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961.
Shore platforms frequently exhibit steps or risers facing seaward, landwards or obliquely across‐shore. A combination of soft copy photogrammetry, ortho‐rectification, geo referencing and field measurement of step height are linked in a GIS environment to measure step retreat on chalk shore platforms at sample sites in the south of England over two periods, 1973–2001, 2001–2007. The methods used allow for the identification, delineation and measurement of historic change at high spatial resolution. The results suggest that while erosion of chalk shore platforms by step backwearing is highly variable, it appears to be of similar magnitude to surface downwearing of the same platforms measured by micro‐erosion meters (MEMs) and laser scanning, in a range equivalent to 0·0006 – 0·0050 m y?1 of surface downwearing. This equates to annual chalk volume loss from the platforms, by the two erosion processes combined, of between 0·0012 m3 m?2 and 0·0100 m3 m?2. Results from the more recent years' data suggests that step retreat has variability in both space and time which does not relate solely to climatic variability. The results must be viewed with caution until much larger numbers of measurements have been made of both downwearing and step erosion at higher spatial and temporal resolution. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
962.
The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian-Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a). 相似文献
963.
964.
通过对塔里木盆地巴麦地区寒武—奥陶系地震、沉积特征研究,运用地震、钻井岩心资料,对该区层 序特征分析,巴麦地区经历了由碳酸盐岩缓坡型台地向镶边斜坡型台地演化,主要控制因素是构造活动和海平面变化早— 中寒武世为缓坡型台地演化阶段,由于海平面频繁升降变化,台地边缘经历3次迁移;晚寒武世该区处于拉张环境形 成被动大陆边缘,海平面开始上升,发育镶边斜坡型台地,海平面相对上升速率小于沉积物供应速率,台地边缘向 盆地方向迁移;早奥陶世,海平面上升速率加快,大于沉积速率,台地以追补型叠加形式向台地方向迁移. 相似文献
965.
966.
967.
ZOU Yongliao ZHANG Liyan LIU Jianzhong MU Lingli REN Xin ZHANG Guangliang CHANG Jin YAN Jun ZHANG Nan ZHANG Hongbo Lü Chang LIU Jianjun ZUO Wei SU Yan WEN Weibin BIAN Wei WANG Min XU Chun LI Chunlai OUYANG Ziyuan 《《地质学报》英文版》2011,85(6):1299-1309
Gamma-ray spectrometer (GRS) is one of the main payloads on the Chang’E-1 (CE-1) lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03:58 on 28 November 2007, it performed the first observation of the lunar gamma rays. As of 24 October 2008, 2105?h of effective gamma rays spectra had been acquired by CE-1 GRS, which covers the whole surface of the moon. This paper mainly describes the data processing procedures and methods of deriving the elemental abundances by using the CE-1 GRS time series corrected spectra: first, to bin data into pixels for mapping; then, to perform a background deduction of the cumulative spectra and obtain a peak area of the elements; and finally, to use the elemental abundances inversion model to produce the elemental abundances. Based on these processing methods, the global abundance maps of U, K, and Th at a 5°×5° equal-area pixel are acquired by CE-1 GRS data. The paper gives a preliminary analysis of the uncertainties of the elemental abundances 相似文献
968.
A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (天山). The sample site temperature of -9.6 ℃ indicates that the unique glaciochemical re-cord was well preserved and suitable for the reconstruction of air pollution levels in this previously un-explored region. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4+, Cl-, SO42-, NO3-, HCOO-, and CH3COO-). NO3- and SO42- were characterized by significant high levels of pollution con-centration. Most air masses ... 相似文献
969.
芒亨河断裂的次级断裂是主要控矿构造,含矿围岩为上三叠统小定西组(T3xd)富钠质安山岩、玄武岩。受构造、层位、碎屑粒度的制约。 相似文献
970.
曼远铁矿以磁铁矿、赤铁矿、磁赤铁矿为主,赋存于澜沧群勐井山组上段中部。该组地层中夹多层中性—基性火山岩、火山凝灰岩,属典型的火山沉积变质型铁矿。 相似文献