A Paleomagnetic Assessment of Footwall Tilting During Large Magnitude Extensional Deformation: A Case Study of the Miocene South Mountains Metamorphic Core Complex.

许多大规模地壳伸展的地区，如美国西部的盆地和山脉省，暴露出了倾角非常浅的非活动拆离断裂面（100度）。然而，对当今世界各地地震的断层面分析表明，具有如此浅倾角的断层通常不具有地震活动性。因此，对于这些断裂在起源时的原始倾角问题，存在着很大的争议。该项目将测试以下假设：(1)断层起源于100度或更小的倾角，并保持在该方向上；(2)断层起源于300度至600度的倾角，随后发生倾斜。对亚利桑那州南山一个这样的剥离断层下盘的选定岩石单元的古地磁分析将提供测试。研究结果对大面积伸展大陆地壳的构造演化具有重要意义。

Many areas of large-scale crustal extension, such as the Basin and Range province of western USA, have exposed inactive detachment fault surfaces with very shallow dips (10o). However, fault-plane analysis of present-day earthquakes worldwide shows that faults with such shallow dips are not usually seismically active. Thus much controversy has arisen over the original angle of dip of these faults at their initiation. This project will test the hypotheses that (1) the faults initiated at dips of 10o or less and remained in t hat orientation, and (2) they initiated at dips of 30o to 60o and were subsequently tilted. Paleomagnetic analysis of selected rock units from the footwall of one such detachment fault in South Mountains, Arizona, will provide the test. The results will have substantial significance for the tectonic evolution of large areas of extended continental crust.