Bruce Forbes Bohor, the 2011 Barringer Medalist of the Meteoritical Society (Glass, 2011), passed away at his home in Green Valley, Arizona, on November 17, 2019. Bruce is best known in our community for his discovery of shocked quartz in layers marking the Cretaceous–Tertiary (K‐T, now called the Cretaceous–Paleogene, K‐Pg) boundary in the central United States in the early 1980s, following the famous paper by Alvarez and co‐authors in Science in 1980, in which they report geochemical evidence for an asteroid impact from K‐Pg layers in Italy. The so‐called asteroid impact hypothesis to explain the mass extinction at the K‐Pg boundary had created quite a controversy in the early 1980s, as some researchers (unencumbered by knowledge of planetary processes such as impact cratering or shock effects) had contemplated multiple other explanations for the geochemical signals.

In the early 1980s, Bruce was studying the geology of some Late Cretaceous coal deposits in the Western Interior, USA. In particular, he was using tonsteins (altered volcanic ash beds) to date and correlate individual coal beds. Even though he was previously not involved in impact cratering or extinction studies, Bruce thought that he could try to test the Alvarez hypothesis against the competing volcanic theory, and so he began to study earlier research on impact cratering and shock metamorphism. In this respect, he began to investigate the mineralogy of the various K‐Pg clay layers in the area, using his background in the study of tonsteins. As other research (and controversy) centered on the geochemical signatures in K‐Pg boundary samples, especially the platinum‐group elements, Bruce began a search for mineralogical evidence of an impact. Several attempts to submit grant applications were unsuccessful, but Bruce continued his work, leading to his important 1984 Science paper. In this publication, Bruce and colleagues were the first to report the presence of shock‐metamorphosed quartz grains in samples from the K‐Pg clay layer. It is worth citing from the abstract of this paper: “….A thin claystone layer..[contains]…mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. …. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.” The clarity and succinctness of this finding and how it is conveyed cannot be overstated.

Bruce F. Bohor (1937–2019) (photo at the Meteoritical Society meeting in Chicago, 2000, by D. Jalufka).

The 1984 paper by Bohor and colleagues caused quite some interest in both the mass extinction and impact/planetary (and mineralogy, petrography) communities, with the latter immediately accepting this as convincing evidence that there was a large impact event at the end of the Cretaceous, whereas the former, in their distaste for extraterrestrial explanations, now tried to discredit decades of shock metamorphic studies by claiming that other (internal) geological processes, such as volcanism, can also create shock lamellae. Bruce would not have any of this. He went on to demonstrate the presence of trace amounts of the high‐pressure quartz polymorph stishovite in the K‐Pg layer, and, in a series of subsequent papers, Bruce and colleagues continued to describe shocked mineral grains (quartz, feldspar, chromite, and zircon) and other evidence of an impact in K‐Pg layers from many locations around the globe.

Bruce and Leah Bohor at the Cretaceous–Tertiary boundary in Frontale, Marche Region, Italy, near the Osservatorio Geologico di Coldigioco, and not far from the site in Gubbio where the first evidence for an impact was discovered through geochemical data in 1980, and confirmed by Bruce Bohor by shock metamorphic studies in 1984.

Another important publication was a second Science paper, in 1987, demonstrating the global distribution of the shocked minerals, all in the same coeval layer. His work, with colleagues, on the geographic variations in size of shocked quartz grains in K‐Pg layers of various locations led to the proposal that the geographic variation in the maximum size of shocked quartz grains and the ratio between shocked and unshocked quartz grains suggested that the source crater is on or close to the North American plate, helping to narrow down possible locations of the source crater (which ultimately resulted in the discovery of the Chicxulub impact structure). In addition, the 1987 paper contained data that indicated that the impact was into continental crust rather than oceanic crust as previously proposed, and they that the geochemical evidence for a basaltic target rock was rather the result of a vaporized mafic chondritic projectile forming a major component of the layer, especially at the more distal sites.

