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1.
Stefanie Cable Bo Elberling Aart Kroon 《Boreas: An International Journal of Quaternary Research》2018,47(2):423-442
This paper presents the history and cryostratigraphy of the upper permafrost in the High‐Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain‐size distribution, and were 14C‐ and OSL‐dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid‐Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi‐syngenetic permafrost with microlenticular, lenticular, suspended and organic‐matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi‐syngenetic permafrost aggradation; lobes, in contrast, were ice‐poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi‐syngenetic permafrost formation on a weathered bedrock plateau. Landform‐scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground‐ice contents and upscale from core to landform scale in mountainous permafrost landscapes. 相似文献
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Coastal lagoons and beach ridges as complementary sedimentary archives for the reconstruction of Holocene relative sea‐level changes 
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下载免费PDF全文 Lasse Sander Mikkel U. Hede Mikkel Fruergaard Lars Nielsen Lars B. Clemmensen Aart Kroon Peter N. Johannessen Lars H. Nielsen Morten Pejrup 《地学学报》2016,28(1):43-49
Coastal lagoons and beach ridges are genetically independent, though non‐continuous, sedimentary archives. We here combine the results from two recently published studies in order to produce an 8000‐year‐long record of Holocene relative sea‐level changes on the island of Samsø, southern Kattegat, Denmark. The reconstruction of the initial mid‐Holocene sea‐level rise is based on the sedimentary infill from topography‐confined coastal lagoons (Sander et al., Boreas, 2015b). Sea‐level index points over the mid‐ to late Holocene period of sea‐level stability and fall are retrieved from the internal structures of a wide beach‐ridge system (Hede et al., The Holocene, 2015). Data from sediment coring, georadar and absolute dating are thus combined in an inter‐disciplinary approach that is highly reproducible in micro‐tidal environments characterised by high sediment supply. We show here that the commonly proximate occurrence of coastal lagoons and beach ridges allows us to produce seamless time series of relative sea‐level changes from field sites in SW Scandinavia and in similar coastal environments. 相似文献
3.
The Late Cenozoic Eridanos delta system in the Southern North Sea Basin: a climate signal in sediment supply? 总被引：1，自引：0，他引：1
ABSTRACT The Eridanos fluvio‐deltaic system, draining most of north‐western Europe, developed during the Late Cenozoic as a result of simultaneous uplift of the Fennoscandian shield and accelerated subsidence in the North Sea Basin. This seismo‐stratigraphic study aims to reconstruct the large‐scale depositional architecture of the deltaic portion of the basin fill and relate it to external controls. A total of 27 units have been recognized. They comprise over 62×103 km3 in the Southern North Sea Basin alone, and have an average delta surface area of 28×103 km2, which suggests that the size of the drainage area was about 1.1×106 km2. Water depth in the depocentre is seen to decrease systematically over time. This trend is interrupted by a deepening phase between 6.5 and 4.5 Ma that can be correlated with the simultaneous occurrence of increased uplift of the Fennoscandian shield, increased subsidence of the Southern North Sea Basin, and a long‐term eustatic highstand. All these observations point to a tectonic control on long‐term average rates of accommodation and supply. Controls on short‐term variations are inferred from variations in rates of sediment supply and bifurcation of the delta channel network. Both rates were initially low under warm, moist, relatively stable climate conditions. The straight wave‐dominated delta front gradually developed into a lobate fluvial‐dominated delta front. Two high‐amplitude sea‐level falls affected the Pliocene units, which are characterized by widespread delta‐front failures. Changes in relative sea level and climate became more frequent from the late Pliocene onward, as the system experienced the effects of glacial–interglacial transitions. Peaks in sedimentation and bifurcation rates were coeval with cold (glacial) conditions. The positive correlation between rates of supply and bifurcation on the one hand, and climate proxies (pollen and δ18O records) on the other hand is highly significant. The evidence presented in this study convincingly demonstrates the control of climate on time‐averaged sediment supply and channel‐network characteristics, despite the expected nonuniformity and time lags in system response. The presence of a clearly discernible climate signal in time‐averaged sediment supply illustrates the usefulness of integrated seismo‐stratigraphic studies for basin‐wide analysis of delta evolution on geological time scales. 相似文献
4.
