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.

切尔西·麦卡曼·洛夫兰（Chelsea Mackaman-Lofland）博士在康涅狄格大学（UCONN）教授朱莉·福斯迪克（Julie Fosdick）和迈克尔·赫伦（Michael Hren）的指导下，被授予NSF耳朵博士后奖学金，以在康涅狄格大学（UCONN）进行研究，专业发展和教育活动。该项目调查了南美洲南部安第斯山脉南部（〜30°S）建造中地壳变形的空间和临时尺度。项目结果将改善对促进俯冲相关山建筑的力和地球动力学机制的科学理解。安第斯山脉定义了在连续板下俯冲的海壳期间山地建筑的主要例子，并且是地球系统不可或缺的，包括海洋/大气循环模式，生物多样性以及自然危害和资源分布。在〜30°s时，安第斯山建筑的对比模型调用了连续的地壳缩短，而在覆盖板中的情节缩短，延伸和可能的中性条件。该项目集成了基岩和杂种盆地的结构图，盆地分析，地理/热量教学以及在〜30°S的填充到（1）解决相互矛盾的缩短，扩展和/或中性变形模式的解释，以及（2）量化的时间，尺寸，尺寸和速率，并量化了变形，表面的尺寸和速率。研究和专业发展将涉及阿根廷和智利学生的地质现场培训以及主持人的活动。 UConn本科生将通过新资助的地理学家实习和职业学业计划招募，该计划强调招募和保留代表性不足的学生团体。项目结果将纳入阿根廷和智利学生的实地考察，并为“山脉，河流和碳”以及UConn的“山脉，河流和碳”和“古地理，构造和全球气候”教育外展计划纳入实地考察。长期以来，与俯冲相关的山建筑长期以来一直归因于板收敛的边缘尺度变化后，压倒板的连续缩短和增厚。然而，越来越多的结构，地层和岩浆证据表明，在建造山芯兰科伦斯期间，潜在的区域缩短，扩展和/或中性机制可能会缩短，扩展和/或中性状态。沿着从中部到南安第斯山脉（〜25-35°S）的过渡，上板变形涉及从连续缩短到混合模式变形的明显转移。表征这种过渡的性质对于理解收敛余量过程的时机，节奏和空间连续性至关重要，但是现有的重构在〜30°S沿单个造山带沿单个造山带沿最明显的构造构造条件。这项研究旨在解决冲突的变形模式解释，并提供地理和时机参数，以审问控制山脉变形的潜在区域或板规尺度机制。联合锆石LU-HF（Lutetium-Hafnium）和U-PB（铀铅）地质学，低温热量学和稳定的同位素古钙化分析将建立变形，挖掘，外壳增厚和表面上升的定量关系。前体变形和沉降历史的重建将提供一个框架，以研究遗传性构造制度和盆地体系结构对现代安第斯山脉新近纪的生长的影响。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力和更广泛的影响来通过评估来通过评估来获得支持的珍贵。

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