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Spillway Formation

Spillway Fm

Period:

Permian

Age Interval:

Lower Permian, but originally mapped as Upper Carboniferous to Lower Permian (4)

Province:
Sibumasu: Upper Peninsula

Type Locality and Naming

Named after the spillway of Kaeng Krachan Dam, Phetchaburi province, where the type section is located. Originally deﬁned by Raksaskulwong & Wongwanich (1993). Chaodumrong et al. (2004, 2007) suggest that the Spillway Formation is the lateral equivalent of the upper part of their Laem Mai Phai Fm. Lower-middle formation in the Kaeng Krachan Gr.

Synonym: หมวดหินสปิลเวย์

Lithology and Thickness

Sequence of laminated mudstone and thin to medium bedded sandstone. Ripple marks, load cast, slump structure and hummocky cross stratification are present. 120 m thick.

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Laem Mai Phai Fm (conformable) by Chaodumrong et al. (2004, 2007); or equivalent Khao Wang Kradat Fm (subdivisions of Kaeng Krachan Gr by Rakaskulwong & Wongwanich, 1993).

Upper contact

Conformably overlain by Ko He Fm (glacial-marine).

Regional extent

Upper Peninsula: Phetchaburi province

GeoJSON

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Fossils

Age

Early Permian (Chaodumrong and others, 2004, 2007), but originally mapped as Upper Carboniferous to Lower Permian (Raksaskulwong and Wongwanich, 1993). Constrained as Asselian-Sakmarian by approximate ages of other formations in this succession.

Age Span:

Beginning stage:

Asselian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

297.19

Ending stage:

Sakmarian

Fraction up in the ending stage:

0.0

Ending date (Ma):

295.50

Depositional setting

Interpreted as Stormy shelf deposits by Chaodumrong et al. (2004, 2007). Aternatively, partly Glacial-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.