Mae Sot Gr

Mat Sot Basin; Mae Sot district, Tak province. This basin lies on the Myanmar border and is bounded on its north by the Mae Ping Fault. Upward succession of Mae Sot Basin Coals (informal name here), Mae Ramat Fm, Mae Pa Fm and Mae Sot Fm. However, " It is stated in the International Stratigraphic Guide that the geographic name of the original unit (for example “Mae Sot”) should not be employed for any of its subdivisions." (Lexicon of Stratigraphic Names of Thailand of 2013)

Synonym: กลุ่มหินแม่สอด

Stratigraphy at Mae Tun coalfield at Mae Ramat in the northern part of the basin. "Ratanasthien (1990) describes the coals as being of Late Eocene–Early Oligocene age, unconformably overlain by Upper Oligocene–Lower Miocene strata. Flooding has now made those units inaccessible and the oldest beds now visible comprise the Mae Ramat Fm which, according to Ratanasthien (1990), comprises 240 – 600 m of alluvial sandstone, conglomerate and green, grey and red mudstone. Paleogene plant fossils have been collected including Ficus sp., Alangium sp., Magnolia sp., Persia sp., Sassafras cf. subtrilobata and Leguminositis sp. The overlying Mae Pa Fm is over 1300 m thick and is composed of mudstone, marl, limestone and shale. The Mae Sot Fm is the youngest unit and comprises shale, mudstone, oil shale and some sandstone beds. Watanasak (1989) sampled the Mae Sot Fm from another DMR borehole (IMS1) between 866 and 454 m depth, and determined an early Middle – late Early Miocene age for those beds." (Morley & Racey, 2011)

See lithology description above.

Rift basin syn-rift to post-rift; alluvial to lacustrine.

Confusingly, " The Mae Sot series (Brown and others, 1951) has been used for Tertiary basin in northern Thailand. The Mae Sot formation has been used in Fang and Chiang Mai basins. The Mae Sot formation (Piyasin and others, 1977, 1978) has been used in Lampang basin." (Lexicon of Stratigraphic Names of Thailand of 2013)