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

G Plenier (1) , P Camps (2) , Benoît Henry (3) , B Ildefonse (2)

1 LDL - Laboratoire Dynamique de la Lithosphère
2 Tectonophysique - Laboratoire de Tectonophysique
3 IPG Paris - 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 the axis 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 analysis not being decisive for choosing between the two solutions, geological and geomorphological observations were finally used to obtain confident interpretations. The results of this study enable the supposed eruptive centres of the Kerguelen Archipelago to be located more precisely.

Keywords: lava flows; magnetic susceptibility; shape preferential orientation; anisotropy; Kerguelen Archipelago

Domains: Geophysics [physics.geo-ph]; Volcanology

G Plenier, P Camps, Benoît Henry, B Ildefonse. Determination of flow directions by combining AMS and thin-section analyses: implications for Oligocene volcanism in the Kerguelen Archipelago (southern Indian Ocean). Geophysical Journal International, 2004, 160 (1), pp.63-78. ⟨10.1111/j.1365-246X.2004.02488.x⟩. ⟨insu-01516139⟩