Stress field evolution of the Gerecse Mountains in the light of the published data about the Transdanubian Range, Hungary

Abstract

After discussing the results gathered with respect to the structural geology of the Gerecse Mts and the whole
Transdanubian Range, tensional-transtensional stress states with a north-northeast–south-southwest extension can be
suggested for the Early and Middle Jurassic. In the Late Jurassic, a change in the stress state occured and this can be observed:
the stress field shifted to a compressional or strike slip, and the direction of the compression was mainly north-south.
The stress state in the Early Cretaceous — assuming minor undulation in the stress directions — was primarily
similar to the Late Jurassic stress state in a northeast–southwest direction. A notable change occurred in the
Aptian–Albian ages in the stress properties: the shortening direction rotated counterclockwise through north–south to
northwest–southeast during the Late Albian age. Sparse and uncertain stress data on the Late Cretaceous and the
Palaeocene are published in the study, albeit with evidence of major contradictions. This data cannot be precisely
incorporated into the structural evolution model of the Transdanubian Range.
The supposedly stable strike-slip stress conditions with a northwest–southeast trending and shortening direction
were present from the Eocene to the Ottnangian (Early Miocene). In the Karpatian (at the latest Early Miocene), a
variation in the stress conditions can be observed: the stress state changes from strike-slip to tensional or transtensional.
In the Badenian age (early Middle Miocene) the stress properties varied again. The shortening direction rotates clockwise
from the northwest–southeast to the northeast–southwest in the Sarmatian (late Middle Miocene). The tensiondominated stress regime seems to be common but, locally, strike-slip stress fields can be observed. After the Badenian
(early Middle Miocene) the tensional direction also rotates from northwest–southeast to the west-northwest–eastsoutheast, with the fluctuation of tensional–transtensional properties.