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61.
东濮凹陷是渤海湾盆地的一个次级构造单元,其古近系的两个沉积旋回发育了四套盐岩,分别位于沙河街组第三段的第四亚段(S34)、第三亚段(S33)、第二亚段(S32)和沙河街组的第一段(S1)。主要分布在凹陷北部。每套盐岩又由若干个盐韵律组成,每一单韵律由盐岩和泥岩组成。两套等时对比标志层(深湖沉积)之间盐岩与砂泥岩存在着相变关系。盐岩是在深盆背景下干旱成因的,盐类物质来自地下深处上涌的卤水,分层卤水是盐形成的基本形式,上涌通道是基底大断裂,动力基础是岩浆活动。盐的阻隔作用使其对下部地层的温度、压力均有影响,这种影响有利于加快盐下地层中的有机质成熟与演化。盐又是良好的盖层,且在高温、高压下盐呈塑性状态。勘探实践看出东濮凹陷的岩性油气藏与盐岩的沉积有密切的关系,因此搞清盐岩的分布规律对东濮凹陷下步勘探有着极为重要的意义。 相似文献
62.
63.
R. C. Doel D. Field M. D. Gray R. N. F. Walker 《Astrophysics and Space Science》1990,171(1-2):167-172
There is a large, diverse and rapidly growing body of OH observations from regions associated with star formation, the physical conditions of which are of great interest. To interpret these observations we need to calculate the populations of the OH energy levels using as accurate a model as is feasible. We have developed a large velocity gradient (LVG) model using the lowest 48 hyperfine states of OH and including the phenomenon of far-infrared line overlap using a new theory which treats all thermal and velocity overlaps. If we use a theory of maser propagation (Field and Gray, 1988) we are then able to see how competing maser lines develop.The generic behaviour which we find is in good agreement with the extensive maser observations of Gaume and Mutel 1987 and our calculations allow us to associate general physical conditions with the four ground state maser frequencies. In addition we are able to present preliminary results of the interpretation of the OH absorption observations of Guilloteauet al. (1984) and Walmsleyet al. (1986) for the compactHII region DR21.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain 相似文献
64.
The approach taken by Burnham and Chong to explain the occurrence of Hendra virus incidents in Australia, while analytically valid, is compromised by erroneous and incomplete biological data underpinning the analyses. Firstly, they erroneously state the peak mating, pregnancy and birthing periods in black, grey-headed and little red flying-foxes, thus their related interpretations and conclusions are flawed. Secondly, the reported association between grey-headed flying-fox density and HeV incidents is at odds with recent findings suggesting grey-headed flying-foxes are an insubstantial host. While this broader epidemiological perspective was not within their stated aims, it is appropriate that it be canvassed in discussion of their geo-spatial analyses given the level of horse-industry, public and media interest in Hendra virus and the potential for confusion and mixed messages regarding HeV exposure risk management. We suggest that a broader collaborative cross-disciplinary approach offers synergies that produce robust, real-world ‘one health’ outputs. 相似文献
65.
Deniz Karagulle Charlie Frye Roger Sayre Sean Breyer Peter Aniello Randy Vaughan Dawn Wright 《Transactions in GIS》2017,21(5):1040-1060
In 1964, E.H. Hammond proposed criteria for classifying and mapping physiographic regions of the United States. Hammond produced a map entitled “Classes of Land Surface Form in the Forty‐Eight States, USA”, which is regarded as a pioneering and rigorous treatment of regional physiography. Several researchers automated Hammond?s model in GIS. However, these were local or regional in application, and resulted in inadequate characterization of tablelands. We used a global 250 m DEM to produce a new characterization of global Hammond landform regions. The improved algorithm we developed for the regional landform modeling: (1) incorporated a profile parameter for the delineation of tablelands; (2) accommodated negative elevation data values; (3) allowed neighborhood analysis window (NAW) size to vary between parameters; (4) more accurately bounded plains regions; and (5) mapped landform regions as opposed to discrete landform features. The new global Hammond landform regions product builds on an existing global Hammond landform features product developed by the U.S. Geological Survey, which, while globally comprehensive, did not include tablelands, used a fixed NAW size, and essentially classified pixels rather than regions. Our algorithm also permits the disaggregation of “mixed” Hammond types (e.g. plains with high mountains) into their component parts. 相似文献
66.
