--> Abstract: Tectonics as the Main Control of Bathymetric Changes in the Hungarian Paleogene Basins, by A. Nagymarosy, O. Sztano, and M. Horvath; #90942 (1997).

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Abstract: Tectonics as the Main Control of Bathymetric Changes in the Hungarian Paleogene Basins

NAGYMAROSY, ANDRAS, ORSOLYA SZTANO & MARIA HORVATH

The Hungarian Paleogene Basins are found in the Intra- Carpathian area, in a tectonically active belt.

Subsidence and deposition started in the Middle Eocene and continued until the Early Miocene. Meanwhile there was a clear shift of depocenters from the southwest to the northeast. On a larger scale each subbasin seemingly shows a two-phase bathymetric history: initial shallow marine conditions followed by very rapid deepening that introduced a longer period of bathyal deposition. In the second phase gradual shallowing upward occurred, and particularly at basin margins erosion took place.

Paleobathymetric data based on foraminifera ecology were combined with sediment thicknesses to compile plots of accommodation and thus curves of relative sea-level changes. Time-scale, nannoplankton zonation and numerical values of third-order eustatic sea-level curve by Haq et al. (1987) were used to remove the eustatic signal from the curves of relative sea-level changes and to reveal signals left by subsidence or uplift of basin floor.

The main results of the modeling are
1. Tectonic subsidence and uplift of the basin floor pro-
duced the greatest amplitude signals above 1000m/myr in case
of subsidence and 200-400 m/half myr in case of uplift.
2. Change in sediment accumulation rates caused an order
of magnitude smaller signals.
3. The eustatic sea-level changes had a minimum effect on
the bathymetric conditions of the basin.

This study has shown that in such a tectonically active belt tectonic signals are at least an order of magnitude greater than signals left by eustatic sea-level changes and changes in sedimentation rates.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria