Preliminary geologic map of the Skull Springs quadrangle, Malheur County, Oregon

Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

“…Clinoptilolite nearly completely replaces ash, and forms euhedral crystals in void space. Brooks and O'Brien (1992), Ferns and O'Brien (1992), Lees (1994), Binger (1997), Evans and Binger (1998a;, Johnson et al (1998), Evans and Binger (1999a;, Camp et al (2003), Nash and Perkins (2012), Ferns and McClaughry (2013), Coble and Mahood, in press, this study (see Appendix A for analyses and description of analytical technique).…”

“…Previous mapping near the Crowley Ranch (C in Fig. 1) (Rytuba and Vander Meulen, 1991;Ferns et al, 1993b;Evans and Binger, 1999a;Evans and Binger, 1999b) indicates that there are rhyolite lavas and several relatively small ignimbrites, but further work is required to determine if any of them are caldera-forming units and whether they are Mid-Miocene in age. It seems more likely that silicic volcanism in this area is Late Miocene in age and is associated with the Newberry/High Lava Plains Trend (Ford et al, 2013), given that it is located near the initiation point of this westward-younging trend of small centers dominated by rhyolitic lava domes (Fig.…”

The Littlefield Rhyolite, Eastern Oregon: Distinct Flow Units and Their Constraints on Age and Storage Sites of Grande Ronde Basalt Magmas

“…Following the pioneering work by Kittleman et al (1965Kittleman et al ( , 1967, a small number of researchers have touched upon various aspects of this extensive rhyolite formation during their investigations. These investigations include more recent 1:24,000 scale geological mapping of select 7.5 minute quadrangles that contain portions of the Littlefield Rhyolite O'Brien, 1992a, 1992b;Evans, 1990Evans, , 1994aEvans, , 1994bEvans, , 1996Evans and Binger, 1996, 1999a, 1999b, 1999c, 1999dEvans and Keith, 1996;O'Brien, 1992a, 1992b) (Figure 6), along with studies of stratigraphic and geochemical correlations of Miocene volcanism in Eastern Oregon (Binger, 1997;Camp et al, 2003;Lees, 1994;Ferns & McClaughry, 2013), and a study of the stratigraphic and structural evolution of the Oregon-Idaho graben (Cummings et al, 2000). Each of these subsequent investigations have shed new light on select portions and various characteristics of this extensive rhyolite, while raising further questions concerning its identity, number of eruptive units, age, emplacement processes, and potential relationship to time-correlative Columbia River Basalt Group (CRBG) magmatism.…”