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Tai Formation

Tai Fm

Period:

Neogene

Age Interval:

Lower Miocene (1)

Province:
Andaman Sea: Mergui Basin

Type Locality and Naming

In the Tai Well, the central High, Andaman Sea. Tai limestone was proposed by Nakanart and Mantajit (1983), and was replaced by Tai Formation by Polachan (1988). Parent unit: Mergui Gr.

Synonym: หมวดหินใต้

[Figure 1: Map of the Mergui Basin showing the main structural features including basin depocentres, based on an extensive grid of 2D seismic reﬂection data. (From C K Morley & A Racey, 2011)]

Lithology and Thickness

A basal unit of interbedded anhydrite, dolomite, shale and sandstone; a middle unit of massive coral-algal reef limestone; and upper unit of calcarenites interbedded with silty shales and sandstones. Subdivisions: Subdivided into 3 informal units: basal unit, middle unit, and upper unit. Thickness: 585 m at the type locality well, the Tai well, to 768 m in the D-1 well.

[Figure 2: Stratigraphy and cross-section through the Mergui Basin, Andaman Sea, based on data in Polachan & Racey (1994) and Andreason et al. (1997). (a) Oligocene–Recent stratigraphy of the Mergui Basin; (b) stratigraphy of the syn-rift section (Oligocene–early Miocene) schematically illustrating the east–west variation in stratigraphy across the basin and the effect of rift-basin highs (e.g. Central High horst block) on large-scale distribution of sedimentary facies, modiﬁed from Andreason et al. (1997); (c) east–west cross-section through the Mergui Basin illustrating the typical half-graben geometries of the basin (modiﬁed from Polachan & Racey 1994). (From C K Morley & A Racey, 2011)]

Lithology Pattern:

Reef limestone

Relationships and Distribution

Lower contact

Yala Fm (unconformable)

Upper contact

Trang Fm (unconformable); coeval or interfingering with Kantang Fm (unconformable)

Regional extent

Andaman Sea: south Mergui Basin – platform carbonates developed on local highs. Correlation: Peutu Fm of the North Sumatra basin; Tai Limestone Fm of Nakanart and Mantajit (1983).

GeoJSON

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Fossils

Age

Lower Miocene; Coeval with Kantang Fm; but for graphic purposes shown here as only upper Aquitanian

Age Span:

Beginning stage:

Aquitanian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

21.75

Ending stage:

Aquitanian

Fraction up in the ending stage:

1.0

Ending date (Ma):

20.45

Depositional setting

Basal sabkaha/lagoon; Middle massive coral-algal limestone; fore-reef environment in the upper unit.

Depositional pattern:

Additional Information

Compiler:

Wen Du - modified from- C. K. Morley & A. Racey, 2011, Chapter 10 Tertiary 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.