Determination of flow directions combining AMS and thin section analyses : implications for the Oligocene volcanism in the Kerguelen Archipelago (southern Indian Ocean)

Guillaume Plenier (1) , Pierre Camps (2) , Bernard Henry (3) , Benoit Ildefonse (2)

1 Department of Earth and Planetary Sciences [Santa Cruz]
2 Tectonophysique - Laboratoire de Tectonophysique
3 IPGP - Institut de Physique du Globe de Paris

We report an Anisotropy of Magnetic Susceptibility (AMS) study carried out on seven Oligocene volcanic sections widely distributed on the surface of the Kerguelen Archipelago. The statistical results at flow scale and at section scale were checked with AMS density diagrams and thin section analysis. Because of axes permutations frequently observed for lava flows, two possible flow directions were nicely defined for the majority of the sections. We then used two alternative approaches (imbrication of the minimum axis and symmetry of the AMS distribution) to infer a flow direction for each section. These two methods and thin section analyses not being decisive for choosing between the two solutions, geological and geomorphological observations were finally used for confident interpretations. The results of this study helped to more precisely locate the supposed eruptive centers of the Kerguelen archipelago.

Mots clés: Lava flows; anisotropy; magnetic susceptibility; Shape Preferential Orientation; Kerguelen Archipelago; AMS; paleomagnetism

Domaines: Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]; Volcanologie

Guillaume Plenier, Pierre Camps, Bernard Henry, Benoit Ildefonse. Determination of flow directions combining AMS and thin section analyses : implications for the Oligocene volcanism in the Kerguelen Archipelago (southern Indian Ocean). Geophysical Journal International, 2005, 160, pp.63-78. ⟨10.1111/j.1365-246X.2004.02488.x⟩. ⟨hal-00003065⟩