Rozpoziomowanie i korelacja utworów serii żarnowieckiej i kambru dolnego zachodniej części syneklizy perybałtyckiej, na podstawie badań geofizyki wiertniczej
Abstract
IDENTIFICATION AND CORRELATION OF ŻARNOWIEC SERIES AND LOWER CAMBRIAN ROCKS IN WESTERN PART OF THE PERI-BALTIC SYNECLIZE ON THE BASIS OF WELL LOGS
Summary
In western part of the Peri-Baltic Syneclize (Fig. 1), top of crystalline basement has been reached by 12 drillings. Geophysical surveys covering the drillings included gamma and neutron-gamma, resistance, acoustic and diameter loggings. The well logs were used in establishing lithostratigraphic correlations, a new geophysical subdivision (including subdivision into sedimentary cycles), interpretation of lithological columns and more accurate drawing of stratigraphic boundaries. Lower Cambrian rocks were divided into 5 complexes, 12 subcomplexes and 38 geophysical horizons. Eight erosional (or sedimentary) breaks were found and 7 sedimentary cycles traced (Figs. 2 - 3). Geophysical interpretations and correlations (Fig. 2) made it possible to find that rocks of the Żarnowiec series (the age of which was hitherto debatable) should be assigned to the Lower Cambrian.
A comparative analysis of geophysical-geological data (Figs. 4 - 7) showed that upper boundary of the Lower Cambrian should be drawn at the base of subcomplexes Vb, and that of the Żarnowiec series - at the top of complex I. Upper boundary of the Mobergella Zone is drawn at the base of complex III, and that of the Holmia Zone (and eventually Protolenus Zone) - at the base of subcomplex Vb. The latter subcompley and complex VI are assigned to the Paradoxides Zone. The obtained data may contribute to verification of earlier interpretations and views on geological structure of the above strata.
Summary
In western part of the Peri-Baltic Syneclize (Fig. 1), top of crystalline basement has been reached by 12 drillings. Geophysical surveys covering the drillings included gamma and neutron-gamma, resistance, acoustic and diameter loggings. The well logs were used in establishing lithostratigraphic correlations, a new geophysical subdivision (including subdivision into sedimentary cycles), interpretation of lithological columns and more accurate drawing of stratigraphic boundaries. Lower Cambrian rocks were divided into 5 complexes, 12 subcomplexes and 38 geophysical horizons. Eight erosional (or sedimentary) breaks were found and 7 sedimentary cycles traced (Figs. 2 - 3). Geophysical interpretations and correlations (Fig. 2) made it possible to find that rocks of the Żarnowiec series (the age of which was hitherto debatable) should be assigned to the Lower Cambrian.
A comparative analysis of geophysical-geological data (Figs. 4 - 7) showed that upper boundary of the Lower Cambrian should be drawn at the base of subcomplexes Vb, and that of the Żarnowiec series - at the top of complex I. Upper boundary of the Mobergella Zone is drawn at the base of complex III, and that of the Holmia Zone (and eventually Protolenus Zone) - at the base of subcomplex Vb. The latter subcompley and complex VI are assigned to the Paradoxides Zone. The obtained data may contribute to verification of earlier interpretations and views on geological structure of the above strata.