Platformowe utwory dolnego kambru z wierceń Rajbrot 1 i 2 na południe od Bochni

Abstract

CAMBRIAN PLATFORM DEPOSITS IN BOREHOLES RAJBROT 1 AND RAJBROT 2 SOUTH OF BOCHNIA (SOUTHERN POLAND) Summary The sandy-silty lithologies of the Cambrian age have been found under the carbonate rocks of the Middle Devonian, Late and Early Carboniferous ages in boreholes Rajbrot 1 and Rajbrot 2 situated south of Bochnia (Fig. 1). These rocks occur at the depth of 4322 m in borehole Rajbrot 1 and the depth of 3828 m in the borehole Rajbrot 2. Their age was determined basing on the investigation of the organic microfossils Acritarcha. Rich assemblages determined here are represented by such genera as Tasmanites, Leiosphaeridia, Ceratophyton (Fig. 5). This indicates the Early Cambrian age of lithologies studied (subholmia horizon). The more detailed Lower Cambrian profile was studied in the borehole Rajbrot 1 (Fig. 3). The lower part of this profile consists of sandy silts intercalcited with silts and fine-grained sands tones. Fine grained and sometimes medium-grained, arkose sands tones intercalcited and laminated with siltstones dominate in the upper part of the profile. In the borehole Rajbrot 2, only the top stratum of the Cambrian rocks was discovered. This is represented by fine-grained arkose sandstones. The Lower Cambrian rocks determined in the boreholes were termed "Formation Rajbrot" and the sandstones and silty members were distinguished. The Lower Cambrian deposits of the platform character which were determined here appear not to be tectonicaly disturbed. The dips of the strata range from 2-15°.