Geology in the Falkland Islands   总被引：2，自引：0，他引：2  

RICHARD CLARK  EMMA EDWARDS  STEPHEN LUXTON  TOM SHIPP &  PETER WILSON 《Geology Today》1995,11(6):217-223

In the next few years we are likely to hear and learn much about the offshore geology of the Falkland Islands as exploratory drilling for hydrocarbons begins. The offshore geology may become better known than the onshore, of which there has been little detailed investigation in the 200+ years since settlements were established. Here we outline the history of geological investigations and present information gathered during recent fieldwork.  相似文献   

Terrigenous sand in Labrador Sea hemipelagic sediments and paleoglacial events on Baffin Island over the last 100,00 years     

RICHARD H. FILLON  GIFFORD H. MILLER  JOHN T. ANDREWS 《Boreas: An International Journal of Quaternary Research》1981,10(1):107-124

Eight Labrador Sea piston cores with faunal and ash-zone stratigraphies correlated to deep-sea oxygen isotope stages were used to compute Labrador Sea terrigenous sand input rates (mg/cm²/1000 years) during the last 100,000 years. Sources of the sand in Labrador Sea cores are likely to be ice-rafting, turbid glacial meltwater inflow or deflation and wind erosion of unvegetated landscapes in the wake of retreating continental ice sheets. High levels of sand input to the Labrador Sea are therefore undoubtedly glacier-related while low levels of sand input are not. Comparison of the history of Labrador Sea sand input with the chronology of glacial and non-glacial events on Baffin Island reveals that the era of highest sand input rates, the isotopic stage 5a/4 transition, closely coincided with an episode of early Foxe glacier advance to tidewater (Ayr Lake Stade) along the outer coast of Baffin Island ca. 80,000 B.P. to 60,000 B.P. The period of lowest Labrador Sea sand input rates, late isotopic stage 3 to the present, largely corresponds to a major disconformity in the raised marine and glacigenic sediments on Baffin Island, but includes also the late Foxe/early Holocene Cockburn glacial advance (which did not reach the outer coast of the island) and the modern glacial minimum. Labrador Sea and central-subpolar North Atlantic sand input histories are reciprocally related over the last 80,000 years. Accelerated sand input in the Labrador Sea during times of reduced sand input in the North Atlantic implies: (1) major early Wisconsin glacier expansion in the circum Labrador Sea/Baffin Bay region and/or; (2) a surface circulation pattern in the North Atlantic which inhibited iceberg melting there while delivering icebergs and relatively warm surface water into the Labrador Sea. Conversely, reduced sand input in the Labrador Sea during times of accelerated sand input in the North Atlantic implies: (1) late Wisconsin glacier recession in the circum Labrador Sea/Baffin Bay region and/or; (2) a circulation pattern which carries icebergs southward and eastward away from the Labrador Sea. These implications are discussed in the light of paleoceanographic evidence for three periods - 80,000 B.P. to 57,000 B.P.; 25,000 B.P. to 13,000 B.P.; and 13,000 B.P. to 9800 B.P  相似文献   

Fiji Labour Migration to New Zealand in the 1980s     

WAYNE LEVICK  RICHARD BEDFORD 《New Zealand geographer》1988,44(1):14-21

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Charles Darwin's geologist's field guide     

RICHARD WILDING 《Geology Today》1989,5(5):166-169

From observations carried out on his 'Beagle' voyage, Charles Darwin made a number of important contributions to geological science. He showed himself to be a meticulous observer and an imaginative field worker. His methods are probably best summarized in a contribution on field geology that he made to the Admiralty Manual of Scientific Enquiry, published in 1849. That paper contains some important clues for the historian of early nineteenth-century geology.  相似文献   

The latest vertebrates are the earliest     

RICHARD J. ALDRIDGE  DEREK E. G. BRIGGS  IVAN J. SANSOM  M. PAUL SMITH 《Geology Today》1994,10(4):141-145

The teeth, or elements, ofconodonts are among the most important Palaeozoic microfossils. Despite this, the biological relationships of conodonts have long remained enigmatic. Recent evidence of their soft anatomy, and of the ultrastructure of the elements, has finally revealed that they are vertebrates. These discoveries push vertebrate origins firmly back into the Cambrian and add a large cohort of specialists to the ranks of the vertebrate palaeontologists.  相似文献   

Metamorphic Evolution of Iron-rich Mafic Cumulates from the Otztal-Stubai Crystalline Complex, Eastern Alps, Austria     

KONZETT  JURGEN; MILLER  CHRISTINE; ARMSTRONG  RICHARD; THONI  MARTIN 《Journal of Petrology》2005,46(4):717-747

