Reconciling Invariant Topography with Along-Strike Gradients in Climate and Tectonics in the Greater Caucasus Mountains

大高加索山脉不变地形与气候和构造沿走向梯度的协调

• 批准号: 1450970
• 负责人: Kelin Whipple
• 金额: $ 28.27万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1450970&HistoricalAwards=false
• 关键词: Reconciling; Invariant; Topography; Along; Strike

The concept of plate tectonics describes the large scale structural formation of mountain belts. However, the more fundamental processes that create the topography of an active mountain range are not fully understood. In particular, does the tectonic deformation or climate control the erosion that generates the mountain topography? Despite many different types of studies, the relative importance of tectonics versus climate in controlling erosion rates and topography remains unresolved. This study takes advantage of the interesting case of the Greater Caucasus Mountains (Azerbaijan and Georgia) where the topography is constant but the mean annual precipitation (climate) and the collision rate between Arabia and Eurasia (tectonics) change along the range length. By measuring erosion rates along the range, the research team will assess the relative importance of tectonic versus climate in topographic development of this actively deforming mountain range. The project has potential to benefit society or advance desired societal outcomes by: (1) improved STEM education through development of learning materials and lab modules; (2) improved well-being of individuals in society through better understanding of natural hazards; (3) development of a competitive STEM workforce through the training of undergraduate students and a foreign graduate student plus support for an early career researcher; and (4) increased partnerships through international collaboration.The Greater Caucasus Mountains are a young predominantly east-west striking orogen that lie between the Black and Caspian Seas and represent the locus of northeast-southwest directed convergence in the central Arabia-Eurasia collision zone. Despite significant along-strike gradients in climate, convergence rate, structural geometries, crustal structure and exposed rock types, the topography of the Greater Caucasus is remarkably invariant. The western end of the range is a predominantly one-sided, south-directed orogen, with hinterland exposures of basement, that experienced slab-detachment, has a low modern convergence rate of 1-4 mm/yr and a high mean annual precipitation of 1-2 m/yr. In contrast, the eastern end of the range is a doubly-vergent orogen, is devoid of basement exposures, is underlain by a subducting slab, and experiences a convergence rate of 8-12 mm/yr and mean annual precipitation of only 0.1-0.5 m/yr. On their own, the gradients in climate and convergence predict a narrow and low elevation range in the high-precipitation, low-convergence west and a wide and high elevation orogen in the low-precipitation, high-convergence east. However, remarkably similar maximum elevations, 2.5 km scale relief, orogen width, and cross-sectional area along the strike of the range instead characterize the actual topography of the Greater Caucasus. This project tests the hypothesis that this along-strike similarity in the topography reflects a similarity in erosional flux out of the orogen along-strike. Specifically, tectonics is the primary control on the topographic form of the Greater Caucasus such that the combination of variations in convergence rate and structural style combine along-strike to produce similar rates of accretion into the orogen, and thus similar rates of rock uplift and erosion along-strike. The hypothesis will be tested by measuring basin averaged erosion rates along the southern flank of the Greater Caucasus using cosmogenic radionuclide dating of 10Be in quartz sampled from modern river sediments to measure these basin averaged erosion rates - a well-developed and time-proven method to gauge millennial-scale catchment mean erosion rates. Available historical climate and river discharge data will be used to assess the potential influence of runoff variability on modulating changes in erosional efficiency along-strike.This project is supported by the Tectonics Program, the Geomorphology and Land Use Dynamics Program, and NSF International Science and Engineering.

板块构造的概念描述了山脉带的大规模构造形成。然而，创造活动山脉地形的更基本的过程还没有完全了解。特别是，构造变形或气候是否控制了产生山地地形的侵蚀？尽管进行了许多不同类型的研究，但构造与气候在控制侵蚀速率和地形方面的相对重要性仍然没有得到解决。这项研究利用了大高加索山脉（阿塞拜疆和格鲁吉亚）的有趣的情况下，地形是恒定的，但平均年降水量（气候）和阿拉伯半岛和欧亚大陆（构造）之间的碰撞率变化沿着范围长度。通过测量沿着山脉的侵蚀率，研究小组将评估构造与气候在这一活跃变形山脉地形发展中的相对重要性。该项目有可能通过以下方式造福社会或促进预期的社会成果：（1）通过开发学习材料和实验室模块改善STEM教育;（2）通过更好地了解自然灾害改善社会中个人的福祉;（3）通过培训本科生和外国研究生以及支持早期职业研究人员，发展有竞争力的STEM劳动力;（4）通过国际合作加强伙伴关系。大高加索山脉是一个年轻的、主要是东西走向的造山带，位于黑海和里海之间，代表着阿拉伯-欧亚大陆碰撞带中部东北-西南走向的汇聚点。尽管在气候，收敛速度，结构几何形状，地壳结构和暴露的岩石类型显着沿走向梯度，大高加索地区的地形是显着不变的。该山脉的西端主要是一个单侧的、向南的造山带，具有基底的腹地暴露，经历了板片拆离，具有1-4 mm/年的低现代会聚速率和1-2 m/年的高平均年降水量。与此相反，该山脉的东端是一个双辐合造山带，没有基底暴露，下面是俯冲板片，并经历了8-12毫米/年的收敛速度和平均年降水量只有0.1-0.5米/年。气候和辐合的梯度本身就预示着，在降水量高、辐合量低的西部，有一个狭窄而低的海拔范围，而在降水量低、辐合量高的东部，有一个宽阔而高海拔的造山带。然而，非常相似的最大海拔，2.5公里的规模救济，造山带宽度，和横截面积沿着走向的范围，而不是大高加索地区的实际地形特征。这个项目测试的假设，这种沿走向相似的地形反映了相似的侵蚀流量的造山带沿走向。具体而言，构造是大高加索地区地形形态的主要控制因素，因此收敛速率和构造样式的变化组合沿走向联合收割机产生了相似的造山带增生速率，因此沿走向产生了相似的岩石隆起和侵蚀速率。该假设将通过测量盆地平均侵蚀率沿着大高加索南翼使用宇宙成因放射性核素测年的10 Be在石英采样现代河流沉积物来测量这些盆地平均侵蚀率-一个完善的和时间证明的方法来衡量千年尺度的流域平均侵蚀率。现有的历史气候和河流流量数据将用于评估径流变化对沿strik.This项目的侵蚀效率的调制变化的潜在影响是由构造计划，地貌和土地利用动力学计划，和NSF国际科学与工程。