Evolution of the Seven Devils Volcanic Arc and Period of Amalgamation with the North American Craton Based on Zircon U/Pb Geochronology and Hf Isotope Geochemistry of Intrusions in the Seven Devils Mountains,Western Idaho (USA)     

Casares  H. L.  Nicholson  K. N.  Malone  Sh. J. 《Geotectonics》2021,55(2):293-306

Geotectonics - The Seven Devils Mountains are located in the Wallowa-Whitman National Forest in western Idaho. These mountains expose a geologically complex and variably metamorphosed terrane which...  相似文献   

Early Mesoproterozoic evolution of midcontinental Laurentia: Defining the geon 14 Baraboo orogeny     

L. Gordon Medaris  Brad S. Singer  Brian R. Jicha  David H. Malone  Joshua J. Schwartz  Esther K. Stewart  Amanda Van Lankvelt  Michael L. Williams  Peter W. Reiners 《地学前缘(英文版)》2021,12(5):101174

New geochronologic data from midcontinental Laurentia demonstrate that emplacement of the 1476-1470 Ma Wolf River granitic batholith was not an isolated igneous event,but was accompanied by regional metamorphism,deformation,and sedimentation.Evidence for such metamorphism and deformation is best seen in siliciclastic sedimentary rocks of the Baraboo Interval,which were deposited closely following the1.65-1.63 Ga Mazatzal orogeny.In Baraboo Interval strata,muscovite parallel to slatey cleavage,in hydrothermal veins,in quartzite breccia,and in metamorphosed paleosol yielded ~(40)Ar/~(39)Ar plateau age s of 1493-1465 Ma.In addition,U-Th-total Pb dating of neoblastic overgrowths on detrital monazite gave an age of 1488±20 Ma,and recrystallized hematite in folded metapelite gave a mean U/Th-He age of 1411± 39 Ma.Post-Baraboo,arkosic polymictic conglomerate,which contains detrital zircon with a minimum peak age of 1493 Ma,was intruded by a 1470 Ma granite porphyry at the northeastern margin of the Wolf River batholith.This episode of magmatism,regional deformation and metamorphism,and sedimentation,which is designated herein as the Baraboo orogeny,provides a midcontinental link between the Picuris orogeny to the southwe st and the Pinware orogeny to the northeast,completing the extent of early Mesoproterozoic(Calymmian) orogenesis for 5000 km along the southern margin of Laurentia.This transcontinental orogen is unique among Precambrian orogenies for its great width(～1600 km),the predominance of ferroan granites derived from partial melting of lower continental crust,and the prevalence of re gional high T-P metamorphism related to advective heating by granitic magmas emplaced in the middle to upper crust.  相似文献   

SOLAR ENERGETIC ION AND ELECTRON LIMITS FROM HIREGS OBSERVATIONS     

Feffer  P. T.  Lin  R. P.  Slassi-Sennou  S.  McBride  S.  Primbsch  J. H.  Zimmer  G.  Pelling  R. M.  Pehl  R.  Madden  N.  Malone  D.  Cork  C.  Luke  P.  Vedrenne  G.  Cotin  F. 《Solar physics》1997,171(2):419-445

The HIgh-REsolution Gamma-ray and hard X-ray Spectrometer (HIREGS) consists of an actively shielded array of twelve liquid-nitrogen-cooled germanium detectors designed to provide unprecedented spectral resolution and narrow-line sensitivity for solar gamma-ray line observations. Two long-duration, circumpolar balloon flights of HIREGS in Antarctica (10–24 January, 1992 and 31 December, 1992–10 January, 1993) provided 90.9 and 20.4 hours of solar observations, respectively. During the observations, eleven soft X-ray bursts at C levels and above (largest M1.7) occurred, and three small solar hard X-ray bursts were detected by the Compton Gamma-Ray Observatory. HIREGS detected a significant increase above 30 keV in one. No solar gamma-ray line emission was detected. Limits on the 2.223-MeV line and the hard X-ray emission are used to estimate the relative contribution of protons and electrons to the energy in flares, and to coronal heating. For the 2.223-MeV line, the upper limit fluence is 0.8 ph cm^-2 in the flares, and the upper limit flux is 1.8 × 10^-4 ph s^-1 cm^-2 in the absence of flares. These limits imply that 6 × 10³⁰ (2) protons above 30 MeV were accelerated in the flares, assuming standard photospheric abundances and a thick target model. The total energy contained in the accelerated protons >30 MeV is 4 × 10²⁶ ergs, but this limit can be more than 10³⁰ ergs if the spectrum extends down to 1 MeV. The upper limit on the total energy in accelerated electrons during the observed flares can also exceed 10³⁰ ergs if the spectrum goes down to 7 keV. Quiet-Sun observations indicate that 10²⁶erg s^-1 are deposited by energetic protons >1 MeV, well below the10²⁷ –10²⁸ erg s^-1 required for coronal heating, while <3 × 10²⁷ erg s^-1 are deposited by energetic electrons, which does not exclude the possibility of coronal heating by quiet-time accelerated electrons. The quiet-Sun observations also suggest that if protons stored in the corona are to supply the energy for flares, as suggested by Elliot (1964), the proton spectrum must extend down to at least 2 MeV. However, collisional losses at typical coronal-loop densities prevent those low-energy protons from being stored for 10⁴ s. It therefore seems unlikely that the energy for flares could come from energetic protons stored over long periods.  相似文献   

