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Forbes
6 days ago
- General
- Forbes
Cretaceous Amber Deposits Reveal Large-Scale Tsunamis
Amber concentration in deep-sea sediments. Traces of tsunamis are hard to identify in the fossil record. Tsunami deposits along a coast are washed away or can be confused with other high-energy events, such as storms. In a new study, Aya Kubota and colleagues from the Geological Survey of Japan and Chuo University analyzed an extraordinarily rich amber-concentrated beds found in a quarry on Hokkaido Island in northern Japan. Between the grey layers of sand- and mudstone deposited on the seafloor, the yellow amber — fossil tree resin formed typically on land — sticks out. Based on radiometric dating of zircon grains preserved in tuff layers interbedded between the mudstone and amber beds, the entire sedimentary succession formed around 116 and 114 million years ago. So-called flame structures, which form when soft material is folded or flattened before fully hardening, help to explain how the strange amber deposits formed. Amber layers seen under fluorescent light and daylight show flattening of the single amber ... More fragments, suggesting they were deposited as still soft tree resin. In the early Cretaceous, while the region was a oceanic basin, large amount of tree resin was rapidly swept out from a nearby coast to the open ocean by the backwash from one or more tsunamis. The tree resin then sank to the seafloor where it was covered by a sediments, deforming the single fragments and preserving them as amber. Similar concentrations of material originating on land and transported to open waters may be helpful in finding further tsunamis, the researchers conclude. Most tsunamis are generated by earthquakes, when the seafloor shifts suddenly and displaces a large quantity of water, but they can also be triggered by a landslide, a volcanic eruption or a meteor impact. Modern databases list more than 2.000 tsunamis in the last 4.000 years. Most of these records are based on historical documents and likely underestimate the real number. Geological evidence can provide a deeper understanding of past extreme events and is critical for hazard preparation and risk assessment now and in the future. The study,"Neon Isotopes in Geothermal Gases From the Kenya Rift Reveal a Common Deep Mantle Source Beneath East Africa," was published in the journal Geophysical Research Letters. Additional material provided by the Nature Publishing Group.
The Independent
16-05-2025
- Science
- The Independent
Scientists discover possible evidence of a 116-million-year-old tsunami recorded in amber
Scientists believe they have found evidence of a 116-year-old tsunami in amber, potentially the oldest recording of one to date. Investigating deep-sea sediment on Hokkaido Island in northern Japan, researchers Aya Kubota, Yusuke Takeda, Keewook Yi, Shin-ichi Sano and Yasuhiro Iba discovered 'extraordinarily rich amber concentrations' in sediment from the early Cretaceous period, dating to between 116 and 114 million years ago. In a report on their findings, published in Nature's Scientific Reports, the researchers suggested the amber had likely been swept into the ocean by one or more tsunamis, with little contact with air. Amber, which is fossilised tree resin, is a relatively fast drying substance. The researchers said it usually solidifies in as little as a week when exposed to air. But in the sediment examined by researchers, they found 'distinctively deformed' amber deposits, some deformed with so-called flame structures suggesting the resin was being altered by flowing water, and other flat bands of amber suggesting that soft resin had 'flowed and spread viscously into the seafloor'. 'The most plausible cause for the presence of this enigmatic amber in a deep-sea setting is large-scale tsunamis,' they said. 'These resin deformations occurred underwater, implying their direct transport from the forest to the pelagic seafloor. Such rapid and direct transport of terrestrial materials from land to ocean could be driven by a tsunami.' The researchers said other evidence in the ancient sediment backed up that theory, including large amounts of plant debris from land and large driftwood chunks, which bore little evidence of decay that suggested 'rapid transportation' out to the open ocean. 'The occurrence of the trunks in the claystone ... indicates that the enormous number of wood was discharged, drifted, and sank to the pelagic sea floor, not transported by turbidity currents,' the paper said. They suggested that other open ocean sediments could provide more evidence of large-scale ancient tsunamis or similar events. The researchers said tsunami deposits aren't normally identified any earlier than the young Holocene period, or from roughly 4,200 years onwards, due partially to the lack of definite features in the widespread destruction they cause.
