The age,extent and geomorphological significance of the Sassafras basalt,south‐eastern New South Wales     

R. W. Young  Ian McDougall 《Australian Journal of Earth Sciences》2013,60(4):323-331

Basalt at Sassafras was erupted in the Middle Eocene. The K‐Ar ages average 45.3 ± 4.9 Ma on whole rock and 48.4 ± 1.9 Ma on plagioclase. The basalt is not limited to a plateau capping, but extends 150 m down into adjacent valleys. Comparison with nearby Eocene basalts shows that there was in excess of 250 m of local relief in the central Shoalhaven valley by the Early Tertiary. The basalts were extruded at high elevation, and denudation of the coastal margin of the upland was already well advanced. Post‐basaltic denudation has been very slow, and the Early Tertiary landscape is well preserved.  相似文献   

Late Holocene vertical land motion and relative sea‐level changes: lessons from the British Isles     

Ian Shennan  Glenn Milne  Sarah Bradley 《第四纪科学杂志》2012,27(1):64-70

Vertical land motion caused by continuing glacial isostatic adjustment is one of several important components of sea‐level change and is not limited just to previously glaciated regions. A national‐scale analysis for the British Isles shows an ellipse of present‐day relative uplift (relative sea‐level fall), ～1.2 mm a^?1, broadly centred on the deglaciated mountains of Scotland. The pattern of three foci of relative subsidence, ～1 mm a^?1, results from the additional interactions of the deglacial meltwater load on the Atlantic basin and the continental shelf, and the signal due to far‐field ice sheets. At a local scale, sediment compaction can more than double the rate of relative land subsidence. Relative land‐level change (the negative of relative sea‐level change) is not the same as vertical land motion. There is a spatial pattern in the difference between relative land‐level change and vertical land motion, with differences at present of approximately ?0.1 to ?0.3 mm a^?1 around the British Isles and +2.5 to ?1.5 mm a^?1 globally. For the wider scientific and user community, whether or not the differences are considered significant will depend upon the location, time frame and spatial scale of the study that uses such information. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Epikarst hydrology and implications for stalagmite capture of climate changes at Grotta di Ernesto (NE Italy): results from long‐term monitoring     

Renza Miorandi  Andrea Borsato  Silvia Frisia  Ian J. Fairchild  Detlev K. Richter 《水文研究》2010,24(21):3101-3114

Grotta di Ernesto is a cave site well suited for palaeoclimate studies because it contains annually laminated stalagmites and was monitored from 1995 to the end of 2008 for microclimate, hydrology and hydrochemistry. Long‐term monitoring highlighted that cave drips show three different hydrological responses to rainfall and infiltration: (1) fast seasonal drips in the upper part of the cave, which are mostly fed by fractures, (2) slow seasonal drips, located at mid‐depth in the cave characterized by mixed feeding and (3) slow drips, mostly located in the deeper gallery, which are fed by seepage flow from bulk porosity with a minor fracture‐fed component. The slow drips display daily cycles during spring thaw. Monitoring also indicated that drip waters are only slightly modified by degassing within the soil zone and aquifer and by prior calcite precipitation. Hydrochemical studies show a clear seasonality in calcite saturation index, which results in most cave calcite precipitation occurring during late autumn and winter with similar amounts of precipitated calcite on most stalagmites, regardless of drip rate (discharge) differences. Drip rate, and drip rate variability, therefore, has a minor role in modulating the amount of annual calcite formation. In contrast, drip rate, when associated with moderate reduction in calcite saturation index, clearly influences stalagmite morphology. Increasing drip rate yields a passage from candle‐, to cone‐ to dome‐shaped stalagmites. Very high drip rates feed speleothems with flowstone morphology. In summary, monitoring provides information about the karst aquifer and how hydrology influences those physical and chemical characteristics of speleothems which are commonly used as climate proxies. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Chronology of the pressure-temperature history recorded by a granulite terrain   总被引：5，自引：1，他引：5  

