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排序方式: 共有445条查询结果,搜索用时 31 毫秒
31.
Jaume Vergés Yohann Poprawski Ylènia Almar Peter A. Drzewiecki Mar Moragas Telm Bover-Arnal Chiara Macchiavelli Wayne Wright Grégoire Messager Jean-Christophe Embry David Hunt 《Basin Research》2020,32(6):1653-1684
Integration of extensive fieldwork, remote sensing mapping and 3D models from high-quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N–S Miravete anticline, the NW-SE Castel de Cabra anticline and the NW-SE Cañada Vellida ridge in the Maestrat Basin (Iberian Ranges, Spain). The pre shortening diapiric structures are defined by well-exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt-bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and was rejuvenated during Cenozoic shortening. Its evolution is separated into four halokinetic stages, including the latest Alpine compression. Regionally, the well-exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat Basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500-m-long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE-directed salt extrusion. A regional E-W cross section through the Ababuj, Miravete and Cañada-Benatanduz anticlines shows typical geometries of salt-related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well-developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat Basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque-Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/year. The transtensional regime is interpreted to have played a role in diapiric development. 相似文献
32.
33.
James C. Hower John K. Hiett Garry D. Wild Cortland F. Eble 《Natural Resources Research》1994,3(3):216-236
The Eastern Kentucky coal field, along with adjacent portions of Virginia and southern West Virginia, is part of the greatest production concentration of high-heating-value, low-sulfur coal in the United States, accounting for over 27% of the 1993 U.S. production of coal of all ranks. Eastern Kentucky's production is spread among many coal beds but is particularly concentrated in a limited number of highquality coals, notably the Pond Creek coal bed and its correlatives, and the Fire Clay coal bed and its correlatives. Both coals are relatively low ash and low sulfur through the areas of the heaviest concentration of mining activity. We discuss production trends, resources, and the quality of in-place and clean coal for those and other major coals in the region. 相似文献
34.
35.
Ammonium excretion by benthic invertebrates and sediment-water nitrogen flux in the Gulf of Mexico near the Mississippi River outflow 总被引:1,自引:0,他引:1
Wayne S. Gardner Elva Escobar Briones Elizabeth Cruz Kaegi Gilbert T. Rowe 《Estuaries and Coasts》1993,16(4):799-808
Benthic macroinvertebrate biomass and ammonium excretion rates were measured at four stations in the Gulf of Mexico near the Mississippi River mouth. Calculated areal excretion rates were then compared to sediment-water nitrogen fluxes measured in benthic bottom lander chambers at similar stations to estimate the potential importance of macroinvertebrate excretion to sediment nitrogen mineralization. Excretion rates for individual crustaceans (amphipods and decapods) was 2–21 nmoles NH4 + (mg dry weight)?1 h?1. The mean excretion rates for the polychaetes, Paraprionaspio pinnata [6–12 nmoles NH4 + (mg dry weight)?1h?1] and Magelona sp. [27–53 nmoles NH4 + (mg dry weight)?1h?1], were comparable or higher than previous measurements for similar size benthic or pelagic invertebrates incubated at the same temperature (22±1°C). Although the relatively high rates of excretion by these selective feeders may have been partially caused by experimental handling effects (e.g., removal from sediment substrates), they probably reflected the availability of nitrogen-rich food supplies in the Mississippi River plume. When the measured weight-specific rates were extrapolated to total areal biomass, areal macroinvertebrate excretion estimates ranged from 7 μmole NH4 + m?2h?1 at a 40-m deep station near the river mouth to 18 μmole NH4 + m?2h?1 at a shallower (28-m deep) station further from the river mouth. The net flux of ammonium and nitrate from the sediments to the water measured in bottom lander chambers in the same region were 15–53 μmole NH4 + m?2h?1 and ?25–21 μmole NO3 ? m?2h?1. These results suggest that excretion of NH4 + by macroinvertebrates could be a potentially important component of benthic nitrogen regeneration in the Mississippi River plume-Gulf shelf region. 相似文献
36.
Results from a new model of river basin evolution 总被引:1,自引:0,他引:1
This paper briefly describes a model of the erosional development of catchments and their channel networks. The model differentiates between the dominant transport processes in hillslope and channels. The development of channels and hillslopes occurs in an integrated manner as a function of physically observable mechanisms. The growth of a river basin is qualitatively described. The model concepts are used to study the basin during periods of growth (transient periods), as well as during dynamic equilibrium. This leads to hypotheses about the relationship between slopes, relief, tectonic uplift, erodability, runoff, and catchment area. It is shown that the model leads to very reasonable and desirable behaviour of hillslopes during retreat and degradation. 相似文献
37.
Boundary-layer depth and entrainment zone characterization with a boundary-layer profiler 总被引:13,自引:0,他引:13
A technique for determining the height of the convective atmospheric boundary layer (CBL) with a 915 MHz boundary-layer profiler is discussed. The results are compared with CBL heights determined from radiosonde measurements. The profiler provides continuous CBL height measurements with very good time resolution (30 minutes or less), allowing for detailed understanding of the growth and fluctuations of the CBL. In addition, the profiler provides information about the degree of definition of the CBL top and the thickness of the entrainment zone. The measurements discussed were taken during the Rural Oxidants in the Southern Environment II (ROSE II) experiment. 相似文献
38.
A. M. Dziewonski J. E. Franzen J. H. Woodhouse 《Physics of the Earth and Planetary Interiors》1985,40(4):249-258
Centroid-moment tensor solutions are presented for 170 earthquakes that occurred during the first quarter of 1985. The solutions are obtained using corrections for aspherical Earth structure. 相似文献
39.
A.M. Dziewonski J.E. Franzen J.H. Woodhouse 《Physics of the Earth and Planetary Interiors》1984,34(4):209-219
Centroid-moment tensor solutions are presented for 148 earthquakes that occurred during the first quarter of 1984. The solutions are obtained using corrections for aspherical Earth structure. 相似文献
40.
Structural similarities between dry diopside melt and superhydrous albite melt (X
w
>0.5) — both lack three-dimensional silicate units — suggest that thermodynamic relations may be similar. A model based on that assumption successfully predicts diopside melting relations and H2O solubilities. For the model, the three partial differential equations describing solution of H2O in albite melt for X
w
>0.5 have been integrated for diopside melt from X
w
=0 to X
w at least as large as 0.76, with two exceptions: an alternative partial differential equation for Henrian solution of H2O in dilute melts was applied for X
w
<0.20, and an alternative differential equation for the pressure dependence of a
w
at pressures below 2 kbar was developed. The latter alternative equation yields relatively small ¯Vw's at low pressures rather than the large ¯Vw's calculated from the equation from the albite system. Available experimental solubility data are not precise enough to offer a choice between the small-¯Vw and large-¯Vw equations. Integration of all the partial differential equations was constrained solely by the P and T of a single experimentally-determined point on the H2O-saturated solidus.Solubilities calculated by a Henrian-analogue solution model (a
di=X
di
2
) from the experimental H2O saturated solidus lie outside experimental solubility constraints for dilute melts. On the other hand, a Henrian model (a
di=Xdi) successfully predicts solubilities in dilute melts. The formulation of the Henrian model and magnitudes of model molar entropies of solution are consistent with the hypothesis that H2O dissolves in diopside melt as an essentially undissociated species with little ordering on melt structural sites. That species could in turn be consistently, if not uniquely, interpreted to be molecular H2O or a hydroxylation (OH–) complex formed from nonbridging oxygens. 相似文献