Sedimentary evolution of a Late Pleistocene temperate red algal reef (Coralligène) on Rhodes,Greece: correlation with global sea‐level fluctuations     

JÜRGEN TITSCHACK  CAMPBELL S. NELSON  TIM BECK  ANDRÉ FREIWALD  ULRICH RADTKE 《Sedimentology》2008,55(6):1747-1776

Autochthonous red algal structures known as coralligène de plateau occur in the modern warm‐temperate Mediterranean Sea at water depths from 20 to 120 m, but fossil counterparts are not so well‐known. This study describes, from an uplifted coastal section at Plimiri on the island of Rhodes, a 450 m long by 10 m thick Late Pleistocene red algal reef (Coralligène Facies), interpreted as being a coralligène de plateau, and its associated deposits. The Coralligène Facies, constructed mainly by Lithophyllum and Titanoderma, sits unconformably upon the Plio‐Pleistocene Rhodes Formation and is overlain by a Maerl Facies (2 m), a Mixed Siliciclastic‐Carbonate Facies (0·2 m) and an Aeolian Sand Facies (2·5 m). The three calcareous facies, of Heterozoan character, are correlated with established members in the Lindos Acropolis Formation in the north of the island, while the aeolian facies is assigned to the new Plimiri Aeolianite Formation. The palaeoenvironmental and genetic‐stratigraphic interpretations of these mixed siliciclastic‐carbonate temperate water deposits involved consideration of certain characteristics associated with siliciclastic shelf and tropical carbonate shelf models, such as vertical grain‐size trends and the stratigraphic position of zooxanthellate coral growths. Integration of these results with electron spin resonance dates of bivalve shells indicates that the Coralligène Facies was deposited during Marine Isotope Stage 6 to 5e transgressive event (ca 135 to 120 ka), in water depths of 20 to 50 m, and the overlying Maerl Facies was deposited during regression from Marine Isotope Stage 5e to 5d (ca 120 to 110 ka), at water depths of 25 to 40 m. The capping Aeolian Sand Facies, involving dual terrestrial subunits, is interpreted as having formed during each of the glacial intervals Marine Isotope Stages 4 (71 to 59 ka) and 2 (24 to 12 ka), with soil formation during the subsequent interglacial periods of Marine Isotope Stages 3 and 1, respectively. Accumulation rates of about 0·7 mm year^?1 are estimated for the Coralligène Facies and minimum accumulation rates of 0·2 mm year^?1 are estimated for the Maerl Facies. The existence of older red algal reefs in the Plimiri region during at least Marine Isotope Stages 7 (245 to 186 ka) and 9 (339 to 303 ka) is inferred from the occurrence of reworked coralligène‐type lithoclasts in the basal part of the section and from the electron spin resonance ages of transported bivalve shells.  相似文献   

Fountains in Magma Chambers   总被引：5，自引：3，他引：5  

CAMPBELL  IAN H.; TURNER  J. S. 《Journal of Petrology》1989,30(4):885-923

Cyclic layering is a common feature of the ultramafic zone oflayered intrusions and is usually attributed to the entry ofnew pulses of dense magma into the chamber. Since the crystallizationof olivine and bronzite lowers the density of the magma, a newpulse of the parent magma will be denser than the fractionatedmagma in the chamber. If the new pulse enters with excess momentumit will initially rise up into the host magma to form a fountain,then fall back around the feeder when negative buoyancy forcesovercome the initial momentum of the pulse. Laboratory experimentsusing aqueous solutions with both point and line sources havebeen conducted to obtain a quantitative understanding of thefluid-dynamical processes that are important in fountains. Itis observed that convection within the fountain is highly turbulent,resulting in appreciable entrainment of the host magma. A gravity-stratifiedhybrid layer develops at the floor and this breaks up into aseries of double-diffusive convecting layers if the new pulseis hotter than the host magma. The number of layers that formdepends on a number of factors, especially R, the ratio of thecontributions of composition and heat to the total density differencebetween the host magma and the new pulse. Raising the valueof R, results in the formation of more, thinner layers. The thickness of the hybrid layer at any time t is given byH = h₀+(V₀/A)t where V₀ is the volume flux through the feederand A is the horizontal area of the chamber. h₀ is related tothe initial steady-state height of the fountain and, for a linesource, is given by h₀=CU₀^4/3 d^–1(g/)^–2/3 whereU₀ is the volume flux per unit length, g is the accelerationdue to gravity, d is the width of the feeder, is the densityof the host magma, is the density difference between the magmasand C is a constant. Calculations based on these results and the consideration ofthe flow in the feeder dykes below the chamber indicate thata fountain will rise at least 350 m in a continental magma chamberif the feeder width is greater than 10 m. This will lead toextensive mixing between the new pulse and the fractionatedmagma in the chamber, producing a zoned hybrid layer at thefloor that is commonly over 1000 m thick. If the chamber receivesmany pulses of dense magma, the resulting zoning may persistthroughout much of the life of the chamber, especially if thefirst pulse to enter becomes contaminated by light magma releasedby melting at the margins. The highest Mg/Fe ratio for olivineand pyroxenes from cyclic units from the ultramafic zones oflayered intrusions is often well below the value expected forminerals crystallizing from a melt derived directly from themantle, supporting the hypothesis that new pulses of dense magmacan mix extensively with the fractionated magma in the chamber. The feeder dykes to some oceanic magma chambers, such as theBay of Islands Ophiolite, are believed to be narrower, so thatfountains do not rise more than a few metres above the floorof the chamber. This restricts mixing between the input magmaand the host magma and can result in the formation of a hybridzone that is only a few metres thick.  相似文献   

