Collaborative Research: ST. Elias Erosion/tectonics Project (STEEP)

这是一项多学科的研究，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化。这个造山带是在过去的几百万年里随着雅库塔地块的形成而形成的，雅库塔地块是一个大陆-海洋地体，它试图俯冲到阿留申弧沟系统东端的下方。约500公里长、150公里宽的圣埃利亚斯山脉是地壳汇聚引起的快速隆升与大型快速移动的温带冰川区域系统快速折返之间动态平衡的产物。大多数沉积物要么沉积在宽阔的陆架上，要么沉积在深海扇体中，并提供了伴随造山作用的构造、气候、侵蚀和海平面事件的完整记录。该项目的总体目标是为圣埃利亚斯造山带开发一个综合模型，该模型考虑了区域板块构造过程、构造发展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折返的系统内变形的分配。这项研究将在一系列条件下研究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的区域变形模式，以及沿深冰川山谷的集中侵蚀是否足以定位地壳应变？-变形是如何划分为岩石圈缩短和抬升与分离地壳的侧向挤压，强烈侵蚀是否影响这种划分？造山作用主要是由浮力大洋高原的俯冲驱动的，还是由附着在异地洋壳上的小型微大陆块体的碰撞驱动的？解决这些问题对于总体上理解斜碰撞的地球动力学具有广泛的意义。不同机制在远场造山作用发展中的作用，以及斜向收敛过程中侵蚀对滑移分配发展的控制作用。该项目还对小型大陆地体相对于海洋高原的俯冲/吸积如何促进大陆变形，以及这些碎片在建造地壳拼贴中的最终命运具有普遍意义，而地壳拼贴几乎是所有大陆的典型。具体地说，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、大地测量仪、冰川学家、地球年代学家和地球动力学建模人员的多学科方法。

0409162KoonsThis 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.