Abstract Extension is a key process controlling the post-orogenic exhumation of metamorphic rocks in subduction and collision zones. Previous studies have largely focused on the mechanics of localized core-complex style post-orogenic extension and the large-scale effects of various internal (e.g. rheology) and external (e.g. plate motions) parameters on the mode of extension. However, many regions on earth underwent rock exhumation during post-orogenic extension, which is characterized by distributed rather than localized deformation. We explore conditions of distributed deformation as illustrated by the Pelagonian unit in the Aegean subduction system. In particular, we explore the influence of structural inheritance related to the pre-extension shortening and mechanical stratigraphy on the localization of extension on the scale of the upper crust through detailed structural analysis on the islands of Skiathos and Skopelos. Additionally, the time frame of deformation has been established by 40Ar/39Ar dating of key shear zones. Shortening on the islands predominantly took place by ductile top-SW thrusting under low-grade metamorphic conditions, localized in weak calcite marble layers within the Upper Cretaceous and Upper Triassic carbonates at ~55 Ma. We show that the presence of shallow decoupling levels in the upper crust resulted in the formation of thin (several 100 m thick) thrust sheets that are defined for the first time on Skiathos. The Early Paleogene accretion of the Pelagonian upper crust to the upper plate (Eurasia/Rhodopia) was followed by the extensional inversion of the nappe stack. Extension was accommodated by opposite-sense, generally top-NE, ductile to brittle shearing, which localized at inherited heterogeneities such as reverse-sense shear zones and stratigraphic contacts at around 35 Ma, as suggested by our 40Ar/39Ar age spectra. The dense network of such northerly-dipping, inherited weakness zones resulted in a highly distributed pattern of extensional deformation dominated by layer-parallel shearing. We argue that the distribution of crustal heterogeneities substantially influences the style of post-orogenic extension.

中文翻译：

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大陆上地壳埋藏和挖掘过程中的应变定位：来自北斯波拉德斯的案例研究（希腊Pelagonian 逆冲床）

摘要 伸展是控制俯冲碰撞带变质岩造山后折返的关键过程。以前的研究主要集中在局部核心复杂型后造山运动的力学和各种内部（例如流变学）和外部（例如板块运动）参数对伸展模式的大规模影响上。然而，地球上许多地区在造山后伸展过程中经历了岩石折返，其特征是分布而不是局部变形。我们探索了分布变形的条件，如爱琴海俯冲系统中的 Pelagonian 单元所示。特别是，我们通过对斯基亚索斯岛和斯科派洛斯岛的详细构造分析，探讨了与伸展前缩短和机械地层相关的构造继承对上地壳尺度伸展定位的影响。此外，变形的时间框架已通过关键剪切带的 40Ar/39Ar 测年确定。岛屿上的缩短主要是在低等级变质条件下通过韧性顶部西南逆冲推力发生的，位于上白垩统和上三叠统碳酸盐岩中约 55 Ma 的弱方解石大理岩层中。我们表明，上地壳中浅层解耦层的存在导致了在斯基亚索斯岛首次定义的薄（几个 100 m 厚）逆冲片的形成。Pelagonian 上地壳的早古近纪增生到上板块（欧亚大陆/Rhodopia）之后是推覆叠层的伸展反转。正如我们的 40Ar/39Ar 年龄谱所表明的那样，延伸是由相反方向的，通常是顶部 NE，韧性到脆性剪切所适应的，这些剪切位于继承的异质性，例如 35 Ma 左右的反向剪切带和地层接触。这种向北倾斜的、继承性弱区的密集网络导致了高度分布的拉伸变形模式，以层平行剪切为主。我们认为，地壳非均质性的分布对造山后伸展的类型有重大影响。如我们的 40Ar/39Ar 年龄谱所示，通常是顶部 NE，韧性到脆性剪切，其位于遗传的不均匀性，例如 35 Ma 左右的反向剪切带和地层接触。这种向北倾斜的、继承性弱区的密集网络导致了高度分布的拉伸变形模式，以层平行剪切为主。我们认为，地壳非均质性的分布对造山后扩张的类型有重大影响。如我们的 40Ar/39Ar 年龄谱所示，通常是顶部 NE，韧性到脆性剪切，其位于遗传的不均匀性，例如 35 Ma 左右的反向剪切带和地层接触。这种向北倾斜的、继承性弱区的密集网络导致了高度分布的拉伸变形模式，以层平行剪切为主。我们认为，地壳非均质性的分布对造山后扩张的类型有重大影响。继承的薄弱区导致高度分布的拉伸变形模式，以层平行剪切为主。我们认为，地壳非均质性的分布对造山后扩张的类型有重大影响。继承的薄弱区导致高度分布的拉伸变形模式，以层平行剪切为主。我们认为，地壳非均质性的分布对造山后伸展的类型有重大影响。