Beitrag zur Frage des Gleichgewichtes im System Düne-Strand-Vorstrand an der Ostseeküste

Zusammenfassung Faziesstudien an Abrasions-, Anlandungs- und stabilen Küsten der Ostsee lassen erkennen, daß der Zustand eines Küstenabschnittes abhängig ist von dem Verhältnis zwischen den Kornverteilungen des Vorstrandes, Strandes und der Düne. Zur Charakteristik der litoralen Sedimente wird der große Viertelgewichtsdurchmesser (Q₇₅) herangezogen, der sich aus der Summenkurve der Sandanteile ergibt. Die Kiese werden vernachlässigt, da sie anderen Transport-bedingungen unterliegen. Stabile Küsten, deren verschiedene Faziesbereiche sich im Gleichgewicht befinden, sind gekennzeichnet durch Zustandsquotienten Q₇₅-Strand/Q₇₅-Vorstrand>1 und Q₇₅-Strand/Q₇₅-Düne=1-1,4. Anlandungsküsten zeigen stets Werte zwischen 1,0 und 1,4, Abrasionsküsten Quotienten <1. Die Ermittlung des Zustandsquotienten erweist sich als eine einfache Methode zur Kennzeichnung stabiler und unstabiler Küstenbereiche der Ostsee.     

Die Altersstellung der terrestren Wettiner Schichten bei Halle auf Grund sedimentpetrographischer Untersuchungen

Zusammenfassung Mit Hilfe der Schwermineralanalyse ist es möglich, die terrestren Schüttungen des Jungpaläozoikums im Gebiet des östlichen Harzvorlandes und um Halle zu gliedern. Als einheitliche Schichtserien erweisen sich einerseits die Mansfelder und andererseits die Wettiner und unterrotliegenden Zwischensediment-Schichten. Die Frage, ob die Grenze zwischen Mansfelder und Wettiner Schichten mit der Zeitgrenze Oberkarbon—Rotliegend zusammenfällt, wird offen gelassen.     

Petrographie und Mineralfazies einer konglomeratischen Tanner Grauwacke aus dem Unterharz

A very coarse grained graywacke from Strassberg in the Lower Harz Mountains (Germany) consists of rock-fragments, feldspars, quartz, chlorites, micas, accessories and ores. Low grade metamorphic mineral reactions are indicated by the formation of 2M-muscovite +chlorite+sphene+albite in the matrix of the graywacke, by prehnite+chlorite+ sphene+calcite+sericite+albite (±quartz) in volcanic rock-fragments, and by prehnite +calcite+quartz along fine fissures. The newly formed minerals in the coarse grained graywacke belong to the laumontite-prehnite-quartz-facies of the burial metmorphism. However, the formation of the low grade minerals is caused by thermal metamorphism in outer contact zones of the Ramberg granite intrusion in the Strassberg area.     

Variations in the Number of Intestinal Loops in Scaphopoda (Mollusca)

Abstract. The intestinal loops of two species of the genus Bathoxiphus (Entalinidae) and of Cadulus aberrans (Gadilidae) have been reconstructed from serial sections. The results are compared to the 'textbook scaphopod' Antalis dentalis having the hindgut coiled in three loops. Bathoxiphus ensiculus has four or five intestinal loops, B. sp. S 153 four, and C. aberrans two. The buccal pouch contents included Foraminifera in all species, with agglomerates of sediment being found only in Bathoxiphus and Antalis. The mean ratio of intestinal length to body length ranges from 1.05 in B. ensiculus , over 0.98 in the four-looped B. sp. S 153, to 0.7 in A. dentalis and 0.6 in the twice-looped C. aberrans. The correlation of intestinal length with diet—additional deposit-feeding in Bathoxiphus and highly specialized 'carnivory' in C. aberrans —is probable. Despite the differences in feeding ecology, the elongated hindgut of both deep-sea species of Bathoxiphus resembles the adaptations of some bivalves to poorly nutritious deep-sea sediments.     

In situ hydrocarbon concentrations from pressurized cores in surface sediments, Northern Gulf of Mexico

Two newly developed coring devices, the Multi-Autoclave-Corer and the Dynamic Autoclave Piston Corer were deployed in shallow gas hydrate-bearing sediments in the northern Gulf of Mexico during research cruise SO174 (Oct–Nov 2003). For the first time, they enable the retrieval of near-surface sediment cores under ambient pressure. This enables the determination of in situ methane concentrations and amounts of gas hydrate in sediment depths where bottom water temperature and pressure changes most strongly influence gas/hydrate relationships. At seep sites of GC185 (Bush Hill) and the newly discovered sites at GC415, we determined the volume of low-weight hydrocarbons (C₁ through C₅) from nine pressurized cores via controlled degassing. The resulting in situ methane concentrations vary by two orders of magnitudes between 0.031 and 0.985 mol kg^− 1 pore water below the zone of sulfate depletion. This includes dissolved, free, and hydrate-bound CH₄. Combined with results from conventional cores, this establishes a variability of methane concentrations in close proximity to seep sites of five orders of magnitude. In total four out of nine pressure cores had CH₄ concentrations above equilibrium with gas hydrates. Two of them contain gas hydrate volumes of 15% (GC185) and 18% (GC415) of pore space. The measurements prove that the highest methane concentrations are not necessarily related to the highest advection rates. Brine advection inhibits gas hydrate stability a few centimeters below the sediment surface at the depth of anaerobic oxidation of methane and thus inhibits the storage of enhanced methane volumes. Here, computerized tomography (CT) of the pressure cores detected small amounts of free gas. This finding has major implications for methane distribution, possible consumption, and escape into the bottom water in fluid flow systems related to halokinesis.     

