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

Abstract With an area of over half a million square kilometres, or roughly that of France, Thailand is second only to Myanmar in size among the countries which make up mainland SE Asia. It lies entirely within the tropics and the distance between its northern point (latitude c. 20°30′N) and its southern point (latitude c. 5°30′N) is a distance of over 1600 km. About four-fifths of the country forms a compact northern land area bordered by Myanmar, Laos and Cambodia. The southern part of the country partly surrounds the Gulf of Thailand (an inlet of the South China Sea), the western arm of this embrace forming the Thai Peninsula which extends south to the border with Malaysia. The western side of the peninsula is partly bordered by southernmost Myanmar and partly by the Andaman Sea.

Abstract The Triassic sedimentary rocks of Thailand represent the beginning of a Mesozoic regression which saw widespread marine conditions gradually giving way to continental conditions which spread from the east to the west. The most marine of the Mesozoic systems is therefore the Triassic, which contains in places rich faunas that prove an almost complete succession to be present. This was a period of considerable tectonic and igneous activity and Palaeotethys, which separated the terranes of Sibumasu and Indochina, probably closed at this time. The Triassic granite chains which run the length of the country are described by Cobbing (2011) while the belts of volcanic rocks, many of them Triassic, which run through Northern, NE and SE Thailand, are described by Barr & Charusiri (2011) .