Determining sedimentation ages of high-grade metamorphic gneisses by their palynological record: a case study in the northern Schwarzwald (Variscan Belt, Germany) |
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Authors: | M Hanel M Montenari A Kalt |
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Institution: | (1) Mineralogisches Institut, Im Neuenheimer Feld 236, D-69120 Heidelberg, Germany Fax: +49 6221 544805 e-mail: mhanel@classic.min.uni-heidelberg.de, DE;(2) Geologisches Institut, Albertstrasse 23b, D-79104 Freiburg, Germany, DE |
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Abstract: | In the northern Schwarzwald (Moldanubian Zone of the Variscan belt), paragneisses drilled from approximately 2500 m depth
at the Bühl-1 drilling site have experienced amphibolite-facies metamorphism and were later partly transformed to mylonites
under greenschist-facies conditions. Completely graphitised acritarchs and chitinozoans were recovered from these paragneisses
and mylonitic gneisses. Whereas both groups of palynomorphs give evidence of a marine depositional environment, only the chitinozoans
are stratigraphically useful in this case and indicate a Paleozoic age. Previous findings of acritarchs in a different high-grade
metamorphic gneiss unit within the Schwarzwald indicate an Upper Proterozoic marine sedimentation age. The spectrum of palynomorphs
found thus far in the Schwarzwald in combination with petrological data suggests that within the Moldanubian domain of the
Armorican microplate, rocks with different sedimentary records later experienced diverging prograde metamorphic histories.
In general, the results reveal that palynological studies in combination with petrological data are a promising tool for reconstructing
pre-orogenic settings in collisional belts.
Received: 17 July 1998 / Accepted: 19 January 1999 |
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Keywords: | Palynology Sedimentation age Amphibolite-facies gneisses Schwarzwald Variscan belt |
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