Collaborative Research: Solid Earth Response of the Patagonian Andes to Post-Little Ice Age Glacial Retreat

合作研究：巴塔哥尼亚安第斯山脉对小冰期后冰川退缩的固体地球响应

• 批准号: 1714154
• 负责人: Douglas Wiens
• 金额: $ 58.73万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1714154&HistoricalAwards=false
• 关键词: Collaborative; Research; Solid; Earth; Response

The goal of this project is to understand how the Earth responds to a cryospheric mass imbalance ona time scale of centuries in a compact, well-monitored region of Patagonia, a region of complex Neogene ridge subduction and youthful volcanism. The problem of glacial isostatic adjustment (GIA) is an important problem and critical to understanding the viscosity and time-scales of deformation in the upper mantle. The PI team will try to quantify and model the isostatic response to ice and sediment loading and unloading. A primary driver of modern rock uplift beneath and surrounding the Southern Patagonia Icefield (SPI) is interpreted to be ice loss following the peak advances of the Little Ice Age (LIA). Recent geodetic studies reveal remarkably rapid uplift rates (up to 40 mm/yr and averaging ~20 mm/yr around the SPI). These rates are the fastest modern geologic uplift rates; ones that demand a low viscosity mantle. In Patagonia, the presence of a somewhat poorly understood slab window that developed during Late Cenozoic time supports speculation that a low-viscosity zone underlies the region where GIA is veryrapid.This team will explore the causes of high rates and spatial-temporal pattern of the inferred GIA using: (1) a regional broadband seismological array to delineate the crustal and upper mantle structure and viscosity and observe seismicity (currently undefined) along the subducting Austral slab; (2) shipboard reflection seismic data and sediment cores to image and date the young pro- and subglacial sediments deposited in the glacial troughs (now fiord-like lakes) carved by advancing ice with a goal of defining both the geometry of ice and volume of deposited sediment through time; (3) new mapping and dating of the subaerial morainal sequence to define the time-varying spatial geometry of the SPI along its two largest outlet glaciers; and (4) improved geophysical models of glacier and solid earth responses.

该项目的目标是了解地球如何在几个世纪的时间尺度上对巴塔哥尼亚一个紧凑、监测良好的冰冻圈质量不平衡做出反应，巴塔哥尼亚是一个复杂的新近纪山脊俯冲和年轻火山活动的地区。冰川均衡调整（GIA）问题是一个重要问题，对于理解上地幔变形的粘度和时间尺度至关重要。 PI 团队将尝试量化和模拟冰和沉积物装载和卸载的均衡响应。 南巴塔哥尼亚冰原（SPI）下方和周围现代岩石隆起的主要驱动力被解释为小冰期（LIA）高峰期后的冰损失。最近的大地测量研究表明，SPI 周围的抬升率非常快（高达 40 毫米/年，平均约 20 毫米/年）。这些速率是现代最快的地质抬升速率；需要低粘度地幔的那些。在巴塔哥尼亚，人们对晚新生代时期形成的板状窗口的存在知之甚少，这支持了这样的推测：GIA 速度非常快的区域下方存在一个低粘度区域。该团队将探索高速率的原因和时空模式。推断 GIA 使用：(1) 区域宽带地震阵列，用于描绘地壳和上地幔结构和粘度，并观察沿俯冲的南方板片的地震活动（目前未定义）； (2) 船上反射地震数据和沉积物岩心，用于对沉积在冰川前进的冰槽（现在的峡湾状湖泊）中的年轻的前冰期和冰下沉积物进行成像和年代测定，目的是确定冰的几何形状和冰的体积。随着时间的推移沉积的沉积物； (3) 地面冰碛序列的新测绘和测年，以定义 SPI 沿其两个最大出口冰川的时变空间几何形状； (4) 改进了冰川和固体地球响应的地球物理模型。

项目成果

Lithospheric Erosion in the Patagonian Slab Window, and Implications for Glacial Isostasy

• DOI: 10.1029/2021gl096863
• 发表时间: 2022-01
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: H. Mark;D. Wiens;E. Ivins;A. Richter;W. Ben Mansour;M. Magnani;E. Marderwald;Rodrigo Adaros;S. Barrientos

Mantle Flow Pattern Associated With the Patagonian Slab Window Determined From Azimuthal Anisotropy

由方位各向异性确定的与巴塔哥尼亚板片窗相关的地幔流动模式

• DOI: 10.1029/2022gl099871
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Ben‐Mansour, Walid;Wiens, Douglas A.;Mark, Hannah F.;Russo, Raymond M.;Richter, Andreas;Marderwald, Eric;Barrientos, Sergio
• 通讯作者: Barrientos, Sergio