Druckspannungsindizien in den Sedimenttafeln des Rheinischen Schildes

Zusammenfassung Die Horizontalstylolithen im Deckgebirge des Rheinischen Schildes zeigen eine N-S-gerichtete Verkürzung der Schichttafel an. Dabei schwenkt die Hauptspannungsrichtung linksrheinisch nach NNW, rechtsrheinisch nach NNE und NE um. Die Verkürzung der Schichttafel liegt in der Größenordnung von 0,3 bis 0,7%. Die Querplattung des Unteren Muschelkalks wird als eine materialbedingt andersartige Reaktionsvariante desselben Spannungsplanes gedeutet. Sie sollte treffender als Längsplattung bezeichnet werden.

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Horizontal stylolites in the mesozoic sedimentary plateaus on either side of the Rhein-Graben indicate a shortening in N-S-direction. The direction of main stress turns to NNW on the left, and to NNE-NE on the right side of the graben. The shortening of the plateau amounts to the order of 0,3–07%. Querplattung (dip slab jointing), typical of the lower Muschelkalk, is conditional to the material interpreted as another reaction belonging to the same stress system, and should be defined as Längsplattung (longitudinal slab jointing).

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Résumé Les stylolites horizontaux du plateau mésozoique des deux côtes du Fossée Rhénan indiquent un resserrement en direction N-S. La direction de la pression principale de la rive gauche du Rhin se tourne vers NNW, de la rive droite vers NNE et NE. Le resserrement du plateau range dans l'ordre de grandeur de 0,3–0,7%. Les diaclases plaquetées croisées (Querplattung) du Muschelkalk inférieur sont interprétées comme une autre variante de réaction du même plan, occasionée par la différence du materiel. On devrait les definir plus exactement comme diaclases plaquetées longitudinales (Längsplattung).

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N-S . NNW NNE NE. 0,3%–0,7%.

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Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet.     

Grußwort

Ohne Zusammenfassung     

Natural arsenic in Triassic rocks: A source of drinking-water contamination in Bavaria, Germany

 The aquifer system of the Upper Triassic Keuper Sandstone, an important source of drinking water in northern Bavaria, is affected by elevated arsenic concentrations. Within the study area of 8000 km², no evidence exists for any artificial source of arsenic. Data from about 500 deep water wells show that in approximately 160 wells arsenic concentrations are 10–150 μg/L. The regional distribution of arsenic in the groundwater shows that elevated arsenic concentrations are probably related to specific lithofacies of the aquifers that contain more sediments of terrestrial origin. Geochemical measurements on samples from four selected well cores show that arsenic has accumulated in the rocks. This indigenous arsenic is the source of arsenic in the groundwater of certain facies of the middle unit of the Keuper Sandstone. Received, June 1998 / Revised, January 1999, May 1999 / Accepted, June 1999     

Blaue Objekte in der Umgebung von M31 II. Häufigkeitsverteilung und Statistik

This paper presents a statistical investigation of 999 blue objects [U(–B) 0.00, limiting magnitude U = 20, B = 21], the majority of which is newly discovered on M31-plates (predominantly taken by F. Börngen ) of the large Schmidt telescope of the Karl Schwarzschild Observatory Tautenburg. A list of the objects is given elsewhere [G. A. RICHTER (1973)].For “very blue objects” [(U – B) -0.40] the number per square degree brighter than magnitude B is as follows: log N_B = 0.72 B -13.1 (starlike objects), log N_B = 0.63 B -12.0 (diffuse and probably diffuse objects). This confirms the results of other authors: log N_B increases more rapidly than in the case of constant density (0.6); there are about 10 QSOs brighter than B = 20 per square degree. A detailed discussion concerning the optical identification of discrete radio sources will soon be given.     

Speciation of Trace Elements in Acidic PoreWaters from Waste Rock Dumps by Ultrafiltration andIon Exchange Combined with ICPMS and ICPOES

A speciation procedure developed on reactive acidicpore water samples from mining areas is presented.Methods with low consumption of solution are requiredthat allow rapid sample preparation to avoid equilibriumchanges as far as possible. The entire procedure includesonly three parallel separation steps. One aliquot is filteredthrough an 1 kd ultrafiltration membrane to separate traceelements adsorbed or complexed by colloids. One cationand one anion exchange are performed with two additionalaliquots to determine simple hydrated ions and smallinorganic complex ions. Commonly used procedures ofion exchange seem to be problematic. This new techniqueis based on a novel ion exchanger. Subsequently the threefractions obtained from the separation procedures and theoriginal pore water sample are analysed by ICPMS, ICPOES,ET-AAS, Flame-AAS, FES and IC to determine the concentrationsof the major ions and additionally up to 50 trace elements. Theinfluence of pH-values and several dissolved compounds iscontrolled in experiment series with synthetically preparedsolutions to reveal potential artifacts.     

Sediment dynamics and geohazards off Uruguay and the de la Plata River region (northern Argentina and Uruguay)

The continental margin off Uruguay and northern Argentina is characterized by high fluvial input by the de la Plata River and a complex oceanographic regime. Here we present first results from RV Meteor Cruise M78/3 of May?CJuly 2009, which overall aimed at investigating sediment transport processes from the coast to the deep sea by means of hydroacoustic and seismic mapping, as well as coring using conventional tools and the new MARUM seafloor drill rig (MeBo). Various mechanisms of sediment instabilities were identified based on geophysical and core data, documenting particularly the continental slope offshore Uruguay to be locus of submarine landsliding. Individual landslides are relatively small with volumes <2km³. Gravitational downslope sediment transport also occurs through the prominent Mar del Plata Canyon and several smaller canyons. The canyons originate at a midslope position, and the absence of buried upslope continuations strongly suggests upslope erosion as main process for canyon evolution. Many other morphological features (e.g., slope-parallel scarps with scour geometries) and abundant contourites in a 35-m-long MeBo core reveal that sediment transport and erosion are controlled predominantly by strong contour currents. Despite numerous landslide events, their geohazard potential is considered to be relatively small, because of their small volumes and their occurrence at relatively deep water depths of more than 1,500?m.     

Focused subaerial erosion during ridge subduction: impact on the geomorphology in south‐central Peru

Data obtained from low‐temperature thermochronometers such as apatite fission‐track and (U‐Th)/He are combined with morphometric information extracted from digital elevation models. This combination shows several geomorphological effects that are caused by the migration of the Nazca Ridge along the Peruvian Coastal margin. Offshore, the depth of the deep‐sea trench decreases by ～1500 m where the Nazca Ridge collides with the continental South American Plate. Onshore the ridge causes an uplift of at least 800 m in the Coastal Cordillera. This uplift results in a westward shift of the coastline thereby focusing and increasing erosion in the uplifted areas. At the trailing edge, the shelf subsides and the coastline retreats eastwards, producing at least part of the indentation observed between Paita and Pisco. The Ridge acts therefore like a wave uplifting the Andean margin as it traverses inland and southwards leaving a clear fingerprint on the topographic evolution of the Peruvian coastal margin.