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ตะรุเตาเอีย เตชวาลนิ Tarutaoia techawani, จี่หนานเนีย สิรินธรเน่ Tsinania sirindhornae A, Ao Phante Malacca section at low tide. B, hummocky cross-stratified sandstone bed at Ao Talo Udang. D, ball-and-pillow structures at 4.6 m above the base in the Ao Phante Malacca section. Wernette, Hughes, Myrow & Sardsud, 2023 DOI: 10.1002/spp2.1516 |
Abstract
Tuff-bearing upper Cambrian to lowermost Ordovician strata on Ko Tarutao island, Satun province, southernmost peninsular Thailand, contain a rich trilobite fauna relevant to global biostratigraphy, peri-Gondwanan palaeogeography and shifting evolutionary mode. This area of Sibumasu, a lower Palaeozoic marginal Gondwanan terrane, is shown to have been closely associated with Australia, North China (Sino-Korea) and other continental fragments from the supercontinent's northern equatorial sector, including South China at that time. Shared faunas also suggest a Kazakhstani and Laurentian association. Collections from eight sections yielded 10 newly discovered species and one new genus from ancient shoreface and inner shelf siliciclastic deposits. With the new taxa and revision of taxa known previously, we refine the age of the upper two formations of the Tarutao Group to the middle of Cambrian Stage 10, and lower–middle Tremadocian. Two biozones are erected for Sibumasu: the Eosaukia buravasi Zone, encompassing all Cambrian sections from Ko Tarutao, and the Asaphellus charoenmiti Zone, encompassing the Tremadocian fauna discussed herein. The new genus is Tarutaoia and new species are Tsinania sirindhornae, Pseudokoldinioidia maneekuti, Pagodia? uhleini, Asaphellus charoenmiti, Tarutaoia techawani, Jiia talowaois, Caznaia imsamuti, Anderssonella undulata, Lophosaukia nuchanongi and Corbinia perforata. Other taxa reported for the first time from Tarutao are Mansuyia? sp., Parakoldinioidia callosa Qian, Pseudagnostus sp., Homagnostus sp., Haniwa mucronata Shergold, Haniwa sosanensis? Kobayashi, Lichengia simplex Shergold, Pacootasaukia sp., Wuhuia? sp., Plethopeltella sp., Apatokephalus sp., Akoldinioidia sp. 1 and Koldinioidia sp.
Keywords: Thailand, Trilobita, Cambrian, Ordovician, Sibumasu, Gondwana
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| Map of Ko Tarutao. AML, Ao Mo Lae; APM, Ao Phante Malacca; ATD, Ao Talo Udang; ATT, Ao Talo Topo; ATTw, Ao Talo Topo west; ATW, Ao Talo Wao, type section of the Talo Wao Formation; LHN, Laem Hin Ngam; S1–S3, ATD Sections 1–3. Modified from Burrett & Chaodumrong (2017). |
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| A, Ao Phante Malacca section at low tide. B, hummocky cross-stratified sandstone bed at Ao Talo Udang; hammer is 18.5 cm long. C, hummocky cross-stratified and coquina beds at the 3.4–3.7 m zone at Ao Mo Lae; pencil is 14 cm long. D, ball-and-pillow structures at 4.6 m above the base in the Ao Phante Malacca section; coin is 18 mm in diameter. E, ball-and-pillow structures above two thin carbonate layers at Ao Phante Malacca 12.5 m; hammer is 18.5 cm long. F, tuff (38 cm thick) at Ao Phante Malacca 22.5 m; hammer is 35 cm long. |
CONCLUSIONS:
• The trilobite fauna of the Tarutao Group is significantly more diverse than previously known, with this work introducing 11 new species and 1 new genus, making for 42 discrete taxa, 25 of which have species-level resolution.
• The Ao Mo Lae Formation dates to the middle of Cambrian Stage 10, correlative with the Eosaukia, Mictosaukia perplexa and Mictosaukia striata zones of South Korea, Australia and South China, respectively.
• The Talo Wao Formation is middle Tremadocian where its fauna is most diverse, and may extend down into the lower Tremadocian.
• Sibumasu's first two formal biozones are erected, the Eosaukia buravasi Zone, encompassing all known sections of the Ao Mo Lae Formation, and the Asaphellus charoenmiti Zone, encompassing all known sections of the Talo Wao Formation. Their correlations are as noted in Conclusions 2 and 3 and Figure 12.
• Shared trilobite species and genera from these formations suggest that during the latest Furongian and early Tremadocian Sibumasu was palaeogeographically associated with South China, North China and Australia, with a less strong, but still notable, association with Kazakhstan. Sibumasu shared more taxa with Laurentia than did most other parts of Gondwana.
Shelly J. Wernette, Nigel C. Hughes, Paul M. Myrow and Apsorn Sardsud. 2023. Trilobites of Thailand's Cambrian–Ordovician Tarutao Group and their geological setting. Papers in Palaeontology. DOI: 10.1002/spp2.1516
1. จี่หนานเนีย สิรินธรเน่ Tsinania sirindhornae 2. ซูโดโคลดินิออยเดีย มณีขัติย์ Pseudokoldinioidia maneekuti
3. พาโกเดีย เออเลนนิ Pagodia? uhleini 4. อซาเฟลลัส เจริญมิตรติ Asaphellus charoenmiti
5. ตะรุเตาเอีย เตชวาลนิ Tarutaoia techawani 6. จิเอีย ตะโละวาวอิส Jiia talowaois
7. แคซนาเอีย อิ่มสมุทรติ Caznaia imsamuti 8. แอนเดอร์สันเนลล่า อันดูลาตา Anderssonella undulata
9. โลโฟซอเกีย นุชอนงค์งิ Lophosaukia nuchanongi 10. คอร์บิเนีย เพอร์ฟอราต้า Corbinia perforata
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