Palynology and palynofacies of Miocene coal-bearing (clastic) sediments of the Hausruck area (Austria)

Abstract

Two drill cores with coal-bearing sediments from the localities Lukasberg and Kalletsberg of the Hausruck area were investigated. Particular attention was paid to the clastic intercalations between and within the coal seams to complete the previous database of the coal-petrological and geochemical analyses of the coals made by Gruber and Sachsenhofer (1999) and Bechtel et al. (2003). In this work, pollen and spores, the acid-resistant organic components (palynofacies), and the total organic carbon content (TOC) of the clastic sediments have been examined in order to interpret the palaecological conditions of the different plant habitats. The TOC and structured components of the Lukasberg site displayed a recurring cyclicity between coal seams and are interpreted as frequent changes of the depositional environment: coal swamps and peat bogs, lacustrine conditions (lake or pond) and marshes or clastic swamps. It is therefore assumed that the Hausruck area, particularly at the Lukasberg locality, was subjected to periodical submersions, in which the ground-water level repeatedly flooded the coal swamps. This cyclicity is unfortunately not clearly documented at the Kalletsberg locality. In addition, the occurrence of up to 32% fusinite in the palynofacies from some samples of both sites and charred logs at the Lukasberg open cast mine indicate the presence of palaeo-wildfires within forests of the Hausruck area. The age of the sedimentary succession is late Sarmatian to the early/middle Pannonian (upper Middle Miocene to lower Upper Miocene). The frequent occurrences of pollen of Mastixia, a warmth loving plant, which during this time interval occurred sporadically and in low numbers, suggest that the Hausruck was a relict area with a particular humid and warm climate.