D/H ratios in speleothem fluid inclusions: A guide to variations in the isotopic composition of meteoric precipitation?     

Russell S. Harmon  Henry P. Schwarcz  James R. O&#x;Neil 《Earth and Planetary Science Letters》1979,42(2):254-266

D/H ratios of fluid inclusion waters extracted from²³⁰Th/²³⁴U-dated speleothems that were originally deposited under conditions of isotopic equilibrium should provide a direct estimate of the hydrogen isotopic composition of ancient meteoric waters. We present here D/H ratios for 47 fluid inclusion samples from thirteen speleothems deposited over the past 250,000 years at cave sites in Iowa, West Virginia, Kentucky and Missouri. At each site glacial-age waters are depleted in deuterium relative to those of interglacial age. The average interglacial/glacial shift in the hydrogen isotopic composition of meteoric precipitation over ice-free areas of east-central North America is estimated to be ?12‰. This shift is consistent with the present climatic models and can be explained in terms of the prevailing pattern of atmospheric circulation and an increased ocean-continent temperature gradient during glacial times which more than compensated for the increase in deuterium content of the world ocean.  相似文献   

Acceptance speech for the V. M. Goldschmidt Medal     

Harmon Craig 《Geochimica et cosmochimica acta》1980,44(8):1234-1236

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Potential response of pacific northwestern forests to climatic change,effects of stand age and initial composition     

Dean L. Urban  Mark E. Harmon  Charles B. Halpern 《Climatic change》1993,23(3):247-266

We used an individual-based forest simulator (a gap model) to assess the potential effects of anthropogenic climatic change on conifer forests of the Pacific Northwestern United States. Steady-state simulations suggested that forest zones could be shifted on the order of 500–1000 m in elevation, which could lead to the local extirpation of some high-altitude species. For low-elevation sites, species which currently are more abundant hundreds of kilometers to the south would be favored under greenhouse scenarios. Simulations of transient responses suggested that forest stands could show complex responses depending on initial species composition, stand age and canopy development, and the magnitude and duration of climatic warming. Assumptions about species response to temperature, which are crucial to the model's behaviors, were evaluated using data on species temperature limits inferred from regional distributions. The high level of within-species variability in these data, and other confounding factors influencing species distributions, argue against over-interpreting simulations. We suggest how we might resolve critical uncertainties with further research.  相似文献   

LIBS analysis of geomaterials: Geochemical fingerprinting for the rapid analysis and discrimination of minerals     

Russell S. Harmon  Jeremiah Remus  Nancy J. McMillan  Catherine McManus  Leslie Collins  Jennifer L. Gottfried Jr.  Frank C. DeLucia  Andrzej W. Miziolek 《Applied Geochemistry》2009

Laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopy technique capable of real-time, essentially non-destructive determination of the elemental composition of any substance (solid, liquid, or gas). LIBS, which is presently undergoing rapid research and development as a technology for geochemical analysis, has attractive potential as a field tool for rapid man-portable and/or stand-off chemical analysis. In LIBS, a pulsed laser beam is focused such that energy absorption produces a high-temperature microplasma at the sample surface resulting in the dissociation and ionization of small amounts of material, with both continuum and atomic/ionic emission generated by the plasma during cooling. A broadband spectrometer-detector is used to spectrally and temporally resolve the light from the plasma and record the intensity of elemental emission lines. Because the technique is simultaneously sensitive to all elements, a single laser shot can be used to track the spectral intensity of specific elements or record the broadband LIBS emission spectra, which are unique chemical ‘fingerprints’ of a material. In this study, a broad spectrum of geological materials was analyzed using a commercial bench-top LIBS system with broadband detection from ∼200 to 965 nm, with multiple single-shot spectra acquired. The subsequent use of statistical signal processing approaches to rapidly identify and classify samples highlights the potential of LIBS for ‘geochemical fingerprinting’ in a variety of geochemical, mineralogical, and environmental applications that would benefit from either real-time or in-field chemical analysis.  相似文献   

Geochemistry of four tropical montane watersheds,Central Panama     

Russell S. Harmon  W. Berry Lyons  David T. Long  Fred L. Ogden  Helena Mitasova  Christopher B. Gardner  Kathleen A. Welch  Rebecca A. Witherow 《Applied Geochemistry》2009

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Radar imagery of the southern Caloris region, Mercury     

