Collaborative Research: Non-equilibrium Topography and Crustal-scale Imbrication in an Arc-continent Collision, Taiwan

该项目将与来自台湾的科学家合作，研究台湾中部山脉的形变、折返和地貌演变，重点是最近发现的横跨山脉顶端的高海拔低起伏地块，与预测的陡峭而崎岖的地形形成鲜明对比，造山系统被认为已达到稳定地貌。研究小组将测试这样一种观点，即这些低起伏地区是在最近岩石抬升速率瞬时加速之前形成的残存地貌的隆起残留物，以及根据地震层析分析的初步解释，隆起的加速是由地壳规模的叠置作用驱动的。为了验证这些相互关联的假设，该小组将开展三个相关的研究方向：1)地貌和宇宙成因分析(详细分析地形；详细绘制河流阶地实地测绘；以及主要利用10Be确定低起伏地区的侵蚀速率)；2)野外和地壳尺度的运动学分析(记录露头尺度断层和运动学的空间分布、相对年龄和方向；确定主要变形机制；以及反演断层地震数据以确定应变椭球体的形状和方向)；3)热计时研究。这项研究的综合数据集有可能改变对活动的弧陆碰撞的典型例子之一的地壳形变和地形演化的理解。台湾是地球上最活跃的构造环境之一。该岛标志着吕宋火山弧和亚洲被动边缘之间的碰撞，几十年来，这种碰撞激发了地球动力学模型来解释世界各地许多山脉的演化。台湾的模式是，东北-西南方向的被动边缘和南北方向的火山弧之间的倾角导致了山带的稳定向南传播和时空对等，因此可以将山带的横截面视为特征演化中不同阶段的时间片。此外，造山带相对恒定的宽度导致许多工作人员主张建立一种地形稳定状态，在这种状态下，物质的流入通过侵蚀来平衡。这个项目的目的是检验这样一种观点，即山脉地带被时断时续的事件打断，这些事件扰乱了稳态系统。该项目得到了地球科学部构造计划和美国国家科学基金会国际科学与工程办公室的支持。

This project, in collaboration with scientists from Taiwan, will study of the deformation, exhumation, and landscape evolution of the Central Range of Taiwan with focus on recently recognized patches of low relief at high elevations that straddle the crest of the range and stand in stark contrast to the steep and rugged topography predicted for an orogenic system considered to have reached steady-state topography. The research team will test the idea that these areas of low relief are uplifted remnants of a relict landscape that formed prior to a recent transient acceleration in rock uplift rate and that the acceleration in uplift was driven by crustal-scale imbrication as suggested by preliminary interpretations of seismic tomographic analyses. To test these linked hypotheses, the team will carry out three related lines of research: 1) geomorphology and cosmogenic analyses (detailed analysis of the topography; detailed field mapping of fluvial terraces; and determination of erosion rates for the areas of low relief primarily using 10Be); 2) field-based and crustal-scale kinematic analyses (documentation of the spatial distribution, relative age, and orientation of outcrop-scale faults and kinematics; determination of the dominant deformation mechanisms; and inversion of fault earthquake data for the shape and orientation of the strain ellipsoid); 3) thermochronometry studies. The integrated dataset from this study has the potential to transform understanding of the crustal deformation and landscape evolution of one of the type examples of an active, arc-continent collision.Taiwan represents one of the most active tectonic environments on Earth. The island marks the collision between the Luzon volcanic arc and the passive margin of Asia and for decades the collision has motivated geodynamic models to explain the evolution of many mountain belts around the world. The paradigm for Taiwan is that the obliquity between the northeast-southwest trending passive margin and the north-south trending volcanic arc has led to steady southward propagation of the mountain belt and a time-for-space equivalence so that cross sections of the belt can be treated as time slices for different stages in a characteristic evolution. Moreover, the relatively constant width of the orogen has led numerous workers to argue for a topographic steady state where the influx of material is balanced by erosion. This project aims to examine the idea that the mountain belt is punctuated by episodic events that perturb the steady state system.This project is supported by the Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.