ZAPIS LITOLOGICZNY I MIKROFACJALNY OSADÓW EUKSYNICZNYCH KAMBRU GÓRNEGO I TREMADOKU OBNIŻENIA BAŁTYCKIEGO (PÓŁNOCNA POLSKA)

Abstract

A LITHOLOGICAL AND MICROFACIES RECORD OF THE UPPER CAMBRIAN AND TREMADOCIAN EUXINIC DEPOSITS IN THE POLISH PART OF THE BALTIC DEPRESSION (NORTHERN POLAND)Abstract. The paper presents microfacies characteristics of Upper Cambrian and Tremadocian siliciclastic and carbonate rocks from the Polish part of the Baltic Depression (Northern Poland). Whitin the Upper Cambrian and Tremadocian sequence two different groups of hydrogenic microfacies can be distinguished: terrigenous (siliciclastic) and carbonate microfacies. The terrigenous (siliciclastic) group consists of three microfacies types: sandy conglomerates and sandy-glauconitic conglomerates (COsa–COsa-gl); quartz sandstones (arenites) (SAqw), black bituminous claystones (shales) and black bituminous siltstones (SLbi–CLbi). The carbonate group consists of four microfacies types: bioclastic grainstones (GRbc), bioclastic grainstones/packestones (GRbc/PAbc); bioclastic packstones/wackestones (PKbc/WKbc) and sparites and microsparites (LMre). Stratigraphic range of the carbonate mocrofacies is spatially variable and assigned respectively to the Upper Cambrian Agnostus pisiformis–Acerocare zones in the sections from the western part of the Baltic Depression, and to the Olenus and Agnostus (Homagnostus) obesus–Parabolina spinulosa zones (Młynary Formation) in the sections from the central part. The total thickness of the Upper Cambrian Tremadocian siliciclastic-carbonate sequence varies from 34.5 m in the western and north-western part of the Baltic Depression (21-1/95 borehole) to 0.05 m in its easternmost area (Jezioro Okrągłe IG 2 borehole).