Along-Strike Variation of the Uplift and Exhumation of the Pyrenean Orogen: Constraining the Evolution of an Intraplate Collisional Orogen

西班牙和法国的比利牛斯山脉为研究与板内造山系统形成有关的基本构造过程提供了一个极好的自然实验室。比利牛斯造山带形成于大约8000万年前伊比利亚板块和欧洲板块之间的大陆-大陆融合的结果。在比利牛斯山脉中部，由于辐合作用导致的缩短最初被容纳在辐合之前形成的残余伸展构造上，当时该地区是一个伸展盆地。当残余的伸展构造不能再适应缩短时，逆冲断层上的运动承担了变形，导致叠置反形式推覆体的形成。板块重建和平衡剖面显示西向变形年轻，西向辐合量减少，山脉构造变化较大。本项目采用中低温热年代学方法，对比利牛斯山脉内岩石的时温历史变化进行了研究。利用磷灰石裂变径迹热年代学、磷灰石铀-钍-氦测年和钾长石氩-氩分析对比利牛斯山脉中部和西部花岗岩块体的热蚀史和剥蚀史进行了横向（南北走向）和顺向（东西走向）变化。剥蚀史的变化被用来评估汇聚/逆冲的开始与隆升和侵蚀是同步的还是历时的，剥蚀是否在西部发生，剥蚀量是否向西减少，以及沿范围的横向剥蚀模式是对称的还是不对称的。这些结果被用来量化比利牛斯大陆碰撞造山带的四维演化，并评估与板内造山带系统形成有关的过程。这项研究的结果引起了许多研究造山系统的地球科学家的兴趣，包括热年代学家、构造学家、地球动力学家、反射地震学家、沉积学家和盆地分析学家。基金为博士后研究助理和本科生提供研究培训和教育。该项目的实地和实验室组成部分促进了研究与教学活动的整合。通过促进包括实地考察、项目讨论和共享分析设施在内的访问，与西班牙同事的合作加强了国际科学合作和教育培训。

The Pyrenean Mountains of Spain and France provide an excellent natural laboratory to study fundamental tectonic processes involved in the formation of intraplate orogenic systems. The Pyrnenean Orogen formed as a result of continent-continent convergence between the Iberian plate and the European Plate, beginning ~80 million years ago. In the central Pyrenees, shortening due to convergence was initially accommodated on relict extensional structures, formed prior to convergence, when the region was an extensional basin. When relict extensional structures could no longer accommodate shortening, deformation was taken up by movement on thrust faults that led to the formation of stacked antiformal nappes. Plate reconstructions and balanced cross-sections indicate deformation youngs to the west, the amount of convergence decreases to the west and the structure of the mountain range varies considerably. This project uses low to medium temperature thermochronologic methods to constrain the variation in the time-temperature history of rocks within the Pyrenean mountain belt. The across-strike (north-south trend) and along-strike (east-west trend) variation in the thermal, and denudation history of the orogen are being constrained using apatite fission track thermochronology, apatite Uranium-Thorium-Helium dating and Argon-Argon analysis of potassium feldspars on selected granite massifs from the central and western Pyrenees. The variation in the denudation history is being used to assess whether the onset of convergence/thrusting is synchronous or diachronous with uplift and erosion, whether denudation youngs to the west, if the amount of denudation decreases westward, and if the across-strike denudation pattern is symmetric or asymmetric along the range. These results are being used to quantify the four dimensional evolution of the Pyrenean continental collisional orogen and to evaluate processes associated with the formation of intraplate orogenic systems. The outcome of this research is of interest to a wide range of earth scientists who study orogenic systems, including thermochronologists, tectonicians, geodynamicists, reflection seismologists, sedimentologists and basin analysts. Funding provides research training and education for a postdoctoral research associate and undergraduate students. Field and lab based components of this project promote integration of research with teaching activities. Collaboration with Spanish colleagues enhances international scientific cooperation and educational training, by facilitating visits that include fieldwork, project discussions, and shared use of analytical facilities.