The Waqf as Suwwan crater,Eastern Desert of Jordan: aspects of the deep structure of an oblique impact from reflection seismic and gravity data     

Till Heinrichs  Elias Salameh  Hani Khouri 《International Journal of Earth Sciences》2014,103(1):233-252

The deeply eroded Waqf as Suwwan ring structure was recently discovered to be a large impact, the first identified in the near east. Large-scale reflection seismic structure shows the impact situated high on the northeastern flank of the Jordan Uplift sloping into Wadi Sirhan Basin. If exhumation is linked to the Arabia–Eurasia collision, a likely time window for the impact event may be latest Eocene to Late Oligocene. Impact into a shallow sea seems an optional scenario. Old reflection seismic lines offer limited insight into the deep structure of the rim and part of the central uplift of the complex crater. An important structural clue is provided by a well-resolved seismic horizon of a yet tentative correlation with a Paleozoic black shale. The central gravity high is compatible with a mass surplus by the uplift of denser Paleozoic basement below the central uplift. The gravity model further indicates a ring of dense Paleozoic sediments rising from below into the ring syncline. Seismics show presumably radial synclines in the central uplift which are interpreted by centripetal constrictional flow during crater collapse. Beneath the final crater’s outer boundary, a shallow-dip normal fault zone, subtle seismic structure in uncollapsed footwall segments reveal an asymmetry of strain. The asymmetry is attributed to the cratering flow by an oblique impact directed toward NE. The finding provides independent support to an earlier suggestion of impact obliquity based on vergency of folds exposed on the central uplift.  相似文献   

The Two Micron All Sky Survey     

S. G. Kleinmann  M. G. Lysaght  W. L. Pughe  S. E. Schneider  M. F. Skrutskie  M. D. Weinberg  S. D. Price  K. Matthews  B. T. Soifer  J. P. Huchra  C. A. Beichman  T. J. Chester  T. Jarrett  G. L. Kopan  C. J. Lonsdale  J. Elias  J. W. Liebert  P. Seitzer 《Astrophysics and Space Science》1994,217(1-2):11-17

  相似文献   

Modeling watershed-scale sequestration of soil organic carbon for carbon credit programs     

Vineet Yadav  George P. Malanson  Elias Bekele  Christopher Lant 《Applied geography (Sevenoaks, England)》2009,29(4):488-500

Impending risks associated with climate change have forced the global community to devise tradable pollution permit or “cap and trade” approaches to control the release of greenhouse gases. In the U.S, soils have the potential to offset about 10 percent of annual CO₂ emissions; however, if carbon credits are to be included in greenhouse gas control programs, soil organic carbon (SOC) sequestration rates associated with agricultural land uses must be computed at a watershed scale. The Soil Water Assessment Tool (SWAT) water quality model, the Water Erosion Prediction Project (WEPP) erosion model, and the CENTURY 4.0 a soil carbon model were used to simulate carbon sequestration rates for 160 crop-tillage rotations in 272 sub-basins of the Big Creek watershed (12,300 hectares). Under annual crops, only no-till in a corn-soybean rotation, on low to moderate slopes results in net gains in SOC. Substantial annual rates of SOC sequestration occur only under perennial crops such as Conservation Reserve Program (CRP; 0.14 t/ha without erosion; 0.08 with erosion), pasture (0.67 t/ha without erosion; 0.58 with erosion), hay (0.88 t/ha without erosion; 0.52 with erosion), and forest (2.66 t/ha without erosion; 2.49 with erosion). Erosion thus has a large effect on the spatial distribution of field-measured SOC by moving it down slope and increasing its spatial variability. Because of this, carbon credit programs should be based on field practices, thus targeting the locations where the sequestration of atmospheric carbon actually occurs and minimizing monitoring costs. Developing model-based estimates of SOC sequestration rates of field practices at many locations would thus greatly serve the needs of carbon crediting programs.  相似文献   

Modeling soil erosion using RUSLE and GIS in a watershed occupied by rural settlement in the Brazilian Cerrado   总被引：1，自引：0，他引：1  

Elias Rodrigues da Cunha  Vitor Matheus Bacani  Elói Panachuki 《Natural Hazards》2017,85(2):851-868

