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131.
Steve E. J. Richardson Richard J. Davies Mark B. Allen Simon F. Grant 《Basin Research》2011,23(6):702-719
The Quaternary to late Pliocene sedimentary succession along the margin of the South Caspian Basin contains numerous kilometre‐scale submarine slope failures, which were sourced along the basin slope and from the inclined flanks of contemporaneous anticlines. This study uses three‐dimensional (3D) seismic reflection data to visualise the internal structure of 27 mass transport deposits and catalogues the syndepositional structures contained within them. These are used to interpret emplacement processes occurring during submarine slope failure. The deposits consist of three linked structural domains: extensional, translational and compressive, each containing characteristic structures. Novel features are present within the mass transport deposits: (1) a diverging retrogression of the headwall scarp; (2) the absence of a conventional headwall scarp around growth stratal pinch outs; (3) restraining bends in the lateral margin; (4) a downslope increase in the throw of thrust faults. The results of this study shed light on the deformation that occurred during submarine slope failure, and highlight an important geological process in the evolution of the South Caspian Basin margin. 相似文献
132.
The level of Cliff Lake, a small, subalpine, moraine-dammed lake in California’s south central Sierra Nevada, was approximately
5 m lower than present for 50 years or more approximately 600 years ago, this determined by radiocarbon dating of wood recovered
from a submerged tree stump found in the lake. This finding corresponds to commensurate data from throughout much of western
North America, suggesting the duration and magnitude of terminal medieval megadrought was similar throughout the region. Ultimately
this datum helps give credence to the perspective that though late Holocene climate in California was indeed variable, the
effects of terminal Medieval megadrought was similar across both time and broad geographic expanse. 相似文献
133.
W. Earl Bardsley 《Natural Resources Research》2008,17(4):197-204
A sustainable global silicon energy economy is proposed as a potential alternative to the hydrogen economy. This first visualization
of a silicon energy economy is based on large-scale and carbon-neutral metallic silicon production from major smelters in
North Africa and elsewhere, supplied by desert silica sand and electricity from extensive solar generating systems. The resulting
“fuel silicon” is shipped around the world to emission-free silicon power stations for either immediate electricity generation
or stockpiling. The high energy density of silicon and its stable storage make it an ideal material for maintaining national
economic functioning through security of base load power supply from a renewable source. This contrasts with the present situation
of fossil fuel usage with its associated global warming and geopolitical supply uncertainties. Critical technological requirements
for the silicon economy are carbon-neutral silicon production and the development of efficient silicon-fired power stations
capable of high-temperature rapid oxidation of fuel silicon. A call is made for the development of research effort into these
specific engineering issues, and also with respect to large-scale economical solar power generation. 相似文献
134.
Supriyo Kumar Das Joyanto Routh Alakendra N. Roychoudhury J. Val Klump 《Journal of Paleolimnology》2008,39(3):349-360
We used elemental carbon, nitrogen, phosphorus and hydrogen ratios (C/N, N/P and H/C) with total organic carbon (TOC) and
total phosphorus (TP) as well as stable carbon and nitrogen isotopes (δ13C and δ15N) to investigate the source and depositional conditions of organic matter in sediments from Zeekoevlei, the largest freshwater
lake in South Africa. Typical C/N (10–12), H/C ratios (≥1.7) and δ13Corganic values (−22 to −19‰) together with the increase in TOC concentration indicate elevated primary productivity in lower middle
(18–22 cm) and top (0–8 cm) sections of the sediment cores. Seepage of nutrients from a nearby waste water treatment plant,
rapid urbanization and heavily fertilized farming in the catchments are responsible for the increased productivity. Consistent
with this, measured δ15Norganic values (∼11‰) indicate increased raw sewage input towards the top-section of the core. Although cyanobacterial blooms are
evident from the low δ15N values (∼3‰) in mid-section of the core, they did not outnumber the phytoplankton population. Low N/P ratio (∼0) and high
TP (100–2,200 mg l−1) support cyanobacterial growth under N limited condition, and insignificant input of macrophytes towards the organic matter
pool. Dredging in 1983, caused sub-aerial exposure of the suspended and surface sediments, and affected organic matter preservation
in the upper mid-section (12–14 cm) of the core. 相似文献
135.