Yahoo
15-05-2025
- Science
- Yahoo
Dinosaur age tsunami revealed from tiny chunks of Japanese amber, study finds
When you buy through links on our articles, Future and its syndication partners may earn a commission. Scientists have discovered evidence of an ancient tsunami in Japan — which is hidden in tree amber that dates to the age of the dinosaurs. The amber samples are deformed in a particular way that suggests trees and plant debris were rapidly swept out to the ocean and sank to the seafloor around 115 million years ago, the researchers said, which the team interpreted as evidence of one or more tsunamis. The scientists published their findings today (May 15) in the journal Scientific Reports. Scientists typically estimate when tsunamis happened in the past using geological evidence such as giant fossilized boulders that were swept away and deposited onto coasts, or by looking at abrupt changes in sediment deposits near coastlines. However, it can be difficult to differentiate tsunami traces in the fossil record from severe storms, which leave similar deposits. Amber, which is fossilized tree resin — a fluid produced by trees — can also be transported to the ocean when a tsunami sweeps trees and plant debris out to sea, leaving behind a record of the tsunami event. In the new study, the researchers analyzed amber-rich silica deposits from the Shimonakagawa Quarry in northern Hokkaido, Japan, which were deposited sometime between 116 million and 114 million years ago, during the Early Cretaceous period (145 million to 100 million years ago), when this region was deep seafloor. The team used fluorescence imaging — a technique that photographs the amber samples while shining ultraviolet light onto them — to observe the amber's structure. The amber samples showed a pattern similar to what geologists call "flame structures," a deformation that happens when soft sediment is deposited somewhere and changes shape before fully hardening — resulting in upward-pointing, flame-shaped tongues between the sediment layers. Amber deposits more commonly form other shapes, as tree resin dries when exposed to air. The research team interpreted the flame structures to mean the amber was suddenly swept out from the land to the ocean by one or more tsunamis, without being exposed to the air (which would have hardened it), then sank to the seafloor. The amber would have then been covered by a layer of silt and preserved for millions of years. "Identifying tsunamis is generally challenging," and it was not immediately apparent that tsunamis were behind the unusual amber samples, study co-author Aya Kubota, a paleontologist at Chuo University in Tokyo, told Live Science in an email. "By combining detailed field observations with the internal structures of amber, we were able to conclude that the most plausible cause was tsunamis." RELATED STORIES —Tsunamis up to 90 feet high smash into New Zealand every 580 years, study finds —1st mega-tsunami on record since antiquity was triggered by Tonga volcanic eruption —'Another piece of the puzzle': Antarctica's 1st-ever amber fossil sheds light on dinosaur-era rainforest that covered South Pole 90 million years ago Other evidence from the area backed up this hypothesis, including signs of a nearby landslide around the same time that may have been caused by an earthquake; large chunks of mud seemingly ripped up by the destruction of the seafloor; and large tree trunks on what was at the time the seafloor. Severe storm waves would not have affected the seafloor in this way, and if the tree trunks were stacked slowly over time they would have shown evidence of erosion, which these trunks did not — meaning all the evidence points to a huge amount of plant debris being transported quickly and suddenly to the seafloor. The researchers suggested that looking at ocean floor geological and fossil evidence — that is, beyond just coastal evidence — paints a more complete picture of previous tsunamis, and that examining amber deposits can provide information that helps differentiate tsunamis in the prehistoric record from severe storms. "Resin offers a rare, time-sensitive snapshot of depositional processes," Kubota said. Although the study of amber has typically focused on organisms like insects trapped inside samples, "the emerging concept of 'amber sedimentology' holds exciting potential to provide unique insights into sedimentological processes," Kubota added.
