ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Description / Table of Contents:
Zusammenfassung Das Rhät-Lias-Profil am westlichen Stadtrand von Göttingen wurde optisch, röntgenographisch, chemisch und mit der Differentialthermoanalyse untersucht. Es handelt sich um ein einheitliches Profil aus teils mergeligen, aber stets karbonatführenden Tonen mit zwischengeschalteten, teils kalkigen Sandsteinen. Der Tonmineralbestand setzt sich aus Illit als Hauptbestandteil, Kaolinit, Chlorit und Wechsellagerungen Illit/ Montmorillonit und Illit/Chlorit zusammen. Die Zusammensetzung des Karbonatbestandteils ändert sich im Profil vom Liegenden zum Hangenden von einem Karbonat mit 60 Mol-% Ca und 40 Mol-% Mg (unten) zu reinem Kalzit (oben). In der obersten untersuchten Schicht, dem Angulaten Sandstein, wurden einige Basaltgeröllchen und Schwerminerale basaltischer Herkunft gefunden.
Notes:
Abstract A petrographical study of the Rhät-Lias succession of rocks exposed in the quarries of some brickworks at Göttingen has been carried out by optical and chemical methods and by means of X-ray diffraction and differential thermal analysis (DTA). These sediments consist of dark grey shales with interbedded marl and fine- to mediumgrained sandstones. With the exception of one rocktype viz., the Hagenowi Sandstone, all the other rocks contain carbonate in smaller or larger amounts. In the present section, the mineralogical composition of the elastic constituents is almost uniform from top to bottom. The coarse fractions (〉 6,3 μ) are composed of quartz, mica (muscovite and biotite), feldspars (Na and K), quartz-mica aggregates, chlorite, haematite and heavy minerals (tourmaline and zirkon). The clay fractions are characterised by a predominance of dioctahedral illite. Other components of the clay fractions are kaolinite, chlorite and irregular illite-montmorillonite mixed layers. Regular illite-chlorite mixed layers have also been found in the fine fraction of the Hagenowi Sandstone. Quantitative determination of the clay minerals was made partly with DTA and partly from the X-ray diffraction patterns. The carbonates show, on the other hand, a striking qualitative variation. The lower part of the section is characterised by the occurrence of a mixed carbonate approaching dolomite in composition (35–40 Mol-% Mg), which is replaced more and more towards the top by pure calcite. The latter is the dominant carbonate in the upper beds. Authigenic pyrite, gypsum, barite and lepidocrocite have been found. Pebbles of basalt and heavy minerals of basaltic origin such as augite and hornblende found in the uppermost bed i. e., the Angulaten Sandstone, have geological significance, because until now evidence of volcanic activity in Mesozoic has not been known from the northern part of Middle Europe.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01139671
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