A. S. Cohen  R. K. O'Nions  R. Siegenthaler  W. L. Griffin 《Contributions to Mineralogy and Petrology》1988,98(3):303-311

Coronite-bearing anorthositic granulites consisting of olivine, orthopyroxene, clinopyroxene, garnet and plagioclase assemblages are particularly well preserved at Gaupås and Holsnöy in the Bergen Arc of West Norway. The coronites are considered to have formed near T= 900° C and P=10 Kb by two stages of subsolidus reaction from an anorthositic gabbro parent. The first reaction involved ol+plagcpxI+opxI+sp and the second cpxI+opxI+sp+plcpxII+opxII+gn. The incomplete reaction products are preserved to varying extents in different corona structures. Sm-Nd isotopic data for each of four coronas yield precise isochrons, and demonstrate isochronism both between the constituent phases of the corona assemblages and dispersed ground mass phases. Three individual coronas not associated with shear zones yield ages of 907±9 my, 912±18 my and 905±37 my. Eclogite facies mineralogy is developed locally in shear zones, which are shown by Sm-Nd and Rb-Sr analyses to be Caledonian in age. Where relict corona structures survive unsheared within these zones, Nd exchange between the constituent phases cannot be resolved. This observation together with sympathetic Ca/Mg and Sm/Nd zoning preserved at T900° C in the garnet mantles of coronites places a limit on the diffusivity of Nd in pyropic garnets which is no higher than published experimental values for Mg in pyrope-almandine garnets. Consequently even in slowly-cooled granulite terrains, garnet grains are expected to yield Sm-Nd chronologies very close to the time of mineral growth.  相似文献   

Determination of the Rare-Earth Elements and Yttrium In 37 International Silicate Reference Materials By Inductively Coupled Plasma-Atomic Emission Spectrometry     

Kym E. JARVIS  Ian JARVIS 《Geostandards and Geoanalytical Research》1988,12(1):1-12

The rare-earth elements (REE) and yttrium have been determined in 37 international rock and mineral reference materials. Samples were prepared using conventional rock-dissolution techniques, and the REE and yttrium were separated from the other constituents using cation-exchange chromatography. The REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) and yttrium were determined simultaneously by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Results for four well-characterised USGS standard rocks agree favourably with "recommended" values and with REE determinations made previously by workers using ICP-AES, isotope dilution mass spectrometry, instrumental neutron activaton analysis and X-ray fluorescence spectrometry.
Les éléments de terres rares (TR) et yttrium ont été dosés dans 37 échantillons internationaux de réféence. Les échantillons ont été décomposés par dissolution acide et les TR séparés par résine échangeuse de cations. Les TR (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) et yttrium ont été dosés simultanément par la spectrométrie d'émission-plasma inductif. Les résultats obtenus pour quatre échantillons de référence bien charactérisés de I'USGS se comparent favorablement avec ceux obtenus par la spectrométrie d'émission-plasma, la dilution isotopique, I'activation neutronique et par la spectrométrie d'é fluorescence-X.  相似文献   

Limitations and feasibility of the land disposal of organic solvent-contaminated wastes     

W. R. Roy  R. A. Griffin  J. K. Mitchell  R. A. Mitchell 《Environmental Geology》1989,13(3):225-231

The limitations and feasibility of the land disposal of solid wastes containing organic solvents and refrigerants (chlorinated fluorocarbons) were investigated by evaluating the attenuation capacity of a hypothetical waste-disposal site by numerical modeling. The basic theorem of this approach was that the land disposal of wastes would be environmentally acceptable if subsurface attenuation reduced groundwater concentrations of organic compounds to concentrations that were less than health-based, water-quality criteria. Computer simulations indicated that the predicted concentrations of 13 of 33 organic compounds in groundwater would be less than their health-based criteria. Hence, solid wastes containing these compounds could be safely disposed at the site. The attenuation capacity of the site was insufficient to reduce concentrations of four compounds to safe levels without limiting the amount of mass available to leach into groundwater. Threshold masses based on time-dependent migration simulations were estimated for these compounds. The remaining 16 compounds, which consisted mainly of chlorinated hydrocarbons and fluorocarbons could not be safely landfilled without severe restrictions on the amounts disposed. These organic compounds were candidates to ban from land disposal.  相似文献   

Book reviews     

A. D. Sneyd  W. E. Sharp  Ian Lerche 《Mathematical Geosciences》1989,21(3):395-400

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Hydraulic processes on alluvial fans,R. H. French,Developments in Water Science 31, Elsevier Science Publishers,Amsterdam, 1987. No. of Pages: 244. ISBN 0–444–42781–3     

Ian Reid 《地球表面变化过程与地形》1988,13(7):664-664

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Book reviews     

F. Alejandro Nava  Manfred Koch  Andrzej Hanyga  Jacek Leliwa-Kopystyński  Frazer Tabeart  Sueo Veno  Andrzej W. Wernik  Yu. N. Korenkov  Kenji Satake  Carlos Lozano  Aysel Karafistan  Ian N. James  Anthony Dore  Jacek Wałczewski  Krzysztof Haman  Brian F. Farrell 《Pure and Applied Geophysics》1994,143(4):753-780

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Book reviews     

Edward Theriot  Ian R. Walker 《Journal of Paleolimnology》1994,11(2):205-208

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