Collaborative Research: Surface Uplift and Climate Change in the Southern Altiplano: Evaluating Mechanisms for Surface Rise and the Effects of Tectonics on Climate

合作研究：南部高原的地表隆起和气候变化：评估地表上升机制和构造对气候的影响

• 批准号: 0635678
• 负责人: Carmala Garzione
• 金额: $ 18.59万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-15 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635678&HistoricalAwards=false
• 关键词: Collaborative; Research; Surface; Uplift; Climate

This study will examine the Miocene climate and elevation history of the Andean plateau by combining a new carbonate environmental geothermometer, based on clumping of carbon-12 and oxygen-18 into bonds with each other in the carbonate mineral lattice, with conventional analyses of the stable isotope compositions of soil carbonates, lake carbonates, and fossil mammal teeth. Previous studies in the Andean plateau have estimated paleoelevations based on paleobotanical data, the delta oxygen-18 of sedimentary carbonates, and the new clumped isotope method. However, these studies estimate elevation by assuming a base level climate similar to today, with today's relationships among altitude, mean annual surface temperature, and the delta oxygen-18 of meteoric waters. This assumption is a source of uncertainty unless the temperature or starting composition of the vapor source can be constrained. Part of this study will establish a low elevation climate record from the Subandes against which the paleoelevation records from the Altiplano can be compared. By this approach, a more accurate record of elevation will be extracted by calibrating against secular variations in climate observed in the Subandes. Importantly, this new approach will allow study of the entire plateau, including its arid southern half, which has resisted attempts to determine paleoelevation based on delta oxygen-18 of surface carbonates alone.With a better resolution of the spatial and temporal variation in the magnitude of surface uplift of the Andes, the broader significance of this study will be an understanding of processes that lead to surface uplift of mountain belts, including thickening of crustal and mantle lithosphere and removal of dense, thickened lower lithosphere. Recent studies of the elevation history of the northern Altiplano suggest that rapid surface uplift ( approximately 3 km in 3 million years) occurred in the late Miocene, postdating major crustal thickening by upper crustal folding and faulting. There is evidence of similar-age surface uplift across the width of the Andes for over greater 5 degrees of latitude, implicating the removal of mantle lithosphere as an important mechanism for surface uplift. However, independent data have only predicted mantle lithosphere removal in the southern Altiplano and Puna. Documentation of the timing and magnitude of surface uplift along strike in the Andes will shed light on the combined roles of these processes as well their regional extent.Additional broader impacts of this work are to examine the effects of mountain building on regional climate. This project will examine the spatial variations in climate from middle Miocene to recent over different latitudes in the Altiplano, as well as from low to high elevation along the eastern flank of the Andes, to evaluate the potential influence of surface uplift on local climate. A pilot study of the tooth enamel of late Miocene to modern large, water-dependent grazers shows that these animals were ingesting surface water similar in composition to modern rainfall. These data will be extended back to the middle Miocene to evaluate whether the Late Miocene to modern pattern of rainfall resulted from regional surface uplift. In addition, temporal changes in low elevation and high elevation precipitation amount will be evaluated to test the hypothesis that late Miocene surface uplift of the Altiplano forced climate change that was manifested by an increase in low elevation rainfall amount and a simultaneous decrease in high elevation rainfall amount. This study will provide a model for a new and widely applicable approach to reconstructing past climates and paleoelevation through the clumped carbon-12 and oxygen-18 paleothermometry method to reconstruct past temperatures and conventional stable isotope studies to reconstruct patterns of precipitation.

这项研究将通过结合新型碳酸盐环境地温计来研究安第斯高原的中新世气候和海拔历史，该温度计基于碳酸盐矿物晶格中碳 12 和氧 18 相互聚集成键，并与稳定的常规分析相结合。土壤碳酸盐、湖泊碳酸盐和哺乳动物牙齿化石的同位素组成。先前在安第斯高原的研究根据古植物学数据、沉积碳酸盐的δ氧18以及新的聚集同位素方法估计了古海拔。然而，这些研究通过假设与今天相似的基准气候，以及今天的海拔高度、年平均地表温度和大气水域的氧气 18 增量之间的关系来估计海拔。这种假设是不确定性的来源，除非可以限制蒸汽源的温度或起始成分。这项研究的一部分将建立苏班德斯山脉的低海拔气候记录，以便与高原的古海拔记录进行比较。通过这种方法，将通过根据苏班德斯地区观测到的气候长期变化进行校准来提取更准确的海拔记录。重要的是，这种新方法将允许研究整个高原，包括其干旱的南半部，该南半部一直抵制仅根据表面碳酸盐的δ氧18来确定古海拔的尝试。关于安第斯山脉表面隆起的研究，这项研究的更广泛意义将是了解导致山脉表面隆起的过程，包括地壳和地幔岩石圈的增厚以及致密、增厚的下部岩石圈的去除。最近对高原北部海拔历史的研究表明，地表快速隆起（300 万年约 3 公里）发生在中新世晚期，晚于上地壳褶皱和断层造成的地壳主要增厚。有证据表明，在安第斯山脉宽度范围内超过 5 度的纬度范围内，存在类似年龄的地表隆起，这表明地幔岩石圈的去除是地表隆起的重要机制。然而，独立数据仅预测了高原和普纳南部地幔岩石圈的去除。对安第斯山脉沿走向地表隆起的时间和幅度的记录将揭示这些过程的综合作用及其区域范围。这项工作的其他更广泛的影响是研究造山对区域气候的影响。该项目将研究高原不同纬度从中新世中期到近代的气候空间变化，以及安第斯山脉东侧从低海拔到高海拔的气候空间变化，以评估地表隆升对当地气候的潜在影响。对中新世晚期的现代大型依赖水的食草动物的牙釉质进行的初步研究表明，这些动物摄入的地表水的成分与现代降雨的成分相似。这些数据将追溯到中新世中期，以评估晚中新世到现代的降雨模式是否是由区域表面隆升造成的。此外，还将评估低海拔和高海拔降水量的时间变化，以检验中新世晚期高原地表抬升迫使气候变化的假设，表现为低海拔降水量增加和高海拔降水量同时减少数量。这项研究将为重建过去的气候和古海拔提供一种新的、广泛适用的方法，通过聚集碳12和氧18古测温方法来重建过去的温度，并通过传统的稳定同位素研究来重建降水模式。