Session 19: Climatic, oceanographic and tectonic forcing of sedimentary systems

Marc Krecher

(krecher@mibm.ruf.uni-freiburg.de)

Geologisches Institut, Universität Freiburg, Albertstraße 23b, D-79104 Freiburg, Germany

The Southern Vosges are part of the "Moldanubian", which is the inner zone of the Variscan Orogen in middle Europe. The Devonian-Carboniferous rock record is nonmetamorphic and cleavage is rarely observed. The presence of K-calc-alcaline volcanism and epiclastic rocks associated with a monotonous deep marine sedimentation led to the interpretation of the Southern Vosges as a Lower Carboniferous island-arc setting. Petrographical and geochemical development of volcanic rocks and paleontological data provide the basis for a primitive subdivision in a lower and middle marine and an upper continental unit. In the Upper Carboniferous tilting, folding and some thrusting of the rock record resulted in steep dipping successions, so that facies variation is much more apparent for the vertical than the horizontal development of the strata. Block rotations are responsible for a mosaic of tectonogeographic areas. The sedimentary facies associations of the middle unit show a probable lower slope setting in the Oderen and the Markstein tectonogeographic areas. This interpretation is based on thick pelitic successions (mainly turbiditic in origin) associated with slumps, debris flows, probably channelized carbonate deposits, a widespread occurrence of olistoliths and thick bedded massive and partly amalgamated turbidite successions. Laminated mudstone is the dominant facies. Sedimentary structures typical for shallow water processes cannot be found. There exists no description of synsedimentary compressional tectonics. Isolated olistoliths south of Willer, with about 100 m in length, and thick successions (at least 1000 m) of deep marine sediments led the author to assume a subsiding continental slope setting (due to extensional tectonics?) for the middle unit (Upper Visean). Sedimentation rate must have been more than 5 cm / 1000 a. Paleotransport directions seem to be perpendicular to Upper Carboniferous deformation. Paleogeographic relations to the Saxothuringian, petrographic provenance studies and biostratigraphic work should be objects of future research.