Aspects of Ordovician conodonts and the stratigraphy of Thailand, Malaysia, and Tasmania
Creators: name: Cantrill, Robin C.
Publisher: name: University of Tasmania
Year: 2023

description: Ordovician conodonts from the shallow tropical Lower Setul Limestone from the Langkawi Islands, Malaysia range from the Tremadoc to Ashgill. Species included Acodus oneotensis, Ansella jemtlandica, Baltoniodus prevariabilis, Cordylodus lindstromi, Cornuodus longibasis, Dapsilodus mutatus, Drepanodus toomeyi, Drepanoistodus basiovalis, Hamarodus europaeus, Juanognathus variabilis, Jumudontus gananda, Oepikodus evae, Oistodus cf. lanceolatus, Panderodus gracilis, Panderodus nogamii, Protopanderodus liripipus, Scolopodus rex, Scolopodus bassleri, Scolopodus staufferi, Semiacontiodus cf. bulbosus and Triangulodus variabilis. Walliserodus ethingtoni ranges from the Upper Ordovician to the Lower Silurian.Two hundred and seventy Ordovician conodonts specimens collected from the shallow tropical Thung Song Limestone of mainland Thailand and Ko Tarutao, Thailand range from the Lower Ordovician to the Upper Ordovician. Species include Acanthodus uncinatus, Acodus deltatus, Acontiodus latus, Amorphognathus tvaerensis, AnseIla jemtlandica, Baltoniodus prevariabilis, Bergstroemognathus extensus, Bergstroemognathus kirki, Cordylodus caseyi, C. drucei, C. lindstromi, C. prion, C. rasmosus, Drepanodus sp., Erraticodon cf. hexianensis, Juanognathus serpagli, jaanussoni, J. variabilis, Oistodus sp., Loxodus bransoni, Oepikodus evae, Panderodus nogamii, Paracordylodus elongatus, Parapaltodus simplicissimus, Periodon cf. flabellum, Phragmodus flexuosus, Protopanderodus elongatus, P. cooperi, P. robustus, Scalpellodus striatus and Triangulodus variabilis.A small number of conodont specimens were recovered from the deeper water Pa Kae Formation in Thailand. These include a single specimen of Amorphognathus ordovicicus. Other species include Ansella jemtlandica, Baltoniodus navis, Cornuodus longibasis, Dapsilodus mutatus, Drepanodus amplissimus, Drepanoistodus basiovalis, Harmarodus europaeus, Protopanderodus insculptus, Protopanderodus liripipus, and Walliserodus ethingtoni. All species indicate a range from Darriwilian to the Ashgill. FORTEY'S (1997) study of deeper water trilobites (Upper Caradoc to the Lower Ashgill) from the Pa Kae Formation agrees with this range.A small Ordovician conodont fauna from the Flowery Gully Limestone at Beaconsfield in northern Tasmania includes Acodus combsi, Acontiodus iowensis, Drepanodus sp., Juanognathus variabilis, Protopanderodus varicostatus, Scolopodus gracilis and Scolopodus rex that range from the Arenig to Darriwilian.250 conodont specimens from the Karmberg Limestone of central southern Tasmania include Aurilobodus ?leptosomatus, Bergstroemognathus extensus, Bergstroemognathus kirki, Glyptoconus quadriplicatus, Juanognathus jaanusonni, Protopanderodus elongatus, Protopanderodus gradatus, Ruetterodus andinus, Rossodus manitouensis, Scolopodus floweri, Scolopodus krummi, Scolopodus giganteus and Variabiloconus variabilis. Several conodont species have not been reported in earlier reports on Tasmanian Ordovician conodont faunas. The age of the conodont fauna reviewed indicated an age from the 0. evae through to the E. variabilis Zone. Older species such as Oenotodus nakamuri, Variabiloconus variabilis and Glyptoconus quadriplicatus appear in the lowest units of the Karmberg Limestone but they may have come from reworked material from the top of the Upper Florentine Valley Formation.Three species of the genus Phragmodus from the Gordon Limestone Group (Middle to Upper Ordovician) of Tasmania; Phragmodus flexuosus, Phragmodus undatus and a new species of Phragmodus tasmaniensis are described. These species permit the correlation of North American Midcontinent conodont faunas with species that occupied comparatively shallow, warm water, offshore biofacies around the continental margins of Gondwana.Panderodus nogamii (LEE) has a peri-Greater Gondwana distribution in the shallow temperate to tropical water limestones of Argentina, Thailand, Tasmania, Australia, Malaysia and the north and south China blocks.Conodonts from the Lower Setul Limestone in the Langkawi Islands, the Thung Song Group on Ko Tarutao and mainland Thailand, and Tasmania show close affiliation to the Ordovician conodont fauna from Argentina and with Australian conodont fauna from the Canning Basin, and the Georgina Basin. Conodonts species including Bersgtroemognathus extensus, Drepanodus arcuatus, Juanognathus variablis, and Scolopodus rex from the deep water Hensleigh Siltstone of central N.S.W. (Early Ordovician, Bel to Be2) occur in Tasmania, Southeast Asia, and Argentina. Several genera are represented in the Ordovician conodont faunas reported from Utah and Nevada in the U.S.A.The CAI values range of 2.0 to 5.0 for the conodonts from the Langkawi Islands, Malaysia may reflect their proximity to Mesozoic granitic intrusions. The conodonts from the Thung Song Formation have a range from 1.5 to 2.0 on Ko Tarutao and mainland Thailand. The range of 2.0 to 3.0 for conodonts from the Pa Kae Formation may be a function of the thickness of the overburden which covered the formation.