Strain partitioning in the northern Walker Lane, western Nevada and northeastern California
- 作者：Cashman ; Patricia H. ; Fontaine ; Sheryl A.
- 关键词：Walker Lane ; strain partitioning ; block notation ; intracontinental strain
- 刊名：Tectonophysics
- 出版年：2000
- 期刊代码：82_00401951
- 类别：ear
- 出版时间：November 10, 2000
- 卷：326
- 期：1-2
- 页码：111-130
- 文件大小：738 K
摘要
Paleomagnetic studies constrain both the kinematics and the timing of Neogene intracontinental strain in the Walker Lane of northwestern Nevada–northeastern California. The northwest-trending Walker Lane is a zone of complex faulting and dextral offset along the boundary between the Sierra Nevada and the Basin and Range. Here, an extensive Tertiary volcanic section provides a paleomagnetic test for vertical-axis rotation. The 25.1Ma Nine Hill tuff covered the two structural domains of northern Walker Lane and parts of the adjacent provinces. In the northernmost domain, the Pyramid Lake domain, the Nine Hill tuff is unrotated or rotated slightly counter-clockwise. In contrast, Nine Hill tuff is rotated 35–44° clockwise in the northeastern part of the adjacent Carson domain. Usable exposures of the tuff are lacking elsewhere in the Carson domain, but 9–13Ma basalts record 37°–51° clockwise vertical-axis rotation. These basalts were sampled at three sites encompassing the N–S length of the Carson domain. Younger basalts from the Carson domain show smaller clockwise rotations. The paleomagnetic studies show that the deformation in the northern Walker Lane is partitioned into domains dominated by translation, rotation and extension. Dextral slip along the Walker Lane is accommodated primarily by northwestward translation in the Pyramid Lake domain, and by clockwise vertical-axis rotation in the Carson domain. Some Neogene extension is also accommodated in the Walker Lane, but most of it is occurring to the west of the Walker Lane, along the edge of the Sierra Nevada.Comparison of paleomagnetic results from rocks of different ages constrains the timing of the present deformation regime in the Walker Lane. The similar rotations recorded in 25Ma and 9–13Ma rocks indicates that virtually all of the rotation in the Carson domain occurred after the eruption of the 9–13Ma basalts. Smaller rotations recorded in younger rocks constrain rotation rate.