Kambr na Pomorzu i przyległym akwenie Bałtyku

Abstract

Przedstawiono charakterystykę stratygraficzno-litologiczną osadów kambru z obszaru Pomorza i przyległego polskiego akwenu Bałtyku, opartą na danych pochodzących z wierceń. Wyróżniono kambr dolny, środkowy i górny. Profil kambru nie jest pełny, zawiera liczne luki stratygraficzne. Podstawą podziału stratygraficznego stanowiły nie tylko kryteria faunistyczne (głównie trylobity), lecz przede wszystkim zmienność litologiczna osadów, odczytana z wykresów profilowania geofizycznego.

CAMBRIAN IN POMERANIA AND ADJACENT BALTIC BASIN

Stratigraphic-lithologic description of the Cambrian sediments from Pomerania and adjacent Baltic

Basin is based on data from boreholes and geophysic curves. The Cambrian sediments are underlain by deposits of the Żarnowiec Formation, the age of which was defined at Upper Vendian – Lower Cambrian. The upper part of this formation is represented by sediments of land-marine environment and was included into the Cambrian. A biostratigraphic section of the Cambrian is not complete as comprises stratigraphic breaks, mainly of primary origin. If referred to key sections of Scandinavia, the Middle as well as the Upper Cambrian here does not contain two trilobite horizons (K. Lendzion, 1983a, b). Besides there are also local smaller breaks that comprise only fragments of individual horizons.

A stratigraphic subdivision of the Cambrian sediments is based on trilobite and mobergelles, and to a smaller degree on brachipods and conodonts (K. Lendzion, 1983a, b; W. Bednarczyk, 1984). Cambrian sediments were usually only partly cored and so, palynologic material is rare and limited to small fragments.

In the basin the Upper Cambrian was subdivided as well as the upper Middle Cambrian on the basis of fossil fauna whereas the remaining part of the Cambrian section could have lithologic variability distinguishsd from curves of geophysic sounding. Presence of some faunistic horizons in the Middle Cambrian is indicated by trilobites but their thicknesses and limits were determined on the basis of lithologic criteria.

Stratigraphic interpretation of geophysic curves was done for these boreholes in which the Cambrian was fully cored (e.g. Żarnowiec IG 1-70%, Darżlubie IG 1-100%) and contained rich paleontologic material. In this way outstanding geophysic complexes could be correlated with lithologic ones connected with individual faunistic horizons.

Analysis of boreholes, clastic samples and geophysic curves proved that lithofacial variability in the Cambrian, generally of meridional direction, is consistent and dependent on the occupied place within a basin. Observed variability is typical for a sublittoral zone.