Abstract Coal (which for the purpose of this chapter includes lignite) has been produced in Thailand for over a century and until the late 1970s remained at a modest level, not exceeding one million tonnes per year. However, production grew rapidly from about 1979, reaching a plateau rate of about 20 million tonnes per year, but peaking at over 22 million tonnes per year in 1997. By the end of 2000 cumulative coal production had reached over 245 million tonnes and the Thai Government estimated remaining reserves at 1372 million tonnes ( Mineral Fuels Division 2001 ). The Electricity Generating Authority of Thailand (EGAT) reported in its 2009 annual report that power generated from domestically-mined coal accounted for 19.77% of the country’s total electrical power consumption in that year. Coals occur in the Carboniferous, Jurassic-Cretaceous and Tertiary of Thailand (Fig. 14.1 ). The Jurassic-Cretaceous coals occur widely in the Phra Wihan Formation of the Khorat Group in some north-eastern provinces, such as Sakhon Nakhon, Kalasin and Nakhon Ratchasima, mainly as coalified stumps of tree trunks. However, these coals are economically unimportant and so only the Carboniferous and Tertiary coals are described in this chapter. Carboniferous coals were formerly mined in Na Duang District (Loei Province) and were also mined in Na Klang District (Nong Bua Lamphoo Province, formerly part of Udorn Thani Province), both in NE Thailand. Tertiary coals have always been the most important economically. Seams range from less than 1 m thick up to 25 m thick or

Abstract Due to the economic importance of its hydrocarbon and coal resources, more is known of the Tertiary than of any other part of the stratigraphic succession in Thailand. Tertiary sedimentary rocks occur both on- and offshore and they are generally associated with rift basins formed in extensional, transtensional or strike –slip settings (Fig. 10.1 ). In the Gulf of Thailand and Central Thailand the rift basins have been covered by extensive post-rift sag basins, while the Mergui Basin is in a post-rift passive margin setting. Thermal subsidence has yet to cover the rift basins of Northern Thailand. The basins trend north-south through the centre of the country onshore, and underlie much of the Gulf of Thailand and Andaman Sea. The Tertiary was a period of considerable tectonic activity and hence the timing of a basin’s subsidence, its location and the nature of its basin-fill and lateral facies variations are all tied to its structural development. The Tertiary structure is discussed by Morley et al. (2011) and further data on the Tertiary stratigraphy and structure are to be found in Ratanasthien (2011) and Racey (2011) ; the wider plate-tectonic context of the Tertiary structure is discussed by Searle & Morley (2011) . Information on the offshore Tertiary basins has been obtained entirely through hydrocarbon exploration and production activities since the late 1960s, and comprises seismic (both 2D and 3D) and borehole data. A number of the onshore basins in Northern and Central Thailand have

Abstract The regression which commenced in the Triassic continued through the Jurassic, with marine sediments confined to the western side of Northern, Western and Peninsular Thailand, while continental red-beds were deposited in Northern and Northeast Thailand. The marine facies are predominantly sandstone, conglomerate, mud-stone and limestone, and contain a fauna which includes bivalves, gastropods, corals, ammonites, brachiopods and foraminifera which indicate that the succession is of Toarcian to Aalenian or possibly Early Bajocian age. With caveats discussed below, non-marine Jurassic rocks are widespread in NE Thailand where they are more than 1000 m thick and form part of the Khorat Group of the Khorat Plateau. They also occur, but are less widespread, in Northern and Peninsu lar Thailand. Age determinations are based mainly on vertebrates, bivalves and palynomorphs, although the position of the Jurassic-Cretaceous boundary remains under discussion. After the widespread volcanic activity of the Triassic, the Jurassic was a period of apparent volcanic quiescence and there are no confirmed occurrences of volcanic rocks of this age.