The Cumbre Nueva collapse (La Palma, Canary Islands): New age determinations and evidence of an isotopic excursion

Abstract

Episodic giant landslides characterize the history of intraplate oceanic volcanic islands, disrupting the gradual accumulation of eruptive products during shield-building stages. On La Palma (Canary Islands), the giant Cumbre Nueva collapse, which ended volcanic activity at the Paleo-Cumbre Nueva rift, formed the 11 km wide “Caldera de Taburiente” collapse embayment. Lavas erupted before and after this collapse have been studied, and 40Ar/39Ar ages of groundmass separates from key flows are presented, particularly from the small post-collapse Bejenado volcano that grew within the collapse scar. The new data constrain the age of the Cumbre Nueva collapse to between 519 ± 20 ka and 529 ± 12 ka (2s) and confirm that it occurred during a period of rapid re-surfacing of the island. This study has also constrained the duration of activity of the post-collapse Bejenado volcano, and the results indicate that this was also brief (529 ± 12 ka to 491 ± 16 ka). Starting just before the time of the collapse, the radiogenic isotope compositions of the lavas shifted temporarily to more depleted compositions, perhaps indicating that an isotopically distinct magma source was being tapped. However, an isotopic excursion of similar magnitude also occurred later in the post-collapse activity, suggesting that the changes in isotope composition of the magma source continued after the collapse.