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41.
Naveed Ur RAHMAN XIAN Benzhong FANG Linhao CHEN Sirui CHEN Peng Zaheen ULLAH WANG Pengyu 《《地质学报》英文版》2024,98(3):753-770
The Carnian Pluvial Episode (CPE) fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province (LIP). However, the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood. Records of negative carbon isotopic excursions (NCIEs), mercury (Hg), Hg/TOC, and Hg enrichment factor (HgEF) from oil shales in a large-scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions. The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe, the UK, and South and North China. The U-Pb geochronology indicates a Ladinian–Carnian age for the Chang 7 Member. A comprehensive overview of the geochronology, NCIE correlation, and previous bio- and chronostratigraphic frameworks shows that the Ladinian–Carnian boundary is located in the lower part of Chang 7 in the Yishicun section. HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions. The records of Hg, Hg/TOC, HgEF, and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies, indicating a global response to the Wrangellia LIP during the CPE. Anoxia, a warm-humid climate, enhancement of detrital input, and NCIEs are synchronous with the CPE interval in the Ordos Basin, which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin. 相似文献
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W. J. Vreeken 《地球表面变化过程与地形》1984,9(1):1-18
This paper is about conditions and processes during the accumulation of the Upper Pleniglacial Middle and Upper Silt Loam complexes at Nagelbeek, Limbourg, a Weichselian stratigraphical type locality. The complexes correlate with Hesbayan and Brabantian loesses in Belgium, formed between 28,000 and 12,400 yrs BP. They are characterized by sediment features (cracks, mass deformations, and cut-and-fill features) that are ascribed to a cryogenic regimen. The main Middle Silt Loam subunit contains contraction cracks deformed and further modified by masswasting. Intra-Upper-Pleniglacial pedogenic intervals are inferred from three greyish bands, from a truncated weathered zone surmounting the Middle Silt Loam, and from an aeolian-cumulic palaeosol at the base of the Upper Silt Loam. Latter two zones and an intervening erosional unconformity were cryogenically reworked, less than 22,000 yrs BP, to form a complex stratigraphical marker-zone: the ‘Horizon à Langues de Nagelbeek’. Morphological variants of the marker-zone are described. The geomorphic evolution of the Nagelbeek upland, from Saalian to Holocene times, is summarized in unconformity maps and a time diagram. 相似文献
45.
Noel Cressie 《Mathematical Geology》1985,17(7):693-702
The relative variogram has been employed as a tool for correcting a simple kind of nonstationarity, namely that in which local variance is proportional to local mean squared. In the past, this has been linked in a vague way to the lognormal distribution, although if {Zt; t D}is strongly stationary and normal over a domain D,then clearly {exp (Zt); t D}will stillbe stationary, but lognormal. The appropriate link is made in this article through a universal transformation principle. More general situations are considered, leading to the use of a scaled variogram. 相似文献
46.
利用船测数据以及Landsat-7 ETM+影像评估南极海冰区AMSR-E海冰密集度 总被引:2,自引:1,他引:2
利用第26次中国南极科学考察期间收集的海冰密集度船基观测资料以及由Landsat-7 ETM+得到的海冰密集度来验证AMSR-E南极海冰区海冰密集度产品的精度。AMSR-E海冰密集度与船基目视观测的海冰密集度存在着一定的线性关系(R2=0.816), 但两者匹配得并不是很好。与ETM+海冰密集度相比,AMSR-E数据趋向于低估海冰密集度,在25景晴空条件下的ETM+影像中,平均海冰密集度偏差(AMSR-E海冰密集度-ETM+海冰密集度)从-5.33%到-21.5%,而相应的均方根误差RMSE (Root Mean Squared Errors)从13.7%到33.8%。依据Landsat-7 ETM+ 海冰分类,AMSR-E数据海冰密集度最大的误差产生于新冰区。 相似文献
47.
