Results of the gravity field interpretation in the Turčianska Kotlina Basin

Abstract

The paper deals with the quantitative interpretation of the gravity field in
the Turčianska Kotlina Basin. The interpretation was done by means of the application
of the 2D density modelling method using the GM-SYS software. Geophysical constraints
of the density models are represented by the existing geophysical measurements and interpretations.
The Turčianska Kotlina Basin in the picture of the regional gravity field is
characterized by the local gravity low with amplitude of about 12 mGal. The source of
this gravity low is low density Tertiary sediments, which fill the basin. From the Tertiary
sediments the Neogene sediments play dominant role in observed gravity, because their
gravity effects are considerably larger in comparison with the gravity effects of the Paleogene
sediments. The contacts between the Malá Fatra and Vel’k´a Fatra Mts., and the
Turčianska Kotlina Basin are characterized by the significant gravity gradients. They reflect
tectonic contact between the basin and crystalline core mountains. In the Turčianska
gravity low we can see along the Profile TK-AL three local gravity lows. The highest local
gravity low is explained by the largest thickness of the Tertiary sediments. Another two
local gravity lows are also characterised by thicker layers of the Tertiary sediments. Density
models assume that the eastern (western) part of the basin basement is built by the
Mesozoic (crystalline) rocks. In the central part of the Profile TK-BL the thick Paleogene
sedimentary filling (more than 1 km) compensates the deepest part of the Pretertiary
basement. Density model along the Profile TK-BL does not suggest a presence of the
Paleogene sediments in the basin filling. It is also indicated that the Mesozoic rocks underlie
the Tertiary sediments. The Pretertiary basement was interpreted in the depths
from 0 km up to the 2 km.