Abstract Devonian rocks are exposed in every region of Thailand, commonly occurring in thick sequences of Lower to Upper Palaeozoic sedimentary and volcanic rocks (Fig. 4.1 ). However, a scarcity of marker fossils and generally discontinuous exposures have meant that Devonian rocks are frequently not distinguishable from older and younger rocks. In such cases, the Department of Mineral Resources (the DMR) have inferred Devonian rocks to be present and have mapped them as Silurian-Devonian, Silurian-Carboniferous, or Devonian-Carboniferous ( DMR 1999 ).

Abstract The Carboniferous and Permian systems are important components of the basement rocks in Thailand and crop out widely. The exceptions are the Khorat Plateau, where they occur in the subsurface but are concealed beneath a thick Mesozoic cover, and in the Chao Phraya Central Plain where they are largely covered by Quaternary sediments but crop out in scattered monadnocks (Fig 5.1 ). Most Carboniferous and Permian rocks are of shallow-marine facies although siliceous sediments of ancient ocean-bottom origin are also known in places. Continental deposits are quite rare. The Carboniferous System is dominated by siliciclastic rocks except in northernmost Thailand around the Chiang Mai-Mae Hong Son area where there are large carbonate bodies. In contrast, carbonates are the dominant lithology in the Permian System, forming characteristic karst topography in the tropical humid climate. It has been quarried in some areas, such as Saraburi and Ratchaburi, for flagstones and cement production. In the 1970s and 1980s the Department of Mineral Resources (DMR), Thailand, published a series of 1:250 000 scale geological maps covering the whole of Thailand. That stratigraphic information laid the groundwork for a number of papers on the Carboniferous and Permian systems of this country ( Bunopas 1981 , 1983 , 1992 , 1994 ; DMR 2001 , 2007 ; Raksaskulwong 2002 ; Assavapatchara et al. 2006 ). In parallel with those stratigraphical works, more palaeontological aspects of Carboniferous and Permian strata were summarized ( Toriyama et al. 1975 ; Ingavat