A uranium-thorium dated late Eemian or early midlandian organic deposit from near Kilfenora between Spa and Fenit,Co. Kerry,Ireland     

Henk Heijnis  Julie Ruddock  Peter Coxon 《第四纪科学杂志》1993,8(1):31-43

This paper discusses the dating of stratigraphically important Quaternary sequences from a site near Fenit, Co. Kerry, which have been the subject of debate since they were first described by Mitchell in 1970. The overall stratigraphy of the Quaternary deposits have been investigated and detailed analyses of the organic material carried out. Pollen from biogenic sediments have been analysed and samples of peat dated using the uranium-thorium disequilibrium method. The pollen assemblages match no others previously recorded in Ireland and appear to represent a cool temperate phase following the last interglacial. The uranium-thorium dates of between 114000 and 123 000 yr BP indicate that the deposit dates from Oxygen Isotope Stage 5, possibly post-dating the last temperate stage (the Eemian Stage interglacial; Oxygen Isotope Substage 5e). The dating of this deposit and the realisation that it is not penultimate temperate stage (Gortian) in age invalidates much recent speculation on the age of the Gortian interglacial.  相似文献   

Bodies. Exploring Fluid Boundaries     

Julie Cupples 《New Zealand geographer》2002,58(2):79-80

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Internal structure of mixed-sand-and-gravel beach deposits revealed using ground-penetrating radar   总被引：4，自引：1，他引：4  

Adrian Neal  Nigel I. Pontee†  Ken Pye‡  Julie Richards‡ 《Sedimentology》2002,49(4):789-804

ABSTRACT Mixed‐sand‐and‐gravel beaches are a distinctive type of coarse‐clastic beach. Ground‐penetrating radar (GPR) and photographic records of previous excavations are used to investigate the stratigraphy and internal sedimentary structure of mixed‐beach deposits at Aldeburgh in Suffolk, south‐east England. The principles of radar stratigraphy are used to describe and interpret migrated radar reflection profiles obtained from the study site. The application of radar stratigraphy allows the delineation of both bounding surfaces (radar surfaces) and the intervening beds or bed sets (radar facies). The deposits of the main backshore berm ridge consist of seaward‐dipping bounding surfaces that are gently onlapped by seaward‐dipping bed sets. Good correspondence is observed between a sequence of beach profiles, which record development of the berm ridge on the backshore, and the berm ridge's internal structure. The beach‐profile data also indicate that backshore berm ridges at Aldeburgh owe their origin to discrete depositional episodes related to storm‐wave activity. Beach‐ridge plain deposits at the study site consist of a complex, progradational sequence of foreshore, berm‐ridge, overtop and overwash deposits. Relict berm‐ridge deposits, separated by seaward‐dipping bounding surfaces, form the main depositional element beneath the beach‐ridge plain. However, the beach ridges themselves are formed predominantly of vertically stacked overtop/overwash units, which lie above the berm‐ridge deposits. Consequently, beach‐ridge development in this progradational, mixed‐beach setting must have occurred when conditions favoured overtopping and overwashing of the upper beachface. Interannual to decadal variations in wave climate, antecedent beach morphology, shoreline progradation rate and sea level are identified as the likely controlling factors in the development of such suitable conditions.  相似文献   

A window on West Antarctic crustal boundaries: the junction between the Antarctic Peninsula, the Filchner Block, and Weddell Sea oceanic lithosphere     

Julie K. Ferris  Alan P. M. Vaughan  Edward C. King 《Tectonophysics》2002,347(1-3)

A new airborne magnetic survey of the southeastern Antarctic Peninsula and adjacent Weddell Sea embayment (WSE) region suggests a continuity of geological structure between the eastern Antarctic Peninsula and the attenuated continental crust of the Filchner Block. This has implications for the reconstructed position of the Ellsworth–Whitmore Mountains block in Gondwana, which is currently uncertain. Palaeomagnetic data indicate that it has migrated from a Palaeozoic position between South Africa and Coats Land to its current position as a microplate embedded in central West Antarctica. The most obvious route for migration is between the Antarctic Peninsula and the Weddell Sea embayment. Evidence that geological structures are continuous across the boundary places constraints on the timing and pathway of migration. Magnetic textures suggest the presence of shallow features extending from the Beaumont Glacier Zone (BGZ) in the west for at least 200 km into the Weddell Sea embayment. These data suggest that the Eastern Domain of the Antarctic Peninsula and the stretched continental crust of the Filchner Block share a common recent, probably post-Early Jurassic, history. However, examination of deep anomalies indicates differences in the magnetic characteristics of the two blocks. The boundary may mark either the edge of extended continental crust, or a discontinuity between two, once separated, blocks. This discontinuity, or pre-Late Jurassic Antarctic Peninsula terrane boundaries to the west, may have allowed the passage of the Ellsworth–Whitmore Mountains block to its present location.  相似文献   

