First evidence for episodic flooding events in the arid interior of central Saudi Arabia over the last 60 ka     

Sue J. McLaren  Farhan Al‐Juaidi  Mark D. Bateman  Andrew C. Millington 《第四纪科学杂志》2009,24(2):198-207

Although evidence for Quaternary environmental changes in the Arabian Peninsula is now growing, research has mostly been conducted in the United Arab Emirates (UAE) and in the Sultanate of Oman. There have been virtually no recent studies in Saudi Arabia, especially in the central region such as around Al‐Quwaiayh. In this area there are a series of outwash plains developed along the eastern edge of the Arabian Shield that formed in the late Quaternary. Four sedimentary sections, which are representative of the deposits that have accumulated, have been studied and five luminescence ages obtained. These are the first luminescence ages acquired from Quaternary sediments in central Saudi Arabia. The preserved fluvial deposits in the study area have formed during humid events at ca. 54 ka, ca. 39 ka and ca. 0.8 ka. In more recent times aeolian sands have been encroaching on to the distal parts of the outwash plains. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

鲁西新太古代济宁群含铁岩系形成时代——SHRIMP U-Pb锆石定年   总被引：12，自引：7，他引：5  

王伟  王世进  刘敦一  李培远  董春艳  颉颃强  马铭株  万渝生 《岩石学报》2010,26(4):1175-1181

济宁群以隐伏的地质体分布于华北克拉通鲁西地区,以往被划归古元古代。近年来在济宁群的钻探和地球物理研究中,发现存在较大规模条带状硅铁建造,其形成时代引起地学界极大关注。本文对济宁群变质碎屑沉积岩和长英质火山岩进行了锆石SHRIMP年龄测定。含砾绿泥绢云千枚岩的碎屑锆石年龄主要集中在～2.7Ga,可靠的最年轻碎屑锆石年龄为2.61±0.01Ga。变质长英质火山岩岩浆锆石年龄为2.56±0.02Ga。研究表明,济宁群形成于新太古代晚期,而不是以往认为的古元古代。华北克拉通条带状铁建造主要形成于新太古代晚期。济宁群在岩石组合、变质作用方面与鞍山、冀东以及五台地区同时代含硅铁建造的表壳岩系有差别,但是与本溪南芬铁矿的岩石组合有相似之处。这些可能为我国的隐伏太古宙BIF铁矿的研究与勘探提供了重要依据。  相似文献   

The determination of hydrogen concentration in silicates using ion-beam spectrochemical analysis (IBSCA)     

A. C. McLaren  R. Payling 《Physics and Chemistry of Minerals》1980,5(4):315-326

The spectral analysis of radiation emitted from sputtered particles may be used for the quantitative chemical analysis of solids. An important application is the determination of the hydrogen-content of solids via the Balmer H _α line at 656 nm. It is shown that provided an appropriate working curve can be constructed for the calibration of the instrument, IBSCA can be used for the determination of the bulk hydrogen-content in quartz and other silicates.  相似文献   

Stacking disorder in wollastonite and its relationship to twinning and the structure of parawollastonite     

J. L. Hutchison  A. C. McLaren 《Contributions to Mineralogy and Petrology》1977,61(1):11-13

It has been shown that a unit cell of parawollastonite in a matrix of triclinic wollastonite may be generated by (1) a single stacking fault and (2) by twinning. A wide domain of parawollastite may be produced by stacking faults in every second triclinic unit cell, whereas a twin lamella may be produced by faults in every adjacent triclinic unit cell.  相似文献   

Deformation mechanisms in experimentally deformed plagioclase feldspars     

D. B. Marshall  A. C. McLaren 《Physics and Chemistry of Minerals》1977,1(4):351-370

Optical and transmission electron microscopy have been used to study the microstructures in a series of plagioclase feldspars which had been experimentally deformed in compression. The observations show that deformation takes place by three mechanisms: (1) brittle fracture, (2) twinning and (3) slip due to the generation and motion of dislocations. Optical “deformation lamellae” are shown to be due to bunches of microfractures and to walls of tangled dislocations. Twins and fractures are often intimately associated and dislocations are often generated at fracture steps or voids. Moving dislocations apparently always generate a strip of fault in the slip plane. This, together with structural considerations as well as the visibility of dislocations (under various diffracting conditions) and the orientation of the applied stress, has made it possible to determine the slip systems which have operated in the deformed specimens.  相似文献   

Hydraulic control of grain-size distributions in a macrotidal estuary     

P. McLaren 《Sedimentology》1982,29(3):437-437

  相似文献   

Sediment penetration of Amoco Cadiz oil,potential for future release,and toxicity     

J.H Vandermeulen  D.E Buckley  E.M Levy  B.F.N Long  P McLaren  P.G Wells 《Marine pollution bulletin》1979,10(8):222-227

Weathering states of oil ranging from sheen oil to mousse have significant effects during oil stranding on oil-water and oil-sediment interaction. Observations of oiled sandy beaches suggest two mechanisms of beach contamination—general penetration and contamination of beach substrate by films of sheen oil (probably partially emulsified), and secondly the burial of discrete layers of mousse. Depending on timing of oiling with respect to beach dynamics large amounts of stranded oil can be accommodated within beach sediments. These then become available for later long-term release.Acute lethal toxicity of stranded Amoco Cadiz oil is intermediate to Bunker C and Kuwait crude. Simulated weathering studies suggest that there may be some increase in toxicity with weathering.  相似文献   

NMR and EPR studies of the chemically intermediate plagioclase feldspars     

C. M. Scala  D. R. Hutton  A. C. McLaren 《Physics and Chemistry of Minerals》1978,3(1):33-44

The NMR spectra of ²⁷Al and ²³Na and the EPR spectra of Fe³⁺ and Mn²⁺ have been studied in a range of plagioclase feldspars, of intermediate composition. Many of these crystals have previously been investigated by TEM methods (McLaren and Marshall, 1974). The broad, central ²⁷Al signals observed in labradorites have been interpreted in terms of an overall order/disorder of the Al/Si distribution. Spin Hamiltonian parameters have been determined for the Fe³⁺ spectra observed in labradorites and bytownites; these spectra were similar and yielded evidence of disordering of the Al/Si distribution. The severe limitations imposed by the variety of sites, the complex microstructures and the disordering, limit the structural information available from the resonance methods.  相似文献   

Sediment penetration of Amoco Cadiz oil,potential for future release,and toxicity     

J.H. Vandermeulen  D.E. Buckley  E.M. Levy  B.F.N. Long  P. McLaren  P.G. Wells 《Marine pollution bulletin》1978,9(11):292-293

  相似文献   

Planetary rings,by Larry W. Esposito     

Guy Consolmagno SJ 《Meteoritics & planetary science》2007,42(2):301-302

  相似文献