3D geological modelling of a complex buried-valley network delineated from borehole and AEM data
3D geological modelling of a complex buried-valley network delineated from borehole and AEM data
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DOI：
10.1016/j.jappgeo.2015.09.004
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发表时间：
2015-11-01
影响因子：
2
通讯作者：
Moller, I.
中科院分区：
文献类型：
--
作者：
Hoyer, A. -S.;Jorgensen, F.;Moller, I.
埋藏隧道谷是前冰川地区的常见特征，在存在的地方，它们对地下水的补给和流动非常重要。因此，对地下水绘图来说，结构的描绘和填充物的建模非常重要。通常情况下，钻孔信息过于稀疏，无法详细描绘结构，而密集覆盖的航空电磁数据已被证明是非常有用的。在过去的几十年中，映射方法已被仔细研究，但山谷结构的三维建模尚未被描述到相同的程度。在这项研究中，我们创建了一个三维地质模型的一个区域，其特点是一个复杂的网络，埋山谷映射与空间密集的航空电磁勘探。由于数据集全面，建模需要制定先进的策略。这包含多个步骤，其中基于地质背景知识对AEM导出的电阻率数据进行初始解释，以识别埋藏的山谷并建立概念地质模型。其次，从河谷的走向及其内部的横切关系建立了河谷之间的时代关系。第三，模拟了深部侵蚀面。随后，解释的年龄关系被用来修剪谷底表面，使得较年轻的山谷切割较老。最后，建立体素模型并填充岩相和地层单元。该模型被构造为组合的基于层和体素的模型，以映射整体结构以及3D模型域内的岩性变化。最终的模型包含20个埋藏的山谷，显示了一个复杂的横切设置，表明存在至少八个山谷代。大多数山谷填充物显示岩性变化，因此最终的体素模型包含42个不同的地质单元。(C)2015作者由爱思唯尔公司出版
Buried tunnel valleys are common features in formerly glaciated areas, and where present, they are very important for the groundwater recharge and flow. Delineation of the structures and modelling of the infill is therefore very important in relation to groundwater mapping. Typically, borehole information is too sparse to enable a detailed delineation of the structures, whereas densely covering airborne electromagnetic data have proven to be very useful for this. In the last decades, the mapping approach has been studied carefully, but the 3D modelling of the valley structures has not been described to the same degree yet. In this study, we create a 3D geological model of an area that is characterised by a complex network of buried valleys mapped with a spatially dense airborne electromagnetic survey. Due to the comprehensive dataset, the modelling requires formulation of an advanced strategy. This contains a number of steps, where the AEM-derived resistivity data are initially interpreted based on the geological background knowledge to identify the buried valleys and build a conceptual geological model. Secondly, the age relationships between the valleys are established from the valley orientations and their internal cross-cut relationships. Thirdly, the deep erosional surfaces are modelled. Subsequently, the interpreted age relationships are utilised to trim the valley floor surfaces, such that younger valleys cut older. Finally, a voxel model is built and populated with lithofacies and stratigraphical units. The model is constructed as a combined layer-based and voxel model in order to map both the overall structures as well as the lithological variations within the 3D model domain. The final model contains 20 buried valleys that show a complex cross-cut setting that indicate the presence of at least eight valley generations. Most of the valley infills show lithological variations, and the final voxel model thus contains 42 different geological units. (C) 2015 The Authors. Published by Elsevier B.V.