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991.
Charles K. Paull Robert F. Commeau Joseph R. Curray A. Conrad Neumann 《Geo-Marine Letters》1991,11(1):16-22
A mooring containing diverse carbonate and anhydrite substrates was exposed to bottom waters for 9 months at the base of the
Florida Escarpment to determine the influence of dissolution on the development of this continental margin. Weight loss was
measured on all samples. Etching, pitting, and loss of the original framework components were observed on substrates with
known characteristics. Extrapolations of modern dissolution rates predict only about 1.6 meters of corrosion per million years.
However, more rapid anhydrite dissolution, up to 1 km per million years, would cause exposed anhydrite beds to undercut and
destabilize intercalated limestones. 相似文献
992.
993.
Charles Linder 《Aquatic Sciences - Research Across Boundaries》1952,14(2):338-347
Summary The Lac de Bret, formerly an “oligotrophic” lake, has by several artificial risings of its level become “eutrophic” with the
drawbacks of that state during the summer stagnation. A plant of partial underwater aeration has improved the situation and
has been described in this Review (11, 423 [1949]). The above study compares the zooplancton of this lake in the years 1902/03 when it was yet oligotrophic with
its plancton in the year 1943 during the investigations in the lake become eutrophic and finally in the year 1951 when it
had again grown sound after five seasons of estival acration.
相似文献
994.
995.
996.
Field experiences continue to be a hallmark of a geographer's education and, for that matter, reeducation, as we all strive to remain current in the real world. Academic geographers beginning their ascent towards tenure and promotion might consider augmenting their portfolios with materials emerging from field teaching and learning activities. 相似文献
997.
The Neoproterozoic Ikorongo Group, which lies unconformably on the late Archaean Nyanzian Supergroup of the Tanzania Craton, is comprised of conglomerates, quartzites, shales, siltstones, red sandstones with rare flagstones and gritstones and is regionally subdivided into four litho-stratigraphic units namely the Makobo, Kinenge, Sumuji and Masati Formations.We report geochemical data for the mudrocks (i.e., shales and siltstones) from the Ikorongo basin in an attempt to constrain their provenance and source rock weathering. These mudrocks are compositionally similar to PAAS and PS indicating derivation from mixed mafic–felsic sources. However, the siltstones show depletion in the transition elements (Cr, Ni, Cu, Sc and V) and attest to a more felsic protolith than those for PAAS and PS. The Chemical Index of Alteration (CIA: 52–82) reveal a moderately weathered protolith for the mudrocks. The consistent REE patterns with LREE-enriched and HREE-depleted patterns ((La/Yb)CN = 7.3–38.3) coupled with negative Eu anomalies (Eu/Eu* = 0.71 on average), which characteristics are similar to the average PAAS and PS, illustrate cratonic sources that formed by intra-crustal differentiation.Geochemical considerations and palaeocurrent indications suggest that the provenance of the Ikorongo Group include high-Mg basaltic-andesites, dacites, rhyolites and granitoids from the Neoarchaean Musoma-Mara Greenstone Belt to the north of the Ikorongo basin. Mass balance calculations suggest relative contributions of 47%, 42% and 11% from granitoids, high-magnesium basaltic-andesites and dacites, respectively to the detritus that formed the shales. Corresponding contributions to the siltstones detritus are 53%, 43% and 4%. 相似文献
998.
999.
Kolawole J. Osinubi Charles M. O. Nwaiwu 《Geotechnical and Geological Engineering》2008,26(5):603-611
Specimens prepared from three lateritic soil samples were subjected to drying under laboratory conditions. Volumetric shrinkage
strains were measured at the end of the drying period. Results of this study indicate that, for the lateritic soils tested,
volumetric shrinkage strains are influenced by soil composition and compaction conditions. Volumetric shrinkage strain increased
with higher compaction water content. The influence of compaction water content on measured volumetric shrinkage strain was
more pronounced in specimens with higher fines content. A regression equation was developed from the data to estimate volumetric
shrinkage strain given the compaction water content relative to optimum, plasticity index, fines content and compactive effort. 相似文献
1000.
The location of new homes defines the urban–rural fringe and determines many facets of the urban–rural interaction set in
motion by construction of new homes in previously rural areas. Home, neighborhood and school district characteristics play
a crucial role in determining the spatial location of new residential construction, which in turn defines the boundary and
spatial extent of the urban–rural fringe. We develop and apply a spatial hedonic variant of the Blinder (J Hum Resour 8:436–455,
1973) and Oaxaca (Int Econ Rev 9:693–709, 1973) price decomposition to newer versus older home sales in the Columbus, Ohio metropolitan area during the year 2000. The preferences
of buyers of newer homes are compared to those who purchased the nearest neighboring older home located in the same census
block group, during the same year. Use of the nearest older home purchased in the same location represents a methodology to
control for various neighborhood, social–economic-demographic and school district characteristics that influence home prices.
Since newer homes reflect current preferences for home characteristics while older homes reflect past preferences for these
characteristics, we use the price differentials between newer and older home sales in the Blinder–Oaxaca decomposition to
assess the relative significance of various house characteristics to home buyers.
相似文献
Joni S. CharlesEmail: |