EAR-PF Continuous vs. mixed-mode deformation during construction of the southern central Andes: Investigating the spatiotemporal scales of Cordilleran tectonic regimes

安第斯山脉中南部建造过程中的 EAR-PF 连续变形与混合模式变形：研究科迪勒拉构造体系的时空尺度

• 批准号: 1952791
• 负责人: Chelsea Mackaman-Lofland
• 金额: $ 17.4万
• 依托单位: Mackaman-Lofland, Chelsea
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952791&HistoricalAwards=false
• 关键词: EAR; PF; Continuous; vs.; mixed

Dr. Chelsea Mackaman-Lofland has been awarded an NSF EAR Postdoctoral Fellowship to conduct research, professional development, and educational activities at the University of Connecticut (UConn) under the mentorship of Professors Julie Fosdick and Michael Hren. This project investigates the spatial and temporal scales of crustal deformation during construction of the southern central Andes (~30°S) in South America. Project results will improve scientific understanding of the forces and geodynamic mechanisms driving subduction-related mountain building. The Andes define key examples of mountain building during the subduction of oceanic crust beneath a continental plate, and are integral to Earth systems including ocean/atmospheric circulation patterns, biological diversity, and natural hazard and resource distribution. At ~30°S, contrasting models of Andean mountain building invoke continuous crustal shortening vs. episodic shortening, extensional, and possibly neutral conditions in the overriding plate. This project integrates structural mapping, basin analysis, geo/thermochronology, and paleoaltimetry of bedrock and hinterland basin fill at ~30°S to (1) resolve conflicting shortening, extensional, and/or neutral deformation mode interpretations and (2) quantify the timing, magnitude, and rates of deformation, crustal evolution, surface uplift, and establishment of the Andean Cordillera. Research and professional development will involve geological field training for Argentine undergraduate students and training for an undergraduate thesis project at the host institution. The UConn undergraduate will be recruited through the newly funded GEOPAths internship and career-mentoring program, which emphasizes the recruitment and retention of underrepresented student groups. Project results will be incorporated into a field trip for Argentine and Chilean students and activities for the “Mountains, Rivers, and Carbon” and “Paleogeography, Tectonics, and Global Climate” educational outreach programs at UConn. Subduction-related mountain building has long been attributed to continuous shortening and thickening of the overriding plate following margin-scale changes in plate convergence. However, an increasing body of structural, stratigraphic, and magmatic evidence points to episodic deformation, with potentially regional shortening, extension, and/or neutral regimes during the construction of Cordilleran orogens. Along the transition from central to southern Andes (~25−35°S), upper-plate deformation involved an apparent shift from continuous shortening to mixed-mode deformation. Characterizing the nature of this transition is fundamental to understanding the timing, tempo, and spatial continuity of convergent margin processes, but existing reconstructions invoke conflicting tectonic conditions most apparent along a single orogenic transect at ~30°S. This research seeks to resolve conflicting deformation mode interpretations and provide geographic and timing parameters with which to interrogate potential regional or plate-scale mechanisms controlling Cordilleran deformation. Combined zircon Lu-Hf (Lutetium-Hafnium) and U-Pb (Uranium-Lead) geochronology, low-temperature thermochronology, and stable isotope paleoaltimetry analyses will establish quantitative relationships between deformation, exhumation, crustal thickening, and surface uplift. Reconstruction of precursor deformation and sedimentation history will provide a framework with which to investigate the influence of inherited tectonic regimes and basin architectures on Neogene growth of the modern Andes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Chelsea Mackaman-Lofland博士获得了NSF博士后奖学金，在Julie Fosdick教授和Michael Hren教授的指导下在康涅狄格大学（UConn）进行研究，专业发展和教育活动。本项目调查南美洲安第斯山脉中南部（~30°S）建造期间地壳变形的空间和时间尺度。项目成果将提高对驱动与俯冲有关的造山运动的力量和地球动力机制的科学认识。安第斯山脉是大洋地壳在大陆板块下俯冲过程中造山作用的重要实例，是地球系统的组成部分，包括海洋/大气环流模式、生物多样性、自然灾害和资源分布。在南纬30°附近，安第斯山脉造山运动的对比模型显示，地壳持续缩短，而上覆板块则出现了阶段性缩短、伸展和可能的中性状态。该项目综合了构造测绘、盆地分析、地质/热年代学以及对~30°S处基岩和腹地盆地填充物的古高度测量，以（1）解决相互矛盾的缩短、伸展和/或中性变形模式解释，（2）量化变形、地壳演化、地表隆起和安第斯山脉建立的时间、幅度和速率。研究和专业发展将包括对阿根廷本科生进行地质实地培训，以及在东道机构进行本科论文项目培训。康州大学的本科生将通过新资助的GEOPATs实习和职业指导计划招募，该计划强调招募和保留代表性不足的学生群体。项目成果将被纳入阿根廷和智利学生的实地考察，以及康州大学的“山脉、河流和碳”和“古地理学、构造学和全球气候”教育推广计划的活动。与俯冲有关的造山运动长期以来被认为是板块会聚边缘尺度变化后，上覆板块不断缩短和增厚的结果。然而，越来越多的机构的结构，地层和岩浆的证据表明，幕式变形，潜在的区域缩短，延伸，和/或中性制度在建设的科迪勒拉造山带。沿着从中部到南部的安第斯山脉（~25−35°S）的过渡，上层板块的变形明显地从连续缩短转变为混合模式变形。描述这种转变的性质对于理解会聚边缘过程的时间、克里思和空间连续性至关重要，但是现有的重建引起了相互冲突的构造条件，最明显的是沿着一个单一的造山带样带，在~30°S。本研究旨在解决相互冲突的变形模式的解释，并提供地理和时间参数，以询问潜在的区域或板块规模的机制控制科迪勒拉变形。结合锆石Lu-Hf（Lutetium-Hafnium）和U-Pb（Uranium-Pb）地质年代学、低温热年代学和稳定同位素古测高学分析，将建立变形、折返、地壳增厚和地表隆起之间的定量关系。前兆变形和沉积历史的重建将提供一个框架，以研究继承的构造体制和盆地结构对现代安第斯山脉新近纪增长的影响。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

项目成果

Causes of Variable Shortening and Tectonic Subsidence During Changes in Subduction: Insights From Flexural Thermokinematic Modeling of the Neogene Southern Central Andes (28–30°S)

俯冲变化过程中可变缩短和构造沉降的原因：新近纪安第斯山脉中南部（南28-30°）弯曲热运动模型的见解

• DOI: 10.1029/2022tc007334
• 发表时间: 2022
• 期刊: Tectonics
• 影响因子: 4.2
• 作者: Mackaman‐Lofland, Chelsea;Horton, Brian K.;Ketcham, Richard A.;McQuarrie, Nadine;Fosdick, Julie C.;Fuentes, Facundo;Constenius, Kurt N.;Capaldi, Tomas N.;Stockli, Daniel F.;Alvarado, Patricia
• 通讯作者: Alvarado, Patricia