Khorat Plateau - Geology

Geology

The plateau uplifted from an extensive plain composed of remnants of the Cimmerian microcontinent, and terranes such as the Shan–Thai Terrane, either late in the Pleistocene or early in the Holocene Epoch, approximately Year 1 of the Holocene calendar. Much of the surface of the plateau was once classified as laterite, and layers that can easily be cut into brick-shaped blocks are still so called, but the classification of soils as various types of oxisols is more useful for agriculture. Oxisols of the type called rhodic ferralsols, or Yasothon soils, formed under humid tropical conditions in the early Tertiary. When portions of the plain uplifted as a plateau, these relict soils, characterized by a bright red color, wound up on uplands in a great semicircle around the southern rim. These soils overlie associated gravel horizons cleared of sand by field termites, in a prolonged and still on-going process of bioturbation. Xanthic ferralsols of the Khorat and Udon Series, characterized by a pale yellow to brown color, developed in midlands in processes still under investigation; as are those forming lowland soils resembling European brown soils.