Title: Preliminary investigation of the magnetostratigraphy of the Ringold Formation
Abstract: The Ringold Formation consists of lacustrine and fluvial deposits overlying the Columbia River Basalt. The Ringold Formation, because of its thickness, extent, and age, is an excellent unit in which to detect and possibly data the deformation that has occurred since deposition of the basalt. One objective of this study was to investigate the paleomagnetism of the upper Ringold unit exposed at one location in the White Bluffs in enough detail to resolve, with reasonable confidence, the magnetostratigraphy of the rock units sampled. The other objective was to evaluate, in a preliminary manner, the paleomagnetic favorability and magnetostratigraphy of the subsurface Ringold Formation in the Pasco Basin and at selected exposures outside the Pasco Basin. The scope of this study was the collection of 300 paleomagnetic samples, their measurement, and analysis. Samples were collected from the White Bluffs, from core recovered from six drill holes on the Hanford Site, and from two surface exposures outside the Pasco Basin. A total of 294 samples was collected, and 2928 paleomagnetic measurements were performed on these samples. The samples were measured by means of a three-axis super-conducting rock magnetometer having a sensitivity of 10/sup -8/ emu/cm/sup 3/ and were demagnetized progressively in a 400-hertz alternating field (AF). All data were recorded and processed during measurement by an on-line computer.The declination, inclination, and intensity of magnetization of the samples from the various sections are plotted as a function of their stratigraphic position. The directions of the magnetization of the various sections are also plotted as a group on Wulff equal-angle stereonets. 22 figures, 8 tables.