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241.
Linda K. Ayliffe Gavin J. Prideaux Michael I. Bird Rainer Grün Richard G. Roberts Grant A. Gully Rhys Jones L. Keith Fifield Richard G. Cresswell 《Quaternary Science Reviews》2008,27(17-18):1784-1788
A well-stratified succession of fossiliferous sediments occurs in Tight Entrance Cave, southwestern Australia. These infill deposits contain the remains of megafauna and have accumulated intermittently since the Middle Pleistocene: >137, 137–119 and 50–29 ka, according to the results of 14C, U–Th, ESR and OSL dating techniques. Megafaunal species richness was highest in the latest part of the penultimate glacial maximum and during the subsequent last interglacial (137–119 ka), but remains are less abundant following an apparent 70 ka depositional hiatus in the sequence. Most megafaunal specimens from the upper (<44 ka) units are fragmentary, and reworking from older strata cannot yet be ruled out. However, one specimen of Simosthenurus occidentalis (a large extinct kangaroo), a pair of articulated dentaries showing no signs of secondary transportation, was found within a sedimentary layer deposited between 48 and 50 ka. This represents one of the youngest demonstrably in situ occurrences of an Australian megafaunal taxon. 相似文献
242.
Late syn‐rift evolution of the Vingleia Fault Complex,Halten Terrace,offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models
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Gavin M. Elliott Christopher A.‐L. Jackson Robert L. Gawthorpe Paul Wilson Ian R. Sharp Lisa Michelsen 《Basin Research》2017,29(Z1):465-487
Rift basin tectono‐stratigraphic models indicate that normal fault growth controls the sedimentology and stratigraphic architecture of syn‐rift deposits. However, such models have rarely been tested by observations from natural examples and thus remain largely conceptual. In this study we integrate 3D seismic reflection, and biostratigraphically constrained core and wireline log data from the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway to test rift basin tectono‐stratigraphic models. The geometry of the basin‐bounding fault and its hangingwall, and the syn‐rift stratal architecture, vary along strike. The fault is planar along a much of its length, bounding a half‐graben containing a faultward‐thickening syn‐rift wedge. Locally, however, the fault has a ramp‐flat‐ramp geometry, with the hangingwall defined by a fault‐parallel anticline‐syncline pair. Here, an unusual bipartite syn‐rift architecture is observed, comprising a lower faultward‐expanding and an upper faultward‐thinning wedge. Fine‐grained basinfloor deposits dominate the syn‐rift succession, although isolated coarse clastics occur. The spatial and temporal distribution of these coarse clastics is complex due to syn‐depositional movement on the Vingleia Fault Complex. High rates of accommodation generation in the fault hangingwall led to aggradational stacking of fan deltas that rapidly (<5 km) pinch out basinward into offshore mudstone. In the south of the basin, rapid strain localization meant that relay ramps were short‐lived and did not represent major, long‐lived sediment entry points. In contrast, in the north, strain localization occurred later in the rift event, thus progradational shorefaces developed and persisted for a relatively long time in relay ramps developed between unlinked fault segments. The footwall of the Vingleia Fault Complex was characterized by relatively low rates of accommodation generation, with relatively thin, progradational hangingwall shorelines developed downdip of the fault block apex, sometime after the onset of sediment supply to the hangingwall. We show that rift basin tectono‐stratigraphic models need modifying to take into account along‐strike variability in fault structure and basin physiography, and the timing and style of syn‐rift sediment dispersal and facies, in both hangingwall and footwall locations. 相似文献
243.
244.
Daniel G. Gavin Andrew C.G. Henderson Karlyn S. Westover Sherilyn C. Fritz Ian R. Walker Melanie J. Leng Feng Sheng Hu 《Quaternary Science Reviews》2011,30(9-10):1243-1255
Several abrupt climate events during the Holocene, including the widely documented oscillation at 8.2 thousand years before present (ka), are attributed to changes in the North Atlantic thermohaline circulation. Additional mechanisms, such as interactions between atmospheric circulation, ice-sheet dynamics, and the influence of solar irradiance, also have been proposed to explain abrupt climatic events, but evidence remains elusive. This study presents evidence from multi-proxy analyses on the Holocene sediments of Eleanor Lake, interior British Columbia. Climatic inferences from our decadal-resolution record of biogenic silica (BSi) abundance are supported by changes in diatom and pollen assemblages from the same core and correlations with existing regional climate records. The BSi record reveals abrupt and persistent climatic shifts at 10.2, 9.3, and 8.5 ka, the latter two of which are coeval with major collapses of the Laurentide Ice Sheet. The record also reveals a short-term cooling at 8.2 ka that is distinct from the 8.5 ka event and similar in magnitude to several other late-Holocene coolings. BSi is correlated with solar-irradiance indices (r = 0.43–0.61), but the correlation is opposite in sign to that expected from direct solar forcing and weakens after 8 ka. Possible mechanisms causing the abrupt and persistent climate changes of the early Holocene include 1) sudden losses of ice and proglacial lake extent, causing a shift in the meridional structure of atmospheric circulation, 2) a possible link between solar minima and El Niño-like conditions that are correlated with warm spring temperature in interior British Columbia, and 3) the influence of solar irradiance variability on the position of the polar jet, possibly via effects on the strength of the glacial anticyclone. 相似文献
245.
