image: Photomicrograph in plane-polarized light of parallel planar fractures (upper left to lower right) in quartz crystal from an impact-breccia deposit ~20 km southeast of the center of the proposed crater. view more
Credit: Image courtesy of Dayana Schonwalder Angel.
A study suggests that a buried crater in southern Laos might be the long-sought source of a strewn field of glassy rock fragments, or tektites, produced by a meteorite impact approximately 790,000 years ago covering more than one-tenth of Earth's surface. The patterns of tektite size and abundance suggest that the impact occurred in eastern Indochina, but no impact crater has yet been located. Kerry Sieh and colleagues report that the impact site lies buried beneath the Bolaven volcanic field in southern Laos. The geochemical composition of the tektites suggests that most of the variation in elemental composition can be explained by mixing of Mesozoic sandstone and mudstone with varying amounts of volcanic rocks of the type found on the Bolaven Plateau. Argon-argon dating of the lava flows in the region yielded dates younger than the impact in lavas directly above the proposed crater, and dates older than the impact on the periphery of the volcanic field. The authors detected a gravity anomaly consistent with a buried 17x13 km crater. An outcrop 10-20 km southeast of the proposed impact site consists of boulder-sized sandstone and mudstone breccia containing fractured quartz grains, which likely represent proximal ejecta from the impact. According to the authors, the findings are consistent with a buried impact crater beneath the Bolaven field.
Article #19-04368: "Australasian impact crater buried under the Bolaven volcanic field, Southern Laos," by Kerry Sieh et al.
MEDIA CONTACT: Kerry Sieh, Nanyang Technical University, Singapore, SINGAPORE; tel: +65-96745401; e-mail: sieh@ntu.edu.sg; Jason Herrin, Nanyang Technical University, Singapore, SINGAPORE; tel: +65-91788069; e-mail: jsherrin@ntu.edu.sg
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Journal
Proceedings of the National Academy of Sciences