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Khao Khi Ma Formation

Khao Khi Ma Fm

Period:

Carboniferous

Age Interval:

early Mississippian

Province:
Sukhothai Fold Belt

Type Locality and Naming

Type section: North-south trending ridge of Khao Khi Ma (from which the name of the for- mation was taken), south of Ban Dan Lan Hoi district, Sukhothai province. Parent unit: lower formation in Dan Lan Hoi Gr

Synonym: หมวดหินไพโรคลาสติกเขาขี้ม้า , Khao Khi Ma Pyroclastics

Lithology and Thickness

Tuffaceous, coarse-grained sandstone, shale and infrequent layers of graded-bedded, fine-grained agglomerate; agglomerate, mostly andesitic, with medium-sized clasts, with frequent intercalations of green tuff; poorly bedded, green agglomerate, with large clasts. The succession has at its base poorly sorted and weakly bedded greenish agglomerate about 150 m thick. This is overlain by andesitic agglomerate about 70 m thick with frequent intercalations of sandy and silty greenish tuff and succeeded by coarse tuffaceous sandstone and shale about 30 m thick, with frequent layers of graded agglomerate. Rocks of this formation exhibit well-developed slaty cleavage. Thickness: 250 m

Lithology Pattern:

Volcanic ash

Relationships and Distribution

Lower contact

‘

The Khao Khi Ma Fm overlies the Silurian – Devonian Khao Khieo Tuf Fm of the ‘Thung Saliam Gr' (Now Sukhothai Gr) with angular unconformity at Khao Khi Ma (Bunopas 1981). Regionally, the next older unit might be the Thung Saliam Limestone Fm of Devonian.

Upper contact

Conformably overlain by the Lan Hoi Fm.

Regional extent

Correlation: Lower part of the Mae Tha Group, the Mae Sai Formation; Khao Ki Ma Formation

GeoJSON

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Fossils

None

Age

For graphics purposes; put arbitrarily as Tournaisian, assuming Dan Han Hoi Gr spans entire Carboniferous and this formation is approximately the lower 15% of total group thickness.

Age Span:

Beginning stage:

Tournaisian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

358.94

Ending stage:

Visean

Fraction up in the ending stage:

0.0

Ending date (Ma):

346.73

Depositional setting

"The Khao Khi Ma Formation is considered to be a marine mass- flow deposit. Judging from the large volcaniclasts (up to 50 cm maximum size) contained in this formation, it is assumed to have been deposited close to its volcanic source. Bunopas (1981) suggested that these pyroclastic rocks were laid down in a submarine-fan environment, but further sedimentological work is necessary to confirm this." (Ueno & Charoentitirat, 2011)

Depositional pattern:

Additional Information

Remarks: Ueno and Charoentitirat (2011) introduced the Khao Ki Ma Formation to replace the Khao Khi Ma Pyroclastic, with respect to nomenclatural guidelines

Compiler:

Wen Du -modified from Lexicon of Stratigraphic Names of Thailand (2013); and 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.