Paleoenvironmental interpretation of the Amynteon–Ptolemaida lignite deposit in northern Greece based on its petrographic composition

Abstract

The objective of this study was to reconstruct the paleoenviromnent during formation of the deposit at Amynteon–Ptolemaida based mainly on its petrographic but also supported by its paleobotanic character and fossils found in the lignite beds themselves. The deposit of Amynteon occurs in the northern part of the elongated basin of Ptolemaida–Amynteon. The type of lignite formation is, in general terms, similar to the deposit of Ptolemaida, and the lignite is present in the Pleistocene strata of the basin. The alternating nature of lignite and interburden is an important characteristic of the deposit. In this study, we selected 20 samples of lignite from a representative drillhole, namely B-258 in order to discern its petrography. Optical microscopy showed that the huminite group macerals are dominant, ranging from 42.5% to 95.3%. Humotelinite is present in low to high quantities (12.0–79.5%), followed closely by humodetrinite. Humocollinite is present in very small amounts. In addition, macerals of the liptinite and inertinite groups are found in small concentrations, with a few exceptions. A number of indices, such as gelification index (GI), vegetation index (VI), groundwater index (GWI), tissue preservation index (TPI), and their ratios (e.g., VI/GWI, TPI/GI), were used to reconstruct the conditions prevailing during peat formation. The results indicate that the paleoenvironment was mainly limnic at the initial stages and transitioned to limnotelmatic with occasional rheotrophic conditions. The organic matter responsible for lignite formation developed mainly in a forested swamp environment with occasional transitions either towards a wet limnic (open water) or a drier telmatic environment.