Cenozoic

Cretaceous

Jurassic

Triassic

Permian

Carboniferous

Devonian

Early Paleozoic

Select Region(s) to search
Hold Ctrl (Windows/Linux) or Command (Mac) to select multiple

Bo Phloi Formation

Bo Phloi Fm

Period:

Ordovician, Silurian, Devonian

Age Interval:

Hirnantian (latest Ordovician) to mid-Devonian (5)

Province:
Sibumasu: Western Region

Type Locality and Naming

"On the edge of the Central Plain, Khao Ka and Khao Yai, two isolated hills 10 km southeast of Bo Phloi district, about 25 km north of Kanchanaburi city expose the type section of what Bunopas (1981) calls his Bo Phloi Formation. .. Toward the top of the type section are tentaculite-bearing shales which suggest a correlation with the lower part of the Thong Pha Phum Gr." (Ridd, 2011)

Synonym: หมวดหินบ่อพลอย;

Lithology and Thickness

This succession of quartzite, shale, chert, tuff, phyllite and thin limestones has a total thickness of about 350 m. The Bo Phloi Formation correlates to Units F and G of Hagen and Kemper (1976); therefore an upward succession of:

F (lower unit) = Clayey, sandy, marly sequence c. 20 m thick, overlain by a sandy black shale 120–125 m thick with well-developed cleavage.

G (upper unit) = About 20 m of dark-grey calcareous siltstone passing up into medium-grey sandy flaser limestone with bituminous clay laminae, and then light-colored, commonly variegated flaser limestone. (Ridd, 2011)

Lithology Pattern:

Shallow-marine marl

Relationships and Distribution

Lower contact

Overlies the Chao Nin Gr (Tha Manao Limestone Fm)

Upper contact

Unconformity. Regionally, the next younger units are earliest-Carboniferous limestone (unnamed); then the Permian begins with the Pharaka Fm (among other regional names for coeval units in the same Western Region)

Regional extent

Kanchanaburi region; uncertain extent.

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[99.34,16.43],[99.45,16.09],[99.5,15.7],[99.55,15.49],[99.61,15.08],[99.59,14.73],[99.53,14.23],[99.48,13.89],[99.47,13.82],[98.92,14.43],[98.44,14.91],[98.21,15.15],[98.25,15.29],[98.32,15.32],[98.38,15.33],[98.48,15.37],[98.55,15.41],[98.54,15.58],[98.54,15.76],[98.56,15.91],[98.6,16.04],[98.69,16.07],[98.78,16.12],[98.92,16.32],[98.75,16.29],[98.68,16.28],[98.63,16.46],[98.48,16.68],[98.45,16.93],[98.38,17.01],[98.3,17.06],[98.15,17.24],[98.03,17.39],[97.97,17.51],[97.84,17.63],[97.78,17.71],[97.73,17.8],[97.75,17.92],[97.9,17.77],[98.45,17.29],[98.81,16.96],[99.2,16.65],[99.34,16.43]]]]}}

Fossils

F (lower unit) =. About 30 m above the base of the black shale is a layer c. 5 m thick containing Lower and Middle Llandovery (Silurian) graptolites.

G (upper unit) = Upper Silurian conodonts at the base.

Age

Hirnantian (latest Ordovician) to mid-Devonian. There is no lithological break from the Silurian to the Devonian in the Thong Pha Phum area. [Ridd, 2011]

Age Span:

Beginning stage:

Hirnantian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

445.16

Ending stage:

Emsian

Fraction up in the ending stage:

0.0

Ending date (Ma):

407.57

Depositional setting

It is thought to be derived from a volcanic arc, probably a short distance to the east (according to Lexicon of Stratigraphic Names of Thailand, 2013).

Depositional pattern:

Additional Information

"The Lower Paleozoic limestones of Western Thailand are a common host-rock for lead-zinc mineralization. A study of these deposits in Kanchanaburi Province by Diehl & Kern (1981) showed that mineralization took place preferentially in algal- crinoidal reef-like build-ups in the limestone." (Ridd, 2011)

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.