Identification of the ejecta deposit formed by the Australasian Tektite Event at Huai Om, northeastern Thailand

1Toshihiro Tada,1,2,3Ryuji Tada,4Paul A. Carling,5Wickanet Songtham,5Praphas Chansom,1Toshihiro Kogure,1Yu Chang,1Eiichi Tajika
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13908]
1Institute for Geo-Cosmology, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016 Japan
2Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-0033 Japan
3Research Center for Earth System Science, Yunnan University, Chenggong District, Kunming, 650500 People’s Republic of China
4Geography and Environmental Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ UK
5Northeastern Research Institute of Petrified Wood & Mineral Resources, Nakhon Ratchasima Rajabhat University, Baan Kroke Duen Ha, Suranaree Sub-district, Muang Nakhon Ratchasima District, Nakhon Ratchasima, 30000 Thailand
Published by arrangement with John Wiley & Sons

The Australasian Tektite Event, approximately 0.8 Ma, is the youngest record of a large impact event on Earth. Although it is estimated that it occurred somewhere in Indochina based on the distribution of tektites, the crater has never been located. Here, we report the discovery and occurrence of shocked quartz with planar deformation features (PDFs) in the Quaternary depositional sequence at Huai Om in northeastern Thailand. Measurements of the orientation of lamellae using a universal stage microscope as well as observation using scanning electron microscopy and transmission electron microscopy were conducted to confirm the presence of PDFs. Together with the occurrence of in situ layered tektite fragments, we identify the depositional sequence as the ejecta deposit formed by the Australasian Tektite Event. We further describe the detailed lithostratigraphy of the ejecta deposit, which will allow the tracing of its distribution and lateral changes in its thickness, grain size, and grain composition. Further investigation of the lateral distribution of the ejecta deposit would provide information about the location, magnitude, and target rocks of the Australasian Tektite Event.

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