Dolnosylurskie wapienie gruzłowe w północno-wschodniej Polsce

Abstract

LOWER SILURIAN NODULAR LIMESTONES IN NORTH-EAST POLANDSummaryBore holes Pasłęk IG 1, Olsztyn IG 2, Kętrzyn IG 1 and Bartoszyce IG 1, located in the north-eastern area of Poland, show that a complex of nodular limestones overlies the Upper Ashgilian deposits. Scarce fauna ascertained in this area, its situation in the section, and the comparison with the analogous formations, known to occur in the area of Lithuania, allow us to refer the nodular limestones to the Lower Llandovery. As concerns their age, the nodular limestones correspond probably to the graptolite horizons, from Glyptograptus persculptus to Orthograptus vesiculosus. The Lower Silurian nodular limestones of the north-eastern area of Poland resemble breccias or intraformational conglomerates. However, according to the present authors, the influence of mechanical activity of bottom currents, or of waves upon the formation of the final structure of the limestones here considered, seems to be little probable. The carbonate nodules building the rocks under discussion were formed rather as a result of sedimentary boudinage (vide R. G. McCrossan, 1958) related to compaction processes, or to slight submarine slupms. Maybe, the disintegration of the primarily continuous small calcareous banks was predisposed by the dissolving activity of the slow bottom currents. According to the scheme proposed in this paper, the Lower Silurian nodular limestones, found in the north-eastern area of Poland, were formed in the shallow-water environment, however, below the wave base.