排序方式： 共有14条查询结果，搜索用时 375 毫秒
1.
NIGEL R. J. POOLTON LARS BØTTER-JENSEN ANN G. WINTLE PETER J. YPMA KAREN LUISE KNUDSEN VAGN MEJDAHL BARBARA MAUZ HENRIK E. CHRISTIANSEN JØRGEN JAKOBSEN FINN JØRGENSEN FINN WILLUMSEN 《Boreas: An International Journal of Quaternary Research》1996,25(3):195-208
This article describes the development and performance of an integrated optical sensor system that has been designed for rapid analysis of split sediment cores. The primary aim of the system is to obtain information based on optically stimulated luminescence (OSL) techniques; these provide a record of the accrued radiation dose of material since deposition. Particularly after suitable normalization, the luminescence signal recorded along the length of the core will provide information on the relative age of the sediment. Two wavelengths of stimulation are used (infra-red and green) and these probe the feldspar, and combined feldspar and quartz components of the sediment respectively; the ratio of the two signals can thus provide some indication of relative changes in the silicate mineralogy. A secondary use of the system is for optical reflectance measurements. With the addition of a monochromator, optical reflectance spectroscopy can be applied to obtain additional information on down-core mineralogical changes. In this article we describe technical aspects of the sensor system, discuss measurement techniques and consider the relevance of data obtained. Two examples of sediment cores are presented, which demonstrate the applicability of the instrument. 相似文献
2.
3.
AFSOON M. KAZEROUNI METTE L. K. POULSEN HENRIK FRIIS JOHAN B. SVENDSEN JENS P. V. HANSEN 《Sedimentology》2013,60(3):679-692
Detrital glaucony in the Palaeogene glauconitic sandstones in Siri Canyon, Danish North Sea, has been analysed from 15 exploration wells by X‐ray diffraction, electron microprobe and scanning electron microscopy. These sandstones consist of mixed‐layer illite/smectite and have a large variability in chemical composition and structure. In the most shallow wells (ca 1700 m), the glaucony is rich in Fe and consists of mixed‐layer illite/smectite with random‐interstratification (R = 0). In the depth interval from 1700 to 2000 m, the composition changes as Si is incorporated. The structure changes to ordered R = 1. Further increase in burial leads to the loss of Fe. Ordered R = 3 mixed‐layer illite/smectite is recognized from burial depths of 2200 m. The proportion of illite in illite/smectite mixed layers increases only slightly with depth and temperature. Although the structural changes generally are associated with chemical changes, they can also take place isochemically when the detrital glaucony is tightly embedded in earlier cement, which prevented chemical exchange. The glaucony transformation in the Siri Canyon sandstones partly reflects a supply of Si and partly significant loss of Fe. Thus, the glaucony transformation relates to the general diagenesis of the host sandstone. These sandstones are cemented by microquartz at an early stage, followed by precipitation of Fe‐rich grain‐coating berthierine or chlorite. 相似文献
4.
5.
6.
dr. agro. LEIF PETERSEN mag.scient. HENRIK BREUNING MADSEN 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):25-35
Petersen, Leif og Madsen, Henrik Breuning: Possible Effects of Ground Water Lowering on Some Peat Soils in Sjælland. Geografisk Tidsskrift 77:25–35 København, June 1, 1978. In four peatlands in the central part of Zealand nine profiles have been investigated to estimate the effect of a lowering of the groundwater level. 相似文献
7.
Spit systems are seldom recognized in the pre‐Quaternary sedimentary record compared to their common occurrence along present‐day coasts and in Quaternary successions. This lack of recognition may partly be due to the lack of widely accepted depositional models describing the facies characteristics of spit systems and their subaqueous platforms in particular. The Skagen spit system is a large active system that began to form 7150 yr bp and from 5500 bp to Recent times it has prograded 4 m year?1 and accumulated 3·5 × 109 m3 of sand. The spit system provides a unique opportunity for establishing a well‐constrained depositional model because uplift and erosion have made large windows into the preserved facies, while active spit‐forming processes can be examined at the young prograding end of the same system. The depositional model presented here thus builds on excellent outcrops, surface morphology, a well‐defined palaeogeography and detailed C14 age control supplemented with observations from continuous well cores and profiles obtained by ground‐penetrating radar and transient electromagnetic surveys. The factors that have governed the development of the spit system, such as relative sea‐level change, wave and current climate, tidal range, sediment transport and depositional rates are also well‐understood. The sedimentary facies of the spit system are grouped into four principal units consisting from below of thick storm sand beds, dune and bar‐trough deposits, beach deposits and peat beds. These four units form a coarsening and shallowing upward sand‐dominated succession, up to 32 m thick, which overlies offshore silt with a transition zone and is topped by a diastem overlain by young aeolian dune sand. The sedimentary structures and depositional processes are described in detail and integrated into a depositional model, which is compared to other spit systems and linear shoreface models. 相似文献
8.
Predictability of seasonal precipitation in the Nordic region 总被引：1，自引：0，他引：1
HENRIK FEDDERSEN 《地球，A辑:动力气象学与海洋学》2003,55(5):385-400
9.
In the raised bog Draved Mose, rates of peat formation and degrees of humification were determined in two peat sections. Based on 59 calibrated C-14 dates, accumulation rates during the last 6500 years of 0.16 to 0.80 mm/year were found. The peat layers were analyscd for Sphagnum species, rhizopods, and pollen and spores. A clear relation between humification degrees and humidity at the time of formation was found, while the relation between measured growth rates and degrees of humification varied throughout the 2.5 m thick peat section. These variations are thought to be mostly a result of autocompaction. 相似文献
10.
Several well-preserved Late Pleistocene spit systems occur uplifted in northern Jylland, Denmark. Their present-day morphological expression allows detailed study of spit growth patterns while the internal sedimentological organisation can be examined in a series of pits distributed along the length of the spits. Two characteristic vertical sequences are recognized in the systems. The first (Sequence I) consists of a giant-scale cross-bedded foreset unit, overlain by topset and beach units, while the second (Sequence II) consists of the foreset unit overlain by bar-trough and beach units. The two sequence types pass laterally into each other with a short overlap zone. They can be interpreted in terms of Meistrell's (1966, 1972) model for spit-platform growth based on scaled wave tank experiments. The giant-scale cross-bedded unit corresponds to prograding of a coarse-grained subaqueous spit-platform while the topset, bar-trough and beach units reflect the growth of the subaerial spit. The alternation between sequence I and II reflects the inversely related growth of the spit and platform structures: when the rate of subaqueous platform progradation declines, the subaerial spit grows uniformly, and when the platform progrades uniformly spit growth declines. The model is probably only valid for relatively coarse-grained systems because only these deposits would have a relatively steep front. The water depth in which the spit system progrades and thus bottom topography, determines the thickness of the giant-scale cross-bedded foreset unit because the water depth over the top of the platform is relatively constant. If the water is less than a few metres deep the spit-platform is not developed as seen where the Late Pleistocene spit systems prograded over elevations of the sea bottom. Conversely, the correct recognition of spit-platform sequences allows precise determination of sea-level and water depth at the time of formation. Finally, the model adds one further mode of formation of giant-scale cross-bedding to those already known from fluvial transverse, lateral and point bars, subtidal sand waves and Gilbert deltas. 相似文献