Paleomagnetism and potassium-argon ages of some volcanic rocks from the Rio Grande Gorge, New Mexico

This is the authors' abstract. We don't add key points for this paper.

Successive lava flows exposed in the Rio Grande gorge, near Taos, New Mexico, can be divided into three groups, each of different magnetic polarity: the upper and lower groups have a normal polarity, whereas the middle one has a reversed polarity. K-Ar radiometric ages indicate that the base of the upper normal polarity sequence is about 3.7 m.y. old and that the reversed flows range from 3.7 m.y. to 4.4 m.y. The lowermost normal flow has the K-Ar age of 4.5 m.y. The age difference between the base of the upper normal and the top of the adjacent reversed flow group is about 0.05 m.y., indicating rapid, polarity switching.