Petrografia osadów górnojurajskich z otworu wiertniczego Korytków Duży 1

Abstract

PETROGRAPHY OF THE UPPER JURASSIC DEPOSITS PIERCED BY BORE HOLE KORYTKÓW DUŻY 1

Summary

The Upper Jurassic deposits pierced by bore hole Korytków Duży 1, are 283 m in thickness and consist of three series: spongy and marly, mainly silicified limestones, oolitic and dolomitic deposits, as well as conglomeratic and oolitic deposits. The whole rock complex is characterized by a strong fracturing visible along various planes, and by numerous stylolites (K. Radlicz, 1966). In the deposits of the first series are found mainly fragments of sponges, as well as sporadic grains of quartz and glauconite. Silification and consolidation of cherts took place during both diagenesis and epigenesist stages. In the rocks of the second series the author has found fragments of algae that belong to Acicularia and Characaea. Among the oolites the author has encountered oolites of chemical or biochemical origin, and biochemic-mechanical oolites that are referred to the intermediate forms between oncolites and ball-stones. In the third series the deposits are mainly oolitic and conglomeratic, bearing numerous fine crystals of anhydrite and gypsum, their calcite pseudomorphs, or their negatives. Due to a lack of any possibilities to determine the azimuths of fissures and of stylolites in core samples, only dips have been analysed by means of simplified classification method of dip angles in the individual planes, i.e. vertical - 90°, almost vertical - 80 - 90°, oblique - 50 - 80°, acute - 20 - 50°, almost horizontal - 5 - 20°, and borizontal - 0 - 5°. The predominating directions of the fissures and stylolites are determined by vertical and horizontal planes. In addition to the fissures and stylolites there are found also numerous tectonical slickensides. A comparative analysis of the fissures and stylolites allowed the author to distinguish the following systems:

1 - vertical and almost vertical fissures and horizontal fissures, slightly cemented with microcrystalline calcite, or with clay,

2 - vertical and almost vertical fissures related to the older system of stylolites, cicatrized with fine-crystalline or middle-crystalline calcite;

3 - fissures of oblique direction cicatrized with middle-crystalline and coarse-crystalline calcite, with polysynthetic twinnings.

4 - fissures, stylolites and slickendides of sharp planes cicatrized with fine-crystalline and middle-crystalline calcite, or with clay,

5 - fissures and stylolites running almost horizontally, cicatrized with middle-crystalline and coarse-crystalline calcite. At least, three generations of diagenetic and tectoepigenetic character have been distinguished among the stylolites considered. In the systems of fissures and stylolites, two categories of planes have been ascertained: active and passive, or almost passive ones. To the category of active planes belong fissures cicatrized with calcite and pyrite. In this category two varieties have been distinguished: leaching and cicatrization fissures. Under favourable physical and chemical conditions all the active and passive fissures may pass one into another. The leaching fissures may transform into stylolites, or may constitute the initial forms of karst phenomena.