Fungal spores from Neogene sediments of the Hongsa Basin, Lao PDR

Fungal spores in Neogene organic-rich sediments from the Hongsa coalfield in northwestern Lao PDR were studied in detail. Fungal spores and the significance of palynological associations are employed for interpreting depositional environment and paleoclimate. The palynological assemblages, recovered from 34 samples, were rich and diversified, consisting mainly of pollen grains of vascular plants, spores of pteridophytes, and fungal spores. Of all 67 fungal taxa from 22 genera identified in this study, 21 are Amerosporae, 20 Phragmosporae, 18 Didymosporae, and 8 Dictyosporae. Although diversified, they yielded low to very low frequencies compared to total palynomorphs. Most palynological and fungal spores in this investigation indicate a Miocene age of the deposits. The presence of Dyadosporites, Brachysporisporites, Diporicellaesporites, Pluricellaesporites, and Dictyosporites of sub-tropical to warm temperate forests associated with a large number of pteridophytes and evergreen to deciduous vegetation can reinforce the hypothesis of terrestrial origin in a humid and warm climate. Variations in relative abundance and diversity of fungal spores in this study indicate paleoenvironmental fluctuations during deposition, which also conform to the climate interpreted from each palynological zone.