Geomorphology of the Ping and the Wang River Basin, Amphoe Sam Ngao and Ban Tak area Changwat Tak

The study of the geomorphology in the Ping and the Wang Rivers Basin, Amphoe Sam Ngao and Ban Tak area, northwestern Thailand was carried out. The aim is to delineate geomorphological units, to describe kinds and characters of sediments and to investigate the relationship between sediments and their depositional environment. Geomorphologically, the area is situated in the north of the Central Plain, and is sandwiched by western and eastern mountain ranges to the north of Changwat Tak. Landforms in the units of fluvial origins can be divided into 8 geomorphological units including (1) Tertiary landform unit, (2) high terrace, (3) middle terrace, (4) low terrace, (5) floodplain, (6) natural levee, (7) point bar and (8) sand bar. Late Cenozoic fluvialtile sediments have been deposited in the basin. The characteristics of the deposits e.g., the roundness of pebbles and the distribution of sediments but they differ slightly in pebble’s association between the Tertiary and the terrace deposits are generally similar. However, different geomorphological units are clearly different in the degree of erosion, degree of diagenesis, altitude, and lateritic features of the deposits. The features of these sediments enable to conclude that braided riverine environment has played dominant role in the area. Rapid denudation and small tectonic adjustment in association with climatic changes influenced the evolution of landforms in the study area. Young tectonism might cause the deposition up to a hundred meter thick. Climatic changes during Pleistocene led to the variation of base level. The present elevation of terraces found at different levels assumed to have resulted from tectonism and climatic change during Late Tertiary and Pleistocene.