Collaborative Research: Magnitude and timing of shortening in the Greater Caucasus: Locus of Late Cenozoic Arabia-Eurasia convergence?

大高加索山脉在黑海和里海之间延伸近1000公里，形成了阿拉伯-欧亚碰撞带的最北端。这个范围一直被推测为在碰撞中容纳斜辐合的核心作用。最近的全球定位系统研究表明，整个大高加索地区最东端的缩短率为10至13毫米/年，占远场阿拉伯-欧亚大陆会聚总量15至20毫米/年的50至85%。虽然GPS和地震数据清楚地表明，东部大高加索地区现在发挥了核心作用，在容纳阿拉伯-欧亚大陆的收敛，目前可用的数据是不够的，以确定是否有类似的应变集中在整个晚新生代的范围。在这个为期三年的项目中，来自美国、阿塞拜疆、格鲁吉亚和俄罗斯联邦的一个国际科学家小组正在检验以下假设：1）大高加索山脉是阿拉伯-欧亚大陆碰撞中应变局部化形成的一级构造系统; 2）大约1000万年前，由于50%至80%的阿拉伯-欧亚大陆会聚集中在该范围内，表面隆起开始;（3）由于造山带向东的扩展，沿走向由西向东，折返和缩短的时间和幅度都系统地减小;和4）大高加索地区的应变局部化可能是一个残留洋盆消耗的结果，其中黑海和南里海是残留洋盆，在晚新生代造山带形成过程中被捕获。这些假设是通过对大高加索山脉和库拉褶皱冲断带（位于格鲁吉亚和阿塞拜疆山脉东南边缘两侧）的野外综合构造、新构造和热年代学研究来验证的。板块构造理论问世近40年后，地球科学家们仍在争论当两个会聚的板块之间的边界沿着碰撞时，大陆是如何变形的。解决这个问题对于理解地震期间变形在哪里、多久以及为什么沿着沿着突然释放，这些断层如何形成并随着时间的推移而表现，为什么它们在某些地方形成而不是其他地方很重要。 欧亚大陆和阿拉伯大陆之间的持续碰撞产生了欧洲最高的山脉，以及地球上第二大活跃大陆碰撞区域。这次碰撞的中心是大高加索山脉，它在黑海和里海之间延伸了大约1000公里。这条山脉带似乎是在最近500万至1000万年间形成的，因此为研究大陆变形和山脉形成的初始阶段提供了一个不寻常的机会。这项研究的结果将促进对大陆变形的理解，该地区的地质条件导致南里海盆地和阿塞拜疆东部形成丰富的石油储量，以及这个人口稠密和经济重要地区的地震危险。该地区过去曾遭受毁灭性地震的袭击，例如1988年亚美尼亚发生的地震造成至少25 000人死亡。该项目将支持博士学位。该项目为加州大学戴维斯分校和密歇根大学的学生提供了重要的研究机会，同时也为这两所大学的本科生提供了重要的教育和研究机会。

The Greater Caucasus Mountains extend for nearly 1000 km between the Black and Caspian seas and form the northernmost margin of the Arabia-Eurasia collision zone. This range has long been speculated to play a central role in accommodating oblique convergence within the collision. Recent GPS studies indicate shortening rates of 10 to 13 mm/yr across the easternmost Greater Caucasus, which represents 50 to 85% of the total 15 to 20 mm/yr of far-field Arabia-Eurasia convergence. Although GPS and earthquake data clearly imply that the eastern Greater Caucasus now plays a central role in accommodating Arabia-Eurasia convergence, current available data are insufficient to confidently determine if strain has been similarly focused in the range throughout the late Cenozoic. In this three-year project, an international team of scientists from the United States, Azerbaijan, Georgia, and the Russian Federation is testing the hypotheses that: 1) the Greater Caucasus range is a first-order structural system that formed by strain localization within the Arabia-Eurasia collision; 2) surface uplift began approximately 10 million years ago due to focusing of 50 to 80% of total Arabia-Eurasia convergence in the range; 3) the timing and magnitude of both exhumation and shortening systematically decrease from west to east along-strike due to eastward propagation of the range; and 4) strain localization within the Greater Caucasus may be the result of the consumption of a relict ocean basin, of which the Black and South Caspian seas are remnants, that was trapped during formation of the orogen in the late Cenozoic. These hypotheses are tested through a field-based, integrated structural, neotectonic, and thermochronologic study of the Greater Caucasus Mountains and the Kura fold-thrust belt, which flanks the southeastern margin of the range in Georgia and Azerbaijan.Almost 40 years after the advent of the theory of plate tectonics, earth scientists are still debating how continents deform when they collide along the boundary between two converging plates. Addressing this question is important for understanding where, how often, and why deformation is suddenly released during earthquakes along faults, how those faults form and behave over time, why they form in some places and not others. The ongoing collision between the Eurasian and Arabian continents produced the highest mountain range in Europe, and the second largest region of active continental collision on Earth. The center of this collision is defined by the Greater Caucasus Mountains, which extend for approximately 1000 km between the Black Sea to the west and Caspian Sea to the east. This mountain belt appears to have formed in only the last 5 to 10 million years, thus providing an unusual opportunity to study the initial stages of continental deformation and mountain building. Results from this research will advance the understanding of continental deformation, the geological conditions in this region that led to the formation of rich oil reserves in the South Caspian basin and eastern Azerbaijan, and the earthquake hazards in this heavily populated and economically important region. This region has been struck by devastating earthquakes in the past, such as an earthquake in 1988 in Armenia that killed at least 25,000 people. The project will support the Ph.D. research of students at the University of California at Davis and the University of Michigan, while also providing important educational and research opportunities for undergraduate students at both universities.