The installation of a rural settlement complex in the watershed stream Indaiá has promoted changes in land-use and vegetation cover dynamics; however, the effects of intensive agriculture and cattle farming in rural settlements on soil loss rates are not well known. Predictive models implemented in geographic information systems have proven to be effective tools for estimating erosive processes. The erosion predictive model Revised Universal Soil Loss Equation (RUSLE) is a useful tool for analyzing, establishing and managing soil erosion. RUSLE has been widely used to estimate annual averages of soil loss, by both interrill and rill erosion, worldwide. Therefore, the aim of this work was to estimate the soil loss in the watershed stream Indaiá, using the RUSLE model and geoprocessing techniques. To estimate soil loss, the following factors were spatialized: erosivity (R), erodibility (K), topography (LS), land-use and management (C) and conservation practices (P); the annual soil loss values were calculated using the RUSLE model equation. The estimated value of soil loss in the hydrographic basin ranged from 0 to 4082.16 Mg ha^?1 year^?1 and had an average value of 47.81 Mg ha^?1 year^?1. These results have demonstrated that 68.16 % of the study area showed little or no soil loss based on the Food and Agriculture Organization’s (FAO 1980) classification. When comparing the average value of soil loss obtained using the RUSLE model with the Natural Potential for Erosion, a 16-fold reduction in soil was found, which highlighted the fact that vegetation cover (C factor) has a greater influence than other factors (R, K and LS) on soil loss prediction attenuation. These results lead to the conclusion that soil loss occurs by different methods in each settlement in the basin and that erosive processes modeled by geoprocessing have the potential to contribute to an orderly land management process.  相似文献   

Lithostratigraphic and structural controls of ‘tsavorite’ deposits at Lemshuku,Merelani area,Tanzania     

Julien Feneyrol  Gaston Giuliani  Daniel Ohnenstetter  Elisabeth Le Goff  Elias P.J. Malisa  Mark Saul  Eric Saul  John Saul  Vincent Pardieu 《Comptes Rendus Geoscience》2010,342(10):778-785

The first study of the Lemshuku ‘tsavorite’ mining district is presented. From bottom to top, the lithostratigraphic column corresponds to a metasedimentary sequence composed of quartzite, fine-grained graphitic gneiss, kyanite-graphite gneiss, biotite-almandine gneiss, metasomatized graphitic gneiss and dolomitic marble. ‘Tsavorite’ occurs in quartz veins and rarely as nodular concretions. Two factors control mineralization: (1) lithostratigraphy, with ‘tsavorite’ in association with pyrite and graphite confined to quartz veins within the metasomatized graphitic gneiss; and (2) structure, with the mineralized veins characteristically controlled by tight isoclinal folds associated with shearing.  相似文献   

Groundwater vulnerability and risk mapping in a geologically complex area by using stable isotopes, remote sensing and GIS techniques   总被引：1，自引：0，他引：1  

Elias Dimitriou  Ierotheos Zacharias 《Environmental Geology》2006,51(2):309-323

Groundwater vulnerability and risk mapping is a relatively new scientific approach for facilitating planning and decision making processes in order to protect this valuable resource. Pan European methodology for aquifers vulnerability has recently been developed by assessing all the existing relevant techniques and emphasizing on karstic environments. In the particular study, state-of-the-art methods and tools have been implemented such as remote sensing, isotopic investigations and GIS to map the groundwater vulnerability and pollution risk in a geologically complex area of W. Greece. The updated land use map has been developed from a Landsat 7+TM image elaborated with image analysis software, while the detailed hydrogeologic properties of the area have been recorded with an intensive isotopic study. The local groundwater vulnerability map has been produced following the aforementioned Pan European method, in a GIS environment while the risk map, which was the final product of the study, has been developed after combining the vulnerability and the land use maps. The results indicated that the areas comprised of highly tectonized calcareous formations represented high vulnerability and risk zones while forested areas away from the karstic aquifer illustrated moderate to low vulnerability. Moreover, human activities increase the pollution risk in lowland areas consisting of sedimentary deposits that have been classified as moderate vulnerability. The particular methodology operated efficiently in this study and due to its accuracy and relatively easy implementation can be used as a decision support tool for local authorities.  相似文献   

贵州紫云石炭纪叶状藻礁:藻类繁盛的标志   总被引：7，自引：3，他引：7  

张永利  巩恩普  关长庆  孙宝亮 《沉积学报》2007,25(2):177-182

紫云晚石炭世叶状藻礁发育在碳酸盐台地边缘。叶状藻礁体具有多样性，有叶状藻点礁、多层迭置叶状藻礁和大型叶状藻礁体。叶状藻礁体的建造过程是由叶状藻群落的发展和沉积环境所决定的，叶状藻具有主动建造礁体的能力，构成骨架礁灰岩。礁体建造过程大体上分为三个阶段:①生物碎屑滩的形成；②叶状藻生长及礁体建造；③造礁结束。多层迭置叶状藻礁为以上三个阶段的多次重复；大型叶状藻礁是在礁体发育过程的第二阶段由连续生长的叶状藻五次集中发育建造而成。  相似文献   

