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Klo Tho Formation

Klo Tho Fm

Period:

Jurassic

Age Interval:

early Toarcian (5)

Province:
Sibumasu: Western Region

Type Locality and Naming

Umphang basin, Tak Province. Lowermost formation in the Umphang Gr.

Synonym:

Lithology and Thickness

The characteristic lithology of this formation is dark-grey thin-bedded mudstone with interbedded sandstones and some concretionary horizons. Fining-upwards sequences are present. 60 m thick in its type section

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

The bottom of the group has not been seen, although it is presumed to rest unconformably on the older rocks in the area. Regionally, in this Mae Sariang - Kanchanaburi Basin, the next older unit (Norian-Early Jurassic) is the Kamawkala Limestone Fm.

Upper contact

Overlain by the Ta Sue Kho Fm

Regional extent

Umphang basin, Tak Province. "It is also exposed along the road from Ban Klo Tho to Umphang town, and also along the road from Ban De Lo Khi to Thi Lo Sue Falls, and in the vicinity of Ban Pa La Tha and Ban Se Pa La, 30 km south of Umphang town. Its thickness other than at the type locality is unknown, but lithologies are similar and there is no reason to expect significant thickness variation." (Meesook & Saengsrichan, 2011).

GeoJSON

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Fossils

The formation is richly fossiliferous with bivalves, ammonites and some plant remains in mudstones, including a 1 m thick ammonite-bearing bed. Based on the ammonites Dactylioceras and Eleganticeras and the bivalve Parvamussium donaiense Mansuy, the formation is considered to be of Early Toarcian age.

Age

Fig. 7.3 in Meesook & Saerngsrichan (2011) indicates a span of early Toarcian.

Age Span:

Beginning stage:

Toarcian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

183.70

Ending stage:

Toarcian

Fraction up in the ending stage:

0.5

Ending date (Ma):

178.92

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Wen Du - modified from Ridd. M.F., 2011, Chapter 3 Lower Palaeozoic 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.