Paleoenvironments and correlations of interglacial sediments in the North Sea

Benthic foraminiferal faunas suggesting interglacial climatic conditions are present in several shallow drillings in the North Sea and in northern Jutland. Denmark. The interglacial deposits in six of the cores arc correlated by means of isoleucine epimerization, paleomagnetic data and environmental inferences. Four episodes of interglacial circulation are recorded in sediments of Brunhes age and one warm episode is found just below the Brunhes Matuyama boundary. The Holocene and Eemian faunas of the North Sea are richer in species and individuals and contain more thermophilous species than the older interglacial faunas. However. a much more northern distribution of Bulimina marginata in sediments of Eemian age suggests that oceanic circulation was different during this period than during the Holocene. Sediments of the three other Brunhes interglacials (the Holsteinian, the Norwegian Trench and the Devils Hole Interglacial) and the Leerdam Interglacial record periods of relatively cooler conditions and possibly reduced inflow of Atlantic water.     

QUANTIFYING SIMILARITY FOR HANDLING INFORMATION IN KNOWLEDGE BASES

When constructing diagnostic systems or using knowledge-based systems,e.g.in analytical chemistry,features of different type and character,represented by numbers,trajectories or linguistic variables suchas intensities or colours,must be considered.To find neighbourhoods or to fill in missing values,thenotion of similarity is of essential importance.The paper presents a new fuzzy-set-theory-based approachto quantifying similarity and provides a system of rules to be implemented into the diagnostic part of theknowledge base to be used.     

Geochemistry of Holocene salt marsh and tidal flat sediments on a barrier island in the southern North Sea (Langeoog,North‐west Germany)

The barrier islands of the southern North Sea were formed during the Holocene sea‐level rise. These islands form part of a highly dynamic environment whose evolution continues today. Subjected to sea‐level changes, tides and storm events, the sedimentary record reflects processes occurring under varying energy conditions. This article presents geochemical, mineralogical and diatom investigations carried out in the salt marsh of the East Frisian barrier island of Langeoog, which is re‐exposed to a rising sea‐level due to de‐embankment. The major aim of this study is to improve the knowledge of the sedimentological and geochemical development of these deposits under the influence of sea‐level rise, with a special focus on the geochemistry and distribution of heavy mineral‐associated elements. Correlation diagrams between FeO, TiO₂ and MnO, as well as ternary plots (Al₂O₃–SiO₂–Zr or TiO₂), clearly indicate the variable appearance of heavy minerals in different lithological facies, comprising marsh soil, mixed and sand flat, and relocated beach sands. A dominating abundance of ilmenite followed by zircon, garnets and some other heavy minerals is evidenced by Scanning Electron Microscope‐Energy Dispersive X‐ray measurements. The data presented here suggests that these geochemical proxies are useful tools for characterizing depositional energy conditions. Increasing depositional energy is evident for the lithological units in the following order: marsh soil, mixed flat, sand flat and relocated beach sand. The energetic conditions during sediment deposition, as well as the sedimentary history, are confirmed by diatom analyses as an additional independent indicator. Depending on source rock composition, the geochemical parameters used in this study may also help to investigate depositional energy regimes of other siliciclastic sedimentary systems.     

An Object within a Particle of Extraterrestrial Origin Compared with An Object of Presumed Terrestrial Origin 113, 209–210.

Filamentary objects of submicron size isolated from an extraterrestrial particle and from the Gunflint cherts are compared and shown to have similarities of size, shape and interior structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

The type section of the Vikinghôgda Formation: a new Lower Triassic unit in central and eastern Svalbard

