Source of Australasian tektites: Investigating possible impact sites in Laos

Schnetzler, C. C.; McHone, J. F.

doi:10.1111/j.1945-5100.1996.tb02055.x

Cited by 26 publications

(27 citation statements)

References 8 publications

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“…Such a location is consistent with the evidence discussed above, indicating that Site 1144A is closer to the source crater than is any other Australasian microtektite-bearing site. A crater in the Gulf of Tonkin would also explain why searches for the source crater on land have been unsuccessful (e.g., Wasson 1993;Schnetzler and McHone 1996). In addition, a crater site in this location is consistent with the 10 Be data of Ma et al (2004) as discussed above.…”

Section: Location and Size Of The Source Cratersupporting

confidence: 70%

Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of Toba

Glass

Koeberl

2006

Meteorit & Planetary Scien

113

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Abstract-Australasian microtektites were discovered in Ocean Drilling Program (ODP) Hole 1143A in the central part of the South China Sea. Unmelted ejecta were found associated with the microtektites at this site and with Australasian microtektites in Core SO95-17957-2 and ODP Hole 1144A from the central and northern part of the South China Sea, respectively. A few opaque, irregular, rounded, partly melted particles containing highly fractured mineral inclusions (generally quartz and some K feldspar) and some partially melted mineral grains, in a glassy matrix were also found in the microtektite layer. The unmelted ejecta at all three sites include abundant white, opaque grains consisting of mixtures of quartz, coesite, and stishovite, and abundant rock fragments which also contain coesite and, rarely, stishovite. This is the first time that shock-metamorphosed rock fragments have been found in the Australasian microtektite layer. The rock fragments have major and trace element contents similar to the Australasian microtektites and tektites, except for higher volatile element contents. Assuming that the Australasian tektites and microtektites were formed from the same target material as the rock fragments, the parent material for the Australasian tektites and microtektites appears to have been a fine-grained sedimentary deposit. Hole 1144A has the highest abundance of microtektites (number/cm 2 ) of any known Australasian microtektite-bearing site and may be closer to the source crater than any previously identified Australasian microtektite-bearing site. A source crater in the vicinity of 22° N and 104° E seems to explain geographic variations in abundance of both the microtektites and the unmelted ejecta the best; however, a region extending NW into southern China and SE into the Gulf of Tonkin explains the geographic variation in abundance of microtektites and unmelted ejecta almost as well. The size of the source crater is estimated to be 43 ± 9 km based on estimated thickness of the ejecta layer at each site and distance from the proposed source. A volcanic ash layer occurs just above the Australasian microtektite layer, which some authors suggest is from a supereruption of the Toba caldera complex. We estimate that deposition of the ash occurred ∼800 ka ago and that it is spread over an area of at least 3.7 × 10 7 km 2 .

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Section: Location and Size Of The Source Cratersupporting

confidence: 70%

Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of Toba

Glass

Koeberl

2006

Meteorit & Planetary Scien

113

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“…The dashed line delimits the area in which tektite and microtektites have been found, whereas the solid line outlines that for unmelted impact ejecta (shocked quartz, coesite and stisho vite). Adopted from Glass and Pizzuto (1994) and Schnetzler and McHone (1996). (b) Map showing the site of recoveries ofDarwin glasses (shown in dark areas) and the location of the Darwin Crater (after Barnes , 1963;Ford, 1972).…”

Section: Samples and Analytical Methodsmentioning

confidence: 99%

Laser fusion argon‐40/argon‐39 ages of Darwin impact glass

Howard

Chung

et al. 2002

Meteorit & Planetary Scien

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Abstract-Three samples of Darwin Glass, an impact glass found in Tasmania, Australia at the edge of the Australasian tektite strewn field were dated using the 40Ar/ 39 Ar single-grain laser fusion technique, yielding isochron ages of 796-815 ka with an overall weighted mean of 816 ± 7 ka. These data are statistically indistinguishable from those recently reported for the Australasian tektites from Southeast Asia and Australia (761-816 ka; with a mean weighted age of803 ± 3 ka). However, considering the compositional and textural differences and the disparity from the presumed impact crater area for Australasian tektites, Darwin Glass is more likely to have resulted from a distinct impact during the same period of time.

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“…In addition, Ford (1988) noted that the size of Muong Nongtype tektites in Thailand decreased toward the west, and that Muong Nong-type tektites from Hainan Island, China are small. Schnetzler and McHone (1996) noted that a small area in Laos has the greatest concentration of Muong Nong-type layered tektites. All Australasian tektites may be derived from a single sedimentary formation with a narrow range of stratigraphic ages close to ~170 Ma (Fig.…”

Section: Fig 13 Correlation Plots Of Compositional Data From the MImentioning

confidence: 99%

Geochemical studies of tektites from East Asia

Lee

Chen

et al. 2004

Geochem. J.

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Thirty tektites from East Asia (including Wenchang and Penglei of Hainan Island, Maoming of Guandong, China; Khon-Kaen of Thailand; Bao Loc of Vietnam; Rizal of Luzon, Philippines) have been analyzed for major and trace element contents and Rb-Sr isotopic compositions. All the samples studied are splash form tektites. The trace element ratios Ba/Rb (avg. 3.74), Th/Sm (avg. 2.31), Sm/Sc (avg. 0.43), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents of tektites studied are similar to the average upper continental crust. The chemical data of tektites in this study indicate that they were derived from similar target rocks which may be related to post-Archean upper crustal materials. The tektites from East Asia have high positive ε Sr (0) values-ranging from 164.2 to 198.6, indicating that they were not dominantly derived from recent young sediments, such as soil or loess. The Ar-Ar ages (736.8 ± 55.5~814.6 ± 24.4 ka) of tektites of the present study are consistent with the age of other Australasian tektites, which indicates that all Australasian tektites were derived from a single impact event. Previous studies (Koeberl, 1992;Blum et al., 1992;Schnetzler, 1992) and the present chemical data suggest that these tektites are the result of melting at a single site, which is most probably located in the southern part of the Thailand-Laos border. Mixing calculations based on the model suggested by Ho and Chen (1996) for various amounts and combinations of target rocks indicate that the best fit for East Asia tektites is a mixture of 61% greywacke, 32% sandstone and 7% shale.

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Source of Australasian tektites: Investigating possible impact sites in Laos

Cited by 26 publications

References 8 publications

Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of Toba

Australasian microtektites and associated impact ejecta in the South China Sea and the Middle Pleistocene supereruption of Toba

Laser fusion argon‐40/argon‐39 ages of Darwin impact glass

Geochemical studies of tektites from East Asia

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