Dating of the Upper Pleistocene Holocene volcanic activity of La Palma using the unspiked K-Ar technique

Abstract

Combined unspiked K–Ar dating and detailed mapping have established the eruptive chronology of the Cumbre Vieja volcano in the Canary islands. The CV volcano is a large polygenetic volcano (subaerial area: 220 km2, subaerial volume: 125 km3, elevation above sea level: 2000 m), which rests on the southern flank of the older Taburiente-Cumbre Nueva volcano. We defined two stratigraphic units by their relationship to the development of coastal cliffs developed around the Cumbre Vieja volcano: a cliff-forming series and a scree-forming series which is draped over the cliffs and forms the coastal platforms at their bases. K–Ar ages were measured from 20 samples from the two series. There are no discrepancies between K–Ar ages and the stratigraphy, the K–Ar ages of one flow compare well with determinations (: 3.2±0.1 ka; K–Ar: 4±2 ka). The ages of the scree-forming series range from 3±2 ka to 21±2 ka. The cliff-forming series ages range from 20±2 ka to 123±3 ka, but as the base of the sequence is not exposed the growth of the Cumbre Vieja volcano must have begun substantially earlier. The boundary between the two coincides with the low sea-level stand in the last glacial maximum, which we infer to have been a period of intense coastal erosion. Dated samples from the upper part of the Taburiente-Cumbre Nueva volcano range in age from 853±10 ka to 566±8 ka. The age of the youngest Taburiente-Cumbre Nueva volcano sample provides an upper bound on the age of the subsequent Cumbre Nueva giant lateral collapse.