Geologic Constraints on Landscape Evolution of the Sierra Nevada, California: Paleochannels, Magmatism and Structure

加利福尼亚州内华达山脉景观演化的地质约束：古河道、岩浆作用和结构

• 批准号: 0711181
• 负责人: Cathy Busby
• 金额: $ 22.5万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-15 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711181&HistoricalAwards=false
• 关键词: Geologic; Constraints; Landscape; Evolution; Sierra

The age and uplift history of the Sierra Nevada are currently the subjects of geologic debate The goal of this research project is to characterize the landscape evolution of the central Sierra Nevada over a time period of tens of millions of years by using Cenozoic volcanic and sedimentary rocks in order to determine linkages of volcanism and faulting to tectonic events through a three-fold research effort. First, detailed mapping, sedimentary facies analysis, and dating of Tertiary strata preserved in paleochannels are being used to understand the evolution of the central Sierran landscape and how it compares with that of the rest of the range. These paleochannels had their headwaters in central Sierra Nevada, and material within them was transported westward to the present-day Sacramento Valley. Strata preserved in these paleochannels provide a record of uplift and re-incision events that can be linked to tectonic processes. The research project will test the idea that three episodes of Cenozoic uplift may have occurred in the central Sierra and the timing of these may correspond to the: (1) onset of arc magmatism about15 million years ago, (2) onset of Basin and Range faulting about10 million years ago, and (3) arrival of the triple junction about 6 million years ago. Second, structural mapping and dating of volcanic-volcaniclastic and intrusive rocks are being used to determine the inception age of range-front faulting in the central Sierra Nevada, its nature, and whether it proceeded continuously or episodically. Much of the present-day to Quaternary displacement between the Sierra Nevada block and the rest of the Great Basin is being taken up along the western edge of the Walker Lane belt (an approximately 150 km wide complex system of dominantly right-lateral strike slip faults that currently accommodates about 20-25% of the Pacific-North America plate motion) in the range-front faults of the Sierra Nevada. Third, Neogene volcanic and intrusive rocks centers in the central Sierra Nevada are bieing investigated to understand the paleogeographic and tectonic evolution of the Tertiary Ancestral Cascades arc. In particular, the project will explore the idea that three phrases of volcanism may have occurred in the ancestral Cascades arc of the Sierra Nevada: at about 14-15 million years ago, 9-10 million years ago, and 6-7 million years ago.The Sierra Nevada is the longest and tallest mountain chain in the coterminous U.S. It has also long been considered to be among the youngest, with uplift through Late Cenozoic tilting of a rigid block about faults along its eastern margin. More recent research, however, has proposed a more complex uplift history for the Sierra Nevada, and some have argued that the range is very old. Additionally, the Sierra Nevada is considered the prototype of a fundamental process in mountain building, accomplished by foundering of lithosphere into the Earth's mantle (root delamination). This research project will provide new data that will contribute to the understanding of this important mountain range and help resolve some of these controversies. Furthermore, results will inform the history of faulting in a heavily populated area of active seismicity, the Reno-Bridgeport area. Finally, the project will engage students in scientific research and will foster participation of underrepresented groups in the earth sciences.

内华达山脉的年龄和隆起史目前是地质学争论的主题。这一研究项目的目标是利用新生代火山岩和沉积岩来描述内华达山脉中部几千万年来的地貌演变，以便通过三项研究努力确定火山作用和断层与构造事件的联系。首先，对保存在古河道中的第三系地层进行了详细的测绘、沉积相分析和年代测定，以了解西耶兰中部地貌的演变以及它与山脉其他地区的对比情况。这些古河道的源头位于内华达山脉中部，其中的物质被向西输送到今天的萨克拉门托山谷。保存在这些古河道中的地层记录了与构造过程有关的抬升和重新切割事件。该研究项目将检验这一观点，即塞拉利昂中部可能发生了三次新生代隆起，其时间可能对应于：(1)大约1500万年前开始的弧岩浆活动，(2)大约1000万年前的盆地和山脉断层，以及(3)大约600万年前三重交界处的到来。其次，火山-火山碎屑岩和侵入岩的构造制图和年代测定正在被用来确定内华达山脉中部山前断裂的开始年龄、性质以及它是连续进行的还是断续进行的。现今内华达山脉地块和大盆地其余部分之间的大部分到第四纪的位移是沿着内华达山脉前缘的沃克连带(一个大约150公里宽的以右行走滑为主的复杂断层系统，目前容纳了大约20%-25%的太平洋-北美板块运动)被吸收的。第三，对内华达山脉中部的新近纪火山岩和侵入岩中心进行了调查，以了解第三纪祖先级联弧的古地理和构造演化。特别是，该项目将探索内华达山脉的祖先级联弧形火山可能发生的三个阶段：大约1400万至1500万年前，900万至1000万年前，以及600万至700万年前。内华达山脉是毗邻美国的最长、最高的山链。长期以来，它也一直被认为是最年轻的山脉之一，通过晚新生代围绕其东部边缘的断层的刚性地块的倾斜而隆起。然而，最近的研究提出了内华达山脉更复杂的隆起史，一些人认为这一范围非常古老。此外，内华达山脉被认为是造山的基本过程的原型，通过岩石圈下沉到地球地幔(根部分层)来完成。这一研究项目将提供新的数据，有助于了解这一重要的山脉，并有助于解决其中的一些争议。此外，研究结果还将揭示人口密集、地震活跃的雷诺布里奇波特地区的断层历史。最后，该项目将吸引学生参与科学研究，并将促进未被充分代表的群体参与地球科学。