Infrared stellar populations in the central parts of the Milky Way galaxy     

Jacco Th. van Loon  G. F. Gilmore  A. Omont  J. A. D. L. Blommaert  I. S. Glass  M. Messineo  F. Schuller  M. Schultheis  I. Yamamura  H. S. Zhao 《Monthly notices of the Royal Astronomical Society》2003,338(4):857-879

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Fishers' responses to management measures and their socio-economic effects     

Rosenberg  Andrew A.; Glass  Christopher W. 《ICES Journal of Marine Science》2007,64(8):1612-1613

This session presented a wide range of papers on cooperativeresearch, design of alternative gears and fishing strategies,and new analyses to support management. The contributed papersreflected a real desire to explore different approaches andstrategies to fishery management. It is apparent that fishery policy has had a mixed record ofsuccess and failure at best. In most regions of the world, manystocks are still being overfished or have been severely overfishedin the past. Although rebuilding programmes for overfished stockshave been developed, nationally as well as internationally,only a few have been successful, many others are works in progressand, in too many cases, rebuilding  相似文献   

(U‐Th)/He zircon dating of Chesapeake Bay distal impact ejecta from ODP site 1073     

M. B. Biren  J.‐A. Wartho  M. C. VAN Soest  K. V. Hodges  H. Cathey  B. P. Glass  C. Koeberl  J. W. Horton  W. Hale 《Meteoritics & planetary science》2019,54(8):1840-1852

Single crystal (U‐Th)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located ~390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive X‐ray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the ~40 km diameter Chesapeake Bay impact structure. (U‐Th/He) dates for zircon crystals from this sediment range from 33.49 ± 0.94 to 305.1 ± 8.6 Ma (2σ), implying crystal‐to‐crystal variability in the degree of impact‐related resetting of (U‐Th)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverse‐variance weighted mean (U‐Th)/He age of 33.99 ± 0.71 Ma (2σ uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (U‐Th)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, ⁴⁰Ar/³⁹Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event.  相似文献   

No evidence for a 0.8–0.9 m.y. old micro-australite layer in deep-sea cores     

B.P. Glass 《Earth and Planetary Science Letters》1986,77(3-4)

Fission-track and⁴⁰Ar—³⁹Ar dating of Australasian tektites indicates that the australites are older than the rest of the Australasian tektites. Some authors have suggested, therefore, that there should be two microtektite layers in the Australasian region: a younger layer approximately synchronous with the Brunhes/Matuyama geomagnetic reversal boundary (previously described in the literature) and an older layer of Australian microtektites (micro-australites) below the Brunhes/Matuyama reversal boundary and perhaps associated with the end of the Jaramillo event. Fifteen cores already known to contain a layer of Australasian microtektites at or slightly above the Brunhes/Matuyama reversal boundary were searched for an 0.8 to 0.9 m.y. old micro-australite layer. No evidence for this layer was found. Thus, the data do not support the conclusion that the Australasian tektites were produced by two impact events at different times.  相似文献   

Fluorescence spectral analysis of resinite macerals from coals of the Hanna Formation, Wyoming, U.S.A.     

Stan C. Teerman  John C. Crelling  Gary B. Glass 《International Journal of Coal Geology》1987,7(4)