Characteristics and Possible Source of a 1479 A.D. Volcanic Ash Layer in a Greenland Ice Core     

R. Joseph Fiacco  Jr.  Julie M. Palais  Mark S. Germani  Gregory A. Zielinski  Paul A. Mayewski 《Quaternary Research》1993,39(3)

A microparticle concentration peak in a GISP2 ice core contains volcanic glass shards of rhyolitic composition that correspond in age to the 1479-1480 A.D. Mt. St. Helens Wn eruption. These glass shards are compositionally similar to the Wn tephra and constitute 83% of the total particle population. The shards are very coarse-grained (up to 40 μm diameter), suggesting rapid transport from their source to Greenland. A major sulfate peak in the ice occurs approximately 4 months after deposition of the glass shards. This difference in depositional timing suggests primarily tropospheric transport of the ash and stratospheric transport of the sulfate aerosol. Large-scale climatic perturbations following this eruption were evidently negligible. Glaciochemical seasonal indicators suggest a late-fall to early-winter 1479 A.D. eruption.  相似文献   

Enriched back-arc basin basalts from the northern Mariana Trough: implications for the magmatic evolution of back-arc basins   总被引：1，自引：0，他引：1  

Robert J. Stern  Ping-Nan Lin  Julie D. Morris  Michael C. Jackson  Patricia Fryer  Sherman H. Bloomer  Emi Ito 《Earth and Planetary Science Letters》1990,100(1-3)

The composition of basalts erupted at the earliest stages in the evolution of a back-arc basin permit unique insights into the composition and structure of the sub-arc mantle. We report major and trace element chemical data and O-, Sr-, Nd-, and Pb- isotopic analyses for basalts recovered from four dredge hauls and one ALVIN dive in the northern Mariana Trough near 22°N. The petrography and major element chemistry of these basalts (MTB-22) are similar to tholeiites from the widest part of the Trough, near 18°N (MTB-18), except that MTB-22 have slightly more K₂O and slightly less TiO₂. The trace element data exhibit a very strong arc signature in MTB-22, including elevated K, Rb, Sr, Ba, and LREE contents; relatively lowK/Ba and highBa/La andSr/Nd. The Sr- and Nd- isotopic data plot in a field displaced from that of MTB-18 towards Mariana arc lavas, and the Pb-isotopic composition of MTB-22 is indistinguishable from Mariana arc lavas and much more homogeneous than MTB-18. Mixing of 50–90% Mariana arc component with a MORB component is hypothesized. We cannot determine whether this resulted from physical mixing of arc mantle and MORB mantle, or whether the arc component is introduced by metasomatism of MORB-like mantle by fluids released from the subducted lithosphere. The strong arc signature in back-arc melts from the Mariana Trough at 22°N, where the back-arc basin is narrow, supports general models for back-arc basin evolution whereby early back-arc basin basalts have a strong arc component which diminishes in importance relative to MORB as the back-arc basin widens.  相似文献   

Laboratory simulation of diffusion in contaminated marine sediments     

Julie A. Baron  Louis J. Thibodeaux  Danny D. Reible  Paul H. Templet  Charles B. Henry 《Estuaries and Coasts》1990,13(1):81-88

Wastes from offshore oil drilling activities are often discharged to the marine environment. Solid wastes that settle onto the bottom sediment may pose a health threat to marine organisms and eventually to man through the food chain. We need to understand their fate in order to predict the chemical concentration levels and life-times in the sediment and adjoining aquatic boundary layer. A laboratory simulation of selected in-bed processes that addresses contaminant leaching from the sediment is proposed. The process chosen for simulation in this study is the coupled desorption-diffusion of contaminants from the bed to the water column. A simple mathematical model of the process is also proposed. Preliminary results using organic chemicals for both the simulation and the model are presented. The results suggest that the experimental procedure represents a good way of estimating the diffusive leaching rates of hydrophobic compounds from contaminated sediments.  相似文献   

In Situ Surfactant Washing of Polychlorinated Biphenyls and Oils from a Contaminated Site   总被引：5，自引：0，他引：5  

A. S. Abdul  T. L. Gibson  Carolina C. Ang  Julie C. Smith  R. E. Sobczynski 《Ground water》1992,30(2):219-231

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Prehistory of the Eastern Sahara : Fred Wendorf and Romuald Schild. Academic Press, New York, 1980     

Julie K. Stein 《Quaternary Research》1981,15(3):371-372

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Reference Samples for Electron Microprobe Analysis*     

E. JAROSEWICH  J.A. NELEN  Julie A. NORBERG 《Geostandards and Geoanalytical Research》1980,4(1):43-47

The chemical analyses of twenty-six minerals, four natural glasses, and one synthetic glass prepared for use as microprobe reference samples are presented. New chemical analyses of minerals and revised analyses of several minerals published previously are included. Details of sample preparation are described and the homogeneity of the samples has been tested by the homogeneity index.  相似文献