Dan Hammarlund Anson W. Mackay David M. J. Fallon Gemma Pateman Luisa C. Tavio Melanie J. Leng Neil L. Rose 《Journal of Paleolimnology》2008,39(4):463-475
Detailed stratigraphic analyses of sediments deposited in Lake Botjärnen, a small boreal forest lake in the shield terrain of central Sweden, clearly reflect progressively increasing human impact on terrestrial and aquatic ecosystems following settlement and establishment of an iron industry in the 17th century. Rising frequencies of pollen and spores from light-demanding plants provide evidence of extensive forest clearance for charcoal and timber production, which peaked in the early 20th century. An associated increase in catchment erosion is reflected by changing carbon and nitrogen elemental content and carbon–isotope composition of sediment organic matter and by increased magnetic susceptibility of the sediments. Records of air-borne pollutants (lead, zinc and sulphur) can be correlated to the development of local and regional mining and metal industry as inferred from historical accounts. Rapid recession of the iron industry led to re-forestation and recovery of the aquatic nutrient status to pre-industrial conditions over the past 100 years. The chronology of the sediment succession, which is based on 210Pb and 137Cs radionuclide data in combination with radiocarbon dating, is confirmed by historical lead pollution trends established for the region. 相似文献
136.
Brent B. Wolfe Matthew D. Falcone Ken P. Clogg-Wright Cherie L. Mongeon Yi Yi Bronwyn E. Brock Natalie A. St. Amour William A. Mark Thomas W. D. Edwards 《Journal of Paleolimnology》2007,37(2):221-231
Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis
of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments
have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy
studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring
a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake
water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced
by studies conducted over the past 15 years that span Holocene and pre-historical timescales. 相似文献
137.
This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from
the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate
signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 14C yr BP to 11,100 14C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 14C yr BP and finally, at 8,500 14C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500
14C yr BP) to deciduous parkland, followed by grassland at 9,300 14C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent
uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and
geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting
of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused
the lower-elevation Wendel site to capture the ground water of up-gradient lakes. 相似文献
138.
Geoscientific Information Systems (GIS) provide tools to quantitatively analyze and integrate spatially referenced information
from geological, geophysical, and geochemical surveys for decision-making processes. Excellent coverage of well-documented,
precise and good quality data enables testing of variable exploration models in an efficient and cost effective way with GIS
tools. Digital geoscientific data from the Geological Survey of Finland (GTK) are being used widely as spatial evidence in
exploration targeting, that is ranking areas based on their exploration importance. In the last few years, spatial analysis
techniques including weights-of-evidence, logistic regression, and fuzzy logic, have been increasingly used in GTK’s mineral
exploration and geological mapping projects. Special emphasis has been put into the exploration for gold because of the excellent
data coverage within the prospective volcanic belts and because of the increased activity in gold exploration in Finland during
recent years. In this paper, we describe some successful case histories of using the weights-of-evidence method for the Au-potential
mapping. These projects have shown that, by using spatial modeling techniques, exploration targets can be generated by quantitatively
analyzing extensive amounts of data from various sources and to rank these target areas based on their exploration potential. 相似文献
139.
The objective of this study is to find the order and coefficients of non-low-phase causal filters for ARMA (auto regressive moving average) filter model, using the Kurtosis minimization criterion. This method is based on the Kurtosis calculation of the treated sample at the input level and its identification at the output of the ARMA model. For this purpose, the order and coefficients of the AR (auto regressive) part are identified using the Yule-Walker algorithm at order two and then extended to order four. To obtain the MA (moving average) part, the AR components are calculated at first from the ARMA filter by deconvolution. Then, spectrally equivalent and minimum phase (SEMP) MA filter is identified using the Durbin algorithm at second and fourth order. Finally, the correct filter is found when the Kurtosis value of the output ARMA filter reconstituted is the closest to the Kurtosis of introduced signal. The proposed method is then tested on simulated processes and applied to real seismic data to perform blind deconvolution and obtain the reflectivity coefficients of subsoil studied. 相似文献
140.