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Ban Pa Kha Formation

Ban Pa Kha Fm

Period:

Neogene

Age Interval:

Late Oligocene-earliest Miocene (8)

Province:
NW Thailand – Inthanon Zone

Type Locality and Naming

Li Basin (NW Thailand, Inthanon Zone), Lamphun province. Type locality: Pa Kha coal mine, Li district, Lamphun province (Ratanashien, 1990)

Synonym: หมวดหินบ้านป่าคา

[Figure: Map showing the Tertiary basins of Thailand, with Phetchabun basin highlighted. The solid black lines onshore are the principal rivers draining Northern and Central Thailand and the Khorat Plateau (Morley and Racey, 2011, page 224).]

Lithology and Thickness

Coarsening-upward succession of coarse alluvial fan sediments overlain by lacustrine deposits including coals, oil shales and marls (mined at Ban Pu and Ban Pa Kha), interbedded with coarser grained fluvio-alluvial sediments. 250 m. Coal seams are present in both the Ban Pa Kha Fm and the Mae Long Fm and may be up to 20 m thick, frequently with recognizable tree trunks; they are exploited at the Ban Pu and Ban Pa Kha mines. (Morley and Racey, 2011)

Lithology Pattern:

Coarse-grained sandstone

Relationships and Distribution

Lower contact

Not given. Basin is "bounded by hills of pre-Tertiary (commonly Paleozoic – Triassic) sedimentary and igneous rocks" (Morley and Racey, 2011)

Upper contact

Transitional into the lacustrine and coal deposits of the Mae Long Fm.

Regional extent

Present day surface

GeoJSON

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Fossils

"The section immediately above the coal in the Ban Pu Mine has yielded an Early Miocene palynoflora (Fig. 10.4e, Morley 2001) supporting the view that the Ban Pa Kha Formation is of Late Oligocene–Early Miocene age. The pollen from this for- mation is predominantly from warm temperate species and the coals have a low ash content (up to 4%)." (Morley and Racey, 2011).

Age

Late Oligocene-earliest Miocene

Age Span:

Beginning stage:

Chattian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

28.09

Ending stage:

Burdigalian

Fraction up in the ending stage:

0.0

Ending date (Ma):

20.45

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Wen Du - modified from Christopher K. Morley & Andrew Racey, 2011, Chapter 10 Tertiary stratigraphy in: Ridd, M.F., Barber, A.J., and Grow, M.J., editors, The Geology of Thailand, Geol. Soc. of London.; and Lexicon of Stratigraphic Names of Thailand of 2013.