Palaeokarst in the Ordovician of the southern Great Basin, USA: implications for sea-level history     

John D. Cooper  & Martin Keller 《Sedimentology》2001,48(4):855-873

Abundant and regionally unique dolostone lithoclast breccias occur throughout the shallow-marine, Lower to Middle Ordovician Pogonip Group in the Nopah Range and adjacent ranges in eastern California and southern Nevada. Breccia bodies display sharply cross-cutting relationships with host dolostone bedrock stratigraphy. They also show stratigraphic variability in size, shape and dolostone clast composition, but similarity in breccia matrix composition and framework texture and fabric. These characteristics are consistent with a palaeokarst origin. Upsection changes in breccia clast lithology as well as multiple occurrences of associated quartz sand-filled grikes (solution-widened fissures) indicate multiple episodes of carbonate platform exposure and karstification. Repeated karstification is also indicated by stratiform bodies of quartz sand and thin terra rossa palaeosols that locally truncate breccias and grike systems, thus bracketing karstified exposure surfaces. Facies successions and stacking patterns between recognized exposure surfaces are developed as transgressive–regressive cycles and thus show depositional sequence architecture. Hence, these breccias and other associated palaeokarst features are related to a succession of disconformities that provide a sequence-stratigraphic framework for assessing Ordovician relative sea-level history of the south-western Cordilleran margin of Laurentia.  相似文献   

Derivation of water vapor fluxes from Lidar measurements     

W. E. Eichinger  D. I. Cooper  D. B. Holtkamp  R. R. Karl Jr.  C. R. Quick  J. J. Tiee 《Boundary-Layer Meteorology》1993,63(1-2):39-64

Two techniques are described by which the flux of water vapor can be derived from concentration measurements made by a Raman-Lidar. Monin-Obukhov similarity theory and dissipation techniques are used as the basis for these methods. The resulting fluxes are compared to fluxes from standard point instruments. The techniques described are appropriate for measuring the flux of any scalar quantity using Lidar measurements in the inner region of the boundary layer.  相似文献   

On the accuracy of heighting from aerial photographs and maps: Implications to process modellers     

J. G. Fryer  J. H. Chandler  M. A. R. Cooper 《地球表面变化过程与地形》1994,19(6):577-583

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Late quaternary solution of Chalk at Basingstoke,Hants     

D.J. Ward  J. Cooper 《Proceedings of the Geologists' Association. Geologists' Association》1976,87(1):101-102

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Rare-earth and LIL element fractionation in high-grade charnockitic gneisses,south Norway     

D Field  S.A Drury  D.C Cooper 《Lithos》1980,13(3):281-289

High-Fe, intermediate-acid, charnockitic gneisses in the Arendal-Tromøy area of the Svecofennian terrain of southeast Norway comprise two chemically contrasting zones - one with normal large-ion-lithophile (LIL) element characteristics, and the other IIL-deficint. The noramal -LiLL-deficient varitties also have low ΣEEE, commonly with positive Eu anomalies. The normal-LIL rocks are enriched in ?REE, exhibit fractionated patterns and have negative Eu anomalies. Modelling shows that both the LIL and REE patterns are consistent with an essentially primary fractionation process involving the separation of cumulus (LIL-deficient) phases from andesitic-dacitic magma emplaced directly under the high-grade conditions, with the normal-LIL rocks crystallising from the residual melt. This process is interpreted as a deep-seated component of the magma system which culminated in the emplacement of some higher level rapakivi granite late in the Svecofennian event. The model presented does not require anorthosite to be part of the same magma system.  相似文献   

The chemistry and origins of Proterozoic low-potash,high-iron,charnockitic gneisses from Tromøy,south Norway     

