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E-Lert Formation

E-Lert Fm

Period:

Permian

Age Interval:

latest Carboniferous to mid-Middle Permian (14)

Province:
Indochina Block: Loei Fold Belt

Type Locality and Naming

Pha Nok Khao Platform (Loei region): The type section is designated at Huai E-Lert Reservoir (also called Huai Sampod) east of Wang Saphung in Loei Province (DMR 1992). Originally introduced by Charoenpravat & Wongwanich (1976) and Charoenpravat et al. (1984). A middle 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

"Shale, siliceous shale (sometimes identified as chert in the field) and sandstone with locally developed impure bedded limestone and various-sized limestone blocks. Much of the succession is considered to be turbidites. … The whole of the formation at its type section has not been measured, although Ishibashi et al. (1996) illustrated a stratigraphic log of a 45 m thick part of the section." [Ueno and Charoentitirat (2011)]

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Previously widely accepted that the E-Lert Formation simply overlies the Nam Mahoran Fm; but now it is known that it is partly a coeval facies.

Upper contact

Essentially underlies the Pha Dua Fm.

Regional extent

The formation outcrops in a north – south belt at least 80 km long on the west side of the Chiang Khan–Loei–Wang Saphung–Khon San Highway (Route 201).

[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

Fusulines Laosella methikuli, L. parva and L. loeyensis and brachiopods Purdonella magna and Brachythyrina strangwaysi were reported from the type section, which indicated an early Middle Permian (Kubergandian) age of the formation. Ammonoids Agathiceras aff. suessi, Properrinites boesei, Popanoceras sp., Propinacoceras sp. and Artinskia loeiensis were interpreted as early Early Permian (Sakmarian). Latest Carboniferous (Gzhelian) to earliest Permian (Asselian) radiolarians representing the Pseudoalbaillella bulbosa Assemblage .. and Early Permian (probably Sakmarian–Artinskian) radiolarians and ammonoids from this formation." [Condensed from Ueno and Charoentitirat (2011)]

Age

"It was previously widely accepted that the E-Lert Formation simply overlies the Nam Mahoran Fm, and therefore that the E-Lert Formation is Middle Permian (e.g. Bunopas 1988). The paleontological evidence, however, reveals that the E-Lert Formation ranges at least from the very latest Carboniferous to the middle part of the Middle Permian. Thus, the formation exhibits another heteropic facies of the Nam Mahoran Fm."

Age Span:

Beginning stage:

Asselian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

298.88

Ending stage:

Wordian

Fraction up in the ending stage:

0.0

Ending date (Ma):

268.80

Depositional setting

"It represents deeper-marine strata formed in a slope-to-basin environment on the Pha Nok Khao Platform, which is probably the northern continuation of the Nam Duk Basin."

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.;.