Palynology of Coal-Bearing Units in the Mae Ramat Basin, Tak Province, Northern Thailand: Implications for the Paleoclimate and the Paleoenvironment

Abstract

Ten representative samples were collected from a drilled core in the Mae Ramat coal-bearing Tertiary basin, for palynological study. The specimens analyzed were selected from coals and dark gray lignitic mudstone beds covering a successive interval of the rock sequence from 120 to 160 meters in depth. Totally 17 genera and 6 species of palynomorphs were identified, described, and counted. One biozone and two subzones were recognized: Laevigatisporites Biozone, which is dominated by spores of Lavigatisporites sp., Magnastriatites grandiosus Subzone, which is the abundance zone of Magnastriatites grandiosus, and Trilites verrucatus Graminidites Subzone, which is the assemblage zone of Polypodiisporites usmensis, Polypodiaceoisporites sp., Trilites verrucatus, Pinuspollenites sp., Graminidites sp., Momipites coryloides and Liquidambarpollenites sp. Based on both palynological and lithological data, fresh-water lacustrine environment is indicated by the abundance of Magnastriatites grandiosus. Also, a humid temperate climate in the lower part of the sequence changing to warmer and more humid temperate climate trending to be subtropical climate was interpreted by the presence of temperate flora and the subsequent increase of subtropical flora. Although the exact age of the sequence cannot be definitely assigned, it was deduced from the paleoclimate and the time ranges of fossils as Early Miocene.