Flourescence spectral analysis indicates that resinite macerals from Tertiary Hanna Formation coals (Hanna Coal Field, southcentral Wyoming, U.S.A.) can be separated into five distinct groups. The first resinite group fluoresces a a medium green (in blue light); its average spectral maximum occurs at or below 440 mm with a red/green quotient of 0.22. The second resinite group fluoresces yellow-green with an average spectral maximum of 500 nm and a red/green quotient of 0.53. The third resinite group displays a yellow fluorescence having an average spectral maximum of 580 nm and a red/green quotient of 0.86. The fourth resinite group fluorescence orange-brown having an average spectral maximum of 610 nm and a red/green quotient of 1.20. These four groups mostly occur as primary globular resinites exhibiting scratches and fractures, indicating that they are brittle, solid substances. Primary cell-filling and secondary fracture-filling resinites also occur in these four groups. The fifth group only occurs as a secondary void-filling material and lacks evidence of br of brittle properties. It fluoresces a reddish-brown, has a spectral maximum at 690 nm, and a red/green quotient of 1.54. The fifth group has properties resembling exsudatinite. The five resinite groups can be separated on the basis of their nine spectral properties alone, without qualitative petrographic interpretation.The relative quantities of the five resinite groups vary among Hanna Formation coals. The origins of these five resinite groups are probably related to their botanical properties and pre- and post-depossitional conditions. Overall, Hanna Formation resinites have petrographic characteristics similar to other North American resinites; however, only four resinite groups have been distinguished in in certain coals from Utah and New Mexico (U.S.A.), and western Canada.  相似文献   

The Ivory Coast microtektite strewnfield: new data     

B.P. Glass  Peter A. Zwart 《Earth and Planetary Science Letters》1979,43(2):336-342

Ivory Coast microtektites have recently been found in three piston cores from the Atlantic Ocean. In two of these cores, the microtektites occur in a layer above the base of the Jaramillo geomagnetic event indicating that they fell approximately 0.95 m.y. ago. Major element compositions have been obtained for forty-one of the microtektites by electron microprobe and energy-dispersive X-ray analysis. The geographic location, stratigraphic age and major element compositions indicate that these microtektites are part of the Ivory Coast tektite strewnfield. Present data suggest that the Ivory Coast strewnfield may cover an area of about 4.5 million square kilometers and contain about 20 million metric tons of microtektites.  相似文献   

The peterson limestone — early cretaceous lacustrine carbonate deposition in western wyoming and southeastern idaho     

Steven W. Glass  Bruce H. Wilkinson 《Sedimentary Geology》1980,27(2):143-160

The lacustrine Peterson Limestone of western Wyoming and southeastern Idaho comprises six lithofacies throughout its 20,000 km² aerial extent. These are: (1) calcareous sandstone and shale, (2) red nodular limestone, (3) pink sandy micrite, (4) biomicrite, (5) graded silty micrite, and (6) limestone conglomerate. The first two represent floodplain deposition and paleosols, whereas the remaining are shallow nearshore and deeper lacustrine sediments.This sequence was developed in a large fresh, hardwater lake surrounded by fluvial systems and associated flood plains in a warm temperate climate. Well-oxidized sandy terrigenous rocks, together with calcareous paleosol nodules, indicate that flood-plain deposition both preceded and was concurrent with lacustrine carbonate deposition. Micrite and biomicrite formed in deeper parts of the basin while sandy and silty carbonate accumulated in shallower lake-margin areas. Less-calcareous shale units which are interbedded with deeper-water carbonate were deposited either during rapid basin subsidence and deepening of the lake center or during periods of slower carbonate precipitation. Turbidity currents and subaqueous debris flows generated along steeper lake margins, resulted in the deposition of rhythmic layers of graded silty micrite and diamictic limestone conglomerate in the deepest part of the basin. The carbonate-rich sediments comprising these two lithofacies were originally deposited on shallow lake-margin benches and subsequently were transported downslope toward the lake center.Comparison with other carbonate-precipitating lacustrine systems indicates that this lake was not like modern playas. Although no known modern lacustrine system is precisely like Lake Peterson, the flora, fauna, composition, and distribution of facies within modern temperate-region lakes most closely resemble those of the Peterson Limestone.  相似文献   

Tests for size and shape dependency in deep-sea mixing     

W.F. Ruddiman  G.A. Jones  T.-H. Peng  L.K. Glover  B.P. Glass  P.J. Liebertz 《Sedimentary Geology》1980,25(4):257-276

