Offshore Record of Explosive Volcanic Eruptions in the Southern Part of the Panamá Basin During the Past 10 Myr: 1. Tephrostratigraphy, Cross-Correlations and Geochemical Characterization

Abstract

Northern Andean volcanism is characterized by an intense Quaternary activity, whose onshore deposits have partly covered Mio-Pliocene products associated with the early development of the arc, making it difficult to obtain an exhaustive catalog of past eruptions. To improve our knowledge of the largest eruptions that occurred in the Northern Andean arc, we analyzed several cores from drilling sites off Ecuador to seek tephra records. We characterize for the first time the mineralogical and geochemical characteristics of tephra beds recorded in the southern part of the Panamá Basin in the sediments of DSDP and ODP drilling Sites 504, 677, 678, 1238, 1239 and 1240. We show that products of at least 27 major eruptions from the Northern Andes have reached the Pacific Ocean since the Early Pliocene, and we have correlated 11 of them between several drilling sites. Products of the oldest volcanism had mainly rhyolitic compositions belonging to a High-K calc-alkaline magmatic series, whereas magmas display more heterogeneous SiO₂ and K₂O contents from the beginning of the Pleistocene. Correlations established in this work allow us to provide new temporal constraints to age models of sedimentary sequences of Sites 677, 1238 and 1240 constructed based on biostratigraphy. In addition, we show that sediments of ODP Site 1240, the closest to the Galápagos islands, recorded several Pleistocene rhyolitic eruptions associated with the hotspot's activity, possibly revealing past oceanic ridge-hotspot interactions.