In the early 1990s, Bruce and colleagues studied zircons recovered from rocks in the Sudbury impact structure and documented a series of textures that they proposed represent different degrees of shock metamorphism. This sets the stage for using zircon as an impact indicator, and, in addition, they found that the degree of resetting of the U‐Pb isotopic system correlates with the degree of shock metamorphism exhibited by the zircons. This helped to tie shocked zircons from all over the world to the Chicxulub structure and provided further evidence that other features, such as the Manson impact structure in Iowa, can be excluded. For his zircon studies, Bruce developed methods for etching zircons to reveal shock textures⁄features that are still used in such investigations. Further work concerned the distinction between the fireball and the fallout layers, or detailed studies of K‐Pg boundary impact spherules, and where he was able, with his background in clay mineralogy, to provide a better understanding of the postimpact environment and the alteration of impact glasses.

Bruce was born on May 4, 1932 in Chicago, Illinois, to Alexandria and Rudolph Bohor, who both were teachers in the Chicago school system. He received his BS from Beloit College in Wisconsin, his Master's Degree from the University of Indiana, and his PhD from the University of Illinois. As a geologist, he began his career at Conoco in Ponca City, Oklahoma, in the Production Research Division; he then moved to the Illinois State Survey in the Clay Mineral Section and then to the United States Geological Survey in Colorado. For his exceptional achievements in the study of impact processes, he was awarded the Barringer Medal at the Meteoritical Society meeting in Greenwich, UK, in 2011, among other awards and recognitions. After his retirement from the U.S. Geological Survey in 1995, he continued as an emeritus and volunteer at the USGS; during this time, he returned to earlier studies of minerals in both ancient and present‐day Mayan potters in the Yucatan Peninsula of Mexico. He authored or coauthored more than 100 technical publications over his research career. Because of health issues, Bruce discontinued his active research and moved to Green Valley, Arizona in 2010. He is survived by his wife of 36 years, Leah, as well as by four children.

Bruce was a very meticulous scientist, who did not rush work or conclusions, and it is interesting to note that his main research on impacts was done in just a bit more than a decade, yet will have long‐lasting consequences. On a personal note, Bruce (with Leah) came to Vienna as a visiting professor at the University of Vienna in 1995, and even though teaching had not been part of his career before, he engaged very successfully with all our students. Bruce had a very dry but acute sense of humor and being with him always was an experience. We will miss him.

布鲁斯·福布斯·博霍尔（Bruce Forbes Bohor），2011年气象学会Barringer奖章获得者（玻璃，2011年）），于2019年11月17日在他位于亚利桑那州绿谷的家中去世。布鲁斯在我们的社区中以在白垩纪-第三系（K-T，现在称为白垩纪-古近纪）的层中发现石英碎石而闻名。 ，1980年代初在美国中部的边界，紧随Alvarez和《科学》杂志的合著者在1980年发表的著名论文之后，他们报道了地球化学证据表明意大利的K-Pg层对小行星有影响。解释小行星撞击在K-Pg边界的所谓小行星撞击假说在1980年代初引起了很大争议，因为一些研究人员（不受撞击坑或撞击效应等行星过程的了解）曾考虑过其他地球化学信号的解释。

在1980年代初期，布鲁斯（Bruce）正在研究美国西部内陆一些晚白垩世煤矿床的地质情况。特别是，他正在使用tonsteins（改变后的火山灰床）进行日期确定和关联各个煤床。即使他以前没有参与撞击坑或灭绝研究，布鲁斯仍认为他可以尝试根据竞争性火山学理论检验阿尔瓦雷斯假说，因此他开始研究撞击坑和冲击变质的早期研究。在这方面，他开始利用研究tonsteins的背景，开始研究该地区各种K-Pg粘土层的矿物学。当其他研究（和争议）集中于K-Pg边界样品中的地球化学特征，尤其是铂族元素时，布鲁斯开始寻找影响的矿物学证据。科学论文。在本出版物中，布鲁斯及其同事是第一个报告在K-Pg粘土层中的样品中存在变质石英颗粒的报告。值得一提的是本文的摘要：“……薄薄的粘土岩层……包含大部分主要为次长石的石英，其中一些具有平面特征。这些平面特征与石英晶格中特定的晶体学方向有关。…。所有这些矿物学特征都是冲击变质的特征，并且有力的证据表明，受冲击的晶粒是大地外物体与地球之间高速撞击的产物。受到冲击的矿物代表了受射弹冲击而注入平流层的硅质靶材。” 这一发现的清晰和简洁性以及如何传达这一发现不能被夸大。