Bioturbation is generally not a strongly size-dependent or shape-dependent process in deep-sea sediments. Different sizes of ash (11–250 μm) deposited during a single eruption are usually mixed about equally, although in a few cores we found minor tendencies toward greater mixing of finer ash. Platey volcanic ash and spherical microtektites initially deposited within a few centimeters of each other in the sediment column are mixed with roughly comparable intensity. Radiocarbon dating of three sizes of CaCO₃ near the top of one box core produced ages within the analytical error; this also suggests no size dependency in the mixing process. Another core showed age differences opposite in sense to those that would be predicted if the finer fractions were more intensely mixed than the coarser fractions.The sizes examined (11–250 μm) encompass most of the sedimentary components used in paleoclimatic analyses of deep-sea cores. From these findings, we infer that significant artificial lead/lag offsets in paleoclimatic signals will not be created by size-selective or shape-selective mixing. Mixing models calibrated on one sediment size fraction should be generally applicable to other sizes and kinds of material.  相似文献   

THE IMPACT-FLOOD CONNECTION: DOES IT EXIST?*     

Alexander Deutsch  Christian Koeberl  Joel D. Blum  Bevan M. French  Billy P. Glass  Richard Grieve  Peter Horn  Elmar K. Jessberger  Gero Kurat  Wolf Uwe Reimold  Jan Smit  Dieter Stöffler  Stuart Ross Taylor 《地学学报》1994,6(6):644-650

In a recent article in Terra Nova, Kristan-Tollmann and Tollmann (1994) suggested that the Biblical Flood can be explained by seven fragments of a comet that impacted the ocean at seven locations on Earth at 03.00h (C.E.T.) on 23 September, 9545 yr BP. We demonstrate that all the ‘geological proofs’ that allegedly support their conclusions are not supported by the available data on impact cratering. Their hypothesis is based on insufficient and ambiguous data, selective citation, and incomplete comprehension of previous research.  相似文献   

Geological overview and cratering model for the Haughton impact structure,Devon Island,Canadian High Arctic     

Gordon R. Osinski  Pascal Lee  John G. Spray  John Parnell  Darlene S. S. Lim  Theodore E. Bunch  Charles S. Cockell  Brian Glass 《Meteoritics & planetary science》2005,40(12):1759-1776

Abstract— The Haughton impact structure has been the focus of systematic, multi‐disciplinary field and laboratory research activities over the past several years. Regional geological mapping has refined the sedimentary target stratigraphy and constrained the thickness of the sedimentary sequence at the time of impact to ?1880 m. New ⁴⁰Ar–³⁹Ar dates place the impact event at ?39 Ma, in the late Eocene. Haughton has an apparent crater diameter of ?23 km, with an estimated rim (final crater) diameter of ?16 km. The structure lacks a central topographic peak or peak ring, which is unusual for craters of this size. Geological mapping and sampling reveals that a series of different impactites are present at Haughton. The volumetrically dominant crater‐fill impact melt breccias contain a calcite‐anhydrite‐silicate glass groundmass, all of which have been shown to represent impact‐generated melt phases. These impactites are, therefore, stratigraphically and genetically equivalent to coherent impact melt rocks present in craters developed in crystalline targets. The crater‐fill impactites provided a heat source that drove a post‐impact hydrothermal system. During this time, Haughton would have represented a transient, warm, wet microbial oasis. A subsequent episode of erosion, during which time substantial amounts of impactites were removed, was followed by the deposition of intra‐crater lacustrine sediments of the Haughton Formation during the Miocene. Present‐day intra‐crater lakes and ponds preserve a detailed paleoenvironmental record dating back to the last glaciation in the High Arctic. Modern modification of the landscape is dominated by seasonal regional glacial and niveal melting, and local periglacial processes. The impact processing of target materials improved the opportunities for colonization and has provided several present‐day habitats suitable for microbial life that otherwise do not exist in the surrounding terrain.  相似文献