Molybdenum and Tungsten Contents of Five CRPG and Eight ANRT Geochemical Reference Materials     

Esma CAMPBELL  Philip J. ARUSCAVAGE 《Geostandards and Geoanalytical Research》1982,6(2):229-231

Mo and W have been determined in five CRPG and eight ANRT geochemical reference samples by spectrophotometric - zinc dithiol procedures. Although data are lacking for adequate comparisons on most samples, our data for tungsten in GIT-IWG MA-N and GIT-IWG BE-N are very near the presently proposed values.  相似文献   

Molybdenum Content of 16 U.S. Geological Survey Standard Rocks     

Philip J. ARUSCAVAGE  Esma Y. CAMPBELL 《Geostandards and Geoanalytical Research》1981,5(2):171-173

The concentration of molybdenum in 16 U.S. Geological Survey (USGS) standard rocks was determined by a colorimetric procedure using zinc dithiol reagent. The molybdenum content in the rocks was found to range from 0.04 to 37 ppm. The precision of the method is generally better than 10% relative deviation when the molybdenum content is >0.3 ppm. A comparison with values stated in the literature shows that the method is accurate for the range of concentrations determined and the rock types analyzed.  相似文献   

Analysis of anthropogenic CO₂ signal in ICARTT using a regional chemical transport model and observed tracers     

J. E. CAMPBELL  G. R. CARMICHAEL  Y. TANG  T. CHAI  S. A. VAY  Y.-H. CHOI  G. W. SACHSE  H. B. SINGH  J. L. SCHNOOR  J. WOO  J. M. VUKOVICH  D. G. STREETS  L. G. HUEY  C. O. STANIER 《Tellus. Series B, Chemical and physical meteorology》2007,59(2):199-210

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Vertical profiles of biospheric and fossil fuel-derived CO₂ and fossil fuel CO₂ : CO ratios from airborne measurements of Δ¹⁴C, CO₂ and CO above Colorado, USA     

By HEATHER D. GRAVEN †  BRITTON B. STEPHENS  THOMAS P. GUILDERSON  TERESA L. CAMPOS  DAVID S. SCHIMEL  J. ELLIOTT CAMPBELL  RALPH F. KEELING 《Tellus. Series B, Chemical and physical meteorology》2009,61(3):536-546

Measurements of  Δ¹⁴C  in atmospheric CO₂ are an effective method of separating CO₂ additions from fossil fuel and biospheric sources or sinks of CO₂. We illustrate this technique with vertical profiles of CO₂ and  Δ¹⁴C  analysed in whole air flask samples collected above Colorado, USA in May and July 2004. Comparison of lower tropospheric composition to cleaner air at higher altitudes (>5 km) revealed considerable additions from respiration in the morning in both urban and rural locations. Afternoon concentrations were mainly governed by fossil fuel emissions and boundary layer depth, also showing net biospheric CO₂ uptake in some cases. We estimate local industrial CO₂:CO emission ratios using in situ measurements of CO concentration. Ratios are found to vary by 100% and average 57 mole CO₂:1 mole CO, higher than expected from emissions inventories. Uncertainty in CO₂ from different sources was ±1.1 to ±4.1 ppm for addition or uptake of −4.6 to 55.8 ppm, limited by  Δ¹⁴C  measurement precision and uncertainty in background  Δ¹⁴C  and CO₂ levels.  相似文献   

