Mid-sized complex crater formation in mixed crystalline-sedimentary targets: Insight from modeling and observation
Mid-sized complex crater formation in mixed crystalline-sedimentary targets: Insight from modeling and observation
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DOI：
10.1111/j.1945-5100.2008.tb00655.x
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发表时间：
2008-12-01
影响因子：
2.2
通讯作者：
Wuennemann, K.
中科院分区：
文献类型：
--
作者：
Collins, G. S.;Kenkmann, T.;Wuennemann, K.
大型撞击坑的形成是一种重要的地质作用，但至今尚未完全认识。目前关于撞击坑形成的范例是以石油模型和对均质目标的撞击观察为基础的。真实的目标很少是均匀的;例如，地球表面的大部分被沉积岩和/或水层覆盖。在太阳系天体中普遍存在的分层使得了解目标属性对陨石坑形成过程的影响非常重要。为了进一步了解陨石坑塌陷的机制以及目标特性变化对石油陨石坑形成的影响，第一次“弥合差距”讲习班建议，地质观测和数值模拟应侧重于中等大小（直径15-30公里）的石油陨石坑。它们大到足以复杂;小到足以以高分辨率进行测绘、测量和建模;数量多到足以将目标推进剂的影响与其他变量的影响分开。本文对德国的里斯、加拿大的豪顿和俄罗斯的埃尔吉格特金三个直径为18-26公里、形成于不同目标岩性的陨石坑的观测和数值模型进行了比较。基于一阶假设，即撞击能量在所有三次撞击中是相同的，我们对每个撞击坑进行了数值模拟，以构建一个简单的定量模型，用于在陆上混合晶体沉积目标中形成中型复杂撞击坑。我们将我们的结果与里斯和豪顿的解释地质剖面进行了比较，这些地质剖面是基于详细的新的和已出版的地质制图以及已出版的地球物理调查。我们的观测和数值模拟工作表明，每个陨石坑之间的主要结构差异可以用每种情况下撞击前沉积覆盖层的厚度差异来解释。我们的结论是，在里斯，而不是在豪顿的内环的存在，是因为比上覆沉积物更强的基底岩石足够接近地表，它们在挖掘过程中被抬升和翻转，并在修改和撞击后的侵蚀后保持为所有抬升的环。对于恒定的冲击能量，瞬态和最终的弹坑直径随沉积物厚度的增加而增加。
Large impact crater formation is all important geologic process that is not fully understood. The current paradigm for impact crater formation is based oil models and observations of impacts in homogeneous targets. Real targets are rarely uniform; for example, the majority of Earth's surface is covered by sedimentary rocks and/or a water layer. The ubiquity of layering across solar system bodies makes it important to understand the effect target properties have on the cratering process. To advance understanding of the mechanics of crater collapse, and the effect of variations in target properties oil crater formation, the first "Bridging the Gap" workshop recommended that geological observation and numerical modeling focussed oil mid-sized (15-30 km diameter) craters oil Earth. These are large enough to be complex; small enough to be mapped, Surveyed and modelled at high resolution; and numerous enough for the effects of target propel-ties to be potentially disentangled from the effects of other variables. In this paper, we compare observations and numerical models of three 18-26 km diameter craters Formed in different target lithology: Ries, Germany; Haughton, Canada; and El'gygytgyn, Russia. Based oil the first-order assumption that the impact energy was the same in all three impacts we performed numerical simulations of each crater to construct a simple quantitative model for mid-sized complex crater formation in a subaerial, mixed crystalline-sedimentary target. We compared our results with interpreted geological profiles of Ries and Haughton, based on detailed new and published geological mapping and published geophysical surveys. Our combined observational and numerical modeling work suggests that the major structural differences between each crater can be explained by the difference in thickness of the pre-impact sedimentary cover in each case. We conclude that the presence of an inner ring at Ries, and not at Haughton, is because basement rocks that are stronger than the overlying sediments are sufficiently close to the surface that they are uplifted and overturned during excavation and remain as all uplifted ring after modification and post-impact erosion. For constant impact energy, transient and final crater diameters increase with increasing sediment thickness.