantly, however: T P Wt. %Al2O3 $$\frac{{Ca}}{{Ca + Mg}} \times 100$$ °C kbar in opx in cpx in opx in cpx 900 15 3.55 2.92 0.72 47.05 900 30 1.62 0.92 0.81 47.30 1,100 20 1.11 0.92 1.22 45.20 1,100 40 1.26 0.88 0.81 45.64 The significant variation of A12O3 content with pressure supports its use as a geobarometer. The Ca/Ca +Mg values of coexisting orthoand clino-pyroxene have been used as a geothermometer. However, the present results show that the presence of A12O3 in the pyroxenes decreases significantly the mutual solubility of the pyroxenes, which may cause errors of up to 200° C if the A12O3 effect is ignored. Thermodynamic analyses of the experimental results for the reaction Mg3Al2Si3O12(gar) =Mg3Al2Si3O12(opx) yield average values ofΔH 0 andΔS 0 of 7.4 Kcal and 5.7 eu, respectively, which are in marginal agreement with calorimetric results. Similar analysis of our results for the reaction MgSiO3(cpx)=MgSiO3(opx) support earlier conclusions that MgSiO3 substitution in clinopyroxene behaves as a regular solution (Holland et al. 1979) and that Al substitution is quasi-ideal (Wood 1979). Application of the present results to garnet lherzolites from southern Africa yields a geotherm which is parallel to those previously proposed, although the indicated heat flow is greater. Similar rocks, from the Solomon Islands, show a much steeper geothermal gradient, as expected for an oceanic plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01166769
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of whole catchment liming on the episodic acidification of two adirondack streams (1996)
    Springer
    Biogeochemistry 32 (1996), S. 299-322 
    Details
    ISSN: 1573-515X
    Keywords: acidic precipitation ; adirondack mountains ; liming ; snowmelt ; episodic acidification ; beaver pond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During the fall of 1989 7.7Mg/ha of calcium carbonate was applied on two tributary catchments (40 ha and 60 ha) to Woods Lake, a small (25 ha) acidic headwater lake in the western Adirondack region of New York. Stream-water chemistry in both catchment tributaries responded immediately. Acid-neutralizing capacity (ANC) increased by more than 200 μeq/L in one of the streams and more than 1000 μeq/L in the other, from pre-liming values which ranged from −25 to +40 μeq/L. The increase in ANC was primarily due to increases in dissolved Ca2+ concentrations. Most of the initial response of the streams was due to the dissolution of calcite that fell directly into the stream channels and adjacent wetlands. A small beaver impoundment and associated wetlands were probably responsible for the greater response observed in one of the streams. After the liming of subcatchmentIV (60 ha), Ca2+ concentrations increased with increasing stream discharge in the stream during fall rain events, suggesting a contribution from calcite dissolved within the soil and transported to the stream by surface runoff or shallow interflow. Concentrations of other ions not associated with the calcite (e.g. Na+) decreased during fall rain events, presumably due to mixing of solute-rich base flow with more dilute shallow interflow. The strong relation between changes in Ca2+ and changes in NO 3 − concentrations during spring snowmelt, (r2 = 0.93, slope = 0.96, on an equivalent basis) suggests that both solutes had a common source in the organic horizon of the soil. Increases in NO 3 − concentrations during snowmelt were balanced by increases in Ca2+ that was released either directly from the calcite or from exchange sites, mitigating episodic acidification of the stream. However, high ambient NO 3 − concentrations and relatively low ambient Ca2+ concentrations in the stream during the spring caused the stream to become acidic despite the CaCO3 treatment. In stream WO2 (40ha), Ca2+ concentrations were much higher than in stream WO4 because of the dissolution of calcite which fell directly into the upstream beaver pond and its associated wetlands. Calcium concentrations decreased as both NO 3 − concentrations and stream discharge increased, due to the dilution of Ca-enriched beaver pond water by shallow interflow. Despite this dilution, Ca2+ concentrations were high enough to more than balance strong acid anion (SO 4 − , NO 3 − , Cl−) concentrations, resulting in a positive ANC in this stream throughout the year. These data indicate that liming of wetlands and beaver ponds is more effective than whole catchment liming in neutralizing acidic surface waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187143
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  • 7
    Electronic Resource
    Electronic Resource
    Application of the integrated lake-watershed acidification study model to watershed liming at woods Lake, New York (1996)
    Springer
    Biogeochemistry 32 (1996), S. 363-383 
    Details
    ISSN: 1573-515X
    Keywords: acid mitigation ; ILWAS model ; watershed liming ; watershed modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Woods Lake, in the Adirondack Mountains of New York, was the site of the Experimental Watershed Liming Study (EWLS) in which base addition was investigated as a method for mitigation of lake acidity. In an effort to predict the duration of effects, the treatment was simulated using the Integrated Lake-Watershed Acidification Study (ILWAS) model. To simulate terrestrial liming, calcite was applied to treated subcatchments as a rapidly weathering mineral in the upper horizon. Soil solution and lake outlet chemistry showed a response to calcite addition within four months of the start of the simulation. Calcium concentrations, acid neutralizing capacities (ANC), and pH increased in the upper soil layer and aluminum concentrations decreased in the upper three soil layers (0–70 cm). The response of ANC was delayed in lower soil layers due to proton production associated with aluminum hydrolysis. Moreover, soil water pH in the third soil layer decreased in response to calcite treatment due to the displacement of hydrogen ions by calcium added to the exchange complex. Calcium concentrations, ANC and pH increased and aluminum concentrations decreased in the simulated lake outlet. The modeled effects of calcite treatment on the soil and lake outlet chemistry were not as great as field observations. This was, in part, attributed to the model representation of the watershed, which did not include streams, ponds, or wetlands located in the treated subcatchments. Calcite applied to these saturated areas in the field readily dissolved, supplying ANC to lake water. Additionally, incorporation of calcite into a thick organic layer in the model diminished the possibility of dissolution by contact with overland flow. Observed concentrations of calcium, ANC, and pH in the outlet decreased after high values in the two years after treatment. Although the model failed to match observed short-term data, it may simulate the long-term response as calcium is transported through the soil. A long-term simulation of the model suggests that effects of base treatment will persist for at least 50 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187146
