The upper thermal stability of clinochlore,Mg5Al[AlSi3O10](OH)8, at 10–35 kb P_{{\text{H}}_{\text{2}} {\text{O}}}     

Hubert Staudigel  Werner Schreyer 《Contributions to Mineralogy and Petrology》1977,61(2):187-198

Clinochlore, which is, within the limits of error, the thermally most stable member of the Mg-chlorites, breaks down at = P _tot to the assemblage enstatite+forsterite+spinel+H₂O along a univariant curve located at 11 kb, 838 ° C; 15kb, 862 ° C; and 18 kb, 880 ° C (±1 kb ±10 ° C). At water pressures above that of an invariant point at 20.3 kb and 894 ° C involving the phases clinochlore, enstatite, forsterite, spinel, pyrope, and hydrous vapor, clinochlore disintegrates to pyrope+forsterite+spinel+H₂O. The resulting univariant curve has a steep, negative dP/dT slope of –930 bar/ °C at least up to 35 kb.Thus, given the proper chemical environment, Mg-chlorites have the potential of appearing as stable phases within the earth's upper mantle to maximum depths between about 60 and 100 km depending on the prevailing undisturbed geotherm, and to still greater depths in subduction zones. However, unequivocal criteria for mantle derived Mg-chlorites are difficult to find in ultrabasic rocks.  相似文献   

Zur Sedimentologie eines arktischen Deltas (Colville Delta,Nordalaska)     

Dr. Werner Fürbringer 《International Journal of Earth Sciences》1977,66(1):577-614

Zusammenfassung Im August 1971 wurden vom Verfasser Feldarbeiten zur Sedimentologie des Colville Deltas, Alaska, durchgeführt. Aus subaquatischen Typlokalitäten wurden Probenkerne gezogen und auf Strukturen, Korngrößen und Mineralogie hin untersucht. Neben konventionellen Labormethoden kamen moderne elektronische Verfahren zum Einsatz (Röntgenradiographie, Röntgendiffraktometrie, Elektronenmikroskopie). Die Arbeiten sind Teil eines Programmes, dessen Gesamtleitung Prof. Dr. H. J. Walker, Baton Rouge, USA, hatte und das unterstützt wurde von: Arctic Program and Geography Programs, Office of Naval Research.

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In August 1971, sedimentological field work was carried out by the author in the Colville River delta, Alaska. Short cores were taken from several deltaic environments and analyzed for structure and composition. Laboratory analysis included both conventional laboratory methods and modern electronic techniques (radiography, X-ray diffractometry, electron microscopy). The research reported is part of a program headed by Prof. Dr. H. J. Walker, Baton Rouge, USA, and was supported by the Arctic Program and Geography Programs, Office of Naval Research.

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Résumé En auguste 1971 l'auteur a étudié sur le terrain la sédimentologie du delta de Colville (Alaska). On a prélevé des échantillons dans des profiles de divers environnements typiques; on en a examiné les structures et la composition par les méthodes traditionelles et électroniques (rayons X, radiographie et diffractométrie, microscope électronique). Ces investigations font partie d'un programme sous la direction du Prof. Dr. H. J. Walker, Baton Rouge, USA, subventionné par »Arctic Program and Geography Programs, Office of Naval Research«.

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1971 . , . , . , - , . , . . H. J. Walker, Baton Rouge, USA Arctic Program, and Geography Programs, Office of Naval Research.

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Fatty acids and Pb-210 geochronology of a sediment core from Buzzards Bay,Massachusetts     

John W Farrington  Susan M Henrichs  Robert Anderson 《Geochimica et cosmochimica acta》1977,41(2):289-296

Four sections of a Pb-210 dated core of 62 cm length from Buzzards Bay, Massachusetts, were analyzed for fatty acids. A comparison of fatty acids extracted by Soxhlet extraction (unbound fatty acids) with fatty acids extracted by subsequent saponification extraction of the same sample (bound fatty acids) showed the former did not undergo diagenetic loss any faster than the latter. However, compositional differences between bound and unbound fatty acids were apparent in the top section of 1–2 cm and were less apparent in the 54–58 cm section. At least 14% of the bound fatty acids are esterified to non-solvent extractable material. The net conversion of fatty acids to other compounds is 32 μ/g dry weight sediment over the first 30 yr after deposition.  相似文献   

Seismic reflection coefficients from mantle fault zones   总被引：3，自引：0，他引：3  

Mike Warner &  Susan McGeary 《Geophysical Journal International》1987,89(1):223-230