John K. Harmon 《Icarus》2008,196(1):298-301

Radar imagery from July 2005 Arecibo observations has provided new information on surface relief over the southern portion of Caloris Basin and the smooth plains to the south of the basin. A lobe of smooth plains has been identified in the Mariner-unimaged region southwest of Mozart Crater that coincides precisely with topographically down-bowed terrain seen in earlier Arecibo radar altimetry. A 105-km-diameter crater has been found at 193.6° W, 25.6° N that appears to be the largest crater in the Caloris basin floor.  相似文献   

ON CONFIDENCE INTERVALS FOR THE PRODUCT OF THREE MEANS OF THREE NORMALEY DISTRIBUTED POPULATIONS     

E.A.YFANTIS Computer Science Department  University of Neva  Las Vegas  NV  U.S.A.G.T.FLATMAN U.S.Environmental Protection Agency  E.Harmon  Las Vegas  NV  U.S.A. 《地理学报(英文版)》1991,(3)

In many environmental applications,such as exposure assessment and risk modelling,the desiredestimate is a random variable computed as the product of three independently distributed randomvariables.These variables may not necessarily have the same mean and variance.The method for findingthe 100(1-α)% confidence interval for the mean of the product random variable has been proposed bysome practitioners as the product of the 100(1-α)% confidence interval of the three means.In this paperwe show that the distribution of the product of three independent normal random variables is not normal.We find the mean and variance of the product distribution.Further,we show that although the meanof the product is equal to the product of the means,the product of the three confidence intervals is nota good approximation of the confidence intervals for the mean of the product variable.The confidenceinterval of the mean of the product variable may be estimated by computer simulation.An algorithmfor estimating the confidence interval for the mean of the product random variable is given.The programimplementing this algorithm is given as an appendix.  相似文献   

FACTOR ANALYSIS OF ELEMENTAL ABUNDANCES IN CHONDRITIC AND ACHONDRITIC METEORITES     

Dennis M. Shaw  Russell S. Harmon 《Meteoritics & planetary science》1975,10(3):253-282

Another explorative study of the use of factor analysis in meteorite geochemistry has been made. Forty-two major and trace elements were sought from analyses of 80 stony meteorites in recent articles. Incomplete data reduced the matrix to 30 elements in 55 stones. Missing data were substituted by mean values in the groups CC, (E+H+L+LL) and ACH (13, 28, 14 individuals, respectively): the effect of these substitutions was tested empirically. R-mode analysis with varimax rotation was carried out on these three sub-sets and on the whole set: interpretation focused on factor loadings and scores. Results on the three sub-sets gave little information of geochemical value, although the largest achondrite factor (lithophile elements) permits discrimination of eucrites, aubrites, diogenites and howardites. Analysis of all 55 meteorites showed the variance to be dominated by 1, a refractory-lithophile(Al, Mg, Ca, Zr, Sc, U, Th, La, Eu, Yb) factor, and 2, a volatile-chalcophile (Zn, Te, Cd, Bi, Tl) factor. Factor (1) scores will discriminate chondrites from achondrites: factor (2) scores delineate the compositional trend CC1, CC2, CC3, (E+H+L+LL) except for enstatite chondrites Indarch, Abee which fall with CC1. Further progress would need metal, sulphide and other mineral percentages for each meteorite.  相似文献   

Real-time model parameter estimation for analyzing transport in porous media   总被引：3，自引：0，他引：3  

Juyoul Kim  Yeonjeong Park  Thomas C. Harmon 《Ground Water Monitoring & Remediation》2005,25(2):78-86

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O/O ratios in anhydrous spinel lherzolite xenoliths from the Shavaryn-Tsaram volcano, Mongolia     

R.S. Harmon  P.D. Kempton  H.-G. Stosch  J. Hoefs  V.I. Kovalenko  D. Eonov 《Earth and Planetary Science Letters》1987,81(2-3)

Anhydrous spinel lherzolite xenoliths from the Shavaryn-Tsaram volcano, which represent unusually clinopyroxenerich samples of upper mantle beneath the Tariat Depression in north-central Mongolia, have particularly low δ¹⁸O values of +4.9 to +5.7‰ SMOW. Constituent minerals exhibit small (ca. 0.5–0.7‰) variations in¹⁸O content (olivine = +4.6 to +5.3‰, clinopyroxene = +5.6 to +6.1‰, orthopyroxene = +5.8 to +6.5‰), that are unrelated to xenolith modal mineralogy, chemical composition, radiogenic isotope character, or pyroxene equilibration temperature. This O-isotope character of the Tariat xenoliths is interpreted to reflect the closed-system distribution of oxygen isotopes in a slowly cooling mantle diapir emplaced into the lithosphere from a relatively primitive region of the asthenosphere.  相似文献