Thung Song Limestone Fm

Ko Tarutao (Ridd, 2011); and the north face of Khao Tham Talot, situated on the southern side of Thung Song Town, Lat 8° 09´ 28" N Long 99° 40´ 55" E, map DA3, 751017 (Burton, 1974).
Remarks: The name “Thung Song Limestone” of Brown and others (1951), Burton (1974), and of Ridd (2011) and Thung Song Gr that also includes the overlying Pa Kae Fm are used with different meanings that can cause confusion (Lexicon of Stratigraphic Names of Thailand, 2013).
[Figure: Sketch geological map (from various sources) of the southern part of Peninsular Thailand and Langkawi Island of Malaysia. Note that Thai stratigraphic nomenclature has been extended to Langkawi Island (Ridd. 2011)]

Synonym: หมวดหินปูนทุง่สง

Grey to dark grey, argillaceous limestone, bedded and massive. Thickness: 1,668 m (Burton, 1974)

[Figure: Thung Song Limestone at the SE corner of Ko Tarutao, Satun Province. Agematsu et al. (2008b) collected conodonts from this locality, which indicate an Early Ordovician age. (Ridd. 2011)]

Quote from Ridd (2011): The Thung Song Limestone does not have abundant macrofossils, but several collections have been described. From near the base of the formation on Ko Tarutao, Fortey & Cocks (1998) identified a sparse trilobite and brachiopod fauna including the brachiopods Syntrophina and possibly Archaeorthis; although initially considered to be of Tremadocian age they later revised their determination (Cocks et al. 2005) to Arenig. Also from Ko Tarutao, Stait & Burrett (1984) identified Lower Ordovician nautiloids and Jell et al. (1984) identified the bellerephontoid Peelerephon oehlerti. The Ordovician brachiopods Spanodonta and Aporthophyla were identified by Laurie & Burrett (1992) from the Thai mainland at Khao Tho Thun, near Langu in Satun Province. Hamada (1964) and Kobayashi & Hamada (1964) described a brachiopod fauna supposedly from near Ban Tung Din Lum, about 7 km SE of Thung Wa. Cocks et al. (2005) redetermined the brachiopods as Cyrtonotella sp., Rafinesquina and Oepikina and additionally collected the trilobite Basiliella satunensis from the same location, and considered the fauna to be probably Late Llanvirn to Early Caradoc. This author collected a Middle to Upper Ordovician strophomenid brachiopod and an asaphid trilobite from this location (identified by Dr W. J. Clarke, pers. comm. 1969). (Note, however, that the author was accompanied to this fossil locality in 1969 by a local guide who had previously assisted the Japanese authors; it was about 7 km east of Thung Wa and some distance from Ban Tung Din Lum.)

Lower to Upper Ordovician (Ridd, 2011); but the Cambrian–Ordovician boundary lies somewhere within the upper part of the Tarutao Gr.

Marine