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地带的大规模构造形成。然而，形成活动山脉地形的更基本过程尚不完全清楚。特别是，构造变形或气候是否控制了产生山脉地形的侵蚀？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率和地形方面的相对重要性仍未得到解决。这项研究利用了大高加索山脉（阿塞拜疆和格鲁吉亚）的有趣案例，其中地形恒定，但年平均降水量（气候）和阿拉伯与欧亚大陆（构造）之间的碰撞率沿范围长度变化。通过测量沿线的侵蚀率，研究小组将评估构造与气候在这座活跃变形山脉的地形发展中的相对重要性。该项目有潜力通过以下方式造福社会或推进期望的社会成果：(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来改善社会个人的福祉； (3) 通过本科生和外国研究生的培训以及对早期职业研究员的支持，培养一支有竞争力的 STEM 劳动力队伍； (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、主要呈东西向走向的造山带，位于黑海和里海之间，是阿拉伯半岛-欧亚大陆碰撞带中部东北-西南定向汇聚的所在地。尽管气候、收敛速度、结构几何形状、地壳结构和裸露岩石类型具有显着的沿走向梯度，但大高加索地区的地形却明显保持不变。该山脉的西端主要是一个单侧、南向的造山带，基底腹地暴露，经历了板片分离，现代辐合率较低，为 1-4 毫米/年，年平均降水量较高1-2 m/年。相比之下，该山脉的东端是双辐辏造山带，没有基底暴露，其下方是俯冲板块，辐合速度为 8-12 毫米/年，年平均降水量仅为 0.1-0.5米/年。就其本身而言，气候和辐合的梯度预测在高降水、低辐合的西部有一个狭窄和低海拔的范围，在低降水、高辐合的东部有一个宽阔和高海拔的造山带。然而，非常相似的最大海拔、2.5公里规模的地形、造山带宽度和沿山脉走向的横截面积却是大高加索地区实际地形的特征。该项目测试了以下假设：地形的这种沿走向相似性反映了造山带沿走向的侵蚀通量的相似性。具体而言，构造运动是对大高加索地区地形形态的主要控制，因此收敛速度和结构样式的变化组合与沿走向相结合，产生相似的造山带增生速率，从而产生相似的岩石隆起和侵蚀速率沿罢工。该假说将通过测量大高加索南翼流域平均侵蚀率来检验，使用从现代河流沉积物中采样的石英中的 10Be 宇宙成因放射性核素测年来测量这些流域平均侵蚀率——这是一种成熟且经过时间验证的方法衡量千禧年规模的流域平均侵蚀率。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走向调节侵蚀效率变化的潜在影响。该项目得到了构造计划、地貌和土地利用动力学计划以及美国国家科学基金会国际科学和技术研究中心的支持。工程。