Depositional and post‐depositional history of warm stage deposits at Knocknacran,Co. Monaghan,Ireland: implications for preservation of Irish last interglacial deposits     

A. P. M. Vaughan  L. A. Dowling  F. J. G. Mitchell  S.‐E. Lauritzen  A. M. McCabe  P. Coxon 《第四纪科学杂志》2004,19(6):577-590

Organic‐rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic‐rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high‐energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium–thorium disequilibrium dating suggests that the organic‐rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post‐depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post‐Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A comparative study of the zooplankton in two adjacent embayments,Port Phillip and Westernport Bays,Australia     

William J. Kimmerer  A.David McKinnon 《Estuarine, Coastal and Shelf Science》1985,21(2):145-159

We report on a year's study of spatial and seasonal patterns of zooplankton abundance in Port Phillip and Westernport Bays, July 1982 to August 1983. These two bays, closely adjacent on the southern coast of Victoria, Australia, differ in several respects: Port Phillip is a nearly landlocked bay with a broad basin, while Westernport is an open tidal embayment with extensive mud and seagrass banks. Both bays have a resident zooplankton fauna distinct from that of Bass Strait. Although these resident communities have many species in common, patterns of abundance and dominance are quite different. We found that the holoplankton of Port Phillip was about half copepods, mostly Paracalanus indicus, with 23% Caldocera and 21% larvaceans. Westernport Bay zooplankton was dominated by Acartia tranteri, with no resident cladoceran fauna. Bass Strait species were more often found in Westernport than in Port Phillip Bay, but the resident community of Port Phillip Bay was more similar to that of Bass Strait than to that of Westernport.Although this study was undertaken in an exceptionally dry year, the available historical data show that the overall patterns found in 1982–1983 are typical for these bays. The differences in community composition probably relate to differences in depth profile, predator abundance, and suspended matter between the bays.  相似文献   

Spectral variations of DY Cen     

Sunetra Giridhar  N. Kameswara Rao  David L. Lambert 《Journal of Astrophysics and Astronomy》1996,17(1-2):23-40

Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to 1992  相似文献   

Aquitard Distribution In A Northern Reach Of The Miami Valley Aquifer,Ohio, USA: Part 1. Three-Dimensional Geostatistical Evaluation Of Physical Heterogeneity     

Robert W. Ritzi  David F. Dominic  Kenneth W. Kausch 《Hydrogeology Journal》1996,4(2):12-24

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The morphology of nine radio-selected faint galaxies from deep Hubble Space Telescope imaging     

Nathan D. Roche  James D. Lowenthal  David C. Koo 《Monthly notices of the Royal Astronomical Society》2002,337(3):840-850

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DCMT光电扫描主测微器的设计与研究     

李志刚  李焕信  方福胜  朱紫  许林生 《时间频率学报》1993,(1)

DCMT主测微器不同于其它类型的子午环测微器,它具有自校准测定仪器参数的功能。该测微器采用了活动光栅的方案,其优点是能观测近极星和各类准直像;活动光栅另一个显著优点是不同赤纬星几乎可用相同的观测时间.对“V”形光栅的工作原理和误差进行了详细讨论,并给出了一组严格的公式。其系统误差来源有:光栅形状改正、光栅驱动方向相对于光栅的倾斜、光栅驱动方向相对于赤径方向的倾斜、星径曲率改正。  相似文献   

Late Holocene relative sea level rise and the Neoglacial history of the Greenland ice sheet     

Antony J. Long  Sarah A. Woodroffe  Sue Dawson  David H. Roberts  Charlotte L. Bryant 《第四纪科学杂志》2009,24(4):345-359

In West Greenland, early and mid Holocene relative sea level (RSL) fall was replaced by late Holocene RSL rise during the Neoglacial, after 4–3 cal. ka BP (thousand calibrated years before present). Here we present the results of an isolation basin RSL study completed near to the coastal town of Sisimiut, in central West Greenland. RSL fell from 14 m above sea level at 5.7 cal. ka BP to reach a lowstand of ?4.0 m at 2.3–1.2 cal. ka BP, before rising by an equivalent amount to present. Differences in the timing and magnitude of the RSL lowstand between this and other sites in West and South Greenland record the varied interplay of local and non‐Greenland RSL processes, notably the reloading of the Earth's crust caused by a Neoglacial expansion of the Greenland Ice Sheet (GIS) and the subsidence associated with the collapse of the Laurentide Ice Sheet forebulge. This means that the timing of the sea level lowstand cannot be used to infer directly when the GIS advanced during the Neoglacial. The rise in Late Holocene RSL is contrary to recently reported bedrock uplift in the Sisimiut area, based on repeat GPS surveys. This indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late Holocene, and that there has been a switch from subsidence to uplift at some point in the last thousand years or so. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Carbon isotope fractionation between graphite and diamond during shock experiments     

Teruyuki Maruoka  Christian Koeberl  Jun‐ichi Matsuda  Yasuhiko Syono 《Meteoritics & planetary science》2003,38(8):1255-1262

Abstract— Carbon isotopic compositions were measured for shock‐produced diamond and shocked graphite formed at peak pressures ranging from 37 to 52 GPa. The δ¹³C values of diamonds produced in a sealed container were generally lower than that of the initial graphite. The differences in the carbon isotopic composition between initial graphite and shocked graphite/diamond may reflect kinetic isotopic fractionation during the oxidation of the graphite/diamond and/or analytical artifacts possibly induced by impurities in the samples. The pressure effect on the isotopic fractionations between graphite and diamond can be estimated from the δ¹³C values of impurity‐free diamonds produced using a vented container from which gases, including oxygen, in pore spaces escaped during or after the diamond formation (e.g., 0.039 ± 0.085‰ at a peak pressure of 52 GPa). Any isotopic fractionation induced by shock conversion of graphite to diamond is too small to be detected in natural shock‐induced diamond‐graphite systems related to terrestrial impact cratering processes.  相似文献   

Stellar masses and star formation histories for 10⁵ galaxies from the Sloan Digital Sky Survey     

Guinevere Kauffmann  Timothy M. Heckman  Simon D. M. White  Stéphane Charlot  Christy Tremonti  Jarle Brinchmann  Gustavo Bruzual  Eric W. Peng  Mark Seibert  Mariangela Bernardi  Michael Blanton  Jon Brinkmann  Francisco Castander  Istvan Csábai  Masataka Fukugita  Zeljko Ivezic  Jeffrey A. Munn  Robert C. Nichol  Nikhil Padmanabhan  Aniruddha R. Thakar  David H. Weinberg  Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53

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An HST morphological survey of faint extremely red objects     

David G. Gilbank  Ian Smail  R. J. Ivison  C. Packham 《Monthly notices of the Royal Astronomical Society》2003,346(4):1125-1142

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