--> Abstract: Neogene Structural Evolution of the Carpathian Bend Area, Carpathian Overthrust Belt, Romania, by G. Weir, K. Enzor, M. Donelick, G. Tari, M. Stefanescu, I. Olteanu, and A. Benzal; #90956 (1995).

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Abstract: Neogene Structural Evolution of the Carpathian Bend Area, Carpathian Overthrust Belt, Romania

Gary Weir, Keith Enzor, Margaret Donelick, Gabor Tari, Mihai Stefanescu, Ionel Olteanu, Alexandru Benzal

The Sub-Carpathian thrust sheet is the most external in the Romanian Carpathian Overthrust Belt. In the Carpathian Bend area a major change in structural trend occurs between the north-south trending Eastern Carpathians and the east-west trending Southern Carpathians. The Sub-Carpathian thrust sheet in this area underwent at least three phases of deformation during the Neogene: New Styrian phase (Middle Miocene), Moldavian phase (Late Miocene), and Vallachian phase (Pliocene- Pleistocene).

During the New Styrian phase, east-southeast to southeast directed thrusting continued in the Tarcau and Marginal Folds thrust sheets. During this time, the deformational front propagated into the Sub-Carpathian thrust sheet. This produced a low-amplitude wave train of folds across the area and created sub-basins in the broad intervening synclines. These sub-basins were transported as "piggy-back" basins during subsequent phases of deformation.

During the Moldavian phase of deformation, east-southeast to southeast directed thrusting continued as the Sub-Carpathian thrust sheet was transported onto and across the Moesian, Scythian and Moldavian Platforms. This tectonism produced continued folding and growth of structures within the thrust sheets. Late Miocene syntectonic units thicken rapidly into the synclines, recording the growth history of the structures. Erosional truncation of Late Miocene and older deposits occurred at this time, and younger stratigraphic units were deposited uniformly across most of the structures in the area.

The Pliocene Vallachian phase of deformation was the last major event affecting structures in the Carpathian Bend area. Late Miocene and younger units were folded along the trend of pre-existing structures, with extremely tight folds being formed involving the Neogene section. Kinematic data suggest a north-south shortening direction for the Vallachian phase. The Sub-Carpathian thrust sheet north of the area exhibits north-northeast oriented strike-slip faults in the Neogene section. The faults become dominantly more dip-slip to the Southwest as the thrust sheets curve around the bend. Movement along these faults may be restricted to the section above the Lower Miocene Salt Formation, which could have acted as a secondary detachment surface during deformation.

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