Late Pleistocene Climatic Variations at Achenheim, France, Based on a Magnetic Susceptibility and TL Chronology of Loess

New field investigations of the Achenheim sequence (Alsace, France) allow for the characterization of variations in the low-field magnetic susceptibility over most of the last climatic cycle, i.e., the past 130,000 yr. New stratigraphic data and thermoluminescence measurements permit reassessment of the previous chronological interpretation of the Upper Pleistocene at Achenheim. A high-resolution analysis of magnetic susceptibility discloses the occurrence of a fine-grained “marker” horizon which was also found recently in another section. This horizon is interpreted as a small-scale dust layer deposited prior to the main interval of loess deposition. The horizon, deposited at the marine isotope stage (MIS) 5/4 boundary, has been found in other loess sequences and is especially prevalent in central Europe. It is characterized by low susceptibility values and a grayish color. New thermoluminescence dates indicate that the loess deposition took place after the MIS 5/4 boundary, i.e., after 70,000 yr. These results are consistent with the Greenland GRIP ice-core dust record which also demonstrates a dusty atmosphere after 72,000 yr ago. On a more regional scale, the Achenheim loess sequence demonstrates a reliable correlation between the western side of the Eurasian loess belt and the dust record of the Greenland ice cores.     

Petrographic investigations in cemeteries in Dresden: a scientific view on the tombstone inventory including historic and cultural aspects

Cemeteries give evidence for a continuous change in sepulchral culture and provide insights into the application of characteristical rock materials used for tombstones during different times. Four selected cemeteries in Dresden (the Eliasfriedhof/Elias Cemetery, the Trinitatisfriedhof/Trinity Cemetery, the Johannisfriedhof/Johannis Cemetery, and the Städtischer Urnenhain/Municipal Urn Grove), which are of considerable cultural and historical importance, have been investigated within an ongoing mapping project. First results of this project focussing on the tombstone inventory of the mentioned graveyards and thus the use of building and decoration stones therein between 1680 and 1945 are presented in this paper. It can be demonstrated that the choice, variety, and application of rock material depends on the infrastructure and transport possibilities, but is also strongly influenced by sepulchral cultural trends and the prevailing zeitgeist. Until the middle of the 19th century, nearly solely Elbe sandstone (from the area of the Elbsandsteingebirge/Elbe sandstone mountains), that was transported on the Elbe river by ship, is found as rock material for tombstones in Dresden cemeteries. Rapid construction and development of the railway network starting around 1840 improved the availability, at first, of regional rock material (e.g., from the Lausitz/Lusatia) and, later on, from about 1880, of national and international—especially European—rock material (e.g., from Franken/Franconia, France, Scandinavia). Furthermore, the Friedhofsreformbewegung/cemetery reform movement at the beginning of the 20th century, with its significant effect on the selection of rock types used for tombstones, marks another historical breakthrough.     

10Be exposure age constraints on the Late Weichselian ice‐sheet geometry and dynamics in inter‐ice‐stream areas,western Svalbard

The Late Weichselian ice sheet of western Svalbard was characterized by ice streams and inter‐ice‐stream areas. To reconstruct its geometry and dynamics we investigated the glacial geology of two areas on the island of Prins Karls Forland and the Mitrahalvøya peninsula. Cosmogenic ¹⁰Be surface exposure dating of glacial erratics and bedrock was used to constrain past ice thickness, providing minimum estimates in both areas. Contrary to previous studies, we found that Prins Karls Forland experienced a westward ice flux from Spitsbergen. Ice thickness reached >470 m a.s.l., and warm‐based conditions occurred periodically. Local deglaciation took place between 16 and 13 ka. At Mitrahalvøya, glacier ice draining the Krossfjorden basin reached >300 m a.s.l., and local deglaciation occurred at c. 13 ka. We propose the following succession of events for the last deglaciation. After the maximum glacier extent, ice streams in the cross‐shelf troughs and fjords retreated, tributary ice streams formed in Forlandsundet and Krossfjorden, and, finally, local ice caps were isolated over both Prins Karls Forland and Mitrahalvøya and their adjacent shelves.     

Persönliches

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Der Nordrand des Tauernfensters zwischen Mayrhofen und Inner Schmirn (Tirol)

Zusammenfassung Der innerste Bereich des Tauernfensters kann als Helvet betrachtet werden. Hier findet sich auf dem voralpinen Kristallin oberjurassischer Hochstegenkalk, gefolgt von einer Serie mit Metaarkosen, Brekzien und Schiefern vermutlich kretazischen Alters. Es lassen sich dabei autochthone, parautochthone und allochthone Anteile unterscheiden. Von Süden her überschoben folgt darauf mit verkehrten und aufrechten Serien das penninische Deckensystem der Oberen Schieferhülle. Der Fensterrahmen wird von einer tektonischen Mischserie (Richbergkogelserie) sowie vom unterostalpinen Innsbrucker Quarzphyllit mit dem Tarntaler Mesozoikum gebildet, welch letzteres sich in drei Decken mit unterschiedlicher fazieller Ausbildung gliedern läßt.

