In a section measured at Mogollon, Catron Co, NM, Basin-and-Range province, detailed magnetic studies reveal a simple pattern: Cooney Formation and Whitewater Formation [author is referring to Whitewater Creek Member of Cooney Tuff] are older than the other units (Bikerman, 1972), and they are consistently reversely magnetized. They are overlain by Pacific Quartz Latite, which correlates approximately with Apache Spring Quartz Latite. Pacific Quartz Latite is very stable magnetically, but it has an unusual direction of magnetization--therefore, it probably cooled rapidly during a time when the field was reversing. Both in its direction of magnetization and in its magnetic properties, Pacific bears a surprising similarity to Taylor Creek Rhyolite, but is distinctly older. Pacific underlies a sequence of basaltic andesite and rhyolite: Mineral Creek Andesite, Fanney flow-banded rhyolite [Fanney Rhyolite], and Last Chance Andesite are all normally magnetized. Magnetostratigraphic position of Cooney, Whitewater, Mineral Creek, Fanney, and Last Chance units within a preliminary model of the middle Tertiary paleomagnetic reversal pattern is depicted on fig. 5; Taylor Creek is depicted on fig. 4.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Age changed from Miocene to Oligocene on basis of K-Ar whole rock age of 25.0 +/-0.5 m.y. Part of Mineral Creek was mapped previously as Last Chance Andesite by Ferguson (1927). Mapped area is in the Basin-and-Range province.

Source: GNU records (USGS DDS-6; Denver GNULEX).