[BCG06-P12] Palynomorph assemblage in sedimentary rocks of the Mesoproterozoic Qaanaaq Formation from northwestern Greenland.
Keywords:Acritarchs, Mesoproterozoic, Palynomorph, Greenland
The samples used were greyish shales of the Qaanaaq Formation belonging to the Dundas Group, collected from the Thule Basin in northwestern Greenland during July-August 2018 and 2019. These expeditions were supported by MEXT (Japanese Ministry of Education, Culture, Sports, Science and Technology) through Arctic Challenge for Sustainability (ArCS) the Arctic region research project. The kerogens were separated by HCl and HF treatments of the sediments, and observed under a fluorescent light microscope.
We could identify 8 kinds of acritarchs such as Leiosphaeridia sp., Synsphaeridium sp., Satka sp., Navifusa majensi, Simia sp., Lophosphaeridium sp., Schizofusa sp., Tasmanites sp. and filamental microfossils. Leiosphaeridia sp. is the most abundant in all horizons of the Qaanaaq Formation in our study, and their diameters tend to increase upwards of the horizons. The Leiosphaeridia sp. fossils include several species and cannot distinguish with the broken and isolated colonial cells because their cells have simple structure (Samuelsson et al., 1999). From this fact, the increasing of the fossil sizes observed in our study was presumably affected by the mixture and shift of the several species morphologically identified as Leiosphaeridia. Synsphaeridium sp. and Satka sp. are distinctive features in the aggregates of cellular structures (colonial species), and the relative abundances of these two acritarchs in all assemblage tend to increase in total acritarchs assemblages in the upper horizons. These results indicate that such acritarchs were important for increasing cell size of the eukaryotic algae, and moreover, these evolved to multicellular organisms.