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CHRIS W. LEE 《Geology Today》1991,7(4):133-136
Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times. 相似文献
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U-series Isotope Data on Lau Basin Glasses: the Role of Subduction-related Fluids during Melt Generation in Back-arc Basins 总被引:6,自引:2,他引:6
PEATE DAVID W.; KOKFELT THOMAS F.; HAWKESWORTH CHRIS J.; VAN CALSTEREN PETER W.; HERGT JANET M.; PEARCE JULIAN A. 《Journal of Petrology》2001,42(8):1449-1470
New thermal ionization mass spectrometry U-series disequilibriumdata are presented for 24 basaltic to dacitic glasses from activespreading centres in the back-arc Lau Basin (SW Pacific), togetherwith additional inductively coupled plasma mass spectrometrytrace element analyses and SrNdPb isotope data.Valu Fa Ridge samples, adjacent to the arc front, have highU/Th and (230Th/238U) <1, implying a recent (<<350ka) addition of a U-rich slab-derived fluid. The Valu Fa datacan be combined with existing 230Th238U data for theCentral Tonga arc to infer a fluid addition event at 相似文献
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C.J. STILLMAN 《Geology Today》1986,2(2):43-47
The intense volcanic activity of Ordovician times can be explained in terms of the type of plate-tectonic processes occurring today. Whenever plate tectonics is vigorous, so is volcanism. 相似文献
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KARI GRØSFJELD SVEND FUNDER MARIT-SOLVEIG SEIDENKRANTZ CHRIS GLAISTER 《Boreas: An International Journal of Quaternary Research》2006,35(3):493-520
Marine sediments from river sections in the Mezen River drainage, northwest Russia, have been analysed for dinoflagellate cysts, foraminifers and molluscs. The sediments were dated by pollen analysis and by reference to the local sea-level history, and are Late Saalian to late Eemian (c. 133 to 119.5 kyr in age). The Late Saalian deglaciation was characterized by Arctic conditions, but a few centuries into the Eemian the Gulf Stream system carried warm Atlantic water into the region. At 129.8 kyr BP there was a marked increase in the influx of Atlantic water, and the advection of warm Atlantic water was stronger and probably penetrated further eastwards than at present. The molluscs, dinoflagellate cysts and foraminifers reflect conditions warmer than present and that the optimum temperature occurred at the time of the early Eemian global sea-level rise. Around 128 kyr BP, the eustatic sea-level rise was curbed by isostatic rebound and accompanying regression and constriction of marine passages to the White Sea. Local, low-saline, stratified basins developed and characterized the next five to six millennia. 相似文献
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CHRIS WINDASS 《地球表面变化过程与地形》1996,21(11):1057-1059
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Sustainability: A View From The Paddock 总被引:1,自引:0,他引:1
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Crustal Contamination and Fluid-Rock Interaction during the Formation of the Platreef, Northern Limb of the Bushveld Complex, South Africa 总被引:4,自引:0,他引:4
The Platreef is the main platinum group element (PGE)-bearingfacies of the northern limb of the Bushveld complex, but unlikethe Merensky Reef of the eastern and western limbs, it is indirect contact with the country rock. Mineral separate 相似文献
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CHRIS A. McLINDEN D. J. CHARTRAND E. GRIFFIOEN J. C. McCONNELL C. T. McELROY 《Journal of Atmospheric Chemistry》1997,26(1):29-64
We have developed models of physically-based cloud and ocean surfacesfor use in photochemical models. These surface models are described in termsof a flux albedo and a normalized reflection function.Through these, the dependence of albedo on wavelength, solar zenithangle, cloud optical depth (cloud surfaces) and surface windspeed (ocean surfaces) are allowed for. In addition, the non-Lambertian nature of these surfaces is accounted for.We have integrated these surfacemodels into a multiple scattering radiative transfer model to assess their effects on the stratospheric radiation field and J-values. This was accomplished by comparison with results obtainedusing Lambertian, constant albedo surfaces. Comparisons of stratospheric radiation fields revealed that boththe wavelength and directional dependences of the cloud and oceansurfaces could be large effects.Differences between calculated J-values varied from 0 to 12% depending upon species, solar zenith angle, andheight.The J-values were then used as input for a chemical box model to examine the effects these surfaces had on stratospheric chemistry. Comparisons were made against box model runs using J-values fromconstant surfaces. Overall, the effect was on the order of 10%.Differences in number densities using these different surfacesvaried with latitude, height and species.Runs were made with and without heterogeneous chemistry. 相似文献