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Middle Permian Gigantic Parafusulina from the Zwekabin Range, Southeastern Myanmar; a Potential Significant Genus in Middle Permian of the Eastern Cimmerian Continent
- In the eastern Cimmerian continent (Sibumasu, Baoshan, Tengchong blocks), the Middle Permian is essentially represented by platform carbonate successions. Their fusuline fauna is characterized by the occurrence of Eopolydiexodina together with the fundamental rarity of verbeekinids and neoschwagerinids showing tropical Tethyan affinities although recent studies reported a few forms of these fusulines (such as Pseudodoliolina, Neoschwagerina, Sumatrina) from Midian parts of the successions. In the coeval tropical Tethyan fusuline fauna, Parafusulina is known as one of diagnostic genera apart from verbeekinids and neoschwagerinids. In the eastern Cimmerian continent, however, this genus is only poorly documented in the Permian fusuline faunas. Its paleobiogeographic significance is not clear in peri-Gondwanan areas until now. Recently, we newly found two, gigantic species of Parafusulina from the Sibumasu Block of Myanmar. In this study, we report them and discuss the significance of their occurrence. The gigantic Parafusulina species reported herein came from the Moulmein Limestone of the Zwekabin Range near Hpa-an Township in Kayin State, southeastern Myanmar. This limestone is correlated to the Plateau Limestone of the Shan States of Eastern Myanmar and represents one of Middle Permian successions in the Sibumasu Block. In the Zwekabin Range, the Moulmein Limestone rests unconformably? on Carboniferous to Early Permian clastics of the Taungnyo Group and attains its thickness to be about 430 m. It is composed mainly of bedded limestone with chert nodules and underlies the entire range almost horizontally. The fusuline fauna containing gigantic Parafusulina is found in the upper part of the succession. It yields Parafusulina sp. A, P. sp. B, Minojapanella sp., Yangchienia sp., and Chenella sp. associated with such smaller foraminifers as Abadehella sp., Postendothyra? sp., Multidiscus sp., Pachyphloia sp., Climacammina sp., Palaeotextularia sp., Ichthyofrondina sp., Langella sp., Globivalvulina sp., Lasiodiscus sp., and Tuberitina sp. Judging from the occurrence ofAbadehella sp. and Chenella sp., its age is provisionally assigned as Midian. In the two Parafusulina species, P. sp. B has a shell more than 3 ern in maximum length; longest one attaining 2.1cm half length. In the eastern Cimmerian continent, similar gigantic Parafusulina was reported in the Tengchong Block of West Yunnan, China. Shi et al. (2008) described a gigantic schwagerinid occurring together with Chusenella from the middle part of the Dadongchang Formation under the name of Monodiexodina gigas. However, that species is rather disparate with Monodiexodina and is better subsumed to Parafusulina judging from the general shell features. We consider that these gigantic Parafusulina species constituted a single lineage in schwagerinids in the Middle Permian of the eastern Paleo-Tethys. This lineage is probably endemic in the eastern Cimmerian continent and possesses some paleobiogeographic significance in the Middle Permian of the Eastern Cimmerian Continent.
Tin Tin Latt
- Conference paper
- Thirteenth Regional Congress on Geology, Mineral and Energy Resources of Southeast Asia