"Collaborative Research: Milankovitch-Scale Time Resolution in Growth Strata to Determine Rates and Kinematics of Folding"

“合作研究：生长层中的米兰科维奇尺度时间分辨率以确定折叠速率和运动学”

• 批准号: 0230053
• 负责人: David Anastasio
• 金额: $ 14.35万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-15 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230053&HistoricalAwards=false
• 关键词: Collaborative; Research; Milankovitch; Scale; Time

Using sedimentary cycles generated from orbitally forced climatic changes(~20,000-400,000 year duration Milankovitch rhythms), the PI's seek to elucidate thecomplex kinematics of decollement folds, refine methodological approaches forevaluating growth structures, and determine high-resolution deformation chronologieswith a multidisciplinary structural, stratigraphic, and magnetic study. Decollement foldsare an important structural style in most orogenic belts and dominate where strongcompetency contrasts and thick, weak layers characterize deformed stratigraphicsequences. The interpretation, evaluation, and reconstruction of tectonic structuresrequires an understanding of kinematics and geometry alone cannot constrain thedistribution of deformation, fold kinematics, or fold mechanics. Growth structuresprovide a unique opportunity to deconvolute the deformational and depositionalprocesses of orogenic landscapes. The PI's propose to evaluate spatial variations in deformation patterns as a function of structural geometry, lithology, and stratigraphic position throughout two well-exposed anticlinoria; one at Sierra del Fraile, northeastern Mexico and another in the central External Sierra, north central Spain. Both field areas contain large-scale, evaporite-cored, synsedimentary decollement folds. Prolonged fold growth occurred in varying water depths and depositional environments at each site and were recorded by a variety of unconformity geometries and changes in growth strata thickness. These relationships will allow comparison of the complex interaction between deformational topography and depositional processes and a means to evaluate kinematic controls on growth strata geometries. The PI's will map and sample rocks for magnetic susceptibility, anisotropy of magnetic susceptibility (AMS), and calcite twinning measurements. AMS measurements in pregrowth strata will be used as a proxy for deformation fabric and will be augmented by twinning studies to constrain fold kinematics. Growth strata geometry will be used to distinguish between fixed and migrating axial surfaces as a fully independent means of assessing fold kinematics. Milankovitch-scale correlation of magnetic susceptibility variations and absolute ages will be used to establish a chronostratigraphy allowing for ~20,000 year temporal control on depositional and deformational rates within both the Sierra del Fraile and External Sierra growth strata. Reconnaissance investigations in both field areas provided pilot data confirming unparalleled opportunities to generate high-resolution spatial and temporal analysis of fold kinematics. The combination of excellent exposures of climatically controlled cyclic stratigraphy and synsedimentary deformation in the two field areas provide an exceptional opportunity to determine the kinematics of large-scale decollement folding, an important structural style in most orogenic belts.

利用轨道强迫气候变化产生的沉积旋回（持续时间约20，000 - 400，000年的米兰科维奇韵律），PI试图阐明滑脱褶皱的复杂运动学，改进评估生长结构的方法，并通过多学科的结构，地层和磁性研究确定高分辨率的变形年代学。滑脱褶皱是大多数造山带中的一种重要构造样式，并在强烈的能力对比和厚而弱的层位特征的变形地层序列中占主导地位。构造构造的解释、评价和重建需要运动学和几何学的理解，而仅仅理解运动学和几何学并不能约束变形、褶皱运动学或褶皱力学的分布。生长构造提供了一个独特的机会去卷积造山景观的变形和沉积过程。PI的建议，以评估变形模式的空间变化作为一个功能的结构几何形状，岩性和地层位置在整个两个暴露良好的背斜;一个在塞拉利昂德尔Fraile，墨西哥东北部和另一个在中部外部塞拉利昂，西班牙中北部。两个油田区域都含有大规模的、以辉长岩为核心的同沉积滑脱褶皱。延长褶皱生长发生在不同的水深和沉积环境中，在每个站点，并记录了各种不整合的几何形状和生长地层厚度的变化。这些关系将允许变形地形和沉积过程之间的复杂的相互作用的比较和手段，以评估生长地层的几何形状的运动学控制。PI的将映射和样品的磁化率，磁化率各向异性（AMS）和方解石孪生测量岩石。AMS测量在前生长地层将被用作变形组构的代理，并将通过孪生研究来约束褶皱运动学。生长地层的几何形状将被用来区分固定和迁移的轴向表面作为一个完全独立的手段评估褶皱运动。磁化率变化和绝对年龄的米兰科维奇尺度相关性将用于建立年代地层学，允许对Sierra del Fraile和外部Sierra生长地层内的沉积和变形速率进行约20，000年的时间控制。在这两个领域的侦察调查提供了试点数据，确认无与伦比的机会，以产生高分辨率的空间和时间分析褶皱运动学。气候控制的旋回地层和同沉积变形在两个领域的优秀曝光相结合，提供了一个特殊的机会，以确定大规模的滑脱褶皱，在大多数造山带的重要结构样式的运动学。