Volcanic Ash Layers in the Miocene Lake Clarkia Beds: Geochemistry, Regional Correlation, and Age of the Clarkia Flora
Volcanic Ash Layers in the Miocene Lake Clarkia Beds: Geochemistry, Regional Correlation, and Age of the Clarkia Flora
复制标题
中新世克拉克亚湖床中的火山灰层：地球化学、区域相关性和克拉克亚植物群的年龄
作者：
Jeffery A. Ladderud;J. Wolff;W. Rember;M. Brueseke
摘要本文介绍了爱达荷州北部克拉基亚地区中中新世湖相沉积物中灰层的化学数据。克拉基亚湖床以其特殊的叶子和其他化石保存而闻名。火山灰床有一系列的化学成分，表明在北美西部不同的构造环境中有不同的喷发源：黄石火山热点区、喀斯喀特火山弧，以及潜在的西南内华达州火山区。少数火山灰层可与已知年代的火山灰沉积物相联系。这些相关性表明，中新世湖Clarkia沉积物的年龄介于15.4和16.0 Ma之间。这个湖是在古老的圣马里斯河被瓦纳普姆玄武岩（哥伦比亚河玄武岩群）的祭司急流成员的水流阻塞时形成的，以前被认为是15Ma。
Abstract We present chemical data for ash beds interbedded within mid-Miocene lacustrine sediment in the vicinity of Clarkia, north Idaho. The Clarkia lake beds are well known for their exceptional preservation of leaf and other fossils. The ash beds have a range of chemical compositions, indicating eruption from diverse sources located within different tectonic environments in western North America: the Yellowstone hotspot province, the Cascades volcanic arc, and potentially the Southwest Nevada Volcanic Field. A few ash beds can be correlated with tephra deposits of known age. These correlations indicate that the age of the Miocene Lake Clarkia deposits lies between 15.4 and 16.0 Ma. The lake formed when the ancestral St. Maries River was dammed by a flow of the Priest Rapids Member of the Wanapum Basalt (Columbia River Basalt Group), previously assigned an age of ∼ 15 Ma.