D.C. Cooper  D. Field 《Earth and Planetary Science Letters》1977,35(1):105-115

New major and trace element data for 79 acid-intermediate charnockitic gneisses (the Tromøy gneisses) and 16 associated metabasites from the island of Tromøy show that this part of the 1200–900-m.y. Sveconorwegian zone is occupied by rocks of unusual composition. Overall values for K and Rb are the lowest yet reported for any granulites, and K/Rb ratios are very high. Cs and Th are also low and, abnormally for granulites, so are Ba, Sr and Zr. Ba/Sr ratios are similar to those in other suites, but K/Ba and K/Sr are higher. These features may partially be reflecting unusual pre-metamorphic lithologies, but it is considered more likely that they are largely the product of metamorphically induced depletion processes involving metasomatism. There is some indication that the Na₂O/CaO and normative Ab/An ratios may also have been modified during metamorphism.Data for the presumed relatively immobile elements Cr, Co, Ni and V support an igneous origin for the Tromøy gneisses, but the presence of a paragneiss component cannot be ruled out. A characteristic of the gneisses is their high iron content, and spatial and temporal considerations point towards a genetic link with the iron-rich, intrusive rapakivi suites of Finland, Sweden and south Greenland. If the Tromøy gneisses do represent material of this type, it would seem to follow that potash fractionation has been extreme.  相似文献   

Anhydrous melting and crystallization of peralkaline obsidians     

D. K. Bailey  J. P. Cooper  J. L. Knight 《Bulletin of Volcanology》1974,38(2):653-665

Experimental determinations of the dry liquidus temperatures of two pantellerite, and two pantelleritic trachyte glasses in the pressure range 0–2 kilobars, show minima in the liquidus curves between 0.1 and 0.2 kb. The pantellerite minima are 830°–850° C; the trachyte minima are 920°–940° C. At pressures below the minima a separate vapour phase co-exists with liquid, at higher pressures the intrinsic volatiles are completely soluble in the liquid and the liquidus curves have a positivedT/dP. Similar results have been obtained from a range of other pantelleritic glasses, and together with consistent alkali feldspar compositions (from a wide range of experimental conditions) are indicative of a close approach to equilibrium. The form of the liquidus curves above the minima, if rellecting natural conditions, offers a ready explanation of the near-or super-liquidus aspect of many peralkaline lavas. The temperatures in these anhydrous experiments are 100°–150° C higher than those for similar compositions in the presence of excess water. (Also, in the presence of excess water, the crystallization sequences in the natural glasses are profoundly modified, with pyroxene appearing on the liquidus). At lower pressures, feldspar is the liquidus phase in the dry pantellerites, but is joined by quartz around 1 kb, and superseded by quartz at higher pressures. As pantellerites with quartz phenocrysts are uncommon, low pressure equilibration is perhaps normal in these magmas. Feidspar is the usual liquidus phase in the trachytes, except at very low pressures where it is preceded by iron oxide. Preliminary studies at 5 kb indicate that the pantelleritic and trachytic liquidus curves are converging (in the range 950°–1000° C). Crystallization sequences, and the forms and positions of the solidus curves are therefore of vital importance. These, together with the vapour-present/vapour-absent conditions, are currently under investigation.  相似文献   

Zircon age data from a Greenstone of the archaean Yilgarn Block,Australia: Mid proterozoic heating or uplift?     

J. A. Cooper  Y. B. Dong 《Contributions to Mineralogy and Petrology》1983,82(4):397-402

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A Hybrid Multi-Agent/Spatial Interaction Model System for Petrol Price Setting   总被引：2，自引：0，他引：2  

Alison J Heppenstall  rew J Evans  Mark H Birkin 《Transactions in GIS》2005,9(1):35-51

This paper examines the use of multi‐agent simulations (MAS) to model the petrol market. The development of a purely agent based model for petrol prices is presented. Failings within this model are discussed and an alternative strategy for controlling the price of each petrol station based on population of customers is considered. Individual level modelling of customers is too computationally intensive; therefore a spatial interaction model was used to estimate the sales and linked to the agent system to create a hybrid model. To evaluate how effective this hybrid model was, a comparison was made with an existing data set of real petrol prices collected over a two month period. This was achieved both statistically and visually with the use of a Geographical Information System (GIS). Experimentation revealed that the hybrid model outperformed the agent model. Investigation into the behaviour and sensitivity of the system (for example, how prices diffuse spatially) was undertaken by means of idealised simulations.  相似文献   

Seismogenic zone structure beneath the Nicoya Peninsula, Costa Rica, from three-dimensional local earthquake P- and S-wave tomography   总被引：3，自引：0，他引：3  

Heather R. DeShon  Susan Y. Schwartz  rew V. Newman  Victor González  Marino Protti  LeRoy M. Dorman  Timothy H. Dixon  Daniel E. Sampson  Ernst R. Flueh 《Geophysical Journal International》2006,164(1):109-124

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