The Vikinghøgda Formation (250 m) is defined with a stratotype in Deltadalen-Vikinghøgda in central Spitsbergen. The Vikinghøgda Formation replaces the Vardebukta and Sticky Keep Formations of Buchan et al. (1965) and the lower part of the Barentsøya Formation of Lock et al. (1978) as extended geographically by Mørk, Knarud et al. (1982) in central Spitsbergen, Barentsøya and Edgeøya. The formation consists of three member: the Deltadalen Member (composed of mudstones with sandstones and siltstones), the Lusitaniadalen Member (dominated by mudstones with thin siltstone beds and some limestone concretions) and the Vendomdalen Member (composed of dark shales with dolomite interbeds and nodules). The Lusitaniadalen and Vendomdalen members replace the former Sticky Keep Formation/ Member in the siirne areu. The Vikinghøda Formation can be followed through central and eastern Spitsbergen to Barentøya and Edgeøya and includes all sediments between the chert-rich Kapp Starostin Formation (Permian) and the organic-rich shales of the Botneheia Formation (Middle Triassic). The subdivision into three members is also reflected in the organic carbon content and palynofacies. Upwards. each succeeding member becomes more distal, organic-rich and oil-prone than the one below.
The Vikinghøda Formation is well-dated by six ammonoid zones. although the transitional beds between the Deltadalen and Lusitaniadalen members lack age diagnostic macrofossils. Corresponding palynozonation and magnetustratigraphy have also been determined. The overall stratigraphical development correlates well with other key Triassic areas in the Arctic, although intervals in the late Dienerian and early Smithian may be condensed or missing.     

Spatial gradients in ratios of atmospheric trace gases: a study stimulated by experiments on bird navigation

Numerous experiments with homing pigeons and other birds strongly suggest that birds displaced to unfamiliar remote areas are able to determine their position relative to home by deducing relevant information from atmospheric trace gases perceived by olfaction. These findings induced the hypothesis that ratios between several airborne compounds show roughly monotonic spatial gradients, differently in different directions, over distances of some hundreds of kilometres. To test this hypothesis, 192 air samples were collected, successively in 3 summers, at 96 sites regularly distributed over an area covering a radius of 200 km around Würzburg, Germany. Statistical analysis of the gas chromatographic measurements on these samples revealed that such gradients in the ratios between a number of omnipresent hydrocarbons do in fact exist. The gradients are noisy, but not beyond the range that is compatible with the homing behaviour of pigeons which is noisy as well. The directions of the gradients are remarkably robust against changes of weather, especially of winds. Winds, however, shift the levels of ratios in the whole area without dramatically changing the directional relationships. A systematic angular correlation between variations in space and variations caused by winds could theoretically be utilized by birds for navigational purposes. Our analysis dealt mainly with the most abundant anthropogenic hydrocarbons, which are the best‐suited tracers to detect spatio‐temporal distribution patterns. It is very likely that equivalent patterns exist in naturally emitted volatile compounds as well, given that they are subject to similar variability in the distribution of sources and sinks and similar transport patterns.     

Molluscan and foraminiferal biostratigraphy of an Eemian-Early Weichselian section on Karmøy, southwestern Norway

Sejrup, Hans Petter 1987 03 01: Molluscan and foraminiferal biostratigraphy of an Eemian-Early Weichselian section on Karmøy, southwestern Norway. Boreas , Vol. 16, pp. 27–42. Oslo. ISSN 0300–9483.
At Karmøy, southwestern Norway, a section with marine sediments from the last interglacial (the Avaldsnes Interglacial) and from two ice-free periods (the Torvastad and Bø Interstadial) in the Weichselian have been examined for molluscs and foraminifera. The following conclusions concerning the depositional environments of these sediments can be drawn: (1) The Avaldsnes Interglacial was a high-energy environment with a sea level 20 to 50 m higher than at present, regressing towards the end of the interglacial. Sea temperatures were as in the area today or slightly warmer. (2) During the Torvastad Interstadial (71–85 ka) the sea level was between 0 and c . 20 m higher than at present, and sea temperatures were as between Svalbard and northern Norway today. (3) The Bø Interstadial (40–64 ka) shows a complete interstadial cycle, with changing sea level and temperatures. Its optimum was close to the conditions prevailing in North Norway today or slightly colder. By comparison with other sites, a total of at least four interstadial episodes through the Weichselian in southwestern Norway is proposed. These date to c . 30 ka, 40–64 ka, 71–85 ka and 87–101 ka. The episodes and the glacial advances between them do not directly correlate with published interpretations of changes in surface circulation in the Norwegian Sea through the Weichselian. It is suggested that the nourishment of the southern part of the Scandinavian ice sheet might be more related to sea surface conditions in the North Atlantic than to those of the Norwegian Sea.