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61.
This paper introduces a flexible sediment classification scheme for modern and ancient lake sediments employed at the Limnological Research Center, University of Minnesota. Our classification scheme emphasizes the macroscopic structure and microscopic components of the sedimentary matrix (clastic, chemical and biological) and can be applied to a wide range of lacustrine settings. Such a classification scheme is necessary to i) facilitate communication and collaboration between the highly interdisciplinary community of scientists that study lacustrine archives, ii) create a structure for comparative lacustrine sedimentological studies, and iii) take greater advantage of the great potential information recorded by changing depositional environments. Such a development is needed in light of current and planned Global Lake Drilling efforts and to expedite the creation of on-line, searchable databases of global lacustrine archives. A more comprehensive treatment of the topics discussed in this paper is available at: http://lrc.geo.umn.edu/services/handbook/sedclass.html. 相似文献
62.
Elie Eichenberger F. Klötzli Kerry R. Kelts H. R. Bürgi F. Stössel H. Jäckli 《Aquatic Sciences - Research Across Boundaries》1976,38(2):247-250
Ohne Zusammenfassung 相似文献
63.
Blas L. Valero-Garcés Kathleen R. Laird Sherilyn C. Fritz Kerry Kelts Emi Ito Eric C. Grimm 《Quaternary Research》1997,48(3):359-369
Seismic stratigraphy, sedimentary facies, pollen stratigraphy, diatom-inferred salinity, stable isotope (δ18O and δ13C), and chemical composition (Sr/Ca and Mg/Ca) of authigenic carbonates from Moon Lake cores provide a congruent Holocene record of effective moisture for the eastern Northern Great Plains. Between 11,700 and 950014C yr B.P., the climate was cool and moist. A gradual decrease in effective moisture occurred between 9500 and 710014C yr B.P. A change at about 710014C yr B.P. inaugurated the most arid period during the Holocene. Between 7100 and 400014C yr B.P., three arid phases occurred at 6600–620014C yr B.P., 5400–520014C yr B.P., and 4800–460014C yr B.P. Effective moisture generally increased after 400014C yr B.P., but periods of low effective moisture occurred between 2900–280014C yr B.P. and 1200–80014C yr B.P. The data also suggest high climatic variability during the last few centuries. Despite the overall congruence, the biological (diatom), sedimentological, isotopic, and chemical proxies were occassionally out of phase. At these times the evaporative process was not the only control of lake-water chemical and isotopic composition. 相似文献
64.
K. Kelts U. Briegel K. Ghilardi K. Hsu 《Aquatic Sciences - Research Across Boundaries》1986,48(1):104-115
Various methods are available for coring in lakes. We have developed an integrated coring system based on a modified Kullenberg poston-corer principle which is particularly useful for multiple coring in deep lakes. The selection of sites is guided by concurrent high-resolution (3.5 kHz) continuous seismic profiling. The system is modular for simple transport, and includes a very reliable tripweight gravity corer which uses the same plastic liners as the piston corer. Piston-core lengths are variable in 2, 4, or 5 m sections up to 16 m. This system has been successfully deployed in glacially deepened perialpine lakes (Lakes Zürich, Zug, Greifensee, Lucerne, Walensee, Constance, Murten, Neuchâtel, Geneva, Thun, Brienz, Maggiore, Lugano, Iseo, Garda, d'Annecy, Bourget and Ammersee), deep rift lakes of Africa (Turkana, Albert, Edward, Kiwu), Lake Ohrid (Jugoslavia), Lake Van (Turkey), Qinghai Lake (China), and in very shallow hypersaline lakes Urmia (Iran) and Great Salt Lake (USA). Following numerous requests, this paper describes the system concept and constructional features that have been refined over the last 12 years. Development has stressed increasing simplification and increased reliability. 相似文献
65.
66.
1980年6月,本文作者之一的K. Kelts曾去美国参加由经济古生物学者和矿物学者协会组织的地质旅行。该行主要是观察和研究怀俄明州西南始新统绿河组的沉积环境。对此次旅行中带回瑞士苏黎世联邦理工学院地质研究所的样品,曾作了切片、X-射线衍射和碳氧同位素分析。 相似文献
67.