Prof. Dr. Aart Brouwer 《International Journal of Earth Sciences》1981,70(1):33-39
A slim volume by EduardSuess (1875) exercised a profound influence in France, where particularly MarcelBertrand was stimulated by the concept of horizontal forces involved in the formation of mountain chains. Others in France (Termier, Haug) and in Switzerland (Lugeon, Schardt, Argand) followed in his steps, and eventually their researches lead to the establishment of the nappe theory in the Alps. It was EmileArgand (1924) who linked the nappe theory withWegener's theory of continental drift, and in doing so laid the foundation for a more general theory of crustal mobility.
Zusammenfassung Ein kleines Buch von EduardSuess (1875) hat einen tiefen Einfluß ausgeübt in Frankreich, wo besonders MarcelBertrand angeregt wurde von den Gedanken über horizontale Kräfte in der Entstehung von Gebirgsketten. Andere in Frankreich (Termier, Haug) und in der Schweiz (Lugeon, Schardt, Argand) traten in Bertrands Fußstapfen, und ihre Forschungen führten zur Gründung der Deckentheorie in den Alpen. EmileArgand (1924) hat dann die Deckentheorie mitWegeners Verschiebungstheorie verknüpft und damit die Grundlage geschaffen für eine allgemeine Theorie der krustalen Mobilität.
Résumé Un petit volume d'EduardSuess (1875) a exercé une influence profonde en France où notamment MarcelBertrand fut stimulé par l'idée des mouvements horizontaux dans la génèse des chaînes de montagnes. D'autres marchèrent sur ses traces (Termier etHaug en France,Lugeon, Schardt etArgand en Suisse), et leurs recherches dans les Alpes conduisirent à la théories des nappes. Plus tard EmileArgand (1924) a relié la théorie des nappes à la théorie de la dérive continentale et par là jeté les fondements d'une théorie générale de la mobilité crustale.
(1875) , a Marcel Bertrand . (Termier, Haug) (Lugeon, Schardt, Argand) . Emil Argand (1924)相似文献
5.
Kraft B.J. Overeem I. Holland C.W. Pratson L.F. Syvitski J.P.M. Mayer L.A. 《Oceanic Engineering, IEEE Journal of》2006,31(2):266-283
Geoacoustic properties of the seabed have a controlling role in the propagation and reverberation of sound in shallow-water environments. Several techniques are available to quantify the important properties but are usually unable to adequately sample the region of interest. In this paper, we explore the potential for obtaining geotechnical properties from a process-based stratigraphic model. Grain-size predictions from the stratigraphic model are combined with two acoustic models to estimate sound speed with distance across the New Jersey continental shelf and with depth below the seabed. Model predictions are compared to two independent sets of data: 1) Surficial sound speeds obtained through direct measurement using in situ compressional wave probes, and 2) sound speed as a function of depth obtained through inversion of seabed reflection measurements. In water depths less than 100 m, the model predictions produce a trend of decreasing grain-size and sound speed with increasing water depth as similarly observed in the measured surficial data. In water depths between 100 and 130 m, the model predictions exhibit an increase in sound speed that was not observed in the measured surficial data. A closer comparison indicates that the grain-sizes predicted for the surficial sediments are generally too small producing sound speeds that are too slow. The predicted sound speeds also tend to be too slow for sediments 0.5-20 m below the seabed in water depths greater than 100 m. However, in water depths less than 100 m, the sound speeds between 0.5-20-m subbottom depth are generally too fast. There are several reasons for the discrepancies including the stratigraphic model was limited to two dimensions, the model was unable to simulate biologic processes responsible for the high sound-speed shell material common in the model area, and incomplete geological records necessary to accurately predict grain-size 相似文献
6.