Extensional and compressional structures are globally abundant on Mars. Distribution of these structures and their ages constrain the crustal stress state and tectonic evolution of the planet. Here in this paper, we report on our investigation over the distribution of the tectonic structures and timings of the associated stress fields from the Noachis-Sabaea region. Thereafter, we hypothesize possible origins in relation to the internal/external processes through detailed morphostructural mapping. In doing so, we have extracted the absolute model ages of these linear tectonic structures using crater size-frequency distribution measurements, buffered crater counting in particular. The estimated ages indicate that the tectonic structures are younger than the mega impacts events(especially Hellas) and instead they reveal two dominant phases of interior dynamics prevailing on the southern highlands, firstly the extensional phase terminating around3.8 Ga forming grabens and then compressional phase around 3.5-3.6 Ga producing wrinkle ridges and lobate scarps. These derived absolute model ages of the grabens exhibit the age ca. 100 Ma younger than the previously documented end of the global extensional phase. The following compressional activity corresponds to the peak of global contraction period in Early Hesperian. Therefore, we conclude that the planet wide heat loss mechanism, involving crustal stretching coupled with gravitationally driven relaxation(i.e.,lithospheric mobility) resulted in the extensional structures around Late Noachian(around 3.8 Ga). Lately cooling related global contraction generated compressional stress ensuing shortening of the upper crust of the southern highlands at the Early Hesperian period(around 3.5-3.6 Ga). 相似文献
48.
以震中迁移始发点的前兆讨论了唐山7.8级地震震中位置的预测,并以此为例分析了汶川8级地震和芦山7级地震的前兆问题。另外,从震中迁移延长线上的前兆来讨论了唐山大震的发生时间。 相似文献
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Katy A. Boon Peter Rostron Michael H. Ramsey 《Geostandards and Geoanalytical Research》2011,35(3):353-367
In the assessment of potentially contaminated land, the number of samples and the uncertainty of the measurements (including that from sampling) are both important factors in the planning and implementation of an investigation. Both parameters also effect the interpretation of the measurements produced, and the process of making decisions based upon those measurements. However, despite their importance, previously there has been no method for assessing if an investigation is fit‐for‐purpose with respect to both of these parameters. The Whole Site Optimised Contaminated Land Investigation (WSOCLI) method has been developed to address this issue, and to allow the optimisation of an investigation with respect to both the number of samples and the measurement uncertainty, using an economic loss function. This function was developed to calculate an ‘expectation of (financial) loss’, incorporating costs of the investigation itself, subsequent land remediation, and potential consequential costs. To allow the evaluation of the WSOCLI method a computer program ‘OCLISIM’ has been developed to produce sample data from simulated contaminated land investigations. One advantage of such an approach is that as the ‘true’ contaminant concentrations are created by the program, these values are known, which is not the case in a real contaminated land investigation. This enables direct comparisons between functions of the ‘true’ concentrations and functions of the simulated measurements. A second advantage of simulation for this purpose is that the WSOCLI method can be tested on many different patterns and intensities of contamination. The WSOCLI method performed particularly well at high sampling densities producing expectations of financial loss that approximated to the true costs, which were also calculated by the program. WSOCLI was shown to produce notable trends in the relationship between the overall cost (i.e., expectation of loss) and both the number of samples and the measurement uncertainty, which are: (a) low measurement uncertainty was optimal when the decision threshold was between the mean background and the mean hot spot concentrations. (b) When the hot spot mean concentration is equal to or near the decision threshold, then mid‐range measurement uncertainties were optimal. (c) When the decision threshold exceeds the mean of the hot spot, mid‐range measurement uncertainties were optimal. The trends indicate that the uncertainty may continue to rise if the difference between hot spot mean and the decision threshold increases further. (d) In any of the above scenarios, the optimal measurement uncertainty was lower if there is a large geochemical variance (i.e., heterogeneity) within the hot spot. (e) The optimal number of samples for each scenario was indicated by the WSOCLI method, and was between 50 and 100 for the scenarios considered generally; although there was significant noise in the predictions, which needs to be addressed in future work to allow such conclusions to be clearer. 相似文献