Origin and significance of intra-basement seismic reflections offshore western Norway

We use 3D seismic data to image a series of enigmatic, SW-dipping reflection packets within pre-Mesozoic crystalline basement offshore western Norway. Based on their low-angle dip and complex reflection wave-train our preferred interpretation is that the reflection packets are the seismic expression of mylonitic zones generated by nappe emplacement during the Caledonian orogeny. Late Jurassic faults truncate and offset these reflection packets by several hundred metres, suggesting that these faults did not exploit pre-existing basement weaknesses. Our observations suggest that older basement fabrics may not always play a significant role in determining the geometry of later fault systems.

本研究采用三维地震数据，对挪威西部近海前中生代结晶基底内部一系列产状向南西倾的谜样反射波组进行成像处理。基于其低角度倾角与复杂的反射波列特征，本研究倾向的解释为：该反射波组是加里东造山运动期间推覆体就位作用形成的糜棱岩带的地震响应。晚侏罗世断层将这些反射波组截断并错动数百米，表明此类断层并未利用先期存在的基底薄弱带。本研究观测结果显示，古老的基底构造组构未必总能在控制后期断层系统的几何形态中发挥显著作用。