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升历史目前是地质争论的主题。该研究项目的目标是通过利用新生代火山岩和沉积岩来描述内华达山脉中部在数千万年时间内的地貌演化特征，以便通过三重研究工作确定火山活动和断层活动与构造事件的联系。首先，对古河道中保存的第三纪地层进行详细测绘、沉积相分析和测年，用于了解中部塞拉山脉景观的演变以及它与该范围其他地区景观的比较。这些古河道的源头在内华达山脉中部，其中的物质向西输送到今天的萨克拉门托山谷。这些古河道中保存的地层提供了与构造过程相关的隆起和再切割事件的记录。该研究项目将测试这样的观点，即中山脉可能发生了三期新生代隆升，其时间可能对应于：（1）大约1500万年前弧岩浆活动的爆发，（2）大约1000万年前盆山断层的爆发，以及（3）大约600万年前三重交界点的到来。其次，火山-火山碎屑岩和侵入岩的结构测绘和测年被用来确定内华达山脉中部山脉前缘断层的起始年龄、其性质以及它是连续进行还是间歇进行。内华达山脉地块与大盆地其余部分之间现今至第四纪的位移大部分是沿着内华达山脉前缘断层中的沃克莱恩带（一个宽约 150 公里宽的复杂系统，主要是右旋走滑断层，目前容纳了约 20-25% 的太平洋-北美板块运动）的西缘发生的。第三，正在研究内华达山脉中部的新近纪火山和侵入岩中心，以了解第三纪祖先瀑布弧的古地理和构造演化。特别是，该项目将探讨内华达山脉的原始喀斯喀特弧可能发生过三个阶段的火山活动：大约14-1500万年前、9-1000万年前和6-700万年前。内华达山脉是美国本土最长、最高的山脉。长期以来，它也被认为是最年轻的山脉之一，通过新生代晚期的倾斜而隆起。 沿其东缘断层的刚性块体。然而，最近的研究提出了内华达山脉更复杂的隆升历史，一些人认为该山脉非常古老。此外，内华达山脉被认为是造山基本过程的原型，通过岩石圈沉入地幔（根分层）来完成。该研究项目将提供新数据，有助于了解这座重要山脉并帮助解决其中一些争议。此外，研究结果还将揭示地震活动活跃的人口稠密地区——里诺-布里奇波特地区的断层历史。最后，该项目将使学生参与科学研究，并促进代表性不足的群体参与地球科学。