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Botanical and geological significance of potassium-argon dates from the Juan Fernández Islands

Tod F. Stuessy·K.A. Foland·John F. Sutter·Roger W. Sanders·O. Mario Silva
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Abstract

Potassium-argon dating of five basalts from the three main islands of the Juan Fernández (or Robinson Crusoe) Islands of Chile in the southeastern Pacific gives ages of 1.01 ± 0.12 and 2.44 ± 0.14 million years for Masafuera, 3.79 ± 0.20 and 4.23 ± 0.16 for Masatierra, and 5.8 ± 2.1 for Santa Clara. These ages are much younger than that of the underlying oceanic plate and are consistent with the origin of the island-seamount chain from a mantle hot spot beneath the eastward moving Nazca plate. The young age for the archipelago suggests that speciation within endemic genera has occurred within the past 4 to 5 million years. Endemic genera of apparently more ancient origins, such as Lactoris and Thyrsopteris, have apparently dispersed to the islands and survive refugially.

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Tod F. Stuessy, K.A. Foland, John F. Sutter, Roger W. Sanders, O. Mario Silva. 1984. Botanical and geological significance of potassium-argon dates from the Juan Fernández Islands. https://doi.org/10.1126/science.225.4657.49

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