The first stripped gravity map of the Turčianska Kotlina Basin

Abstract

During the last years, many new results related to the thickness of the sedimentary
fill and other geophysical and geological constrains on the structure of the Turˇcianska
Kotlina Basin have been obtained. It allowed us to calculate the first, original stripped
gravity map in this basin. To obtain this map the 3D gravity effect of the basin sedimentary
fill had to be calculated. The gravity effect of the sediments was determined for two
different density conditions. Firstly, the average density of the sediments was constant
(2.45 g cm−3). Secondly, we supposed that the density of sediments varies exponentially
from 2.00 g cm−3 on the surface up to 2.67 g cm−3 on the pre-Tertiary basement. On the
maps of the calculated gravity effects it can be observed that the maximum amplitudes
reach about -12 mGal. The gravity effect is larger in the case when the densities of the
sedimentary fill vary exponentially. After subtraction of the gravity effects from the map
of complete Bouguer gravity map, the resultant stripped gravity maps were defined. The
detailed analysis of these maps indicates that the northern part of the pre-Tertiary basement
of the basin could be built mostly by the Mesozoic rocks, which belong to the Hronic
and Fatric units. The structure of the basement in the southern part of the basin seems
to be more complicated. This feature probably reflects a presence of Neogene volcanites
in the basin basement belonging to the Kremnick´e vrchy Mts. The picture of the gravity
field in the stripped gravity map predicts that the Paleogene sediments probably do not
build the sedimentary fill in the southern part of the basin.