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The Permian–Triassic boundary (PTB) is defined by the first appearance of the conodont species 'Hindeodus parvus' (Kozur & Pjatakova). It is now indicated to be 252.3 Ma by zircon U-Pb radio-isotopic dating (Mundil et al., 2004; Mundil et al., 2010). Despite decades of searching (e.g. Metcalfe, 1984), the PTB has not been located precisely to date in Malaysia. In Pahang, central Peninsular Malaysia, there are several limestone sections, which have yielded biostratigraphic data indicating the plausible presence of the PTB. Two of them, Gua Bama and Gua Sei, have now emerged as the most promising localities, since they both exhibit carbonate strata ranging from Upper Permian to Triassic. The Triassic nautiloid 'Sibyllonautilus bamaensis' was recently reported from the top of Gua Bama, confirming the presence of the Triassic (Sone et al., 2004). The Triassic nautiloid-bearing deposit accompanies abundant algae, which in general are extremely rare in the Early Triassic; therefore, it is interpreted that the uppermost part of the Gua Bama strata likely extends to the post-Early Triassic, most likely Middle Triassic (Sone et al., 2008). From the base of Gua Bama, Late Permian colaniellid foraminifers have been reported (Lim and Nuraiteng, 1994), and conodonts and brachiopods have recently been discovered. The conodonts include several species of 'Clarkina', 'Hindeodus julfensis' and 'Iranognathus movschovitschi', confirming a Changhsingian age. The brachiopods were found in the siliciclastic strata 2 m below the conodont beds; that is, passage strata from the underlying siliciclastic sequence to the limestones. They include the rare genus 'Dongpanoproductus', known elsewhere only from the upper Changhsingian of South China (He et al., 2005). Thus, the lowest part of Gua Bama is dated as late Changhsingian age, suggesting that the Gua Bama sequence probably includes the PTB transition. |
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