A Refined Age for the Manson Impact Structure by Means of Detailed 40Ar/39Ar Thermochronology of Shocked Microclines

这项研究的目的是重新评估 曼森撞击构造，被认为是 一颗大的小行星或彗星撞击地球的地点， 在100万年前， 在这个星球上的经历。 重要的是， 如果曼森结构的年龄相同， 与其他被提名为对2004年12月12日发生的事件负责的撞击地点一样， 白垩纪/第三纪（K/T）界线，如果曼森和其他 撞击地点的年龄与古生物学定义的 岩石记录中的边界。 到目前为止，唯一的日期 对曼森结构的研究来自于 40 Ar/39 Ar定年方法， 是从地下室岩石中取出的 本身 海流回收熔融玻璃的新测年 曼森油田的钻探计划可能会提供额外的年龄 估计，但进一步分析震惊的晶石提供至少 作为一种有前途的手段，提高精度和准确性， 对曼森长石的年代进行了分析和解释， 应该可以把年龄的精确度和准确度 曼森结构。 目前，这一年龄估计为65.7+1 MA. 随着当前长石技术的应用， 分析和解释，应该有可能带来 精度达到~0.2 Ma或更高;初步“热年代学” 对先前公布的数据的分析也表明， 可能的年龄实际上至少是70万岁。降低，把年龄 曼森撞击器的撞击速度更接近K/T边界的估计值 和加勒比海的撞击物大约64.7 Ma。 额外的好处 通过对曼森遗址辉长岩的详细热年代学分析 将包括了解如何健全的年龄估计， 这些桅杆实际上是，也是对后- 撞击点的撞击热历史。

The object of this study is to reevaluate the dating of the Manson Impact Structure, which has been suggested to be one of the sites where a large asteroid or comet struck the earth some 65 million years ago, causing one of the larger mass extinctions experienced on this planet. It is important to determine with the best possible resolution if the Manson structure is the same age as other impact sites nominated to be responsible for events at the Cretaceous/Tertiary (K/T) boundary, and if Manson and the other impact sites are the same age as the paleontologically defined boundary seen in the rock record. Up to this point, the only date on the Manson structure has come from innovative application of the 40Ar/39Ar dating method to samples of partially reset feldspars which were taken from the basement rock shocked and heated by the impact itself. New dating of melt glasses recovered by the current drilling program at the Manson site may provide an additional age estimate, but further analysis of shocked feldspars offers at least as promising a means of improving the precision and accuracy of the age of the Manson of feldspar analysis and interpretation, it should be possible to bring the precision and accuracy of the age of the Manson structure. Currently, this age estimate is 65.7+1 Ma. With the application of current techniques of feldspar analysis and interpretation, it should be possible to bring the precision to ~0.2 Ma or better; preliminary "thermochronological" analysis of previously published data also suggests that the most likely age may actually be at least 0.7 m.y. lower, putting the age of the Manson impactor much closer to estimates of the K/T boundary and the Caribbean impactor of some 64.7 Ma. Additional benefits from careful thermochronological analysis of Manson-site feldspars will include an understanding of how robust age estimates from these feldspars actually are, and also, a constraint on the post- impact thermal history of the impact site.