Charakterystyka petrograficzna skał ilastych okolic Szczecina

Abstract

PETROGRAPHICAL CHARACTERISTICS OF CLAY ROCKS FROM THE SZCZECIN VICINITIES

The present paper deals with the Oligocene, clay known from the literature as the so-called, "septarian-clays". Macroscopically, are rocks beige, brown-violet, dark grey and black in colour compact and in dry state.

In these days there occur frequently aggregates of automorphic gypsum crystals, too. A determination of mineral composition was made by means of the following methods: microscopic analysis, thermal-differential analysis, colouring analysis and chemical analysis.

The microscopic analysis allowed to distinguish three kinds of clays, differing only in their structure, as follows: 1 - clays of aleuropelitic structure, 2 - clays of pelitic structure, 3 - clays of politic-gelatinous structure.

The thermal-differential curves permitted to refer the clays under study to the illite-montmorillonite type of rocks. The colouring analysis made after indications of N. E. Wiedienieva and M. F. Wikulova (1954) using methylene blue, chrysoidine and benzidine, proved the results of thermal analysis and showed that the clay rocks investigated are mainly built up of, illite (hydromica) and montmorillonite. The chemical analysis, the results of which have been .calculated as percentage mineral composition after·a method given by J. Imbrie and A. Poldervaart (1959) also shows the illite-montmorillonite type of the clays.

Moreover, it was stated on the investigations made that the clays occurring in the area under study mainly consist of a mixture of mite and montmorillonite, subordinately containing quartz, feldspar, glauconite, folidoide, .pyrite, Fe oxides and gypsum. Zircon, epidote, tourmaline and fragments of clay rocks are here accessory components. The occurrence of foraminifers and their assemblages, as well as the presence of montmorillonite and glauconite indicate the marine environment of sedimentation.