Controls on Growth of the Puna Plateau, Northwestern Argentina

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。造山高原的生长机制和控制或限制其生长的过程仍然存在争议。在现今活跃的造山带中，新生代只发育了两个大型造山带高原（西藏和安第斯山脉）。在最广泛的范围内，它们的增长是由持续的板块融合驱动的。如果这种趋同持续到未来，这些平台会继续扩大吗？是什么控制着它们是否达到稳定的大小，持续膨胀，或者开始收缩或坍缩？本研究项目探讨了限制高原生长的因素，以及调节高原边缘地形变化的构造强迫和侵蚀之间的相互作用，并特别关注高原生长的一种模式：在相对干旱时期，与冲断相关的山脉与高山间盆地的填充物同步生长。提出了以盆地-山脉耦合为代表的增强地壳荷载驱动变形向外传播。该项目将集中在普纳高原的东北边缘和邻近的阿根廷西北部的东科迪勒拉地区，该地区位于一个突变的气候边界上，拥有多代晚新生代的逆冲和盆地填充和排空的事件。连续断层逆冲砾岩和河流湖相地层，然后被较年轻的砾石所掩埋。对盆地填充物和砾岩中保存的大量火山灰进行放射性测年，可以对高原边缘的生长和衰败进行严格的时间控制，并为详细重建范围生长、不断演变的河流网络和盆地填充和排空的多个循环之间的相互作用奠定基础。造山高原是一个广泛的地形区域，其特点是高程高，地形起伏小。今天地球上最大的两个高原是由喜马拉雅山脉和安第斯山脉的构造板块汇聚而成的。这些高原的边缘是大地震的发生地（比如四川和克什米尔的破坏性地震）。这些高原是广袤的高地形，通过改变急流的方向、调节季风的强度和路径以及影响降雨模式来影响全球气候。这些高原还为20多亿人提供了水源。对高原如何生长、控制断层发生的因素以及是否存在控制气候变化的地形阈值的进一步了解具有重要的科学和社会价值。该项目集中在阿根廷普纳高原的东翼，在那里，出色的暴露和丰富多样的可测定火山灰允许在详细的时间框架内重建高原生长的历史。这项研究的结果将有助于正在进行的努力，以了解气候和构造之间的相互作用，在大的，积极变形的山脉。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Both the mechanisms of growth of orogenic plateaus and the processes that control or limit their growth remain controversial. Within currently active orogens, only two large-scale orogenic plateaus (in Tibet and the Andes) have developed during Cenozoic times. At the broadest scale, their growth has been driven by sustained plate convergence. If such convergence continues into the future, will these plateaus continue to expand? What controls whether they reach a stable size, continuously expand, or begin to shrink or collapse? This research project explores the factors that limit plateau growth and the interplay between tectonic forcing and erosion that modulates changes in topography along plateau margins with particular focus on one mode of plateau growth: synchronous growth of thrust-related ranges with filling of high, ponded intermontane basins during times of relative aridity. The enhanced crustal loads represented by the basin-range couplet are proposed to drive outward propagation of deformation. This project will be focused along the northeastern margin of the Puna Plateau and the adjacent Eastern Cordillera of northwestern Argentina, a region that lies astride an abrupt climatic boundary and boasts multiple generations of late Cenozoic thrusting and episodes of basin filling and emptying. Successive faults overthrust conglomerates and fluvial-lacustrine strata and are then buried by younger gravels. Radiometric dating of the numerous volcanic ashes that are preserved within the basin fills, as well as within conglomerates will permit tight time control on the growth and decay of the plateau margin and will underpin a detailed reconstruction of the interplay of range growth, an evolving fluvial network, and multiple cycles of basin filling and emptying.Orogenic plateaus represent extensive topographic regions characterized by high elevation, but low topographic relief. The two largest plateaus on earth today have resulted from tectonic plate convergence in the Himalaya and the Andes. The margins of such plateaus are the sites of great earthquakes (such as the devastating ones in Sichuan and Kashmir). Being immense areas of high topography, such plateaus impact global climate by diverting the jet stream, modulating the strength and path of the monsoon, and influencing patterns of rainfall. These plateaus also provide the water that supports over 2 billion people. An improved understanding of how plateaus grow, what controls where faulting occurs, and whether topographic thresholds exist that control climatic change is of significant scientific and societal value. This project focuses on the eastern flank of the Puna Plateau in Argentina, where excellent exposures and a rich diversity of datable volcanic ashes permit reconstruction of the history of plateau growth in a detailed temporal framework. The results of this study will assist the ongoing effort to understand the interactions among climate and tectonics in large, actively deforming mountain ranges.