67.
A Benthic Terrain Classification Scheme for American Samoa 总被引:2,自引:0,他引:2
Emily R. Lundblad Dawn J. Wright Joyce Miller Emily M. Larkin Ronald Rinehart David F. Naar Brian T. Donahue S. Miles Anderson Tim Battista 《Marine Geodesy》2006,29(2):89-111
Coral reef ecosystems, the most varied on earth, continually face destruction from anthropogenic and natural threats. The U.S. Coral Reef Task Force seeks to characterize and map priority coral reef ecosystems in the U.S./Trust Territories by 2009. Building upon NOAA Biogeography shallow-water classifications based on Ikonos imagery, presented here are new methods, based on acoustic data, for classifying benthic terrain below 30 m, around Tutuila, American Samoa. The result is a new classification scheme for American Samoa that extends and improves the NOAA Biogeography scheme, which, although developed for Pacific island nations and territories, is only applicable to a maximum depth of 30 m, due to the limitations of satellite imagery. The scheme may be suitable for developing habitat maps pinpointing high biodiversity around coral reefs throughout the western Pacific. 相似文献
68.
Recognizing that all management decisions have impacts on the ecosystem being exploited, an ecosystem-based approach to management seeks to better inform these decisions with knowledge of ecosystem structure, processes and functions. For marine fisheries in the California Current, along the West Coast of North America, such an approach must take into greater consideration the constantly changing climate-driven physical and biological interactions in the ecosystem, the trophic relationships between fished and unfished elements of the food web, the adaptation potential of life history diversity, and the role of humans as both predators and competitors. This paper reviews fisheries-based ecosystem tools, insights, and management concepts, and presents a transitional means of implementing an ecosystem-based approach to managing US fisheries in the California Current based on current scientific knowledge and interpretation of existing law. 相似文献
69.
Shallow marine carbonate sediments near the Dry Tortugas undergo extensive biogeochemical diagenesis upon deposition, resulting
in postdepositional fabric comprised of micritic aggregates of clay-sized particles, a matrix of peloidal mud, and intraparticular
cementation. Freshly deposited primary skeletons, mostly Halimeda fragments, yield micritic aggregates of clay-sized particles, which then form peloidal mud fabric upon compaction. The cryptocrystalline
particles produced by micritization are later replaced by high magnesian calcite. Cementation is observed in the intra-particular
microenvironment. However, no inter-particular, grain-binding cement was detected throughout the gravity core samples investigated. 相似文献
70.
Danielle Schreve Andy Howard Andrew Currant Stephen Brooks Simon Buteux Russell Coope Barnaby Crocker Michael Field Malcolm Greenwood James Greig Phillip Toms 《第四纪科学杂志》2013,28(2):118-130
This paper reports the discovery of a rare partial skeleton of a woolly rhinoceros (Coelodonta antiquitatis Blumenbach, 1799) and associated fauna from a low Pleistocene terrace of the River Tame at Whitemoor Haye, Staffordshire, UK. A study of the sedimentary deposits around the rhino skeleton and associated organic‐rich clasts containing pollen, plant and arthropod remains suggests that the animal was rapidly buried on a braided river floodplain surrounded by a predominantly treeless, herb‐rich grassland. Highlights of the study include the oldest British chironomid record published to date and novel analysis of the palaeoflow regime using caddisfly remains. For the first time, comparative calculations of coleopteran and chironomid palaeotemperatures have been made on the same samples, suggesting a mean July temperature of 8–11 °C and a mean December temperature of between ?22 and ?16 °C. Radiocarbon age estimates on skeletal material, supported by optically stimulated luminescence ages from surrounding sediments, indicate that the rhino lived around 41–43 k cal a BP. The combined geochronological, stratigraphic and palaeoenvironmental evidence places the assemblage firmly within the Middle Devensian (Marine Oxygen Isotope Stage 3). This would agree with other regional evidence for the timing of aggradation for the lowest terrace of the Trent and its tributary systems. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献