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Maha Sarakham Formation

Maha Sarakham Fm

Period:

Cretaceous

Age Interval:

93 Ma or Cenomanian (13, 14, 15)

Province:
Indochina Block: Khorat Plateau, Indochina Block: Loei Fold Belt

Type Locality and Naming

Drilled well no F-34 at Ban Chiang Hian, 6 miles east of the town of Maha Sarakham, Mueang Maha Sarakham district, Maha Sarakham province. Parent unit: Khorat Gr.

Synonym: หมวดหินมหาสารคาม

[Figure: NE and SE Thailand, showing distribution of Cretaceous outcrops. (Meesook, 2011. Page 170). At least some of the Pre-Cretaceous sedimentary rocks on the map may be Jurassic and the position of the Jurassic-Cretaceous boundary is discussed in Meesook (2011).]

Lithology and Thickness

The uppermost part of the formation consists of red to reddish-brown, ﬁne-grained, laminated sandstone with small-scale cross-bedding, interbedded with siltstone and mudstone with disseminated salt, anhydrite and gypsum. The salt has been mined in places, resulting in collapse sinkholes (Meesook, 2011). Thickness: 1,000 m

[Figure: Low-lying area in Udon Thani Province where salt of the Maha Sarakham Formation has been mined (Meesook, 2011).]

Lithology Pattern:

Gypsiferous claystone

Relationships and Distribution

Lower contact

Khok Kruat Fm (unconformable); above Mid-Cretaceous Unconformity (which spans ca. late-Aptian and early Albian).

Upper contact

Phu Thok Fm (conformable)

Regional extent

The Khorat Plateau. The formation is exposed in the low-lying areas outside the Phu Phan Range, particularly NE and SW of the range of Khorat Plateau.

GeoJSON

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Fossils

Age

Based on palynomorphs, an Albian–Cenomanian age is proposed for the formation by Sattayarak et al. (1991); Upper Cretaceous Gardner and others (1967); but middle Cretaceous (Albian-Cenomanian) by Racey and others (1994); 93 Ma (K/Ar, K/Ca and 87 Sr/86 Sr –composition) or Cenomanian by Hansen and others (2002). Begins in mid-Albian following Booth, J. & Sattayarak N., 2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand.

Age Span:

Beginning stage:

Albian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

106.82

Ending stage:

Cenomanian

Fraction up in the ending stage:

0.5

Ending date (Ma):

97.20

Depositional setting

The Maha Sarakham Formation is interpreted as having been deposited in arid evaporitic conditions, hence fossils are rare (Meesook, 2011).

Depositional pattern:

Additional Information

This formation has been excluded from the Khorat Gr by recent oil companies’ papers, but a local unconformable contact as mentioned by Racey and others (1994) is not sufficient to remove this formation from the group (see: International Stratigraphic Guide (Hedberg, 1976; Murphy and Salvador, 1999)). This formation was also miswritten “Mahasarakham Formation”. Ratanajaruraks (1990) named this formation the Chaturat formation. However, the Maha Sarakham has priority.

Compiler:

Wen Du - modified from- Meesook A., 2011. Chapter 8 Cretaceous in Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London.

Booth, J. & Sattayarak N., 2011, Chapter 9 Subsurface Carboniferous-Cretaceous geology of NE Thailand in Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London; Lexicon of Stratigraphic Names of Thailand of 2013.