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Pha Dua Formation

Pha Dua Fm

Period:

Permian

Age Interval:

Late Permian (14)

Province:
Indochina Block: Loei Fold Belt

Type Locality and Naming

Pha Nok Khao Platform (Loei region): The type section is located at Ban Pha Dua c. 8km west of Loei. Introduced by Charoenpravat & Wongwanich (1976) and

Charoenpravat et al. (1984). "Bunopas (1981) had introduced the name Dan Sai Shale for the same strata with the same type section but, since Amphoe Dan Sai is more than 60 km west of the type section, this proposal is hard to accept." [Ueno and Charoentitirat (2011)] Uppermost formation in the Loei Gr.

Synonym:

[Figure: Late Paleozoic major facies subdivisions on the western margin of the Indochina Block by Ueno and Charoentitirat (2011). (Slightly modiﬁed from Wielchowsky & Young 1985).]

Lithology and Thickness

The major lithology of the Pha Dua Formation is sandstone, siltstone and shale. Ca. 80 m at the type section.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Essentially overlies the E-Lert Fm.

Upper contact

Terminated by the Indosinian I Event (latest Permian); Next higher regional unit is the Hua Hin Lat Fm of late Triassic.

Regional extent

Mainly distributed in the western part of the Loei area.

[Figure: Distribution of Carboniferous and Permian in NE Thailand. Data mainly based on 1:1 million scale geological map of Thailand (DMR 1999) with minor modiﬁcations (Ueno and Charoentitirat 2011).]

GeoJSON

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Fossils

Abundant plant fossils consisting of Sphenophyllum oblongifolium, Pecopteris lativenosa, P. hemiterioides, Shirakiopteris loeiensis, Protoblechnum wongii, Taeniopteris nystroemii, T. hallei, Bicoemplectopteridium longifolium, Bicoemplectopteris hallei and Gigantonoclea lagrelii, of which the latter three taxa belong to the so-called Gigantopteris flora. The Loei flora shows a strong Cathaysian affinity, but is not age-diagnostic.

Age

"Bunopas (1988) noted that, because the Pha Dua Formation essentially overlies the E-Lert Formation, it would probably be Middle – Late Permian. However, neither stratigraphic relationship with the underlying E-Lert For- mation nor other more age-diagnostic fossils have been documented." [Ueno and Charoentitirat (2011)]

Age Span:

Beginning stage:

Wordian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

268.80

Ending stage:

Changhsingian

Fraction up in the ending stage:

0.5

Ending date (Ma):

253.05

Depositional setting

The formation probably represents a paralic or coastal environment.

Depositional pattern:

Additional Information

Compiler:

Wen Du -modified from Ueno K. & Charoentitirat T., 2011, Chapter 5 Carboniferous and Permian, and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London.;.