The oxygen isotopic composition and temperature of Southern Ocean bottom waters during the last glacial maximum     

Mitchell J Malone  Jonathan B Martin  Ulysses S Ninnemann  Timothy S White 《Earth and Planetary Science Letters》2004,222(1):275-283

We provide two new determinations of the oxygen isotopic composition of seawater during the last glacial maximum (LGM). High-resolution oxygen isotopic measurements were made on interstitial waters from Ocean Drilling Program (ODP) Sites 1168 and 1170 in the southeast Indian Ocean sector of the Southern Ocean. We use a diffusion-advection numerical model to calculate the glacial-interglacial change in bottom-water δ¹⁸O_sw from the pore water δ¹⁸O profiles; the first such determinations from this part of the oceans. Statistical analyses of the model runs indicate that Circumpolar Deep Water (CDW) δ¹⁸O_sw changed by 1.0-1.1±0.15‰ since the last glacial maximum (LGM). Our results are consistent with a previous calculation from a South Atlantic Southern Ocean location (ODP Site 1093) also situated within CDW. The new values determined in this study, together with previous estimates, are converging on a global average Δδ¹⁸O_sw of 1.0-1.1‰.Using the calculated bottom-water δ¹⁸O_sw, we have extracted the temperature component from the benthic foraminiferal δ¹⁸O record at Sites 1168 and 1170. Since the LGM, bottom waters at these two sites warmed by 2.6 and 1.9°C, respectively. The absolute temperature estimates for the LGM (−0.5°C [Θ=−0.6°C] at Site 1168 and −0.2°C [Θ=−0.4°C] at Site 1170) are slightly warmer than those reported from previous studies using the same technique, but are consistent with more homogenous deep-ocean temperatures during the LGM relative to the modern.  相似文献   

Magma supply, magma discharge and readjustment of the feeding system of mount St. Helens during 1980     

Roberto Scandone  Stephen D. Malone 《Journal of Volcanology and Geothermal Research》1985,23(3-4)

The landslide and cataclysmic eruption of Mount St. Helens on May 18, 1980 triggered a sequence of explosive eruptions over the following five months. The volume of explosive products from each of these eruptions decreased uniformly over this period, and the character for each eruption progressed from a fairly continuous eruption lasting more than eight hours on May 18 to a series of short bursts, some of which were spaced 12 hours apart, on October 16–18. The transition in the character of these eruption sequences can be explained by a difference between the magma supply rate and the magma discharge rate from a shallow reservoir.The magma supply rate (MSR) is the rate with which magma is supplied to the level where disruption due to vesiculation occurs. It is determined by dividing the dense-rock-equivalent volume of eruptive products by the total duration of each eruption sequence. The magma discharge rate (MDR) is the rate with which the disrupted magma is discharged through the vent. It is determined by dividing the volume of erupted products by the duration of each explosive burst. The relative magnitude of these two quantities controls the temporal evolution of an explosive event. When MDRMSR the explosive phase of the eruption lasts for several hours as a single continuous event. When MDR>MSR, an eruption is characterized by a series of short explosive bursts at intervals of several minutes to several days. The MSR of the eruptions of 1980 decreased with time from 5500 m' s⁻¹ on May 18 to 7 m³ s⁻² on October 16–18 and approximately fits an exponential decay. The MDR for the same events remained approximately constant at 2000 m³ s⁻¹. Each explosive event has been followed by an aftershock-like series of earthquakes located beneath the volcano at depth mostly between 7 and 14 km. The seismic energy released during each of these series is proportional to the corresponding volume of erupted magma. Deformation data between June and November, 1980 indicate a subsidence of the volcanic structure which can be modeled by a volume collapse of 0.25 km³ located at 9 km depth.We propose a model in which magma is supplied from depths of 7–14 km through a narrow conduit during each eruption. It erupts to the surface at a uniform rate during each eruption. The deep seismic activity following each eruption is related to a readjustment and volume decrease in the deep feeding system. The decrease of the MSR over time is explained by an increase in the viscosity of a progressively water-depleted magma. The amount of water necessary to explain the observed decrease of the MSR is of the order of 4.6%.  相似文献   

Paperback, vii + 359 pp, £24.95Fred G. Bell, Engineering Geology , Blackwell Scientific Publications Ltd., Rotterdam, The Netherlands (1993) ISBN 0-632-03223-5.     

