Basement reflectors in the Kerguelen Plateau, south Indian Ocean: Indications for the structure and early history of the plateau

Abstract

The Kerguelen Plateau is a large structure in the south Indian Ocean of which the nature (oceanic or continental) and origin are not known. In this work, multichannel seismic reflection surveys, particularly in the southern domain of the plateau, are used to study its origin. Internal basement reflections characterize most of the investigated area. Basement reflections, together with other geological and geophysical information, indicate that the entire plateau is underlain by a volcanic basement, suggesting that both the northern and the southern domains have an oceanic origin. Basement areas with no internal reflections are associated mostly with basement ridges; basement reflector wedges, associated with volcanic flows from the elevated volcanoes, appear on the flanks of these ridges. We suggest that the basement ridges are the extinct volcanic sources of the Southern Kerguelen Plateau. Typical volcanic morphology is absent in the southern domain, because it was removed during the erosional phase known to have occurred following the emplacement of the plateau and which is apparent in the seismic data. Two types of volcanic sources are identified in the southern domain: isolated volcanoes and linear sources. This pattern is somewhat similar to the volcanic pattern in Iceland, suggesting that the Kerguelen Plateau may have been a similar structure, related to excessive volcanism associated with a hot spot on a mid-ocean spreading ridge in the Early Cretaceous south Indian Ocean.