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191.
192.
Whither stratigraphy? 总被引:2,自引:0,他引:2
Andrew D. Miall 《Sedimentary Geology》1995,100(1-4)
There have been three revolutions in sedimentary geology. The first two began in the 1960s, consisting of the development of process-response sedimentary models and the application of plate-tectonic concepts to large-scale aspects of basin analysis. The third revolution, that of sequence stratigraphy, began in the late 1970s and helped to draw together the main results of the first two: the knowledge of autogenic processes learned through facies analysis, and the understanding of tectonism implicit in the unravelling of regional plate kinematics. Developments in the use of seismic-reflection data and the evaluation of a hypothesis of global eustasy provided considerable stimulation for stratigraphic research.Current developments in the field of sequence stratigraphy are focusing on three areas. (1) Elaboration of the sequence-architecture models for various configurations of depositional environment and sea-level history. (2) Exploration of various mechanisms for sequence generation, especially tectonism and orbital forcing. (3) Attempts to improve the level of precision in stratigraphic correlation and to refine the geological time scale, as a means to test the model of global eustasy.The growth in the power of computers and our knowledge of physical and chemical processes has led to the evolution of an entirely new way of evaluating earth history, termed quantitative dynamic stratigraphy. Mathematical modelling and numerical simulation of complex earth processes are now possible, and require the collection and integration of a wide array of quantitative and qualitative data sets. Applications include the study of the geodynamic evolution of sedimentary basins, modelling of stratigraphic sequences and global climates, studies of Milankovitch cycles (cyclostratigraphy) and simulation of fluid flow through porous media. The Global Sedimentary Geology Program has brought many of these areas of study together in multidisciplinary, global-scale studies of the sedimentary history of the earth. The results of these studies have wide application to many problems of importance to the human condition, including the past history of global climate change and other environmental concerns. The study of stratigraphy is at the centre of the new view of the earth, termed earth-systems science, which views earth as an ‘organic’ interaction between the lithosphere, biosphere, hydrosphere, and atmosphere. 相似文献
193.
Mark S. T. Bukowinski Philip E. Wannamaker Manfred Koch Yukio Fujinawa Dr. Pradeep Talwani D. Möhlmann Andrew H. Knoll Lucia Lovison-Golob Krzysztof Haman Hanna Pawłowska Henryk Piwkowski Dr. Anthony Dore Nguyen Xuan Huy Edward R. Cook Jan Błecki Jacek Leliwa-Kopystynski Magdalena Sroczynska-Kozuchowska 《Pure and Applied Geophysics》1993,140(1):139-177
194.
Andrew J. Krmenec 《The Professional geographer》1991,43(1):60-67
Local governments are under pressure to develop alternative revenue sources to their already strapped property tax bases. Throughout the 1970s, municipal governments nationwide restructured their local taxes by substituing sales tax for property tax revenue. A tax accounting model identified two sources of sales-for-property tax substitution: changes in the tax rates and normal economic growth and decline. Most of the sales-for-property tax substitution experienced in Illinois city finance was attributable to economic change. The critical determinant of this substitution appreared to be the municipality's share of the regional retail market. Cities in higher density metropolitan areas were less likely to experience sales-for-property tax substitution through economic growth than those cities in lower density, less competitive environments. 相似文献
195.
196.
The response of a barotropic coastal ocean on a step-shaped continental shelf to a traveling sinusoidal wind stress forcing is predicted theoretically using a frictional force proportional to the alongshore current velocity. This theory is compared to a small set of observations from the northeast coast of Australia where a sudden widening of the continental shelf provides a geographical origin. The comparison is accomplished by means of frequency response functions relating alongshore wind stress with alongshore velocity. Amplitudes of the response functions are predicted to increase with alongshore distance equatorward and also to decrease with frequency at any location. These predictions are verified by the measurements. Predicted phase lags are generally less than about 30°, with observations agreeing with theory to within about 20°C. In general, the measurements provide reasonable evidence to support the theory of wind-forced continental shelf waves from a geographical origin. 相似文献
197.
Andrew B. Vistelius 《Mathematical Geology》1970,2(1):1-14
An analysis of the results of investigation of the G- 1 and W- 1 samples are given and differ from F. Chayes’ point of view.
Results of the samples can be evaluated by comparison of frequency-distribution properties of determinations for chemical
elements from different laboratories with some standard distribution, which gives the idea of a statistical model. The comparative
results indicate that oxides from minerals of the same density have positive correlations and that oxides from minerals of
different density have negative correlations. The different results therefore are not from the precision of analysis, but
rather from differentiation of sample powder particles by density and shape in the course of preparation. 相似文献
198.
