Extrusion, Extension and Exhumation in an Emerging Mountain Belt, Taiwan

台湾新兴山带的挤压、延伸和折返

• 批准号: 0711353
• 负责人: Timothy Byrne
• 金额: $ 23.69万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711353&HistoricalAwards=false
• 关键词: Extrusion; Extension; Exhumation; Emerging; Mountain

This goal of this project is to test the new hypothesis that extension in southern Taiwan initiated 1 to 2 million years ago as the Philippine Sea plate initially collided with a zone of transitional continental crust (5 to 20 km thick) followed by collision with continental crust of more typical thickness (about 30 km). The transition in collision mode initiated along-strike flow or extrusion and local areas of extension, especially in the southern Central Range of Taiwan. Field-based structural geology (brittle and ductile structural analyses) and low-temperature thermochronology (fission track and (U-Th)/He dating) coupled with seismological (focal mechanisms, cluster geometries) and GPS analysis will be carried out to determine: 1) if and when exhumation changed from relatively slow to fast rates; 2) the regional extent of the any change in exhumation rates; 3) if there has been a change from shortening to extension; 4) determine which structures accommodate extension and rock uplift; and 5) document southward propagation of specific structures, structural sequences or exhumation. The overall goal will be to document the current and past kinematics in the area and then tie the interpreted kinematic evolution to the history of uplift and exhumation as revealed by the thermochronologic data.One of the most significant recent breakthroughs in understanding processes that affect the Earth's surface is the discovery that some contractional orogenic belts also experience horizontal extension. The orogenic belt in Taiwan provides an unusual opportunity to better constrain the origin and significance of synorogenic extension. The orogen straddles the boundary between the Eurasian and Philippine Sea plates and is actively propagating as the two plates collide. In the area where the orogen is just emerging above sea level, a dense GPS network shows a broad zone of relatively fast extensional strains. The topography in this area also climbs to the maximum elevation in the collision zone (just under 4 km) and available thermochronological data suggest relatively high uplift rates. Why is this area of well-documented extension also an area of substantial rock and surface uplift? Answering this question would greatly improve understanding of processes that operate during collisonal mountain building episodes.

该项目的目标是检验新的假设，即台湾南部的扩张始于 1 至 200 万年前，当时菲律宾海板块最初与过渡大陆地壳区域（5 至 20 公里厚）碰撞，随后与大陆地壳碰撞更典型的厚度（约30公里）。碰撞模式的转变引发了沿走向流动或挤压和局部延伸区域，特别是在台湾中部山脉南部。将进行基于现场的构造地质学（脆性和延性结构分析）和低温热年代学（裂变径迹和（U-Th）/He定年）以及地震学（震源机制、簇几何）和GPS分析，以确定： 1) 折返速度是否从相对较慢变为较快； 2) 折返率变化的区域范围； 3) 是否有从缩短到延长的变化； 4) 确定哪些结构能够适应延伸和岩石隆起； 5) 记录特定结构、结构序列或折返的向南扩展。总体目标是记录该地区当前和过去的运动学，然后将解释的运动学演化与热年代学数据揭示的隆起和折返历史联系起来。这是理解影响地球运动过程的最新突破之一。表面上发现一些收缩造山带也经历了水平伸展。台湾造山带为更好地约束同造山运动的起源和意义提供了一个不寻常的机会。造山带横跨欧亚板块和菲律宾海板块之间的边界，并随着两个板块的碰撞而积极传播。在造山带刚刚出现在海平面以上的地区，密集的 GPS 网络显示出广阔的相对快速的伸展应变区域。该地区的地形也攀升至碰撞区的最大海拔（略低于 4 公里），现有的热年代学数据表明抬升率相对较高。为什么这个有据可查的延伸区域也是一个岩石和地表大量隆起的区域？回答这个问题将极大地提高对碰撞造山过程中运作过程的理解。