Exploration geochemistry — 1974: (Proceedings of the 5th international geochemical exploration symposium,Vancouver, British Columbia,April 1–4, 1974.) I.L. Elliot and W.K. Fletcher (editors). Association of Exploration Geochemists Special Publication,no.2, Elsevier Scientific Publishing Company,Amsterdam, 1975, 720 pp., Dfl. 150.00 (US $ 62.50)     

R.J. Allan 《Chemical Geology》1975,16(4):311-314

  相似文献   

Surface circulation of the Indian Ocean during the last glacial maximum, approximately 18,000 yr B.P.     

Warren L. Prell  William H. Hutson  Douglas F. Williams  Allan W. H. B  Kurt Geitzenauer  Barbara Molfino 《Quaternary Research》1980,14(3):309-336

A seasonal reconstruction of the Indian Ocean during the last glacial maximum (18,000 yr B.P.) reveals that its surface circulation and sea surface temperature patterns were significantly different from the modern Indian Ocean. This reconstruction is based on the planktonic foraminiferal biogeography and estimated sea surface temperatures in 42 Indian Ocean samples. Compared to modern conditions, the polar front was 5° to 10° latitude further north during the last glacial maximum; the Subtropical Convergence was 2° to 5° latitude further north. The West Australian Current was more intense as part of the West Wind Drift was deflected northward along the coast of Australia. The Agulhas Current was cooler and weaker during the summer and more saline and subtropical during the winter. In general, the low latitudes underwent little temperature change. The western Arabian Sea was warmer which implies less upwelling and a weaker Southwest Monsoon. On the average, the Indian Ocean was 1.9°C cooler in February and 1.7°C cooler in August during the last glacial maximum.  相似文献   

Environmental implications of a beetle assemblage from the Gervais Formation (early Wisconsinan?), Minnesota     

Allan C. Ashworth 《Quaternary Research》1980,13(2):200-212

The Gervais Formation of northwestern Minnesota is the oldest known Quaternary stratigraphic unit in the Red River Valley. Wood from the fossiliferous silt and peat member is > 46,900 yr old. The age of the unit is uncertain but may be early Wisconsinan. A well-preserved beetle assemblage consisting of extant species is described from the fossiliferous horizon. Presently, most of the species are widely distributed and occur in Minnesota. The remainder have restricted northern distributions. Included in this group is the weevil Vitavitus thulius, known only from two localities in Northwest Territories. The sedimentary environment indicated by the beetles was a small lake, rich in aquatic and semi-aquatic vegetation. The margins were characterized by open areas and spruce woodland. Species with arctic-alpine distributions indicate a cold environment, but whether it was regional or local in extent could not be determined. If regional, a climate similar to that of the tundra-forest transition zone is postulated with mean July temperatures in the range 11° to 14°C. If the cold environment was restricted, however, the climate may have been similar to that of the Lake Superior region with a mean July temperature of 17°C.  相似文献   

Spreadsheet Modeling of Slug Tests Using the van der Kamp Method     

Allan Wylie  Swen Magnuson 《Ground water》1995,33(2):326-329

Slug testing is frequently employed to calculate aquifer transmissivity and hydraulic conductivity. The van der Kamp technique for interpreting slug test data which experience force-free water level oscillations is not routinely employed because it requires adjusting equations to match the observed well response data. This adjustment can be rapid and convenient when a commercial spreadsheet is employed.  相似文献   

The quaternary travertine deposits of Europe and Asia Minor   总被引：7，自引：0，他引：7  

Allan Pentecost 《Quaternary Science Reviews》1995,14(10)

