System rowów trzeciorzędowych w obrazie grawimetrycznym
Abstract
THE SYSTEM OF CENOZOIC TROUGHS IN THE SIGHT OF GRAVIMETRIC SURVEYS
Summary
Gravimetric surveys have shown the presence of a system of negative gravity anomalies with large amplitudes and horizontal gradient in the areas of the Fore-Sudetic Monocline, its north-eastern margin and south-eastern part of the Pomeranian Swell. Longitudinal axes of these anomalies are several times longer than the transversal. The anomalies are related to depressions in Mesozoic basement infilled with Tertiary deposits and often with Tertiary brown coal deposits.
The extent of individual depressions was delineated on the basis of results of semi-detailed gravimetric surveys, presented in the maps of Bouguer and residual anomalies. The depressions were initially interpreted as erosional troughs and, thereafter as tectonic troughs. The author's studies showed that they form a single system which could have been temporarily used by river network. Some meandering sections of the troughs may, in part, represent the result of erosional processes.
The negative gravity anomalies are mainly related to density contrast of Tertiary and Mesozoic, pre-Campanian deposits. In areas of occurrence of Campanian and Maestrichtian rocks with density equal to that of the Tertiary, the presence of Tertiary troughs does not result in origin of any gravity anomalies. The presence of brown coal deposits markedly increases the amplitude of anomalies. It is also not excluded that gravity effect of Mesozoic troughs may he summing up with that of Tertiary troughs.
Summary
Gravimetric surveys have shown the presence of a system of negative gravity anomalies with large amplitudes and horizontal gradient in the areas of the Fore-Sudetic Monocline, its north-eastern margin and south-eastern part of the Pomeranian Swell. Longitudinal axes of these anomalies are several times longer than the transversal. The anomalies are related to depressions in Mesozoic basement infilled with Tertiary deposits and often with Tertiary brown coal deposits.
The extent of individual depressions was delineated on the basis of results of semi-detailed gravimetric surveys, presented in the maps of Bouguer and residual anomalies. The depressions were initially interpreted as erosional troughs and, thereafter as tectonic troughs. The author's studies showed that they form a single system which could have been temporarily used by river network. Some meandering sections of the troughs may, in part, represent the result of erosional processes.
The negative gravity anomalies are mainly related to density contrast of Tertiary and Mesozoic, pre-Campanian deposits. In areas of occurrence of Campanian and Maestrichtian rocks with density equal to that of the Tertiary, the presence of Tertiary troughs does not result in origin of any gravity anomalies. The presence of brown coal deposits markedly increases the amplitude of anomalies. It is also not excluded that gravity effect of Mesozoic troughs may he summing up with that of Tertiary troughs.