Saqqar: A 34 km diameter impact structure in Saudi Arabia
Saqqar: A 34 km diameter impact structure in Saudi Arabia
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萨卡尔：沙特阿拉伯直径 34 公里的撞击结构
DOI：
10.1111/maps.12555
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发表时间：
2015
影响因子：
2.2
通讯作者：
A. S. Neville
中科院分区：
文献类型：
--
作者：
T. Kenkmann;A. Afifi;S. Stewart;M. Poelchau;D. Cook;A. S. Neville
在这里，我们提出了沙特阿拉伯西北部萨卡尔圆形结构撞击起源的第一个证据（Neville 等人），其表观直径为 34 公里，中心位于北纬 29°35′，东经 38°42′。该结构形成于寒武纪-泥盆纪硅质碎屑岩中，并被未变形的白垩纪和古近纪沉积物不整合地覆盖。撞击年龄没有很好的限制，大约在 410 到 70 Ma 之间。地下结构受到二维反射地震剖面和六口钻井的限制。一级构造特征是中央隆起，高出区域基准面约 2 公里，周围环绕着环形向斜。火山口边缘由圆周正断层限定。中央隆起和环向斜分别对应布格重力高点和环形低点。这些井位于中央隆起内，最深超过2公里。这些井的砂岩岩心样本显示出丰富的冲击变质叠印迹象。平面变形特征 (PDF) 的测量方向沿 (0001)、{10 1´ 3}，但较少沿 {10 1´ 1} 和 {10 1´ 4} 测量。平面断裂 (PF) 主要沿 (0001) 和 {10 1´ 1} 发生，并且局部与羽毛特征 (FF) 相关。此外，还发现了一些冲击长石颗粒和强烈变形的云母片。记录的冲击压力范围在 5 至 15 GPa 之间。保留下来的激波水平和没有异地陨石坑填充表明萨卡尔在泥盆纪和马斯特里赫特阶之间被侵蚀了 1-2 公里。明确的冲击特征的记录证明了萨卡尔结构是由超高速撞击事件形成的。
Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al. ), with an apparent diameter of 34 km, centered at 29°35′N, 38°42′E. The structure is formed in Cambrian–Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2‐D reflection seismic profiles and six drilled wells. First‐order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring‐like low, respectively. The wells were drilled within the central uplift, the deepest among them exceed 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {10 1¯ 3}, and less frequently along {10 1¯ 1} and {10 1¯ 4}. Planar fractures (PFs) predominantly occur along (0001) and {10 1¯ 1}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1–2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.
MEMIN 研究单位：实验撞击坑
影响因子：
2.2
作者：
Kenkmann T;Deutsch A;Thoma K.;Poelchau M.H.
通讯作者：
Poelchau M.H.