布鲁斯·布尔（Bruce F. Bohor，1937-2019年）（照片由D. Jalufka在2000年在芝加哥举行的气象学会会议上拍摄）。

Bohor及其同事在1984年发表的论文引起了对生物大灭绝和撞击/行星（以及矿物学，岩相学）界的浓厚兴趣，后者立即接受了这一点，作为有说服力的证据表明白垩纪末期发生了一次重大撞击事件，而前者不愿进行外星人的解释，但现在却声称其他（内部）地质过程（例如火山作用）也可能产生激波片层，从而使数十年的激波变质研究蒙羞。布鲁斯不会有任何这些。他继续论证了K-Pg层中存在痕量的高压石英多晶型辉石，并且在随后的一系列论文中，布鲁斯及其同事继续描述了受冲击的矿物颗粒（石英，长石，铬铁矿，

Bruce和Leah Bohor位于意大利马尔凯地区Frontale的白垩纪-第三纪边界，靠近Osservatorio Geologico di Coldigioco，并且距Gubbio站点不远，1980年通过地球化学数据首次发现了影响的证据，并得到证实由Bruce Bohor在1984年进行的冲击变质研究。

另一个重要的出版物是第二本《科学》1987年的一篇论文，展示了震惊矿物质的全球分布，它们都在同一时期。他与同事一起研究了不同位置的K-Pg层中的冲击石英晶粒尺寸的地理变化，从而提出了这样的建议：建议的冲击石英晶粒最大尺寸的地理变化以及冲击与未冲击石英晶粒之间的比率源陨石坑位于或接近北美板块，从而有助于缩小源陨石坑的可能位置（最终导致了Chicxulub撞击结构的发现）。此外，1987年的论文包含的数据表明，这种影响是进入大陆壳而不是以前提出的洋壳，

在1990年代初期，布鲁斯及其同事研究了从萨德伯里冲击构造中的岩石中回收的锆石，并记录了他们提出的代表不同程度的冲击变质作用的一系列纹理。这为使用锆石作为影响指标奠定了基础，此外，他们还发现U-Pb同位素系统的重置程度与锆石表现出的冲击变质程度相关。这有助于将来自世界各地的震惊锆石与Chicxulub结构联系起来，并提供了进一步的证据，证明可以排除其他特征，例如爱荷华州的曼森撞击结构。在他的锆石研究中，布鲁斯开发了蚀刻锆石的方法，以揭示仍在此类研究中使用的冲击纹理特征。

布鲁斯（Bruce）于1932年5月4日出生于伊利诺伊州芝加哥市，分别是芝加哥学校系统的老师Alexandria和Rudolph Bohor所生。他拥有威斯康星州贝洛伊特学院（Beloit College）的学士学位，印第安纳大学（University of Indiana）的硕士学位和伊利诺伊大学（University of Illinois）的博士学位。作为地质学家，他的职业生涯始于俄克拉荷马州庞卡市康菲科生产研究部。然后，他移至粘土矿产区的伊利诺伊州勘测，然后移至科罗拉多州的美国地质勘测。由于他在影响过程研究方面的杰出成就，他在2011年英国格林威治的气象学会会议上被授予Barringer奖章，以及其他奖项和荣誉。1995年从美国地质调查局退休后，他继续担任USGS的名誉和志愿人员。在此期间，他回到了墨西哥尤卡坦半岛古代和当今玛雅陶器中矿物的早期研究。在他的研究生涯中，他撰写或合着了100多种技术出版物。由于健康问题，布鲁斯（Bruce）停止了他的积极研究，于2010年搬到亚利桑那州的绿谷（Green Valley）。他有36岁的妻子利亚（Leah）和四个孩子，得以幸免。

布鲁斯是一位非常细致的科学家，他并没有着急的工作或得出结论，有趣的是，他对影响的主要研究是在短短十年多的时间内完成的，但将产生长期的影响。就个人而言，布鲁斯（与利亚）于1995年作为维也纳大学的客座教授来到维也纳，尽管以前教学不是他职业的一部分，但他与我们所有的学生取得了非常成功的交往。布鲁斯有着非常干燥但敏锐的幽默感，与他在一起总是一种经历。我们会想念他的。