Magmatic Pulsing and Changes in Titanium Concentration during Miocene Volcanism in Oregon

Abstract

IF a genetically associated section of lavas can be shown to span a considerable part of geological time, then a coarse time factor for any observed geochemical trends may be obtained. Should very large time differences exist between lavas, however, the probability that magmatically discrete phenomena are present (unrelated to progressive chemical changes at depth) increases. To estimate magmatic time factors, therefore, lavas extruded in relatively rapid succession are required. Estimation of the time range then becomes extremely difficult, however. Periods from 10 to 10⁴ yr between successive ancient lavas cannot usually be distinguished with any certainty.