中国南東部、広東省肇慶市の山岳地帯にある深さ90mのボウル形の凹地は、天体衝突で形成されたクレーターであることを、同国の上海と広州の研究者チームが確認した。
Researchers from Shanghai and Guangzhou have confirmed that a bowl-shaped depression, 90 meters deep and located in the mountainous area of Zhaoqing City, Guangdong Province in southeastern China, is a crater formed by a meteorite impact.
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This collision structure is preserved on the mountain slope and has been named the Jinlin Crater. It is large in scale and is believed to have formed in a very recent geological era.
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Jinlin Crater was formed on a granite basement, has a diameter of 900 meters, and is the result of the largest meteorite impact event in the past 12,000 years.
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Based on the measurement results of the surrounding soil erosion, this hole was likely formed in the early to middle Holocene.
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It is an era that began at the end of the last glacial period, about 11,700 years ago.
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The Jinlin Crater, which reaches a maximum diameter of 900 meters, surpasses Russias Macha Crater group with diameters of 60 to 300 meters, formed about 7,000 years ago, making it the largest known impact crater from the Holocene.
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Tran Minh Min Chen, the principal author of this research paper, is affiliated with the Shanghai Branch of the Beijing High Pressure Science Research Center and states, “This discovery indicates that asteroid-Earth collisions during the Holocene were far more significant than previously recorded.”
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The preservation state of this impact crater is exceptionally good, which is remarkable considering that the humid climate of this region tends to accelerate weathering and erosion.
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Because the granite is hard and the collision is relatively recent, the rim of the crater has remained without disappearing.
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The research team confirmed the origin of the meteorite impact by analyzing the rock structure.
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A hypervelocity collision between an asteroid and the Earth may have caused shock metamorphism.
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Destroy the structure of the rock down to the mineral crystal level, forming a planar structure through small cracks.
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The research team investigated quartz crystals and confirmed the presence of planar deformation features PDFs in the granite.
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On Earth, the formation of PDFs in quartz occurs only due to the intense shock waves generated by meteorite impacts.
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The formation pressure of PDFs ranges from 10 to 35 GPa gigapascals, and no geological process on Earth can produce such a strong impact, explained Mr. Chang.
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Currently, only two other meteorite impact craters have been identified in China.
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One example is the Xiuyuan Crater in Liaoning Province, which has a diameter of 1.8 km, but its age of formation has not yet been determined.
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In 2021, it was confirmed that a partially buried basin in Heilongjiang Province was of extraterrestrial origin.
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This hole in Yilan has a diameter of 1.85 km and a depth of over 300 meters, and it is likely that it was formed within the past 50,000 years.
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According to a study published in August 2023, anomalies in the magnetic field and gravity have been observed in the Badain Jaran Desert in northwestern China.
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Since the suspected impact structure is buried beneath the dunes, it has not yet been possible to collect direct samples.
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Furthermore, according to an article from September 2023, it is highly likely that the basin-shaped depression at the summit of Baijifeng Mountain in Tonghua City, Jilin Province, northeastern China, is the rim of an impact crater formed 100,000 years ago.
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Based on the distribution of 200 known meteorite impact structures worldwide, the number of impact structures in China is much lower than the global average.
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Geological surveys are expected to continue discovering traces of past meteorite impact events in the future.
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The article Jinlin crater, Guangdong Province, China: Impact origin confirmed was published in the journal Matter and Radiation at Extremes.
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You can read the full text here.
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Additional materials and interviews were provided by the American Institute of Physics AIP.
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