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Early Paleozoic

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Ko Sichang Limestone Formation

Ko Sichang Limestone Fm

Period:

Ordovician, Silurian, Devonian

Age Interval:

presumed Ordovician-Silurian (6)

Province:
Sibumasu: Central Plain

Type Locality and Naming

The limestone unit is referred to here as the Ko Sichang Limestone from the island Ko Sichang, some 10 km offshore and the northern- most of the islands lying off the east coast of the Gulf. Also spelled Ko Si Chang; plus Khao Chae Chan, Chon Buri province (named by Ridd, 2011).

Synonym: หมวดหินปนู เกาะสีชงั

[Figure: Screenshot from ESRI topographic map of QGIS, with type locality highlighted.]

Lithology and Thickness

Blue-grey, rather uniform-textured marble. Marble was probably caused by contact metamorphism as suggested by the granite intrusion at the south end of the island.

Lithology Pattern:

Limestone

Relationships and Distribution

Lower contact

Debated. Original view was that it was younger than the clastic-dominated Sattahip Fm. For example, " The regional dip of the limestone on the island is thought to be westwards, in which case it probably overlies the granite-intruded quartzite and argillite (both metamorphosed to mica schist) mapped on the islet immediately to the east. " (Kidd, 2011). But detrital-zircon ages of Sattahip might suggest it is coeval? "

Upper contact

Not given

Regional extent

Southeast Thailand. Correlation with the Si Chang Limestone Fm (Buravas, 1957).

GeoJSON

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Fossils

Too altered. However, "Notwithstanding the absence of fossils in the SE Thailand succession described above, there are grounds for considering it to correlate lithostratigraphically with the fossiliferous successions in the southern Peninsula, Western and Northern Thailand, whose ages are well controlled. It appears that the four areas shared broadly similar depositional environments and that similar shelf or slope conditions extended into adjacent NW Malaysia." (Ridd, 2011)

Age

See "Fossils" above. Age based on "assumption that the limestone is the correlative of the Satun Gr limestone" "The limestone NE and east of Sattahip lithologically matches the Satun Gr limestone of the Peninsula more closely than the other limestones of SE Thailand described above." (Ridd, 2011). [This would imply an Ordovician-early Devonian age span.]

Age Span:

Beginning stage:

Floian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

477.72

Ending stage:

Emsian

Fraction up in the ending stage:

0.0

Ending date (Ma):

407.57

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.