COLLABORATIVE RESEARCH: Uplift and Exhumation Along the San Andreas Fault Zone; an Empirical Study of Transpression

平移挤压发生在圣安德烈斯断层系统的沿着42%。因此，它对转换断层行为的影响具有一级重要性，并且可能是全面了解走滑断层和板块边界行为的最重要的复杂因素之一。考虑到这一点，PI提出了一项合作研究，该研究将系统地、定量地整合关于在圣安德烈亚斯断层沿着几个地点适应压扭变形方式的地质约束。对平移挤压的功能性理解将使垂直变形的模式易于预测，其中主要边界条件，如板块运动的垂直度和主要转换断层的力学，是已知的。然而，圣安德烈亚斯断层的材料属性是有争议的，大量的证据表明，次要因素（结构和岩性的异质性，侵蚀性）发挥了重要作用，在塑造地质的转换压力的反应。因此，对于压扭板块运动如何表现为地壳变形的一般性认识还没有发展起来。PI的目标之一是定量评估外部因素对变形分区的影响，这样我们就可以最终评估基于圣安德烈亚斯断层力学性质假设的压扭变形模型。他们的方法将是利用垂直运动的空间和时间分布，表现在基岩隆起（表面隆起+折返），作为一个代表性的平移。他们将结合联合收割机热年代学的限制（（U-Th）/He测年）的年龄和规模的折返与地貌和结构的限制，表面隆起，侵蚀，和架构的变形，驱动这个基岩隆起。他们将使用这些补充技术来确定垂直运动的模式是如何在空间上分布相对于圣安德烈亚斯断层（即近场与远场）及其与板块运动的相似性。因此，PI的目标是开发一个函数之间的关系，transressive变形和这些关键变量。这就需要控制垂直运动的时间顺序如何与每个地点的转换挤压的出现有关，以及控制沿着走向的独立边界条件（如地质、结构、气候）的影响。他们将集中在四个地点（卡里索平原/滕伯勒山脉，圣艾米迪奥山脉，北方圣加布里埃尔山脉，和科切拉山谷），其中每一个代表了一个主要的差距，在理解的transpressure沿着圣安德烈亚斯断层。这些网站的综合结果，与以前的研究合成时，将提供完整的范围内的边界条件和transpressive参数需要创建特定的测试ofdifferent模型的transpressive变形。这项建议的一个关键方面是在实现我们的目标方面将进行的合作。PI对南加州的地质和分析技术有着广泛的了解。斯波蒂拉是第一个应用这种综合方法来理解横岭部分的人。豪斯一直在积极地研究热年代学技术的新应用，这项研究将采用这种技术。布雷迪在构造地质学和地球物理学方面提供了一个坚实的基础，将隆起估计与个别结构联系起来。博士后助理Niemi将在新生代地层学，构造地质学和野外测绘方面增加额外的专业知识。这一数量的PI还将使我们能够同时在所有现场开始工作，并代表一个足够强大的科学团队来解决这一重大问题。

Transpression occurs along 42% of the San Andreas fault system. Its influence on the behavior of the transform fault is thus of first-order importance and may represent one of the most important complications in developing a comprehensive understanding of how strike-slip faults and plate boundaries behave. With this in mind, the PI's propose a collaborative study that will systematically and quantitatively integrate geological constraints on the manner in which transpressional deformation is accommodated at several sites along the San Andreas fault. A functional understanding of transpression would make patterns of vertical deformation easy to predict where primary boundary conditions, such as the degree of plate motion obliquity and the mechanics of the main transform fault, are known. However, the material properties of the San Andreas fault are debated, and considerable evidence suggests that secondary factors (structural and lithologic heterogeneity, erosivity) play a significant role in shaping the geologic response to transpression. As a result, a general understanding of how transpressional plate motion becomes manifest as deformation in the crust has not been developed. One of the PI's objectives is to quantitatively evaluate the effects of external factors on deformation partitioning, so that we may ultimately evaluate models of transpressional deformation that are predicated on assumptions of the mechanical properties of the San Andreas fault. Their approach will be to use the spatial and temporal distribution of vertical motion, manifested in bedrock uplift (surface uplift + exhumation), as a representation of transpression. They will combine thermochronologic constraints ((U-Th)/He dating) on the age and magnitude of exhumation with geomorphic and structural constraints on surface uplift, erosion, and the architecture of deformation that drives this bedrock uplift. They will use these complementary techniques to determine how patterns of vertical motion are spatially distributed with respect to the San Andreas fault (i.e. near vs. far field) and its obliquity to plate motion. The PI's objective is thus to develop a functional relationship between transpressive deformation and these key variables. This will require developing controls on how the chronology of vertical motion relates to the emergence of transpression at each site as well as controls on the effects of independent boundary conditions (e.g. geological, structural, climatic) along strike. They will focus on four sites (Carrizo Plain/Temblor Range, San Emigdio Mountains, northern San Gabriel Mountains, and Coachella Valley), each of which represents a major gap in understanding of transpression along the San Andreas fault. The integrated results from these sites, when synthesized with previous studies, will provide the full range in boundary conditions and transpressive parameters needed to create specific tests ofdifferent models of transpressional deformation. A key aspect of this proposal is the collaboration that will be employed in attaining our goal. The PI's have extensive knowledge of southern California geology and the analytical techniques to be employed. Spotila was among the first to apply this type of integrated approach to understanding portions of the Transverse Ranges. House has actively pursued new applications of the thermochronologic technique that will be employed in this study. Brady provides a robust foundation in structural geology and geophysics that will link uplift estimates with individual structures. Post-doctoral associate Niemi will add an additional expertise in Cenozoic stratigraphy, structural geology, and field mapping. This number of PI's will also enable us to begin work at all field sites concurrently and represents a science team strong enough to tackle this significant problem.