G. S. Lister F. Giovanoli G. Eberli P. Finckh W. Finger Q. He C. Heim K. J. Hsü K. Kelts C. Peng C. Sidler X. Zhao 《Environmental Geology》1983,5(4):191-205
Lake Zürich occupies a glacially overdeepened perialpine trough in the northern Middlelands of Switzerland. A total of 154.4
m of Quaternary sediments and 47.3 m of Tertiary Molasse bedrock has been cored from the deepest part of the lake, some 10
km south of the city of Zürich. Some 16.8 m of gravels and sands directly overlying the bedrock include basal till and probably
earliest subglacial fluvial and lacustrine deposits. These are overlain by 98.6 m of fine-grained, glacial-aged sediments
comprising completely deformed proglacial and/or subglacial lacustrine muds, separated by four basal mud tills. The lack of
interglacial sediments, fossils, and other datable material, and the presence of severe sediment deformation and unknown amounts
of erosion prevent the establishment of an exact chronostratigraphy for sediments older than the upper mud till. Above it
some 8.6 m of lacustrine muds were deposited, folded, faulted, and tilted during the final opening of the lake at about 17,500–17,000
years ago. Superimposed are 30.4 m of final Würm and post-glacial sediments comprising (from oldest): cyclic proglacial mud,
thick-bedded and laminated mud, a complex transition zone, laminated carbonate, laminated marl, and diatom-calcite varves.
These sediments reflect changing catchment and lacustrine conditions including: glacial proximity, catchment stability, lake
inflow characteristics, thermal structure, chemistry, and bed stability. Average sedimentation rates ranged from 11 cm yr−1 immediately after glacier withdrawal, to as low as 0.4 mm yr−1 as the environment stabilized.
The lack of coarse outwash deposits separating the fine-grained glaciolacustrine sediments from a corresponding underlying
basal till suggests that deglaciation of the deep northern basin of Lake Zürich was by stagnation-zone retreat rather than
by retreat of an active ice-front. 相似文献
68.
Ajay Jasra David A. Stephens Kerry Gallagher Christopher C. Holmes 《Mathematical Geology》2006,38(3):269-300
In this paper we develop a generalized statistical methodology for characterizing geochronological data, represented by a distribution of single mineral ages. The main characteristics of such data are the heterogeneity and error associated with its collection. The former property means that mixture models are often appropriate for their analysis, in order to identify discrete age components in the overall distribution. We demonstrate that current methods (e.g., Sambridge and Compston, 1994) for analyzing such problems are not always suitable due to the restriction of the class of component densities that may be fitted to the data. This is of importance, when modelling geochronological data, as it is often the case that skewed and heavy tailed distributions will fit the data well. We concentrate on developing (Bayesian) mixture models with flexibility in the class of component densities, using Markov chain Monte Carlo (MCMC) methods to fit the models. Our method allows us to use any component density to fit the data, as well as returning a probability distribution for the number of components. Furthermore, rather than dealing with the observed ages, as in previous approaches, we make the inferences of components from the “true” ages, i.e., the ages had we been able to observe them without measurement error. We demonstrate our approach on two data sets: uranium-lead (U-Pb) zircon ages from the Khorat basin of northern Thailand and the Carrickalinga Head formation of southern Australia. 相似文献
69.
Kerry L. Sublette J. Bryan Tapp J. Berton Fisher Eleanor Jennings Kathleen Duncan Greg Thoma Josh Brokaw Tim Todd 《Applied Geochemistry》2007
For almost a decade the Tallgrass Prairie Preserve in Oklahoma has been used as a field laboratory for the investigation of aspects of the remediation and restoration of oil and brine spills. Objectives of this work have included: (1) simplification of the remediation process and lowering the cost of remediation; (2) the development of methods to accelerate or jump-start the restoration process; and (3) determining appropriate metrics for assessing the status of soil ecosystem recovery. This research has resulted in a number of lessons learned that will be presented here which can be exported to other exploration and production sites, especially sites located in sensitive ecosystems. Key observations have included the role of a fertilizer amendment in linking the remediation and restoration process at an oil-impacted site, the use of nematodes as ecological indicators in the restoration of oil- and brine-impacted sites, and the development of a two-stage process for remediation of brine impacted sites that does not include significant use of gypsum. 相似文献
70.