A.W. Malone 《Engineering Geology》1994,36(3-4):316-317

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Possibility of ground observations of electron spin-flip radiation from lowerE-region electrons     

J. Renau  D. P. Malone 《Pure and Applied Geophysics》1963,55(1):115-118

Summary Landovitz & Marshall (¹) have suggested a maserlike mechanism to explain the decameter emission from the Jovian ionosphere. Although the application of the suggested mechanism for emission outwards into space from our planet is obvious, it is our purpose to show that if this mechanism is indeed operative, emission of electron spin-flip radiation from the electrons in the lower part of theE-region is also possible. An order of magnitude estimate predicts that thisE-region radiation which travels downward can be observed by ground receivers.  相似文献   

Vegetation succession in deglaciated landscapes: implications for sediment and landscape stability          下载免费PDF全文

Megan J. Klaar  Chris Kidd  Edward Malone  Rebecca Bartlett  Gilles Pinay  F. Stuart Chapin  Alexander Milner 《地球表面变化过程与地形》2015,40(8):1088-1100

Landscapes exposed by glacial retreat provide an ideal natural laboratory to study the processes involved in transforming a highly disturbed, glacially influenced landscape to a stable, diverse ecosystem which supports numerous species and communities. Large‐scale vegetation development and changes in sediment availability, used as a proxy for paraglacial adjustment following rapid deglaciation, were assessed using information from remote sensing. Delineation of broad successional vegetation cover types was undertaken using Landsat satellite imagery (covering a 22 year period) to document the rate and trajectory of terrestrial vegetation development. Use of a space‐for‐time substitution in Glacier Bay National Park, Alaska, allowed ‘back‐calculation’ of the age and stage of development of six catchments over 206 years. The high accuracy (89.2%) of the remotely sensed information used in monitoring successional change allowed detection of a high rate of change in vegetation classes in early successional stages (bare sediment and alder). In contrast, later successional stages (spruce and spruce–hemlock dominated forest) had high vegetation class retention, and low turnover. Modelled rates of vegetation change generally confirmed the estimated rates of successional turnover previously reported. These data, when combined with the known influence of terrestrial succession on soil development and sediment availability, suggest how physical and biological processes interact over time to influence paraglacial adjustment following deglaciation. This study highlights the application of remote sensing of successional chronosequence landscapes to assess the temporal dynamics of paraglacial adjustment following rapid deglaciation and shows the importance of incorporating bio‐physical interactions within landscape evolution models. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Modeling Vulnerability and Resilience to Climate Change: A Case Study of India and Indian States   总被引：2，自引：1，他引：2  

Antoinette L. Brenkert  Elizabeth L. Malone 《Climatic change》2005,72(1-2):57-102

The vulnerability of India and Indian states to climate change was assessed using the Vulnerability-Resilience Indicator Prototype (VRIP). The model was adapted from the global/country version to account for Indian dietary practices and data availability with regard to freshwater resources. Results (scaled to world values) show nine Indian states to be moderately resilient to climate change, principally because of low sulfur emissions and a relatively large percentage of unmanaged land. Six states are more vulnerable than India as a whole, attributable largely to sensitivity to sea storm surges. Analyses of results at the state level (Orissa, and comparisons between Maharashtra and Kerala, and Andhra Pradesh and Himachal Pradesh) demonstrate the value of VRIP analyses used in conjunction with other socio-economic information to address initial questions about the sources of vulnerability in particular places. The modeling framework allows analysts and stakeholders to systematically evaluate individual and sets of indicators and to indicate where the likely vulnerabilities are in the area being assessed.  相似文献   

Emplacement age of the Markagunt gravity slide in southwestern Utah,USA     

McKenna E. Holliday  Tiffany Rivera  Brian Jicha  Robin B. Trayler  Robert F. Biek  Michael J. Braunagel  W. Ashley Griffith  David B. Hacker  David H. Malone  Danika F. Mayback 《地学学报》2023,35(1):66-72

The Markagunt gravity slide (MGS) is a large-volume landslide in southwestern Utah that originated within the Oligocene-Miocene Marysvale volcanic field. Gravity slides are single emplacement events with long runout distances and are now recognized as a new class of volcanic hazard. Accumulation of volcanic material on a structurally weak substrate along with voluminous shallow intrusive events led to collapse. Here, ⁴⁰Ar/³⁹Ar data for landslide-generated pseudotachylyte, the landslide-capping Haycock Mountain Tuff and the deformed Osiris Tuff are combined with a Bayesian age model to determine an emplacement age of 23.05 + 0.22/−0.20 Ma for the MGS. The results suggest a lag time of <200 kyr between the caldera-forming eruption of the Osiris Tuff, additional buildup of the unstable volcanic pile and subsequent mass movement.  相似文献