Paleomagnetism, Potassium-Argon Ages, and Geology of Rhyolites and Associated Rocks of the Valles Caldera, New Mexico

Astronomically calibrated ages for geomagnetic reversals within the Matuyama chron

“…In addition to the Cobb Mountain subchron and Kamikatsura polarity interval, they identified two short normal polarity events, called the Santa Rosa and Punaruu polarity intervals. Recently, Singer and Brown (2002) gave an age of 899 ± 6 ka for the Kamikatsura polarity interval and re-dated the Santa Rosa event recorded in rhyolite domes of Valles Caldera, New Mexico, at 936 ± 8 ka (Table 1), which were originally dated by the K-Ar and 40 Ar/ 39 Ar methods (Doell et al, 1968;Spell and McDougall, 1992;Izett and Obradovich, 1994). This age interpretation is consistent with independent evidence.…”

Evaluation of the potential for surface faulting at TA-63. Final report

“…Gardner and House (1987) provide critical reviews of pertinent literature concerning the tectonic setting of the LANL area, field studies of the Pajarito fault zone, and previous seismologic and site-response investigations. Major stratigraphic and structural relations in the LANL region are adequately known from numerous detailed investigations (Doell et al, 1968;Smith et al, 1970;Budding, 1978;Manley, 1979;Golombek, 1983; 1-4…”

Geologic evolution of the Jemez Mountains and their potential for future volcanic activity

“…The first eruptive sequence, 1.4 Myr ago, 45 deposited about 300 km 3 of rhyolite ash and pumice around the central mass. 39 The roof of the partially emptied magma chamber collapsed, torming the Toledo caldera, 12 km in diameter (Fig.…”

“…42 Possible leakage of magma from the fractures may have produced minor eruptions at that time. 42 Magma pressure continued to increase until, 1.1 Myr ago, 45 the eruptions began, possibly resulting from displacements along the fracture zone reducing the confining pressure on the magma. Rapidly expanding volatiles in the magma whipped the polymerized silicate melt to a froth and forced it upward along the ring fractures, resulting in a thin layer of ejected pumice blanketing the flanks of the volcano.…”