Palynology and stratigraphy of flood-plain sediments along the Mun river, Amphoe Non Sung, Changwat Nakhon Rachasima

Abstract

The fluvial deposits along the Mun river in Tambol Tha Chang, Amphoe Non Sung, Changwat Nakhon Ratchasima yield a rich diversity of fossils. The accurate age of the fluvial system can be estimated from many kind of information. The objective of this study is to establish the lithostratigraphy of the fluvial system. The description and identification of spores and pollens is used to estimate the palynostratigraphy, the age of the sediments and the paleoclimate. The lithostratigraphic column of the sand pit was constructed from a soil proflie of 25.4 m in thickness. It can be divided into three units and six subunits. The units are from top to bottom: Unit 1 floodplain deposits, Unit 2 channel deposits can be devided into six subunits and Unit 3 floodbasin deposits. Forty-two samples of soil were collected from the site and were prepared for palynological slides. Fifteen sediment samples were selected for palynomorph analysis. Fifty-nine taxa were recognized, and fifty-four taxa were described. They are five taxa of fungal spores, twenty-nine taxa of pteridophytic spores, four taxa of gymnospermic pollens and twenty-one taxa of angiospermic pollens. The palynological zone can be classified into two zones from the upper to the lower one. Pinus Zone indicate a temperate climate and Ceratopteris Zone define the tropical climate and is indicator of a humid environment. The age of stratigraphy made from lithostratigraphy associate to palynostratigraphy. They could be interpreted to the boundary of Pliocene/Pleistocene period at the sharp contact hiatus of Subunit 2.6 and Unit 3. Pleistocene/Holocene boundary at the sharp contact hiatus of subunit 2.1 and unit 1.