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Science 6 July 1984:
Vol. 225. no. 4657, pp. 49 - 51
DOI: 10.1126/science.225.4657.49
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Articles

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

TOD F. STUESSY 1, K. A. FOLAND 2, JOHN F. SUTTER 2, ROGER W. SANDERS 3, and MARIO SILVA O. 4

1 Department of Botany, Ohio State University, Columbus 43210
2 Department of Geology and Mineralogy, Ohio State University
3 Department of Botany, Ohio State University
4 Departamento de Botánica, Universidad de Concepción, Concepción, Chile

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.

Submitted on December 15, 1983
Accepted on April 10, 1984


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Allozyme diversity in endemic flowering plant species of the Juan Fernandez Archipelago, Chile: ecological and historical factors with implications for conservation.
D. J. Crawford, E. Ruiz, T. F. Stuessy, E. Tepe, P. Aqeveque, F. Gonzalez, R. J. Jensen, G. J. Anderson, G. Bernardello, C. M. Baeza, et al. (2001)
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Breeding System and pollination of selected plants endemic to Juan Fernandez Islands.
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RAPD marker diversity within and divergence among species of Dendroseris (Asteraceae: Lactuceae).
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