Terrane accretion forms lithospheric-scale fault systems that commonly experience long and complex slip histories. Unraveling the evolution of these suture zone fault systems yields valuable information regarding the relative importance of various upper crustal structures and their linkage through the lithosphere. We present new bedrock geologic mapping and geochronology data documenting the geologic evolution of reactivated shortening structures and adjacent metamorphic rocks in the Alaska Range suture zone at the inboard margin of the Wrangellia composite terrane in the eastern Alaska Range, Alaska, USA. Detrital zircon uranium-lead (U-Pb) age spectra from metamorphic rocks in our study area reveal two distinct metasedimentary belts. The Maclaren schist occupies the inboard (northern) belt, which was derived from terranes along the western margin of North America during the mid- to Late Cretaceous. In contrast, the Clearwater metasediments occupy the outboard (southern) belt, which was derived from arcs built on the Wrangellia composite terrane during the Late Jurassic to Early Cretaceous. A newly discovered locality of Alaska-type zoned ultramafic bodies within the Clearwater metasediments provides an additional link to the Wrangellia composite terrane. The Maclaren and Clearwater metasedimentary belts are presently juxtaposed by the newly identified Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone, the Late Cretaceous plate boundary that initially brought them together. 40Ar/39Ar mica ages reveal independent post-collisional thermal histories of hanging wall and footwall rocks until reactivation localized on the Valdez Creek fault after ca. 32 Ma. Slip on the Valdez Creek fault expanded into a thrust system that progressed southward to the Broxson Gulch fault at the southern margin of the suture zone and eventually into the Wrangellia terrane. Detrital zircon U-Pb age spectra and clast assemblages from fault-bounded Cenozoic gravel deposits indicate that the thrust system was active during the Oligocene and into the Pliocene, likely as a far-field result of ongoing flat-slab subduction and accretion of the Yakutat microplate. The Valdez Creek fault was the primary reactivated structure in the suture zone, likely due to its linkage with the reactivated boundary zone between the Wrangellia composite terrane and North America in the lithospheric mantle.

中文翻译：

---

美国阿拉斯加南部阿拉斯加山脉缝合带中新世-新近纪岩石圈尺度活化的中生代地层增生结构

地层增生形成岩石圈规模的断层系统，通常经历漫长而复杂的滑移历史。弄清楚这些缝合带断裂系统的演化过程，可以得出有关各种上地壳结构的相对重要性及其通过岩石圈的联系的有价值的信息。我们提供了新的基岩地质制图和地质年代学数据，这些数据记录了美国阿拉斯加山脉东部的兰吉利亚复合地层内侧边缘的阿拉斯加山脉缝合线带中重新活化的缩短构造和邻近的变质岩的地质演化。我们研究区的变质岩碎屑锆石铀-铅（U-Pb）年龄谱揭示了两条截然不同的沉积沉积带。麦克拉伦片岩占据了内侧（北）带，它来自白垩纪中晚期的北美西部边缘的地层。相比之下，克利尔沃特变质沉积物占据了外侧（南部）地带，其源于侏罗纪晚期至白垩纪早期在弗兰吉利亚复合地层上建立的弧形。在克利尔沃特元沉积物中新发现的阿拉斯加型带状超镁铁质岩体的位置提供了与Wrangellia复合地层的额外联系。Maclaren和Clearwater沉积沉积带目前与新近识别的Valdez Creek断层并列，该断层是Valdez Creek剪切带的上地壳活化作用，白垩纪晚期的板块边界最初使它们聚集在一起。40Ar / 39Ar云母年龄揭示了悬壁和底壁岩石的独立碰撞后热史，直到大约在瓦迪兹溪断层重新活化。32 Ma。Valdez Creek断层上的滑动扩展成一个逆冲系统，该系统向南发展到缝合带南缘的Broxson Gulch断层，最后进入Wrangellia地层。碎屑锆石的U-Pb年龄谱和断层界新生代砾石沉积的碎屑组合表明，在渐新世和上新世期间，逆冲系统是活跃的，可能是由于雅库塔特不断平板俯冲和增生的远场结果微孔板。Valdez Creek断层是缝合区的主要活化构造，