Collaborative Research: Processes Driving Rock Uplift and Flexural Deformation following Convergent Tectonics: The Fluvial Terrace Record, Ebro Basin, Spain

刘易斯0088714麦克唐纳0088601建立岩石隆起与长期模式和远离板块边缘的河流切割速率之间的动态联系，是当代构造地貌学的主要挑战。我们正在参与一个多方面的项目，解决在地壳活动缩短后山区地形和河流系统如何演变的基本问题。西班牙比利牛斯山脉和邻近的埃布罗盆地是隔离造山带岩石隆起(或下沉)过程的绝佳地点，在那里，活跃的挤压和地壳增厚已经停止。埃布罗盆地的一个显着特征是约2500万年前沉积岩中的溪流切割发生了显着变化。沿盆地轴线切割最小，但在比利牛斯山中南部超过1000米。我们的数据表明，埃布罗盆地两侧山脉河流切割的长期模式和速率是由板内现象驱动的，这形成了我们正在测试的三个相互竞争的假说：该地区的河流切割是对以下一种或多种机制做出反应：(1)对造山带和邻近前陆盆地的物质搬走做出均衡反应的岩石隆起；(2)由热的、可浮的软流圈上涌驱动的岩石隆起，可能与邻近的活跃地壳伸展和火山作用有关；(3)区域基准平面下降，可能与梅西纪盐度危机、第四纪海平面变化或两者都有关。我们正在开发埃布罗盆地选定河流阶地的精确年代地层学(基于放射性碳、发光和宇宙成因核素测年和土壤)，可以重建河流切割的空间和时间速率。结果将被用来为在地壳活动增厚已经停止的造山带中驱动岩石隆起(或下沉)的过程生成一个概念模型。我们的多学科方法需要在构造地质学、土壤地层学、地质年代学、构造地貌学、地球动力学建模和区域地质学方面的专业知识。我们把重点放在比利牛斯山中部，但我们的方法直接适用于世界各地的现代和古代山脉。

Lewis 0088714McDonald 0088601Establishing dynamic links between rock uplift and long-term patterns and rates of fluvial incision away from plate margins is a major contemporary challenge in tectonic geomorphology. We are engaged in a multifaceted project that addresses fundamental questions about how mountainous topography and fluvial systems evolve following active crustal shortening. The Spanish Pyrenees and adjacent Ebro Basin comprise an outstanding locality for isolating processes that drive rock-uplift (or subsidence) in orogens where active compression and crustal thickening have ceased. A marked feature of the Ebro Basin is the striking variation in stream incision into ~25 million year old sedimentary rocks. Incision is minimal along the axis of the basin, but reaches more than 1000 m in the south-central Pyrenees. Our data suggest that long-term patterns and rates of fluvial incision in ranges flanking the Ebro Basin are driven by intraplate phenomena, which form the three competing hypotheses we are testing: Streams in this region incise in response to one, or more, of the following mechanisms: (1) rock uplift by isostatic response to removal of mass from the orogen and adjacent foreland basin; (2) rock uplift driven by upwelling of hot, buoyant asthenosphere perhaps related to adjacent, active crustal extension and volcanism; (3) regional base level lowering, perhaps related to the Messinian salinity crisis, Quaternary eustatic sea level changes, or both. We are developing a precise chronostratigraphy (based on radiocarbon, luminescence, and cosmogenic nuclide dating and soils) of selected stream terraces in the Ebro Basin for which spatial and temporal rates of fluvial incision can be reconstructed. Results will be used to generate a conceptual model for the processes that drive rock-uplift (or subsidence) in orogens where active crustal thickening has ceased. Our multidisciplinary approach requires expertise in structural geology, soil stratigraphy, geochronology, tectonic geomorphology, geodynamic modeling, and regional geology. We focus on the central Pyrenees for this work, but our methodology has direct application to both modern and ancient mountain ranges throughout the world.