Preliminary report on the geology of the Lakeview uranium area, Lake County, Oregon

The Steens Mountain (Oregon) Geomagnetic Polarity Transition: 3. Its regional significance

“…The reversely magnetized Steens Basalt and its equivalents maintain a maximum thickness of 400-500 m throughout a relatively large area represented by five sections, from Abert Rim eastward to Steens Mountain and from there, southward to Orevada View. Throughout this area, the pre-Steens topography was irregular, with local relief of as much as 1000 m [Larson, 1965;Avent, 1970;Wells, 1979;Walker, 1980]. That the reversed-polarity Steens Basalt and its equivalents could infill the low spots to a relatively uniform thickness suggests that the source vents were widely distributed.…”

“…As is stated byMankinen et al [1985], data from the lower part of the Steens Basalt are sparse and modifications to this part of the directional variation curve will probably be required.Abert RimLithologically and stratigraphically[Larson, 1965;Wells, 1979-1, the flow-on-flow sequence of basaltic lavas on Abert Rim(Figure 1)is closely similar to that at Steens Mountain. Additionally, four whole-rock K-Ar age determinations of 15.1 Ma[Walker, 1980], 15.5 Ma [Carlson and Hart, 1983a], and 15.7 and 14.6 Ma [Hart and Mertzman, 1982] from flows high on Abert Rim indicate general contemporaneity with the Steens Mountain section. Additionally, Carlson and Hart [1983a, b] conclude from Nd and Sr isotopic data that the Abert Rim section closely correlates with that on Steens Mountain.The sequence of lava flows at Abert Rim was sampled in two localities (B and C) byWatkins [1963]; all flows proved to be reversely magnetized.…”