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Mae Sot Formation

Mae Sot Fm

Period:

Neogene

Age Interval:

late-Early to early-Middle Miocene (5)

Province:
Sibumasu: Western Region

Type Locality and Naming

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. Youngest formation in the Mae Sot Gr.

Synonym: หมวดหินแม่สอด , also spelled Mae Sod Fm

Lithology and Thickness

Stratigraphy at Mae Tun coalfield at Mae Ramat in the northern part of the basin. "Ratanasthien (1990) describes … 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 late Early - early Middle Miocene age for those beds." (Morley & Racey, 2011). However, Lexicon of Stratigraphic Names of Thailand describes its version as: Red sandstone and siltstone in the lower part; mudstone, coal seams, and oil shale in the middle part; and grey mudstone and sandstone in the upper part. – which seems to apply to entire Mae Sot Gr.

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

Overlies the Mae Pa Fm

Upper contact

Not given

Regional extent

Mat Sot Basin on the Myanmar border and is bounded on its north by the Mae Ping Fault. Use of formation name also extended eastward into Chiang Mae province.

GeoJSON

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Fossils

Age

late Early - early Middle Miocene

Age Span:

Beginning stage:

Burdigalian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

20.45

Ending stage:

Serravallian

Fraction up in the ending stage:

0.0

Ending date (Ma):

13.82

Depositional setting

Fluvial-lacustrine

Depositional pattern:

Additional Information

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)

Compiler:

Modified from Christopher K. Morley & Andrew Racey, 2011, Chapter 10 Tertiary stratigraphy in: Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London. And modified from- Lexicon of Stratigraphic Names of Thailand of 2013