Evolution of a volcanic island on the shoulder of an oceanic rift and geodynamic implications: S. Jorge Island on the Terceira Rift, Azores Triple Junction
Résumé
The S. Jorge Island in the Azores lies on a peculiar setting, the southern shoulder of the Terceira Rift (TR), which raises a series of questions that we address in this study. We first established the main volcanic stratigraphy by recognizing, in the field, the main unconformities/discontinuities and their meaning (major erosion surfaces and faults), then we collected critical samples, and finally dated them by K/Ar to calibrate the stratigraphy and the age of inferred large-scale flank collapses. Based on field, geochronological and marine geophysical data: (1) we found much older rocks in S. Jorge than in previous studies (ca. 1.85 Ma), and established a new volcanic stratigraphy (from bottom to top): Old Volcanic Complex (ca. 1.9–1.2 Ma), cropping out in the eastern third of the island; Intermediate Volcanic Complex (ca. 0.8–0.2 Ma), cropping out in the western two thirds of the island and separated from the underlying complex by a major fault; Young Volcanic Complex (
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https://hal.science/hal-01894661
Soumis le : vendredi 12 octobre 2018-16:02:23
Dernière modification le : lundi 27 mai 2024-14:10:13
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F.O. Marques, A. Hildenbrand, C. Hübscher. Evolution of a volcanic island on the shoulder of an oceanic rift and geodynamic implications: S. Jorge Island on the Terceira Rift, Azores Triple Junction. Tectonophysics, 2018, 738-739, pp.41 - 50. ⟨10.1016/j.tecto.2018.05.012⟩. ⟨hal-01894661⟩
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