Summary. Several bright reflections from structures within the mantle can be seen on BIRPS' deep seismic reflection profiles. We have calculated apparent reflection coefficients for the brightest of these events and obtain values around 0.1. It is not possible to produce such large reflections by either compositional layering or seismic anisotropy if olivine and pyroxene are the only significant minerals in the mantle. These large reflections can be produced by a mafic layer or a partially hydrated layer within normal peridotite. The brightest reflections seem to be best explained as major faults or shear zones within the mantle.  相似文献   

Assessing possible changes in flood frequency due to climate change in mid‐sized watersheds in New York State,USA     

Stephen B. Shaw  Susan J. Riha 《水文研究》2011,25(16):2542-2550

The frequency of flooding is often presumed to increase with climate change because of projected increases in rainfall intensities. In this paper, using 50‐plus years of historical discharge and meteorological data from three watersheds in different physiographic regions of New York State, USA, we find that annual maximum stream discharges are associated with 20% or less of the annual maximum rainfall events. Instead of rainfall events, approximately 20% of annual maximum stream discharges are associated with annual maximum snowmelt events while 60% of annual maximum discharges are associated with moderate rainfall amounts and very wet soil conditions. To explore the potential for changes in future flood risk, we employed a compound frequency distribution that assumes annual maximum discharges can be modelled by combining the cumulative distribution functions of discharges resulting from annual maximum rainfall, annual maximum snowmelt, and occurrences of moderate rain on wet soils. Basing on a compound frequency distribution comprised of univariate general extreme value (GEV) and gamma distributions, we found that a hypothetical 20% increase in the magnitude of rainfall‐related stream discharge results in little change in 96th percentile annual maximum discharge. For the 99th percentile discharge, two waterbodies in our study had a 10% or less increase in annual maximum discharge when annual maximum rainfall‐related discharges increased 20% while the third waterbody had a 16% increase in annual maximum discharges. Additionally, in some cases, annual maximum discharges could be offset by a reduction in the discharge resulting from annual maximum snowmelt events. While only intended as a heuristic tool to explore the interaction among different flood‐causing mechanisms, use of a compound flood frequency distribution suggests a case can be made that not all waterbodies in humid, cold regions will see extensive changes in flooding due to increased rainfall intensities. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

On model integration in operational flood forecasting     

Micha Werner  Doug Whitfield 《水文研究》2007,21(11):1519-1521

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Salinograph trends as indicators of the recession characteristics of stream components     

A. D. Werner  M. Wood  C. T. Simmons  D. A. Lockington 《水文研究》2008,22(16):3020-3028

Compared to hydrograph recession analysis, which is widely applied in engineering hydrology, the quantitative assessment of stream salinity with time (i.e. the salinograph) has received significantly less attention. In particular, while in many previous hydrological studies an inverse relationship between hydrograph and salinograph responses is apparent, the concept of salinity accession (the inversely related salinity counterpart to hydrograph recession) has not been introduced nor quantitatively evaluated in previous literature. In this study, we conduct a mathematical analysis of salinograph accession, and determine new quantitative relationships between salinity accession and hydrograph recession parameters. An equation is formulated that reproduces the general trend in salinity accession. A salinity accession parameter k_c is then introduced and is shown to be the ratio of direct runoff to total stream flow recession parameters: k_r/k. The groundwater recession parameter k_g was estimated using a simple and rapid method that uses both salinograph and hydrograph data. Salinity accession type‐curves illustrate that under certain conditions, the relative steepness of individual salinographs is dependent upon the ratio of groundwater salinity to direct runoff salinity: C_g/C_r. The salinity accession algorithms are applied to two contrasting field settings: Scott Creek, South Australia and Sandy Creek, northern Queensland, Australia. It was found that k_g > k during periods of obvious stream flow recession, for the events analysed. Salinograph accession behaviour was fairly similar for both sites, despite contrasting environments. Using assumed end‐member salinities for groundwater and direct runoff based upon field observations, the behaviour of k_c from the Scott Creek site was approximately reproduced by varying the initial groundwater to runoff flow ratio: Q_g0/Q_r0, within reasonable parameter ranges. The use of salinograph information when used in addition to standard hydrograph analyses provided useful information on recession characteristics of stream components. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Charcoal and fossil wood from palaeosols,sediments and artificial structures indicating Late Holocene woodland decline in southern Tibet (China)     

