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Khao Phra Formation

Khao Phra Fm

Period:

Permian

Age Interval:

mid-Early Permian (4)

Province:
Sibumasu: Upper Peninsula

Type Locality and Naming

Type area at Khao Phra, 8 km west of Don Sai village, near Khao Chao just north of Kaeng Krachan Dam, Phetchaburi Province, Upper Peninsula - Phuket Terrane of Thailand. Proposed by Piyasin (1975), revised by Chaodumrong and others (2004, 2007) and Chaodumrong (2010), Department of Mineral Resources (2007). Chaodumrong et al. (2004, 2007) restrict this to only the upper part of Khao Phra Formation of Piyasin (1975) (Ueno & Charoentitirat, 2011). Parent unit: upper-middle formation in the Kaeng Krachan Gr

Synonym: หมวดหินเขาพระ

Lithology and Thickness

It consists of claystone, laminated claystone, siltstone and sandstone.

Thickness: At the typical section at Khao Chao just north of Kaeng Krachan Dam, the formation is c. 270 m thick. However, is c. 760 m thick at Khao Phrik in Ratchaburi Province, however, where it is conformably overlain by the Ratburi Limestone Fm.

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

Ko He Fm (conformable)

Upper contact

Khao Chao Fm (conformable)

Regional extent

Mainly in upper Peninsular Thailand.

GeoJSON

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Fossils

Fossils occur abundantly throughout, including the bryozoans Fenestella sp. and Polypora sp. and the brachiopods Stereochia koyaoensis, Spiriferellina modesta, Spinomartinia prolifica, Chonetinella andamanensis, Demonedys tricorporum and others. (Ueno & Charoentitirat, 2011) The brachiopod assemblage is similar to that of the Ko Yao Noi Fm in Ko Yao Noi of Phangnga Province (Waterhouse et al. 1981), which was once assigned to the late Sakmarian by Shi & Archbold (1998) and then to the late Artinskian by Archbold (1999).

Age

Late Sakmarian or Late Artinskian

Age Span:

Beginning stage:

Artinskian

Fraction up in beginning stage:

0.6

Beginning date (Ma):

285.22

Ending stage:

Artinskian

Fraction up in the ending stage:

0.5

Ending date (Ma):

286.03

Depositional setting

Shallow-marine

Depositional pattern:

Additional Information

Compiler:

Wen Du - modified from Katsumi Ueno & Thasinee Charoentitirat, 2011, Chapter5 Carboniferous and Permian 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.