Improved assessment of biodegradation extent and prediction of petroleum quality     

Rouven Elias  Andrea Vieth  Angelo Riva  Brian Horsfield  Heinz Wilkes 《Organic Geochemistry》2007,38(12):2111-2130

Biodegradation of crude oil causes volumetrically important compositional changes, which lead to significant deterioration in quality, in particular during the early stages of alteration. To better understand these effects we focussed on a detailed assessment of light to moderate levels of alteration. We investigated a suite of 40 crude oil samples from five different petroleum systems to evaluate the extent of alteration occurring in reservoirs. Based on a comprehensive geochemical characterization, five individual crude oil sequences were defined, where compositional variability is mainly due to microbial activity in the reservoir. In particular, samples from the Gullfaks field (offshore Norway) and from a petroleum system offshore Angola illustrate that conventional molecular biodegradation parameters, such as the Pr/n-C₁₇ and Ph/n-C₁₈ alkane ratios are not suitable for defining the extent of biodegradation in petroleum reservoirs. Here, we suggest a new molecular biodegradation parameter, the degradative loss, that can be used to quantify depletion in individual crude oil constituents. The approach allows improved assessment of the extent of biodegradation in crude oil samples by means of the mean degradative loss. It is demonstrated that crude oil quality, as assessed from API gravity, can be predicted directly from the molecular composition of crude oils. Our data clearly indicate that the degradation patterns of light hydrocarbons and n-alkanes differ in different petroleum systems. This suggests that microbial communities are different and therefore generate different molecular degradation patterns which have to be evaluated individually for each system.  相似文献   

Detecting organic tracers from biomass burning in the atmosphere.   总被引：1，自引：0，他引：1  

B R Simoneit  V O Elias 《Marine pollution bulletin》2001,42(10):805-810

This is a brief review key to the literature on the determination of organic tracers from biomass burning which are detectable even after long-range global transport in total extracts of atmospheric particles. The major tracers are thermal degradation products from the biopolymer cellulose, namely the didehydromonosaccharide derivatives levoglucosan, galactosan and mannosan and the resin acid derivative dehydroabietic acid, with minor beta-sitosterol. Dehydroabietic acid is emitted primarily from burning of conifer fuel and these tracers are found in most aerosol samples from the North American continent. Particulate matter from the atmosphere over oceanic areas contains organic tracers from both natural and biomass burning emissions. The major biomarker compounds characterized are natural products from continental vegetation consisting primarily of epicuticular wax components and trace components from biomass burning emissions. The presence of these tracers in atmospheric particulate matter over the ocean confirms the long-range transport of smoke from biomass burning off the continents.  相似文献   

Chronological variations in concentrations and isotopic compositions of anthropogenic atmospheric lead in sediments of a remote subalpine pond     

H. Shirahata  R.W. Elias  C.C. Patterson  M. Koide 《Geochimica et cosmochimica acta》1980,44(2):149-162

Lead concentrations decrease 4-fold in going from the surface of sediments in a mountain pond to relatively small values in layers 130 yr old. There is a corresponding change in the $\text{Pb}{}^{206}\text{Pb}{}^{207}$ ratio in the sediments from industrial-like values of 1.18 near the surface to natural values of 1.24 at depth. Concentrations of Ca, Sr, and Ba remain relatively constant with depth. The excess Pb is shown to be of eolian anthropogenic origin, through isotopic, chemical, and mass balance relationships with metals in aerosols, dry deposition, and precipitation. This proves that inputs of contamination Pb were nearly absent centuries ago in a remote non-domesticated subalpine canyon, but are present today in that ecosystem in amounts more than 20 times the natural inputs and are irrefutably linked with industrial sources. As a consequence of these inputs, present Pb concentrations have been elevated 5-fold in plants and 50-fold in animals above natural levels. These Pb contamination effects are being caused by present-day atmospheric concentrations of ~10 ng Pb/m³. The ecosystem studied here characterizes the vast remote non-domesticated regions of North America, and these findings indicate that such regions are highly polluted by industrial Pb aerosols.  相似文献