Typy genetyczne skał oraz mikrofacje paleogeografia wapienia cechsztyńskiego (Ca 1) w strefie Koszalina – Chojnic

Abstract

GENETIC TYPES OF ROCKS, MICROFACIES AND PALAEOGEOGRAPHY OF THE ZECHSTEINKALK (Ca 1) IN THE ZONE KOSZALIN-CHOJNICE (NORTH-WEST POLAND)

Summary

Determination of microfacies variability of the Zechstein carbonate series is part of the research on the Permian formation carried on in the Geological Institute. Rocks that in the Koszalin-Chojnice zone correspond startigraphically to the Zechsteikalk, reveal a considerable microfacies variability. There are distinguished here 7 main genetical types of rocks (Figs. 1-7), each formed under different sedimentary conditions. Both organogenic and terrigenous constituents and rock structures have been here a basis to distinguish these types of carbonate rocks. The primary thickness (Fig. 12) and the microfacies differentiation of the Zechsteinkalk (Figs. 9, 10, 11 and 13) depended upon the morphology of the pre-Zechstein surface affected by tectonic and erosional processes. The Zechstein transgression covered the lowest areas of the Koszalin-Chojnice zone, where formations of deeper facies were sedimented, i.e. copper-bearing shales and stratified carbonate deposits of the first phase of sedimentation. Several uplifts, being the culminations of the pre-Zechstein elevations were exposed above the water level. These uplifts yielded original materials for clastic rocks that constituted the bottom and top series, as well as some intercalations within the carbonate rocks. A partial inundation of the uplifts by the waters of the basin, which at the same time became shallower, began the second, shallow-water phase of the Zechsteinkalk sedimentation. The formations of breccia type (Fig. 8), formed diachronically within the areas invaded by the sea during the second phase of sedimentation, cannot correspond stratigraphically to basal conglomerate. The occurrence of the shallow-water complexes is restricted to some narrow, near-shore zones, and local shoals. Such a distribution of the shallow facies of the Zechsteinkalk was due to the differentiated bathymetric conditions in the Koszalin-Chojnice zone.