Olivine-rich rocks containing olivine + orthopyroxene + spinel+ Ca-amphibole ± clinopyroxene ± garnet are presentin the central Ötztal–Stubai crystalline basementassociated with eclogites of tholeiitic affinity. These rockscontain centimetre-sized garnet layers and lenses with garnet+ clinopyroxene ± corundum. Protoliths of the olivine-richrocks are thought to be olivine + orthopyroxene + spinel dominatedcumulates generated from an already differentiated Fe-rich () tholeiitic magma that was emplaced into shallowcontinental crust. Protoliths of the garnet-rich rocks are interpretedas layers enriched in plagioclase and spinel intercalated ina cumulate rock sequence that is devoid of, or poor in, plagioclase.U–Pb sensitive high-resolution ion microprobe dating ofzircons from a garnet layer indicates that emplacement of thecumulates took place no later than 517 ± 7 Myr ago. Aftertheir emplacement, the cumulates were subjected to progressivemetamorphism, reaching eclogite-facies conditions around 800°Cand >2 GPa during a Variscan metamorphic event between 350and 360 Ma. Progressive high-P metamorphism induced breakdownof spinel to form garnet in the olivine-rich rocks and of plagioclase+ spinel to form garnet + clinopyroxene ± corundum inthe garnet layers. Retrogressive metamorphism at T 650–680°Cled to the formation of Ca-amphibole, chlorite and talc in theolivine-rich rocks. In the garnet layers, högbomite formedfrom corundum + spinel along with Al-rich spinel, Ca-amphibole,chlorite, aspidolite–preiswerkite, magnetite, ilmeniteand apatite at the interface between olivine-rich rocks andgarnet layers at P < 0·8 GPa. Progressive desiccationof retrogade fluids through crystallization of hydrous phasesled to a local formation of saline brines in the garnet layers.The presence of these brines resulted in a late-stage formationof Fe- and K-rich Ca-amphibole and Sr-rich apatite, both characterizedby extremely high Cl contents of up to 3·5 and 6·5wt % Cl, respectively. KEY WORDS: cumulates; Variscan metamorphism; SHRIMP dating; högbomite; saline brines  相似文献   

WORLD'S METEORITE CRATERS (“Astroblemes”) Version VII,February 1967     

RICHARD W. BARRINGER 《Meteoritics & planetary science》1967,3(3):151-157

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The trilobite Angelina unstretched     

RICHARD A. FORTEY  ROBERT M. OWENS 《Geology Today》1992,8(6):219-221

The early Ordovician trilobite Angelina sedgwickii has hitherto been known only from stretched and squeezed specimens from North Wales. As a classic example of a deformed fossil, it has featured not only in palaeontological but also in structural geology textbooks, and various methodologies have been employed to attempt to restore it to its original shape. Recently discovered specimens from Shropshire, although flattened, are not sheared and preserve the original bilateral symmetry, affording for the first time an opportunity to find out what this trilobite might really have looked like.  相似文献   

LABORATORY OBSERVATIONS OF SEDIMENT ENTRAINMENT BY FREEZING SUPERCOOLED WATER     

SIMON J. COOK  PETER G. KNIGHT  DEBORAH A. KNIGHT  RICHARD I. WALLER 《Geografiska Annaler: Series A, Physical Geography》2012,94(3):351-362

Debris in basal ice produced by glaciohydraulic supercooling is typically characterized by high proportions of silt. A prominent hypothesis for this silt‐dominance is that frazil ice growing in supercooled water preferentially traps silt from sediment‐laden water percolating through it. It has therefore been suggested that silt‐dominance may be diagnostic of glaciohydraulic supercooling. The aim of our work is to test this hypothesis that freezing sediment‐laden supercooled water necessarily produces ice dominated by silt. We do this by simulating two freezing processes under laboratory conditions: (1) percolation of sediment‐laden water through frazil ice; (2) turbulent supercooling and subsequent freezing of sediment‐laden water. In experiments repeated using different particle sizes (sand, silt and clay in individual experiments) both processes entrained sand most effectively and silt least effectively. In experiments using a sediment mixture dominated by medium to coarse silt, both processes produced ice facies dominated by particle sizes between fine sand and coarse silt. These results suggest that silt‐dominance should therefore not be expected for supercooled freeze‐on, and is not a reliable diagnostic signature for supercooling. The silt‐dominated character of basal ice types associated with supercooling may result from other controls such as a silt‐dominated sediment supply or subglacial water flow rates, rather than the freezing process.  相似文献   

ON A NEW GENUS OF SYRINGOPOROID CORAL FROM THE CARBONIFEROUS OF CHIHLI AND FENGTIEN PROVINCES.     

樂森 《地质学报》1926,(Z1)

In the course of my study on the Chihsia Corals from Central China, Mr. Y. T. Chao my collegue of the Geological Survey was so kind as to hand over to me two specimens of tube corals which he personally found in a limes-  相似文献