A summary is provided of the published information relating to all aspects of Quaternary travertine formation in Europe west of the Ural Mountains. The deposits have been divided into two broad groups, the meteogene travertines, which result primarily from the degassing of soil-borne aqueous CO₂, and thermogene deposits resulting from the degassing of thermally generated CO₂. Meteogene deposits are rare above latitude 58°N, and in regions where the mean annual air temperature is below 5°C. A significant positive correlation exists between mean air temperature and travertine deposit thickness. The combined effects of temperature and rainfall are used to provide a zoned map showing the travertine-forming potential of limestones within the region. Information from ¹⁴C dating indicates that deposition reached a maximum in the period 5–10 ka BP) and is currently limited by land and water management practices in the populated areas. Thermogene deposits occur in regions of high CO₂ discharge resulting from tectonic activity, such as Italy and Turkey where there is much vulcanism. These travertines are frequently more massive and less readily weathered than meteogene deposits. Fully referenced information is provided for 320 important, mostly well studied sites (227 meteogene, 93 thermogene), of which 156 are currently active.  相似文献   

Book reviews     

Allan M. Rubin  Gerardo G. Tango  Jeremy Bloxham  Stanislaw Wybraniec  Adam Łyszkowicz  Gary A. Robbins  Benoit Cushman-Roisin  David S. Gutzler  Carlos Lozano  Hanna Pawłowska 《Pure and Applied Geophysics》1991,137(1-2):147-174

  相似文献   

Comment on “Palaeomagnetic results from volcanic rocks of the Shelve Inlier, Wales: evidence for a wide Late Ordovician Iapetus Ocean in Britain” by C. McCabe and J.E.T. Channell     

Allan Trench  Trond H. Torsvik 《Earth and Planetary Science Letters》1991,104(2-4)

  相似文献   

Suspended sediment load in the Amazon basin: An overview     

Dr. Luiz A. Martinelli  Dr. Reynaldo L. Victoria  Dr. Allan H. Devol  Dr. Jeffrey E. Richey  Dr. Bruce R. Forsberg 《GeoJournal》1989,19(4):381-389

In this report the state of knowledge of sediment transport by rivers of the Amazon drainage basin is reviewed. On an annual basis the Amazon river transports about 1200×10⁶ tons of sediment from the South American continent to the ocean, which puts it among the world's largest rivers in this respect. The main source of sediment is erosion in the Andes mountains and this material is progressively diluted with sediment poor runoff from lowland draining tributaries. Almost half of the Amazon river transport is attributable to one tributary, the Rio Madeira (488×10⁶ t/y). The Rio Negro, which drains the N crystalline shield, has a comparable water discharge to the Rio Madeira, but only contributes 7×10⁶ t/y. In general the sediments in transport are about 1% organic carbon by weight and this results in an annual particulate carbon to the oceans of 13×10⁶ t/y. Total carbon transport, particulate plus dissolved, is about twice this amount.  相似文献   

Mountain environments: An assessment     

Nigel J. R. Allan Dr. 《GeoJournal》1992,27(1):5-11

The celebrated 1972 Stockholm environmental conference focused attention on the condition of the world's environment. A twenty year retrospective summary is provided by the introduction and specialty papers on all facets of mountain society and habitat relationships. Theories, models and paradigms that guided mountain research are critically examined. Specific attention is given to the application of the ecology paradigm. Contemporary discoveries and developments about resource management in mountains are elucidated. Assessments of the mountain environment, including wildlife habitat, tourism and recreation, forests, hazards, deforestation, food plant biodiversity, risk and hazard, are provided by the specialty articles. These papers were prepared for the 1992 Earth Summit in Rio de Janeiro.  相似文献   

Relative stabilities of sedimentary rearranged sterenes as calculated by molecular mechanics: a key to unravel further steroid diagenesis     

J.W. de Leeuw  H.C. Cox  M. Baas  T.M. Peakman  B. van de Graaf  J.M.A. Baas 《Organic Geochemistry》1993,20(8)

Molecular mechanics calculations of rearranged cholestenes revealed that diacholest-13(17)-enes with 10α stereochemistry are more stable than their 10β counterparts and that a partly rearranged sterene with a Δ⁸ double bond and 10β, 14β stereochemistry (compound 7) is relatively stable at thermodynamic equilibrium. The calculated data are in good agreement with sedimentary and experimental data and thus reinforce recent propositions for early-stage diagenesis of steroids.  相似文献