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First Magnetostratigraphic Study of the Pondaung Formation: Implications for the Age of the Middle Eocene Anthropoids of Myanmar

2002; University of Chicago Press; Volume: 110; Issue: 6 Linguagem: Inglês

10.1086/342868

1537-5269

Mouloud Benammi, Aung Naing Soe, Than Tun, Bo Bo, Yaowalak Chaimanee, Stéphane Ducrocq, Tin Thein, San Wai, Jean‐Jacques Jaeger,

Pleistocene-Era Hominins and Archaeology

We report the results of a magnetostratigraphic investigation to improve the stratigraphical and chronological resolution of the Pondaung Formation of central Myanmar. A total of 98 samples were collected from 45 sites through a 319‐m‐thick section at the fossiliferous locality of Yashe Kyitchaung or the Primate Resort (yielding primate species Bahinia pondaungensis, Amphipithecus mogaungensis, and Myanmarpithecus yarshensis) near the Bahin village. Thermal and alternating field demagnetization allowed separation of two remanence components. The high‐temperature component is interpreted as the characteristic magnetization. Rock magnetic experiments show that the remanence magnetization is mainly carried by magnetite. This investigation documents normal polarity remanent magnetization, with a mean direction $$D=336.7^{\circ }$$ , $$I=45.5^{\circ }$$ ($$N=74$$ , $$\alpha 95=7.1$$ , $$k=12$$ ). A local anticlockwise tectonic rotation of about $$32^{\circ }\pm 0.94^{\circ }$$ about a vertical axis is suggested, therefore. The magnetostratigraphic data indicate that the Bahin section can be correlated with chron C17n.1n, and an age of between 37 and 37.4 Ma can thus be assigned to the anthropoid locality.