COLLABORATIVE RESEARCH: St. Elias Erosion/tectonics Project (STEEP)

这是一项多学科研究，旨在研究地球上最高的沿海山脉——阿拉斯加南部和加拿大西北部的圣埃利亚斯山脉的演变。这个造山带在过去的几百万年里随着雅库塔地块（一个大陆-海洋地体）试图俯冲到阿留申弧-海沟体系的东端而形成。约500公里长，150公里宽的圣埃利亚斯山脉是由地壳收敛引起的快速隆起和由大型快速移动的温带冰川区域系统引起的快速发掘之间动态平衡的产物。大多数沉积物要么沉积在广阔的大陆架上，要么沉积在深海扇中，并提供了伴随造山运动的构造、气候、侵蚀和起伏事件的完整记录。该项目的首要目标是为圣埃利亚斯造山带建立一个综合模型，该模型考虑了区域板块构造过程、构造发育和快速侵蚀的相互作用。研究的重点是从上地幔流动到近地表断裂和掘出的系统内部变形划分。该研究将在一系列条件下调查斜碰撞的地球动力学，这将使pi能够解决几个重要和基本的问题：-强烈的第四纪冰川侵蚀是否足以改变造山带中的物质重新分布，以改变区域变形模式，以及沿深冰川山谷的集中侵蚀是否足以确定局部地壳应力？-变形是如何划分为岩石圈缩短和隆起与分离地壳的侧向挤压，强烈的侵蚀是否影响这种划分？-造山运动主要是由浮力海洋高原的俯冲作用驱动的，还是由附着在异域海洋地壳上的小微大陆块的碰撞驱动的？解决这些问题对于理解斜向碰撞的地球动力学、不同机制在远场造山效应发展中的作用、以及斜向辐合过程中侵蚀对滑动分区发展的控制具有广泛的意义。该项目还对小型大陆地体与海洋高原的俯冲/增生如何导致大陆的变形，以及这些碎片在构造地壳拼贴中的最终命运（这是几乎所有大陆的典型特征）具有一般意义。具体来说，P.I.s提出了一种涉及地震学家（地下成像和地震活动）、地质学家、测地线学家、冰川学家、地质年代学家和地球动力学建模师的多学科方法。

0409884HalletThis is a multi-disciplinary study to address the evolution of the highest coastal mountain range on Earth - the St. Elias Mountains of southern Alaska and northwestern Canada. This orogen has developed over the past few million years as the Yakutat block, a continental-oceanic terrane, has attempted subduction beneath the eastern end of the Aleutian arc-trench system. The ~500 km-long, 150 km-wide St. Elias mountain range is the product of the dynamic balance between rapid uplift induced by crustal convergence and rapid exhumation by a regional system of large, fast-moving temperate glaciers. Most sediments are deposited either on a broad shelf or in deepsea fans and provide a complete record of the tectonic, climatic, erosional, and eustatic events that have accompanied the orogeny. The overarching goal of the project is to develop a comprehensive model for the St. Elias orogen that accounts for the interaction of regional plate tectonic processes, structural development, and rapid erosion. The focus of the study is on the partitioning of deformation within the system from upper mantle flow to near-surface faulting and exhumation. The study will investigate the geodynamics of oblique collision under a set of conditions that will allow the PIs to address several important and fundamental questions:- Has intense Quaternary glacial erosion redistributed mass in the orogen sufficiently to change regional deformational patterns, and has focused erosion along deep glacial valleys been sufficient to localize crustal strains?- How is deformation partitioned into lithospheric shortening and uplift versus lateral extrusion of the detached crust, and does intense erosion influence this partitioning?- Is the orogeny driven primarily by subduction of a buoyant oceanic plateau or by collision of a small microcontinental block attached to allochthonous ocean crust?Addressing these questions has broad implications for understanding the geodynamics of oblique collision in general, the role of different mechanisms in development of far-field orogenic effects, and the control of erosion on development of slip partitioning during oblique convergence. The project also has general implications for how subduction/accretion of small continental terranes versus oceanic plateaus contribute to deformation of the continents, and ultimately the fate of these fragments in construction of the crustal collage which is typical of virtually all continents. Specifically, the P.I.s propose a multidisciplinary approach involving seismologists (subsurface imaging and seismicity), geologists, geodesists, glaciologists, geochronologists, and geodynamic modelers.