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Abstract: A Late Triassic Thrust-Fold Belt Beneath the Moesian Platform: Implications for the Cimmeride Orogenic System

Gabor Tari, Georgi Georgiev, Mihai Stefanescu, Gary Weir

Widespread folding of the pre-Jurassic sequence in the Moesian Platform of Romania and Bulgaria is traditionally attributed to a loosely defined Cimmeride phase of compression. Detailed structural analysis of seismic reflection and well data, however, permitted the more specific interpretation of this deformation in terms of a north-vergent thin-skinned thrust-fold belt.

The Cimmeride folds are actually 10-30 km wide ramp anticlines eroded to highly variable stratigraphic levels (Middle Triassic-Silurian). Between the anticlines a 0-2000 m thick Upper Triassic clastic sequence corresponds to the syn-tectonic growth of the structures. The internal geometry of the growth sequence (onlap on the forelimb and thinning and truncation on the backlimb) suggests the fault-bend folding origin of the structures. Whereas the upper decoupling level tends to be localized in a Permian halite and anhydrite horizon, the lower detachment probably runs close to the base of the Paleozoic. Cross-section balancing suggests relatively minor shortening (5-20%) associated with the anticlines.

In a wider paleotectonic scenario the north-vergent anticlines beneath the Moesian Platform are interpreted as the frontal part of the Mediterranean Cimmerides propagating into the foreland. The recognition of widespread Cimmeride deformation in the Balkan region has an important impact for the reconstruction of the western Paleo-Tethys.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France