Stine G. Jensen Troels Aagaard Tom E. Baldock Aart Kroon Michael Hughes 《地球表面变化过程与地形》2009,34(11):1533-1546
Berm formation and morphological development of the beach face have been observed during a neap–neap tidal cycle on the gently sloping and accreting beach at Vejers, Denmark. During the field campaign, an intertidal bar migrated onshore and stabilized as a berm on the foreshore. A new intertidal bar occurred on the lower beach face, migrated onshore on the rising tide and finally merged with the pre‐existing berm. As the tide continued to rise, the new berm translated further onshore as an intertidal bar to the uppermost part of the foreshore. The sediment transport during the berm transition was onshore directed in the upper swash and offshore directed in the lower swash. This berm development can be described through both the neap‐berm, ridge‐and‐runnel and berm‐ridge development concepts proposed by Hine (Sedimentology 1979; 26: 333–351), and all three stages were observed during only three tidal cycles. The main factors controlling this fast transformation were the gentle slope of the cross‐shore profile, rapid water level translation rates, substantial swash overtopping of the berm, and low infiltration rates. Despite the onshore migration of intertidal bars and berm formation, no net foreshore accretion took place during the field campaign. This was largely due to the formation of rip channels with strong rip currents cutting through the intertidal bars and the berm, which acted as a sediment drain in the profile. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Priscila E. Souza Reza Sohbati Andrew S. Murray Aart Kroon Lars B. Clemmensen Mikkel U. Hede Lars Nielsen 《Boreas: An International Journal of Quaternary Research》2019,48(4):841-855
Here we investigate the use of optically stimulated luminescence (OSL) for dating cobbles from the body of successive beach ridges and compare cobble surface‐derived ages to standard quartz OSL ages from sand. Between four and eight cobbles and sand samples (age control) were dated with the luminescence method, taken from the modern beach and from beach ridges on the south and north extremes of a prograding spit on the westernmost coast of Lolland, Denmark. Luminescence‐depth profiles perpendicular to the surfaces of the cobbles show that the feldspar infrared signals stimulated at 50 °C were fully reset to various depths into the cobbles prior to final deposition; as a result, the equivalent doses determined from close to the surface of such cobbles can be used to calculate burial ages. Beach‐ridge burial ages given by the average of ages of individual cobbles taken from the same site are consistent, within errors, with the ages derived from the sand samples. Cobble‐ and sand‐derived ages show that the southernmost beach ridge at Albuen was formed around 2 ka ago, indicating that this sandy spit is younger than other coastal systems in Denmark. The agreement between ages derived from clasts and from standard quartz OSL in this study confirms that, even in the absence of sandy sediments, we can reliably date sites using OSL by targeting larger clasts. In addition, the record of prior light exposure contained in the shape of the cobbles’ luminescence‐depth profile removes one of the major uncertainties (i.e. the degree of signal reset prior to burial) in the luminescence dating of high latitude sites. 相似文献
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Prof. Dr. Aart Brouwer 《International Journal of Earth Sciences》1983,72(2):739-741
Zusammenfassung Nicht ein Aufsatz vonKeilhack, wie in einer in irrtümlicher Weise abgeänderten Fuß-note angedeutet, sondern ein Sammelreferat vonKrenkel veranlaßteWegener im Herbst 1911 sich mit dem Problem der Kontinentverschiebung zu beschäftigen.
In a foot-note erroneously changed by the editorial committee, it was suggested that a paper byKeilhack inducedWegener to study the problem of continental displacement in the autum of 1911. In fact it was a review paper byKrenkel on the African Cretaceous that gaveWegener occasion to study this problem.
Résumé Contrairement à une note infrapaginale (changée par erreur par la Rédaction) suggérant qu'un article de Keilhack aurait amené Wegener à étudier le problème de la dérive des continents au cours de l'automne 1911, c'est en fait une vue d'ensemble de Krenkel sur le Crétacé africain qui, pour Wegener, fut l'occasion de cette étude.
Keilhack'a, , Krenkel'H 1911 .相似文献