The Allerod-Younger Dryas iridium anomaly: comet impact or volcanism

阿勒罗德-新仙女木期铱异常：彗星撞击或火山活动

• 批准号: NE/H011781/1
• 负责人: Donald Porcelli
• 金额: $ 6.7万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH011781%2F1
• 关键词: Allerod; Younger; Dryas; iridium; anomaly

Recent scientific reports have proposed a comet or meteorite struck the Earth about 12,900 years ago causing widespread vegetation burning. This lead to the extinction of many large mammals in North America such as the mammoth and sabre toothed cats and consequently effected some of earliest colonizing human cultures of that continent. It is further proposed that the meteorite impact caused a rapid cooling of the Northern hemisphere climate and a return to glacial conditions in northern latitudes which lasted for about 1,400 years. Part of the evidence presented for this idea is an excess of Iridium, relative to background values, found at one particular horizon and which is associated with an increased abundance of organic matter or charcoal. This is similar to the Iridium anomaly associated with the Chicxulub meteorite impact which occurred 65 million years ago and remains one of the best documented meteorite impacts within the geological record. However the evidence presented for a comet strike has been contested by other scientists and the topic remains the subject of much controversy. It is also recognized that large volcanic eruptions may effect climate in the short term and we suggest volcanism as an alternative explanation. This research aims to clarify the position by using a simple diagnostic test capable of distinguishing a meteoritic from a volcanic signature. Meteorites are found to have higher abundances of the platinum group elements (Iridium, Platinium, Palladium, Rhodium, Ruthenium, Rhenium and Osmium) than ordinary crustal rocks and in proportions similar to those of the most primitive meteorite groups, thought to be representative of material from which the solar system formed. In contrast volcanic processes tend to produce a more variable abundance profile for the platinum group elements because of the different chemical behaviour and properties of each element within this group. We aim to measure the platinum group element abundances in material collected from the organic rich layers, with a previously reported iridium anomaly, from across North America, Europe and from sediment drillcores in the North Atlantic. In addition we will also search for other diagnostic evidence of a meteorite impact such as shocked quartz, enhanced siderophile element abundance and nickel-rich spinels.

最近的科学报告提出，大约12，900年前，一颗彗星或陨石撞击地球，造成广泛的植被燃烧。这导致了北美许多大型哺乳动物的灭绝，如猛犸和剑齿猫，并因此影响了该大陆最早的殖民人类文化。有人进一步提出，陨石撞击造成北方半球气候迅速冷却，并使北方纬度恢复到冰川状态，持续了大约1，400年。为这一观点提供的部分证据是在一个特定的层位发现的铱相对于背景值过量，这与有机物质或木炭的丰度增加有关。这与6500万年前发生的希克苏鲁布陨石撞击相关的铱异常相似，并且仍然是地质记录中最好的陨石撞击之一。然而，彗星撞击的证据受到了其他科学家的质疑，这个话题仍然是一个有争议的话题。人们还认识到，大规模火山爆发可能会在短期内影响气候，我们建议火山作用作为另一种解释。这项研究的目的是通过使用一种能够区分陨石和火山特征的简单诊断测试来澄清位置。陨石中铂族元素（铱、铂、钯、铑、钌、铼和锇）的丰度高于普通地壳岩石，其比例与最原始的陨石群相似，被认为是太阳系形成的代表性物质。相比之下，火山过程往往产生一个更多变的丰度分布的铂族元素，因为不同的化学行为和属性的每一个元素在这个组。我们的目标是测量铂族元素丰度的材料收集的有机丰富的层，与以前报道的铱异常，从整个北美，欧洲和沉积物钻孔岩芯在北大西洋。此外，我们还将寻找陨石撞击的其他诊断证据，如冲击石英，增强亲铁元素丰度和富镍尖晶石。