"False peak" creation in the Flynn Creek marine target impact crater
"False peak" creation in the Flynn Creek marine target impact crater
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DOI：
10.1111/maps.13822
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发表时间：
2022-05-19
影响因子：
2.2
通讯作者：
Collins, G. S.
中科院分区：
文献类型：
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作者：
Bray, V. J.;Hagerty, J. J.;Collins, G. S.
已知对海洋目标的影响会产生异常的火山口形态。我们研究了使用ISALE氢码的直径与4 km直径的Flynn Creek海洋目标冲击器相似的形成。我们将仿真结果与地形概况，矿物压力指标和角砾岩测序进行比较，以确定撞击时最可能的海底（类似于360 MA，田纳西州，美国）：700-800 m。由中央峰形成的冲击和机理产生的峰值冲击压力都随海深度而异。弗林克里克的大中央土墩本来可以以三种不同的方式生产，所有这些都需要海洋存在：（1）作为地面流的一部分到达火山口中心的相对凝聚力的边缘塌陷沉积物，并放在现有的火山口层的顶部； （2）流离失所的混乱恢复与沉积在火山口中心的返回海洋； （3）通过从深海中消除上层压力来促进的大隆起。这些机制中的前两个创建了“假峰”，其中高震振荡的材料和原始火山口地板被埋在相对较低的冲击材料以下。我们的模拟表明，对海洋冲击地点进行钻探可能需要比预期的钻头更深，因此可以访问任何高压矿物学指控者。
Impacts into marine targets are known to create abnormal crater morphologies. We investigate the formation of the similar to 4 km diameter Flynn Creek marine target impact crater using the iSALE hydrocode. We compare simulation results to topographic profiles, mineral pressure indicators, and breccia sequencing from drill cores to determine the most likely sea depth at this location at the time of impact (similar to 360 Ma, Tennessee, USA): 700-800 m. Both the peak shock pressure produced by the impact and the mechanism(s) of central peak formation differ with sea depth. The large central mound of Flynn Creek could have been produced in three distinct ways, all requiring the presence of an ocean: (1) a relatively cohesive rim collapse deposit that reached the crater center as part of a ground flow and came to rest on top of the existing crater stratigraphy; (2) chaotic resurge of ejecta with the returning ocean that deposited at the crater center; (3) large uplift facilitated by the removal of overburden pressure from a deep ocean. The first two of these mechanisms create "false peaks" in which high-shock uplifted material and original crater floor are buried beneath > 200 m of relatively low shock material. Our simulations suggest that drilling of marine impact sites might require deeper than expected drill cores, so that any high-pressure mineralogical indictors at depth can be accessed.