LANDSCAPE CHANGE IN HISPANO AND CHICANO VILLAGES OF NEW MEXICO     

JOHN B. WRIGHT  CAROL L. CAMPBELL 《Geographical review》2008,98(4):551-565

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The role for a geographical information system in a large environmental project     

WILLIAM G. CAMPBELL  M. ROBBINS CHURCH  GARY D. BISHOP  DOROTHY C MORTENSON  SUZANNE M. PIERSON 《International journal of geographical information science》2013,27(4):349-362

Abstract

A geographical information system (GIS) has proved to be a valuable tool in the Direct/Delayed Response Project—a comprehensive examination of the future, long-term chemical response of surface waters to acidic deposition. The role of the GIS within the project includes aggregation, analysis and display of various forms, scales and projections of environmental data related to acidic deposition. The GIS is particularly valuable for effectively communicating key scientific findings and results of regional, national and international importance to a diverse audience.  相似文献   

Cenozoic temperate and sub‐tropical carbonate sedimentation on an oceanic volcano – Chatham Islands,New Zealand     

NOEL P. JAMES  BRIAN JONES  CAMPBELL S. NELSON  HAMISH J. CAMPBELL  JEREMY TITJEN 《Sedimentology》2011,58(4):1007-1029

The Chatham Islands, at the eastern end of the Chatham Rise in the South‐west Pacific, are the emergent part of a Late Cretaceous to Cenozoic stratovolcano complex that is variably covered with limestones and fossiliferous tuffs. Most of these deposits accumulated in relatively shallow, high‐energy, tide‐influenced palaeoenvironments with deposition punctuated by periods of deeper‐water pelagic accumulation. Carbonate components in these neritic deposits are biogenic and dominated by molluscs and bryozoans – a heterozoan assemblage. The widespread Middle to Late Eocene Matanginui Limestone contains local photozoan elements such as large benthonic foraminifera (especially Asterocyclina) and calcareous green algae, reflecting the general Palaeogene sub‐tropical oceanographic setting. More localized Late Eocene to Oligocene deposits (Te One Limestone) as well as Pliocene carbonates (Onoua Limestone) are, however, wholly heterozoan and confirm a generally cooler‐water oceanographic setting, similar to today. Early sea floor diagenesis is interpreted to have removed most aragonite components (infaunal bivalves and epifaunal gastropods). Lack of aragonite resulted in the absence of intergranular calcite cementation during subaerial exposure, such that most carbonates are friable or unlithified. Cementation is, however, present at nodular hardground–firmground caps to metre‐scale cycles. Such cements are microcrystalline or micrometre‐thick isopachous circumgranular rinds with insufficient definitive attributes to pinpoint their environment of formation. The overall palaeoenvironment of deposition is interpreted as mesotrophic, resulting in part from upwelling about the Chatham volcanic massif and in part from nutrient element delivery from the adjacent volcanic terrane and coeval volcanism. Biotic diversity in tuffs is two to three times that in limestones, supporting the notion of especially high nutrient availability during periods of volcanism. These mid‐latitude deposits are strikingly different from their low‐latitude, tropical, photozoan counterparts in the volcanic island–coral reef ecosystem. Ground water seepage and fluvial runoff attenuate coral growth and promote microbial carbonate precipitation in these warm‐water settings. In contrast, nutrients from the same sources feed the system in the Chatham Islands cool‐water setting, promoting active heterozoan carbonate sedimentation.  相似文献   

Decoupling as an alternate model for transpression during the initial opening of the Norwegian-Greenland Sea     

HARMON D. MAHER  JR.  CAMPBELL CRADDOCK 《Polar research》1988,6(1):137-140

Transpressive plate motions during the opening of the Norwegian-Greenland Sea were in some manner responsible for the development of Spitsbergen's Tertiary fold-and-thrust belt. A flower model has been proposed for the large-scale structural architecture of Tertiary deformation (Lowell 1972). An alternate model of decoupling, where convergent and transcurrent motions were accommodated in totally or partially separated, subparallel belts is suggested.  相似文献