Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters
Seismic Reflection Data Reveal the 3D Subsurface Structure of Pit Craters
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DOI：
10.1029/2021je007155
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
C. Magee;C. Kling;P. Byrne;C. Jackson
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文献类型：
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作者：
C. Magee;C. Kling;P. Byrne;C. Jackson
坑坑是在岩石和冰冷的行星体以及许多小行星上观察到的准圆形洼地。坑坑被认为是由覆盖层塌陷成地下空洞或体积枯竭区而形成的。重要的是，坑坑的表面尺寸和分布可能为其他难以接近的地下过程提供重要记录。然而，由于我们无法进入许多行星体的地下，我们依靠物理和数值模型来推断与坑坑形成有关的过程。在这里，我们使用三维地震反射数据来量化澳大利亚西北部近海沉积盆地内埋藏深度约3公里的59个晚侏罗世深坑的古地表和地下几何形状。坑坑是典型的漏斗状，上面有一个倒锥形的部分，下面有一个管道。坑坑深度，即倒锥部分的高度，与它们的平面视图长度相关，与其他地方的坑坑观测一致；这一趋势由于后来的沉积物填充而变得不那么明显。我们第一次展示了一些坑坑管道连接到下面的火成岩岩脉或陡峭的倾斜，可能是正常断层的扩张部分。虽然有些坑坑可能是断裂形成的，有些坑坑可能是岩理作用形成的，但不能根据其表面表现进行区分。我们的数据还表明，坑坑的大小可能与宿主材料的机械性能无关。总之，我们得出的结论是，地球和其他行星体上坑坑的表面表达可能不能诊断地下过程或性质。
Pit craters are quasi‐circular depressions observed on rocky and icy planetary bodies, as well as numerous asteroids. Pit craters are thought to form by overburden collapse into a subsurface cavity or volumetrically depleted zone. Importantly, the surface size and distribution of pit craters may provide an important record of otherwise inaccessible subsurface processes. However, because we cannot access the subsurface of many planetary bodies, we rely on physical and numerical models to infer processes linked to pit crater formation. Here, we use 3D seismic reflection data to quantify the palaeosurface and subsurface geometry of 59 Late Jurassic pit craters buried to depths of ∼3 km within a sedimentary basin, offshore NW Australia. The pit craters are typically funnel‐like, with an inverted conical upper section underlain by a pipe. Pit crater depths, that is, the height of inverted cone sections, correlate with their plan‐view length, consistent with observations of pit craters elsewhere; this trend is rendered less apparent by later sediment‐infilling. For the first time, we show some pit crater pipes connect to underlying igneous dikes or steeply dipping, likely dilatational portions of normal faults. Although some pit craters seemed to have formed due to faulting and others to dyking, they cannot be differentiated based on their surface expression. Our data also suggest pit crater size may not relate to the mechanical properties of the host material. Overall, we conclude that the surface expression of pit craters on Earth and other planetary bodies may not be diagnostic of subsurface processes or properties.