Wrench Tectonics Control on Neogene-Quaternary Sedimentation and Hydrocarbon Accumulation along the Mid-Hungarian Mobile Belt
Pogácsás, György 1; Juhász, Györgyi 2;
Dudás, Árpád 1; Csizmeg, János 1
(1)Physical &
Applied Geology, Eötvös Loránd University, Budapest, Hungary. (2) Exploration
& Production, MOL Hungarian Oil & Gas PLC, Budapest, Hungary.
The Neogene Pannonian Basin is underlain by two main terrains ALCAPA and TISZA on the opposite side of the Mid-Hungarian Mobile Belt. Activity along the Mid-Hungarian Mobile Belt can be characterised by four periods, controlling sedimentation and architecture of the basin:
1. During the Early Miocene, the ALPACA moved eastward, bounded by
dextral strike-slipe fault system along its contact with the Southern Alps and
the TISZA terrain (most intensively 19-16.5 Ma). The TISZA unit moved
northeastward over the remnant Carpathian Flysch Basin. These movements resulted
in right lateral, convergent wide wrench along the Mid-Hungarian Mobile Belt.
2. During the Middle-Miocene (15.5-13.6Ma), the ALCAPA collided
with the European platform, and the eastward movement of the TISZA became
pronounced. A long period of left lateral strike slipe began. Graben opening
began driven by the westward subduction and the eastward motion of the TISZA
unit. Large displacements along listric faults have resulted in tilting of
strata, and formation of a regional unconformity between the Middle and Upper
Miocene. Wrench fault related pull apart basins were filled by terrestrial to
marine sediments.
3. During Late-Miocene (Sarmatian-Pannonian 13.6-6.2 Ma), the
eastward motion of ALPACA was ceised, the Tisza unit was still able to move
eastward. An estimation of 8-10 km magnitude of Late Miocene strike slip was
based on detailed seismic study on the Mid-Hungarian Mobile Belt. The TISZA
unit collided with the European platform (11.5-6.2 Ma), and the
intra-Carpathian stress field changed to the present stress field. During this
time in the studied part of the Basin sediment supply was perpendicular to the
strike of the Mid Hungarian Mobile Belt. Then the structural style chanced and
at SB Pa-4 (appr. 6.8 Ma) a strong relative base level drop occured driven by
the onset of inversion in the coeval marginal areas of the basin.
4. During the Pliocene-Quaternary, the postrift fill of the Pannonian Basin system, related to the regional thermal subsidence, started to undergo an inversion. Pliocene-Quaternary was characterised by 1-5 km left lateral wrenching along the Mid-Hungarian Mobile Belt.
Wrench zones played an important role in the migration and accumulation of hydrocarbons in elevated en echelon folds, faulted en echelon folds and transpressive uplifted blocks bounded by conjugate Riedel faults related to strike-slip motions.
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.