Physical properties of a porcellanite layer (Southwest Indian Ridge) constrained by geophysical logging

A distinct porcellanite layer from the Southwest Indian Ridge intercalated in Pleistocene diatom ooze was studied using nondestructive physical property measurements and sedimentological data. This bed was sampled by two piston cores at a water depth of 2615 m. The 3–5 cm thick porcellanite layer appears in the cores at a depth of 6.03 m (Core PS2089-2) and 7.73 m (Core PS2089-1) below the seafloor. Due to its characteristic physical properties the porcellanite bed can be detected with core measurements, and its distribution and lateral extent mapped with echosounding. The physical index properties, wet bulk density and electrical resistivity, increase significantly across this bed. Magnetic susceptibility is used to compare the lithological units of both cores and to distinguish whether resistivity anomalies are caused by a higher amount of terrigenous components or by the presence of porcellanite. The porcellanite has the special characteristic to affect a positive anomaly in resistivity but not in susceptibility. Most marine sediments, in contrast, show a positive correlation of magnetic susceptibility versus electrical resistivity; therefore a combination of electrical resistivity and magnetic susceptibility logs yields a definite detection of the porcellanite bed. Images from the X-ray CT survey indicate that the porcellanite is lithified and brittle and fragmented when the piston corer penetrated the bed.     

Spring distribution of dissolved organic matter in a system encompassing the Northeast Water Polynya: Implications for early-season sources and sinks

This study addresses sources and diagenetic state of early-season dissolved organic matter (DOM) in the Northeast Water Polynya (NEWP) area northeast of Greenland from distributions of humic substance fluorescence (HSfl), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) in the water column inside and outside the NEWP area. The water masses of the polynya area had acquired their spring/summer temperature–salinity characteristics at the time of sampling, and also had individual, different DOM signatures. DOC concentrations were variable within and among water masses in the polynya area, indicating patchy local sources and sinks of DOC. PySW and polynya intermediate water (PyIW) had higher average DON concentrations and average lower C:N ratios than polynya bottom water (PyBW), indicating a larger fraction of fresh DOM in PySW and PyIW than in PyBW. Ice-covered, polynya area surface waters (PySW) had higher DOC concentrations (113±14 μM, n=68) than surface water (SW) outside the polynya area (96±18 μM, n=6). The DOM C:N ratios in a low-salinity, ice-melt subgroup of PySW samples indicate labile material, and these low-salinity surface waters appeared to have a local DOC and DON source. In contrast, HSfl was significantly lower inside than outside the NEWP area. Despite the lower HSfl values within the NEWP area, the PySW values were high when compared to open-ocean water. There were no local terrestrial sources for HSfl to the NEWP area and the East Greenland Current is therefore proposed as a likely source of allochtonous HSfl. When HSfl was used as a conservative tracer, up to 70% of the water in PySW and PyIW was found to be derived from SW, which contains a high fraction of water from the East Greenland Current. Similarly, a mixing model based on HSfl indicated that 80% of early-season DOC and 90–100% of early-season DON in PySW and PyIW were derived from SW, indicating a potentially high fraction of terrestrially-derived, relatively refractory DOM in the early-season NEWP area.     

Die Sturmfluten vom 9. und 10. Februar 1949 an der deutschen Nordseeküste

Zusammenfassung Es wird der Verlauf des Wasserstandes am 9. und 10. Februar 1949 an der deutschen Nordseeküste an Hand von Pegelaufzeichnungen mehrerer Orte verfolgt. Die zugehörige Wetterlage wird mittels besonderer, zeitlich engabständiger Wetterkarten für die Deutsche Bucht untersucht. Aus der Wetterentwicklung ist der ungewöhnliche Verlauf der Sturmfluten zu erklären. Sie wurden durch das Sturmfeld eines Tiefdrucktroges hervorgerufen, das sich an der nordfriesischen Küste besonders stark auswirken konnte, weil die zugehörige Zyklone im entscheidenden Entwicklungsstadium der Sturmflut am 9. Februar nördlich von Sylt nahezu stationär die Deutsche Bucht nach Norden hin absperrte. Die Wasserstandsaufzeichnungen von Husum und Hamburg, die besonders betrachtet werden, zeigen, da das meteorologische Geschehen den Gezeitenablauf völlig überdecken und Höchst wasserstände unabhängig von diesem erzeugen kann.

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The storm surges of February 9th and 10th, 1949 on the German coast of the North Sea

Summary By the aid of tide gauge records the development of the water level on the German coast of the North Sea on February 9th and 10th, 1949, is discussed. Special weather charts for the German Bight for short intervals are plotted in order to elucidate this unusual development of the tide. Its chief cause was the stormfield of a trough of low pressure whose greatest effect was on the coast of North Friesland, because on February 9 th, at the decisive stage of the tide wave, the storm centre was almost stationary off the Island of Sylt, blocking the outflow of water from the German Bight towards the north. Inspection of the tide curves of Husum and Hamburg demonstrates that the effect of air pressure and wind can mask the normal tides and produce maximum heights independently of the the tidal curve.