Late Miocene-Pliocene Shortening, Uplift and Wrench Tectonics Dominated Canyon Development along the Mid-Hungarian Mobile Belt

Pogácsás, György ¹; Juhász, Györgyi ²; Csizmeg, János ¹; Dudás, Árpád ¹; Német, Norbert ³; Milankovich, András ²; Szonyi, Judit M.¹; Simon, Szilvia ¹; Czauner, Brigitta ¹; Baracsi, Berta ¹; Tomcsányi, Tibor ¹; Szabo, Beata ¹
(1)Physical & Applied Geology, Eötvös Loránd University, Budapest, Hungary. (2) Exploration & Production, MOL Hungarian Oil & Gas PLC, Budapest, Hungary. (3) Geology, University of Miskolc, Miskolc, Hungary.

The most significant neotectonic zone of the Neogene-Quaternary Pannonian Basin is the Mid-Hungarian Mobile Belt. Structural analysis of this zone was carried out on a 100 km x 100 km area, between the Danube and the Tisza Rivers, on the basis of historical industry seismic data. The structural analysis focusing on the Late Miocene and younger sediments was supported by sequence stratigraphic analysis. Interpretation of seismic and well log data on workstation facilitated kinematic evaluation and mapping of Late Miocene-Pliocene structural elements.

Mapping of key chronostratigraphic surfaces (sequence boundaries) and unconformities revealed shortening related folding and uplifting north of the Mecsek Fault. The orientation of mapped Late Miocene faults is ENE-WSW and NE-SW, controlled by the previous, preformed fault pattern and the configuration of the hard rock basement. The master wrench faults seem to be rooted in the Mesozoic-Paleozoic slices of the preneogene basement. Folds are conjugated to the main strike-slip fault zones. The fold axis distribution suggests alternation of a N-S oriented and a NW-SE oriented shortening.

Large canyons incised into the Upper Miocene Pannonian Lake sediments have been recognised in the central part of the study area (Alpár area) along several seismic lines. The canyon system has a surprisingly large size for a lacustrine setting, incised several hundred meters in the pre-existing substrate, into an extremely thick aggrading deltaic complex. The incision surface is connected to sequence boundary SB Pa-4 (6.8 Ma). This SB was considered to have been associated with significant base level fall due to shortening and uplifting. The canyon system occurs at a large releasing bend and/or extensional duplex of Paks-Szolnok strike-slip system, which was active as sinistral during the Late Miocene. The formation of the deep canyons was presumably generated by the interaction of a relative base-level fall, the reactivation and bending/duplexing of a strike-slip system precisely in the same area, and the large sediment supply carried by overfed rivers.

The research work was supported by the Hungarian National Research Fund (OTKA 047159 and 060861). Support of this research by IES Integrated Exploration Service, a Schlumberger Company via PetroMod university grant program is acknowledged

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.