Cold related mortality among people aged over 50 in England and Wales has decreased at a rate of 85 deaths per million population per year over the period 1976–2005. This trend is two orders of magnitude higher than the increase in heat-related mortality observed after 1976. Long term changes in temperature-related mortality may be linked to human activity, natural climatic forcings, or to adaptation of the population to a wider range of temperatures. Here we employ optimal detection, a formal statistical methodology, to carry out an end to end attribution analysis. We find that adaptation is a major influence on changing mortality rates. We also find that adaptation has prevented a significant increase in heat-related mortality and considerably enhanced a significant decrease in cold-related mortality. Our analysis suggests that in the absence of adaptation, the human influence on climate would have been the main contributor to increases in heat-related mortality and decreases in cold-related mortality. 相似文献
246.
247.
Elaine M. Sadler Carole A. Jackson Russell D. Cannon Vincent J. McIntyre Tara Murphy Joss Bland-Hawthorn Terry Bridges Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):227-245
We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 deg2 (about 20 per cent of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio identifications – the largest and most homogeneous set of radio source spectra ever obtained. The 2dFGRS radio sources span the redshift range to 0.438, and are a mixture of active galaxies (60 per cent) and star-forming galaxies (40 per cent). About 25 per cent of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We make a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star formation density of . 相似文献
248.
The Myra mine, now inactive, produced Zn and Cu concentrates from a Zn-rich, Kuroko-type, volcanogenic massive sulfide deposit located in the mountainous interior of Vancouver Island. The climate at the site is classified as “Marine West Coast”, with annual precipitation exceeding 2200 mm. Water from a losing stream on the mountainside above the mine follows preferential, fracture-controlled pathways to the upper workings before draining through the 10-Level portal. With a view toward mine decommissioning, portal discharge rate was monitored continuously over a 17-month period during which 46 water samples were collected. Effluent chemistry, dominated by Ca, HCO3 and SO4, shows moderate to high total base metal concentrations and near-neutral pH. Carbonatization, mainly of mafic rocks in the hangingwall, provides significant acid neutralizing potential. Metal concentrations vary seasonally, with smaller spikes associated with summer storm events, and a main peak associated with flushing of the workings during the first heavy autumn rains. Aqueous speciation modeling suggests that Fe and Al concentrations are controlled by the solubilities of hydrous ferric oxides and microcrystalline gibbsite, respectively. Concentrations of Zn, Cu and Cd appear controlled by sorption rather than by the solubilities of mineral phases. A comparison of precipitate concentrations observed in portal effluent with predictions from mass balance (inverse) modeling results suggests that less than 5% of the precipitated Fe and Al hydroxides are transported from the mine. However, amounts of sorbed Cu, Zn and Cd measured in the effluent are only slightly lower than modeled values. This suggests that the small fraction of (probably finer) Fe precipitates in portal effluent sorbs most of the Zn, Cu and Cd predicted by modeling. Based on mass balance calculations, metal loadings are explained by the oxidation of 3830 kg of pyrite, 600 kg of sphalerite and 190 kg of chalcopyrite, annually. Circum-neutral drainage conditions are maintained by the reaction of almost 19,800 kg of calcite, annually. 相似文献
249.
This study investigated physico-chemical characteristics of the water column and chemistry of suspended particulate material
(SPM) under quiescent, high-wind and high-wind/heavy-rainfall conditions in Homebush Bay, a highly contaminated embayment
of Port Jackson (Australia) to distinguish source and possible adverse effects to benthic and pelagic animals. Mean concentrations
in surficial sediment were <1, 14, 181, 141, 37, 290 and 685 μg g−1 for Cd, Co, Cr, Cu, Ni, Pb and Zn, respectively. Sediment chemistry indicated these metals had multiple sources, i.e. the
estuary, stormwater and industry. Mean total suspended solids (TSS) were 7, 17 and 20 mg L−1 during quiescent, high-rainfall and heavy rainfall/high wind conditions, respectively, whereas SPM Cd, Co, Cr, Cu, Ni, Pb
and Zn concentrations varied between 13–25, 166–259, 127–198, 38–82, 236–305 and 605–865 μg g−1, respectively under these conditions. TSS and total water metal concentrations were lowest during quiescent conditions. High
TSS and metal loads in surface water characterised high-rainfall events. Wind-induced resuspension contributed the greatest
mass of SPM and metals to the water column. Benthic animals may be adversely affected by Pb and Zn in sediment. Total water
Cu and Zn concentrations may pose a risk to filter-feeding animals in the water column due to resuspension of contaminated
sediment. 相似文献
250.
Joseph Arvai Gavin Bridge Nives Dolsak Robert Franzese Tomas Koontz April Luginbuhl Paul Robbins Kenneth Richards Katrina Smith Korfmacher Brent Sohngen James Tansey Alexander Thompson 《Climatic change》2006,78(1):217-225
To date the Intergovernmental Panel on Climate Change (IPCC) has concerned itself with gathering a state of the art review of the science of climate change. While significant progress has been made in enhancing our integrated understanding of the climate system and the dynamics of the social systems that produce an array of potential greenhouse gases, it is also clear from the panel's reports how far the science community is from being able to present a dynamic and synoptic view of the climate system as a whole. Clear evidence of these complexities and uncertainties inherent in the climate system is evident in efforts aimed at designing robust policy interventions. In this paper, we argue that the adaptive management framework in ecosystem management may be a useful model for guiding how the IPCC can continue to be relevant both as a scientific establishment and as a policy-relevant scientific endeavor. 相似文献