Paleomagnetism of small basalt exposures in the West Puget Sound Area, Washington, and Speculations on the accretionary origin of the Olympic Mountains
Paleomagnetism of small basalt exposures in the West Puget Sound Area, Washington, and Speculations on the accretionary origin of the Olympic Mountains
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华盛顿州西普吉特海湾地区小型玄武岩暴露的古地磁学以及对奥林匹克山增生起源的推测
DOI：
10.1029/jb087ib05p03755
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发表时间：
1982
影响因子：
--
通讯作者：
D. Engebretson
中科院分区：
文献类型：
--
作者：
M. Beck;D. Engebretson
在奥林匹克山脉以东的两个可能为始新世的玄武岩小规模出露的22个地点，其平均古地磁方向如下：赤纬176.5°;倾角-66.5 °; 95%置信度的圆8.6°。这是对华盛顿西部或俄勒冈州任何地方的前中新世岩石进行的唯一一项古地磁研究，该研究与北美的极移曲线相匹配。然而，一个显着的扇形古地磁偏角周围的奥林匹克核心表明，在这种情况下的一致性是偶然的，结果从造山弯曲期间或之后立即奥运会。奥林匹克山的形成涉及加厚的玄武质地壳的增生，随后是大量海洋沉积碎屑的俯冲，因为法拉隆板块向东北挤压到由温哥华岛和北喀斯喀特山脉的厚结晶块体形成的凹陷中。
Twenty-two sites from two small exposures of basalt of probable Eocene age immediately east of the Olympic Mountains have the following mean paleomagnetic direction: declination, 176.5°; inclination, −66.5°; circle of 95% confidence, 8.6°. This is the only paleomagnetic study of pre-Miocene rocks anywhere in western Washington or Oregon that matches the polar wandering curve for North America. However, a marked fanning of paleomagnetic declinations around the Olympic core suggests that concordance in this case is fortuitous and results from oroclinal bending during or immediately after Olympic orogenesis. Creation of the Olympic Mountains involved accretion of thickened basaltic crust followed by underthrusting of large quantities of oceanic sedimentary debris, as the Farallon plate pressed northeastward into a recess formed by the thick crystalline blocks of Vancouver Island and the North Cascades.