Fifteen examples of quasi-periodic 2.8 GHz burst emission observed at the La Posta Astrogeophysical Observatory during the period December 1966 through May 1973 were identified. The periods of these events and those of 22 additional events previously reported in the literature were plotted against burst morphological parameters. The relationship between period and event energy was found to be considerably weaker than initially reported by Cribbens and Matthews. 相似文献
199.
Scott?K.?RowlandEmail author Andrew?J.?L.?Harris Martin?J.?Wooster Falk?Amelung Harold?Garbeil Lionel?Wilson Peter?J.?Mouginis-Mark 《Bulletin of Volcanology》2003,65(5):311-330
We have used a suite of remotely sensed data, numerical lava flow modeling, and field observations to determine quantitative characteristics of the 1995 Fernandina and 1998 Cerro Azul eruptions in the western Galápagos Islands. Flank lava flow areas, volumes, instantaneous effusion rates, and average effusion rates were all determined for these two eruptions, for which only limited syn-eruptive field observations are available. Using data from SPOT, TOPSAR, ERS-1, and ERS-2, we determined that the 1995 Fernandina flow covers a subaerial area of 6.5×106 m2 and has a subaerial dense rock equivalent (DRE) volume of 42×106 m3. Field observations, ATSR satellite data, and the FLOWGO numerical model allow us to determine that the effusion rate declined exponentially from a high of ~60–200 m3 s-1 during the first few hours to <5 m3 s-1 prior to ceasing after 73 days, with a mean effusion rate of 4–16 m3 s-1. Integrating the ATSR-derived, exponentially declining effusion rate over the eruption duration produces a total (subaerial + submarine) DRE volume of between 27 and 100×106 m3, the range in values being due to differing assumptions about heat loss characteristics; only values in the higher part of this range are consistent with the independently derived subaerial volume. Using SPOT, TOPSAR, ERS-1, and ERS-2 data, we determine that the 1998 Cerro Azul flow is 16 km long, covers 16 km2, and has a DRE volume of 54×106 m3. FLOWGO produces at-vent velocity and effusion rate values of 11 m s-1 and ~600 m3 s-1, respectively. The velocity value agrees well with the 12 m s-1 estimated in the field. The mean effusion rate (total DRE volume/duration) was 7–47 m3 s-1. Dike dimensions, fissure lengths, and pressure gradients along the conduit based on magma chamber depth estimates of 3–5 km produce mean effusion rates for the two eruptions that range over nearly four orders of magnitude, the range being due to uncertainty in the magma viscosity, dike dimensions, and pressure gradient between magma chamber and vent. Although somewhat consistent with mean effusion rates from other techniques, their wide range makes them less useful. The exponentially declining effusion rates during both eruptions are consistent with release of elastic strain being the driving mechanism of the eruptions. Our results provide independent input parameters for previously published theoretical relationships between magma chamber pressurization and eruption rates that constrain chamber volumes and increases in volume prior to eruption, as well as time constants of exponential decay during the eruption. The results and theoretical relationships combine to indicate that at both volcanoes probably 25–30% of the volumetric increase in the magma chamber erupted as lava onto the surface. In both eruptions the lava flow volumes are less than 1% of the magma chamber volume. 相似文献
200.
Spatial and temporal variability of ground water recharge in central Australia: a tracer approach 总被引:7,自引:0,他引:7
Two environmental tracer methods are applied to the Ti-Tree Basin in central Australia to shed light on the importance of recharge from floodouts of ephemeral rivers in this arid environment. Ground water carbon-14 concentrations from boreholes are used to estimate the average recharge rate over the interval between where the ground water sample first entered the saturated zone and the bore. Environmental chloride concentrations in ground water samples provide estimates of the recharge rate at the exact point in the landscape where the sample entered the saturated zone. The results of the two tracer approaches indicate that recharge rates around one of the rivers and an extensive floodplain are generally higher than rates of diffuse recharge that occurs in areas of lower topographic relief. Ground water 2H/1H and 18O/16O compositions are all depleted in the heavier isotopes (delta2H = -67 per thousand to -50 per thousand; delta18O = -9.2 per thousand to -5.7%o) compared with the long-term, amount-weighted mean isotopic composition of rainfall in the area (delta2H = -33.8 per thousand; delta18O = -6.3 per thousand). This indicates that recharge throughout the basin occurs only after intense rainfall events of at least 150 to 200 mm/month. Finally, a recharge map is developed to highlight the spatial extent of the two recharge mechanisms. Floodout recharge to the freshest ground water (TDS <1,000 mg/L) is approximately 1.9 mm/year compared with a mean recharge rate of approximately 0.2 mm/year to the remainder of the basin. These findings have important implications for management of the ground water resource. 相似文献