Collaborative Research: Fold Form, Strain, and Mechanics at the Whaleback Anticline: New Approaches to a Classic Field Locality

合作研究：鲸背背斜的褶皱形式、应变和力学：经典野外地点的新方法

• 批准号: 1523955
• 负责人: Arlo Weil
• 金额: $ 3.08万
• 依托单位: Bryn Mawr College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1523955&HistoricalAwards=false
• 关键词: Collaborative; Research; Fold; Form; Strain

Folded rock layers are among the most fundamental, instructive and charismatic geologic structures. Folds are studied to investigate mountain building, to understand the engineering properties of rock, to predict the underground movement of water or hydrocarbons, and to give insight into the fundamental processes of folding itself. These applications rely on the accurate interpretation of rock deformation within a fold. Various conceptual and mathematical models predict fold-related deformation. To assess the capabilities of such predictive models, data from natural examples are required. This can be challenging, because most geologic folds at Earth's surface are only partially exposed, with major portions of the fold either buried underground or eroded away. The Whaleback Anticline in Bear Valley, east-central Pennsylvania, is a unique locale where a complete large-scale fold is exposed; strip mining for coal early in the last century revealed it in exquisite detail. This outstanding exposure permits observation of the complete three-dimensional form of the folded surface and provides a highly detailed record of deformation across the fold. This project will use cutting-edge digital imaging techniques and traditional geologic fieldwork to produce a comprehensive data set against which to test hypotheses about folding. In addition to the scientific goals of the project, the research is contributing to achievement of societally relevant outcomes in the areas of science, technology, engineering, and mathematics (STEM) education, including the development of a diverse, globally competitive STEM workforce through graduate and undergraduate student training; the development of research infrastructure of three universities; the broadening of participation of underrepresented groups in science; and increased public scientific literacy and public engagement with science and technology. The Whaleback Anticline is an important educational field trip location for dozens of university geology departments throughout the eastern United States, and it is a well-used recreation site for the local community. As part of this proposed project we will preserve, expand and curate geological observations from the Whaleback, for use by researchers, educators and the community. Deformation associated with folding is recorded by distributed strain and discrete secondary structures. These features are of fundamental importance to understanding mechanisms and sequence of fold evolution and are of practical importance as records and hosts for fluid migration in and around folds. Incomplete data from natural examples limits the ability to evaluate geometric and physics-based models of folding. Recent advances in digital imaging and analysis now make it possible to produce quantitative three-dimensional descriptions of noncylindrical folds and evaluate the relationships of these forms to the distribution and evolution of fold-related strain. This project has the following objectives: 1) to produce a high-resolution digital surface model of an iconic fold, the Whaleback Anticline in Bear Valley, east-central Pennsylvania; 2) to document the spatial variability of strain around the fold with new observations of grain-scale strain, anisotropy of magnetic susceptibility, and detailed mapping of mesoscale structures in the folded layer; 3) to test the hypothesis that surface curvature controls the spatial variation and style of observed strain around a fold; 4) to evaluate stratigraphic and rheological influences on fold strain, through finite element analysis; 5) to demonstrate the utility of structure-from-motion photogrammetry as a tool for structural geology research and 6) to produce educational resources that will preserve and expand access to a world-class field locality and engage the local community.

褶皱岩层是最具基础性、指导性和魅力的地质构造之一。研究褶皱是为了研究山体构造，了解岩石的工程性质，预测水或碳氢化合物的地下运动，并洞察褶皱本身的基本过程。这些应用依赖于对褶皱内岩石变形的准确解释。各种概念和数学模型预测了褶皱相关的变形。为了评估这种预测模型的能力，需要来自自然例子的数据。这可能是具有挑战性的，因为地球表面的大多数地质褶皱只有部分暴露，大部分褶皱要么埋在地下，要么被侵蚀掉。位于宾夕法尼亚州中东部熊谷的Whaleback背斜是一个独特的地点，在那里暴露了一个完整的大规模褶皱；上个世纪初露天开采煤炭时，发现了它的精致细节。这种出色的曝光可以观察折叠表面的完整三维形状，并提供跨折叠变形的非常详细的记录。这个项目将使用尖端的数字成像技术和传统的地质实地工作来产生一个全面的数据集，以对照这些数据集来测试关于褶皱的假说。除了该项目的科学目标外，这项研究还有助于在科学、技术、工程和数学(STEM)教育领域取得具有社会意义的成果，包括通过研究生和本科生培训发展一支多样化的、具有全球竞争力的STEM工作队伍；开发三所大学的研究基础设施；扩大未被充分代表的群体对科学的参与；以及提高公众的科学素养和公众对科学技术的参与。鲸背背斜是美国东部数十所大学地质系的重要教育实地考察地点，也是当地社区经常使用的娱乐场所。作为这个拟议项目的一部分，我们将保存、扩大和管理来自鲸鱼的地质观测，供研究人员、教育工作者和社区使用。与褶皱有关的变形由分布应变和离散的次级构造记录。这些特征对了解褶皱演化的机制和序列具有重要意义，作为褶皱内和褶皱周围流体运移的记录和宿主具有重要的现实意义。来自自然例子的不完整数据限制了评估基于几何和物理的折叠模型的能力。最近在数字成像和分析方面的进展使得能够对非圆柱形褶皱进行定量的三维描述，并评估这些形式与褶皱相关应变的分布和演化的关系。该项目的目标如下：1)制作一个位于宾夕法尼亚州中东部熊谷的标志性褶皱--Whaleback背斜的高分辨率数字地面模型；2)通过对褶皱周围颗粒尺度应变、磁化率各向异性的新观测以及褶皱层中尺度结构的详细绘制，来记录褶皱周围应变的空间变异性；3)检验表面曲率控制褶皱周围观测应变的空间变化和样式的假设；4)通过有限元分析来评估地层和流变对褶皱应变的影响；5)展示运动结构摄影测量作为结构地质学研究工具的效用，6)制作教育资源，以保护和扩大进入世界级野外地点的机会，并使当地社区参与进来。