Kerguelen Plateau - background information

A major study of the Kerguelen Plateau and particularly, the Raggatt Basin, was undertaken by Geoscience Australia in the 1980s in collaboration with French scientists from Le Laboratoire de Gèophysique Marine de l'EOPG, Institut de Physique du Globe, Strasbourg. Since then, Geoscience Australia has conducted two major seismic reflection surveys over the southern Kerguelen Plateau and the Labuan Basin (1997 AGSO surveys 179 and 180).

Interpretation of the seismic data together with available geological and geophysical information was the basis of the major framework study conducted by Geoscience Australia in 1999-2000 (GA Record 2002/05). Two areas of interest are the Elan Bank and the Labuan Basin. For the first time deep multi-channel seismic reflection data has been collected and interpreted in these regions contributing to better understand their origin and structural characteristics.

Due to its large size and remote location, the crustal structure of the plateau remains poorly understood. ODP drilling revealed that the plateau is underlain mostly by magmatic crust generated in the Barremian-Cenomanian (119 - 95 Ma) by excessive volcanism attributed to a large hotspot. The plateau is often described in the literature as a Large Igneous Province or LIP (Coffin and Edholm, 1994). Examples of LIPs include Iceland, Hawaiian Ridge and the Ontong-Java Plateau. The oceanic origin of the plateau has recently been challenged by ODP drilling results on the Elan Bank (Site 1137, Leg 183, Coffin et al., 2000). Gneissic metamorphic and felsic igneous clasts recovered in a fluvial volcanoclastic conglomerate provided unambiguous evidence of its continental origin. Together with geochemical evidence pointing to the presence of continental lithosphere under the southern part of the plateau (Mahoney et al., 1995, Storey et al., 1992), this recent discovery may indicate a more significant involvement of continental crust in the foundations of the plateau than was previously assumed.

High-resolution seismic data collected by Geoscience Australia show considerable stucturing beneath the lava flows ("volcanic basement") on some lines. It seems likely that the plateau is floored by a combination of different crustal blocks, including continental fragments and magmatic crust.