Knut Kaiser  Lars Opgenoorth  Werner H. Schoch  Georg Miehe 《Quaternary Science Reviews》2009,28(15-16):1539-1554

Charcoal and fossil wood taken from palaeosols, sediments and artificial structures were analysed in order to evaluate the regional pedoanthracological potential and to obtain information on Holocene environmental changes, particularly on possible past tree occurrences in southern Tibet. This research was initiated by the question to what extent this area is influenced by past human impact. Even recent evaluations have perceived the present treeless desertic environment of southern Tibet as natural, and the previous Holocene palaeoenvironmental changes detected were predominantly interpreted to be climate-determined. The material analysed – comprising a total of 53 botanical spectra and 55 radiocarbon datings from 46 sampling sites (c. 3500–4700 m a.s.l.) – represents the largest systematically obtained data set of charcoal available from Tibet so far. 27 taxa were determined comprising trees, (dwarf-) shrubs and herbs as well as grasses. The predominant tree taxa were Juniperus, Hippophae, Salix and Betula. According to their present-day occurrence in the region, the genera Juniperus and Hippophae can be explicitly attributed to tree species. Further, less frequently detected tree taxa were Populus, Pinus, Quercus, Taxus and Pseudotsuga. Charcoal of Juniperus mainly occurred on southern exposures, whereas Betula was associated with northern exposures. In contrast, the (partly) phreatophytic taxa Hippophae and Salix showed no prevalent orientation. The distribution of radiocarbon ages on charcoal revealed a discontinuous record of burning events cumulating in the Late Holocene (c. 5700–0 cal BP). For southern Tibet, these results indicated a Late Holocene vegetation change from woodlands to the present desertic pastures. As agrarian economies in southern and south-eastern Tibet date back to c. 3700 and 5700 cal BP, respectively, and the present-day climate is suitable for tree growth up to c. 4600 m a.s.l., we concluded that the Late Holocene loss or thinning out of woodlands had been primarily caused by humans.  相似文献   

Correspondence analysis of water quality data: Implications for fauna deaths at Stillwater Lakes, Nevada     

Susan G. Oleson  James R. Carr 《Mathematical Geology》1990,22(6):665-698

Over the last 2 years, more than seven million fish and 16,000 birds have died from drought-induced disease and suspected poisoning at Stillwater Lakes, Nevada. Correspondence analysis of water samples taken in June and September 1986, from lakes and reservoirs near Stillwater Lakes and four background lakes/reservoirs (not associated with fauna disease and death), is attempted to investigate the correlation among sites associated with fauna deaths. This analysis identifies high correlation between some Stillwater Lakes sites and boron. A correlation between boron and arsenic is also identified. Leaching and transport of toxins to the Stillwater Lakes system is one hypothesis to explain the wildlife deaths. Other hypotheses include the direct introduction of toxins by groundwater associated with geothermal activity. A natural cause for the wildlife deaths is also suggested, a cause not associated with the introduction of toxins.  相似文献   

INTEGRAL/XMM views on the MeV source GRO J1411-64     

Diego F. Torres  Shu Zhang  Olaf Reimer  Xavier Barcons  Amalia Corral  Valentí Bosch-Ramon  Josep M. Paredes  Gustavo E. Romero  Jin Qu  Werner Collmar  Volker Schönfelder  Yousaf Butt 《Astrophysics and Space Science》2007,309(1-4):17-21

The COMPTEL unidentified source GRO J 1411-64 was observed by INTEGRAL and XMM-Newton in 2005. The Circinus Galaxy is the only source detected within the 4σ location error of GRO J1411-64, but in here excluded as the possible counterpart. At soft X-rays, 22 reliable and statistically significant sources (likelihood >10) were extracted and analyzed from XMM-Newton data. Only one of these sources, XMMU J141255.6-635932, is spectrally compatible with GRO J1411-64 although the fact the soft X-ray observations do not cover the full extent of the COMPTEL source position uncertainty make an association hard to quantify and thus risky. At the best location of the source, detections at hard X-rays show only upper limits, which, together with MeV results obtained by COMPTEL suggest the existence of a peak in power output located somewhere between 300–700 keV for the so-called low state. Such a spectrum resembles those in blazars or microquasars, and might suggest at work by the models accordingly. However, an analysis using a microquasar model consisting on a magnetized conical jet filled with relativistic electrons, shows that it is hard to comply with all observational constrains. This fact and the non-detection at hard X-rays introduce an a-posteriori question mark upon the physical reality of this source, what is discussed here.  相似文献