DIAGENEZA KREDY JEZIORNEJ I GYTII W OSADACH HOLOCEŃSKICH PÓŁNOCNO-ZACHODNIEJ POLSKI

Abstract

DIAGENESIS OF LACUSTRINE CHALK AND GYTTJA IN HOLOCENE DEPOSITS FROM NORTHWESTERN POLANDAbstract. The aim of this paper is to present the diagenetic processes occurring within lacustrine chalk and ooze in Holocene deposits from northwestern Poland. The analysed samples came from the Tarda (Iława Lake District) and Suliszewo (Choszczno Lake District) sites. For the purpose of mineral composition determination, both modern and classic (thermal analysis) research methods were applied. Composition analysis on a microprobe (Scanning Electron Microscopy) and X-ray structural analysis (Powder X-ray Diffraction) were used. Effects of early diagenesis processes (eodiagenesis) are observed in these sediments. The most important diagenetic processes include dissolution of carbonate minerals, pyrite and quartz. An important role was also played by pyritization and formation of early carbonate cements. Compaction occurred only on a small scale. Moreover, the sequence of the diagenetic processes was reconstructed. The earliest diagenetic process that occurred within the lacustrine chalk and ooze was the formation of micritic cement and pyritization. Successively, the whole sediment was undergoing dissolution processes, followed by compaction. After dehydration and drying of the samples, gypsum and halite crystallized from the pore waters.