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The lowermost structural elements exposed in the Tauern window can be taken for Helvetikum. Within this unit the crystalline socle is overlain by the Upper Jurassic Hochstegen limestone and a variegated series of meta-arkoses, breccias, and phyllites probably of Cretaceous age. Autochthonous, parautochthonous, and allochthonous elements can be distinguished. Thereupun follows the Penninic nappe system of the Obere Schieferhülle which displays inverted and normal rock sequences. The frame of the Tauern window is formed by a tectonically mixed series (Richbergkogel series) and the Lower East Alpine Innsbruck quartz phyllite with the Tarntal Mesozoic. The latter can be divided into three nappes.

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Résumé La domaine le plus interne de la fenêtre des Tauern peut être considéré comme relevant de l'Helveticum. Ici reposent d'abord sur le cristallin préalpin après un Jurassique inférieur rudimentaire, une épaisse sédimentation transgressive calcaire appartenant au Jurassique supérieur (calcaire de Hochstegen), suivie d'une série de métaarkoses, brèches et phyllites probablement d'âge crétacé. On peut y distinguer des parties autochthones et des parties parautochthones et allochthones.L'élément structural suivant, venu du sud, doit être consideré comme appartenant au Penninicum; c'est le système de nappes de 1'«Obere Schieferhülle», où on peut distinguer des séries renversées et normales.L'enveloppe de la fenêtre des Tauern comprend une série tectonique composite (série de Richbergkogel) ainsi que les Phyllades d'Innsbruck et les séries mésozoïques de la Tarntal.Dans ces dernières, on peut distinguer trois nappes: l'inférieure, celle de Torwand (ou Hippold), avec à la base, des phyllades paléozoïques, des sédiments rudimentaires triasiques, d'épaisses brèches posttriasiques, des radiolarites, et enfin des arkoses, grès et conglomérats avec composantes sporadiques de radiolarite. Au-dessus vient la nappe de Reckner avec des séries triasiques et jurassiques et des serpentinites. En haut se trouve une nappe (nappe de Möls) comprenant des sédiments rudimentaires mésozoïques et les Phyllades d'Innsbruck.

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Mitteilungen

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An experimental study of $$ ^{{{\text{Fe}}^{2 + } {-}{\text{Mg}}}} K_{\text{D}} $$ between orthopyroxene and rhyolite: a strong dependence on H2O in the melt

The effect of temperature, pressure, and dissolved H₂O in the melt on the Fe²⁺–Mg exchange coefficient between orthopyroxene and rhyolite melt was investigated with a series of H₂O fluid-saturated phase-equilibrium experiments. Experiments were conducted in a rapid-quench cold-seal pressure vessel over a temperature and pressure range of 785–850 °C and 80–185 MPa, respectively. Oxygen fugacity was buffered with the solid Ni–NiO assemblage in a double-capsule assembly. These experiments, when combined with H₂O-undersaturated experiments in the literature, show that \( ^{{{\text{Fe}}^{2 + } {-}{\text{Mg}}}} K_{\text{D}} \) between orthopyroxene and rhyolite liquid increases strongly (from 0.23 to 0.54) as a function of dissolved water in the melt (from 2.7 to 5.6 wt%). There is no detectable effect of temperature or pressure over an interval of 65 °C and 100 MPa, respectively, on the Fe²⁺–Mg exchange coefficient values. The data show that Fe-rich orthopyroxene is favored at high water contents, whereas Mg-rich orthopyroxene crystallizes at low water contents. It is proposed that the effect of dissolved water in the melt on the composition of orthopyroxene is analogous to its effect on the composition of plagioclase. In the latter case, dissolved hydroxyl groups preferentially complex with Na⁺ relative to Ca²⁺, which reduces the activity of the albite component, leading to a more anorthite-rich (calcic) plagioclase. Similarly, it is proposed that dissolved hydroxyl groups preferentially complex with Mg²⁺ relative to Fe²⁺, thus lowering the activity of the enstatite component, leading to a more Fe-rich orthopyroxene at high water contents in the melt. The experimental results presented in this study show that reversely zoned pyroxene (i.e., Mg-rich rims) in silicic magmas may be a result of H₂O degassing and not necessarily the result of mixing with a more mafic magma.