Late Tournaisian conodonts from the Taungnyo Group near Loi Kaw, Myanmar (Burma): Implications for Shan Plateau stratigraphy and evolution of the Gondwana-derived Sibumasu Terrane

Abstract

Carboniferous conodonts are reported for the first time from Myanmar (Burma). Conodont faunas representative of the 'Scaliognathus anchoralis' and 'Gnathodus typicus Protognathodus cordiformis' conodont zones date the sampled 'Taungnyo' Group south of Loi Kaw, Kayah State as late Tournaisian confirming a Mississippian (Lower Carboniferous) age for the sampled part of this stratigraphic unit. The dated strata are stratigraphically just below the Tournaisian-Visean (T-V) boundary. Tournaisian strata are thus for the first time unequivocally demonstrated in the Shan Plateau region of Myanmar. Similar conodont faunas from the T-V boundary interval in SE Asia indicate a complete stratigraphic sequence at this level in shallow-marine sequences on intra- Tethyan Cathaysian tectonic blocks (South China) and in deep-marine Palaeo-Tethyan sediments (cherts of the Inthanon suture zone, Thailand). However, in shallow-marine sequences on the Sibumasu Block, located on the NE margin of Gondwana in the Carboniferous, they demonstrate a non-sequence or unconformity at this level, also seen elsewhere in Gondwana. Biogeographic links between upper Tournaisian and early Visean conodonts on the Sibumasu Terrane and Laurentia and Eastern Australian Gondwana support a NW Australian Gondwana margin position for Sibumasu in the Late Palaeozoic.