Collaborative Research: Integrating tectonics, climate, and mammal diversity

研究人员试图了解构造板块的运动是如何控制北美西部哺乳动物的进化和地理分布的。构造板块的运动产生了主要的山脉屏障并影响了区域气候。地球观测可移动阵列（EarthScope Transportable Array）是一个由地震台站组成的网络，它所产生的数据使人们对美国西部的地球结构有了前所未有的了解，这为考虑如何用地震方法成像地球的三维结构提供了一个独特的起点。结合丰富的已发表的记录过去36 Ma板块构造和变形历史变化的结构记录，我们可以在哺乳动物进化的这一重要时期估计整个美国西部的地壳厚度和地形。研究人员建议使用3D模型来了解美国西部地形的崩塌，这导致了哺乳动物多样性的显著变化，这些变化与断层运动记录中记录的应变率变化相吻合。这项研究将通过以下团队的合作来完成：1)改进包含哺乳动物记录的沉积记录的年代测定，以及对代表性不足的地区和时间间隔的化石进行集中采样；2)为考虑热通量和边界条件变化的岩石圈改造制作3D模型；3)建立在地形限制基础上的区域气候模型；4)分析了哺乳动物的物种形成和多样性及其与地形和气候梯度的关系，并将所有结果综合成一个4D模型，反映了过去36 Ma的变化。最终目标是对导致地壳和地形变化的因素以及这些因素如何影响哺乳动物的物种形成和多样化产生更基本的理解。地壳和地幔动力学的定量分析为推进与美国西南部经济地质（矿物带）相关领域的知识提供了一个重要的框架。这项研究将为高中、本科、研究生和博士后研究人员提供宝贵的技术培训。合作团队将开发一些外联产品，包括面向公众的信息视频、密歇根大学自然历史博物馆的博物馆演示和展览材料、石溪的部门博物馆展示材料，以及面向公众的演讲和演示材料。综合地形模型显示，内华达州中部、东部和南部、犹他州西部、加利福尼亚州最东部部分地区和亚利桑那州最西部中部地区的平均海拔为~4.36 +/- 0.4 km（1西格玛）。我们的模型显示，内华达高原连接着一条连续的山脉，穿过亚利桑那州东南部，进入墨西哥北部。这种地形是塞维尔-拉拉米造山运动使地壳缩短的长期历史的结果。从36 Ma到现在，这一巨大山脉的地形崩塌，导致了200%的扩展，形成了今天的盆地和山脉，并沿着增厚地壳带挖掘出变质核杂岩。岩石圈体力的分布至今仍在推动这种崩塌。众所周知，重力势能的差异会导致伸展变形，特别是在极端地形的地区。然而，崩塌时间的原因，以及造成崩塌的偏应力的大小和分布，仍然是个谜。与伸展崩塌相关的地形变化极大地改变了西部科迪勒拉地区的气候和哺乳动物多样性动态。我们的研究主要集中在三个方面：(1)地形、分布和三维偏应力对崩塌历史的影响；(2)气候对崩塌和气候梯度产生的响应；(3)哺乳动物谱系和动物群对地形和气候梯度变化和地形障碍移除的响应。气候梯度及其对哺乳动物多样性影响的研究尚未与大陆形变的定量运动学和动力学重建相结合。这项研究的智力价值包括结合这些领域的力量，同时在分析的所有阶段将形式不确定性纳入模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The researchers seek to understand how movement of tectonic plates, which produced major mountain barriers and influenced regional climate, controlled the evolution and geographic distribution of mammals in western North America. The EarthScope Transportable Array, a network of seismic stations, has produced data that allow an unprecedented view of the Earth's structure in the western United States, providing a unique starting point from which to consider how it came to have the 3-D structure that is imaged by seismic methods. This, combined with a rich published record of structures that record changes in plate tectonics and deformation history over the past 36 Ma, allows us to estimate crustal thickness and topography throughout the western US over this important interval in mammal evolution. The researchers propose to use 3D models to understand the collapse of topography in the western US, which led to marked changes in mammal diversification that coincide with changes in the strain rates recorded in the fault movement record. The research will be accomplished through collaboration of teams that will 1) Improve dating of the sedimentary record that contains the mammalian record, as well as focused sampling of fossils from under-represented areas and time intervals, 2) produce 3D models for lithosphere modification that account for changes in heat flux and boundary conditions, 3) model regional climate that builds on topographic constraints, 4) analyze mammal speciation and diversification and its links over time with topography and climatic gradients, and 5) synthesize all of the results into a 4D model for change through the past 36 Ma. The ultimate goal is to produce a more fundamental understanding of the factors responsible for crustal and topographic changes and how these influence mammal speciation and diversification. The quantitative analysis of crust and mantle dynamics provides an important framework for advancing knowledge in fields linked to the economic geology (mineral belts) of the southwestern US. The research will provide valuable technical training to high school, undergraduate, graduate and post-doctoral researchers. The collaborative team will develop several outreach products, including an informational video for the general public, materials for museum presentations and exhibits at the University of Michigan Museum of Natural History, the departmental Museum Display at Stony Brook, and materials for talks and presentations to the public.The integrated topography model shows a Nevadaplano of ~4.36 +/- 0.4 km (1-sigma) average elevation in central, eastern, and southern Nevada, western Utah, parts of easternmost California, and central portions of westernmost Arizona at 36 Ma. Our model shows that highlands of the Nevadaplano connected to a continuous mountain chain through southeastern Arizona and into northern Mexico. This topography results from the long history of crustal shortening from Sevier - Laramide orogenies. The topography of this massive range collapsed from 36 Ma to the present, leading to as much as 200% extension, the present-day Basin and Range, and exhumation of metamorphic core complexes along the belt of thickened crust. Distributions of lithospheric body forces continue to drive this collapse today. Differences in gravitational potential energy are known to drive extensional deformation, particularly in regions of extreme topography. Yet the reasons for the timing of the collapse, along with the magnitudes and distributions of deviatoric stresses responsible for the collapse, remain enigmatic. The changing topography associated with extensional collapse dramatically altered the climate and mammal diversity dynamics of the western Cordillera. Our research targets three topics within the Integrated Earth System: (1) The topography, distribution, and 3-D deviatoric stresses responsible for the collapse history, (2) The climatic response to the collapse and generation of climate gradients, and (3) The response of mammal lineages and faunas to changing topographic and climate gradients and removal of topographic barriers. No previous study of climate gradients and their impact on mammal diversity has ever been integrated with quantitative kinematic and dynamic reconstructions of continental deformation. The intellectual merit of this study involves the power of combining these fields, while incorporating formal uncertainties in models at all stages of analysis.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.