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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Shallow-marine impact origin of the Wetumpka structure (Alabama, USA)
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Shallow-marine impact origin of the Wetumpka structure (Alabama, USA)

机译：Wetumpka结构的浅海冲击起源（美国阿拉巴马州）

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摘要

The Wetumpka structure, an arcuate, 7.6 km diameter, rimmed feature of the inner Coastal Plain, Alabama, is a Late Cretaceous shallow-marine impact crater. In this paper, we show unequivocal evidence of Wetumpka's impact origin. Within and about this structure, pre-existing Upper Cretaceous stratigraphy was resedimented and(or) deformed, thus creating distinctive intra-structure and extra-structure terrains. These terrains are located, respectively, within Wetumpka's crystalline-rim terrain and adjacent to the structure on the southern side. Core drilling near the structure's geographic center revealed that Wetumpka's basin-filling sequence has two distinctive units, suggestive of a two-stage filling process consisting of (1) fall-back plus resurge followed by (2) a later secondary seawater resurge event. Wetumpka's lower subsurface unit includes polymict impact breccias, which contain quartz grains displaying shock-characteristic multiple sets of planar deformation features. Selected subsurface samples of this breccia also contain elevated Ir, Co, Ni and Cr concentrations indicative of a minor extraterrestrial component.
机译：阿拉巴马州内沿海平原的弧形，直径为7.6公里的弧形特征的Wetumpka结构是晚白垩纪浅海撞击坑。在本文中，我们明确表明了Wetumpka的影响起源。在该结构内部及其周围，对原有白垩纪上地层进行了重新沉积和（或）变形，从而形成了独特的内部构造和外部构造地形。这些地形分别位于Wetumpka的晶体边缘地形内，并与南侧的结构相邻。在该结构的地理中心附近进行的岩心钻探表明，Wetumpka的盆地充填序列具有两个独特的单元，这暗示了一个两阶段充填过程，该过程包括（1）后退加反冲，然后（2）随后的二次海水反冲事件。 Wetumpka的下部地下单元包括多晶撞击角砾岩，其中包含石英粒，这些石英粒显示出具有冲击特征的多组平面变形特征。角砾岩的部分地下样品还含有较高的Ir，Co，Ni和Cr浓度，这表明少量的地球外成分。

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