Chixculub: are more possible (Introduction)

by David Turell , Tuesday, December 05, 2023, 23:39 (353 days ago) @ David Turell

Recent meteorite 800,000 years ago:

https://www.nationalgeographic.com/premium/article/have-scientists-found-800000-year-ol...

"'Tektites,” announced the cashier, handing over a photocopied paper that indicated they formed in a mysterious meteorite strike—Earth’s last major impact, in fact, a catastrophic collision that could have been witnessed by ancient human relatives. As Sieh read about a colossal debris field covering 20 percent of the planet’s landmass, from China to Antarctica, he realized a key detail was missing.

“'I thought, oh my gosh. How could it be that nobody's found the hole?” Now, a dozen years later, Sieh is convinced he has.

"After his jewelry store encounter, Sieh studied the scientific literature and searched satellite images across the region for geological features of interest. He began to suspect that the missing crater, formed some 800,000 years ago, could be in the Bolaven Plateau in southern Laos, buried beneath a young but extensive lava field.

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"These geologic sequences were recorded and measured at hundreds of sites across a 310-mile-wide region on and around the plateau, revealing a radial pattern of thickening deposits that converges on the plateau center. Sieh describes his case for the Bolaven Plateau as now “all but indisputable.”

“'To have a rubbly, poorly sorted deposit made up of stuff we think is from where the crater was, [and] to have it thicken and coarsen toward the source, toward the plateau … offer me some other explanation,” he says.

"But not all scientists are yet convinced. Fred Jourdan, a geochronologist at Curtin University in Perth, Australia, who has used chemical clues from the tektites to date the impact to about 788,000 years ago, says Sieh’s proposal is “very well possible,” though he believes the new findings only offer indirect evidence. He says the study is “not a demonstration of the absolute location,” pointing out that many volcanically active places across Southeast Asia also have sandy surface geology that could have produced the tektites in an impact.

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"In the absence of an impact crater, tektite strewn fields provide the next best record of Earth-shattering meteorite strikes.

"Jourdan’s 2019 dating of the tektites, found today across much of Australia and Southeast Asia, made it the youngest of Earth’s four major tektite strewn fields. The date fueled speculation that ancient Asian hominins such as Homo erectus could have witnessed the explosive event. While a limited fossil record makes that difficult to prove, this planetary collision was clearly best viewed from afar—Jourdan’s analysis showed the tektites formed at temperatures of up to 7,200 degrees Fahrenheit.

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"While Carling’s paper focuses on just one site, he claims to have since mapped this “impact ejecta sequence” across Thailand, southern Laos, Vietnam, and northern Cambodia. He also says that this field work has demonstrated a thickening in these deposits toward southern Laos, supporting Sieh’s case for the Bolaven Plateau as an impact site.

"Carling hopes to publish his team’s wider field analysis next year, adding more clues to this geological puzzle. For Jourdan, though, the final proof can only be found by searching deep underground. “To rally the entire impact community behind the case, they need to drill down to where they think the crater is located,” he says.

"Carling believes an exploration down to about 600 or 700 feet might suffice to find other features like shatter cones, shocked minerals, and melt rocks—all signs of a major impact. “We might also find fragments of the meteor itself,” he says."

Comment: it took many years to have Chixculub accepted. The problem here is not surprising. Areal surveys see craters all over the Earth.