Botanical and Geological Significance of Potassium-Argon Dates from the Juan Fernández Islands

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Abstract

<jats:p> 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 <jats:italic>Lactoris</jats:italic> and <jats:italic>Thyrsopteris</jats:italic> , have apparently dispersed to the islands and survive refugially. </jats:p>

Journal

  • Science

    Science 225 (4657), 49-51, 1984-07-06

    American Association for the Advancement of Science (AAAS)

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