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of watershed liming on the soil chemistry of Woods Lake, New York (1996)
    Springer
    Biogeochemistry 32 (1996), S. 175-194 
    Details
    ISSN: 1573-515X
    Keywords: acid mitigation ; exchangeable chemistry ; soil acidity ; soil chemistry ; watershed liming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The effects of watershed liming on the exchange complex of a forest soil were investigated at Woods Lake, in the west-central Adirondack Park, New York. Attempts to neutralize lake acidity via direct application of calcite during the 1980"s were short-lived due to a short hydraulic retention time. The Experimental Watershed Liming Study (EWLS) was initiated to investigate watershed base addition as a potentially more long-term strategy for mitigation of lake acidity. In this paper we discuss the changes in the exchangeable soil complex which occurred in response to the calcite addition and attempt a mass balance for calcite applied to the watershed. An extensive sampling program was initiated for the watershed study. Soil samples were collected from pits prior to and in the two years following treatment to evaluate changes in soil chemistry. Calcite addition significantly altered the exchange complex in the organic horizon. Increases in pH caused deprotonation of soil organic matter and increases in cation exchange capacity, providing additional exchange sites for the retention of added calcium. Exchangeable acidity decreased to very low values, allowing the base saturation of upper organic horizons to increase to nearly 100 percent. Post-treatment sampling found that approximately 48 percent of the calcite remained undissolved in the soil"s Oe horizon two years later. Dissolution of the calcite was affected by field moisture conditions, with greater dissolution in wetter areas of the watershed. Mass balances calculated for calcium applied to the watershed suggest that only 4 percent of the calcium was removed through the lake outlet. Approximately 96 percent of the calcium applied remained within the watershed; as undissolved calcite, on soil exchange sites or stored in the vegetation, groundwater or surface waters of the watershed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187138
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  • 9
    Electronic Resource
    Electronic Resource
    The relationship between surface water chemistry and geology in the North Branch of the Moose River (1987)
    Springer
    Biogeochemistry 3 (1987), S. 21-35 
    Details
    ISSN: 1573-515X
    Keywords: acidic deposition ; surficial geology ; flow paths
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The chemistry of lakes and streams within the North Branch of the Moose River is strongly correlated with the nature and distrubution of geologic materials in the watershed. The dominance of thin glacial till and granitic gneiss bedrock in the region north and east of Big Moose Lake results in a geologically sensitive terrain that is characterized by surface water with low alkalinity and chemical compositions only slightly modified from ambient precipitation. In contrast, extensive deposits of thick glacial till and stratified drift in the lower part of the system (e.g. Moss-Cascade valley) allow for much infiltration of precipitation to the groundwater system where weathering reactions increase alkalinity and significantly alter water chemistry. The hypothesis that surficial geology controls the chemistry of surface waters in the Adirondacks holds true for 70 percent of the Moose River watershed. Exceptions include the Windfall Pond subcatchment which is predominantly covered by thin till, yet has a high surface water alkalinity due to the presence of carbonate-bearing bedrock. The rapid reaction rates of carbonate minerals allow for complete acid neutralization to occur despite the short residence time of water moving through the system. Another important source of alkalinity in at least one of the subcatchments is sulfate reduction. This process appears to be most important in systems containing extensive peat deposits. An analysis of only those subcatchments controlled by the thickness of surficial sediments indicates that under current atmospheric loadings watersheds containing less than 3 percent thick surficial sediments will be acidic while those with up to 12 percent will be extremely sensitive to acidification and only those with over 50 percent will have a low sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185183
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  • 10
    Electronic Resource
    Electronic Resource
    The historical acceleration of the earth (1973)
    Springer
    Surveys in geophysics 1 (1973), S. 123-145 
    Details
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In this paper, we review the current state of knowledge about the acceleration of the Earth's spin, and about the closely related acceleration of the Moon. It is now established at a high confidence level that the acceleration of the Moon, when taken respect to Universal time, has changed by a large amount, and that it has even changed sign, within historic times. This almost certainly means that the acceleration of the Earth's spin has also changed by a large amount. At present we do not have enough information to say whether the changes have been in the contributions from tidal friction, in the contributions that do not arise from tidal friction, or both. Further, we do not know yet whether or not the variations in the Earth's rotation can account for the observed fluctuations in the longitudes of the Sun, the Moon, and the planets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01449760
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