CRUSTAL STRUCTURE VARIATION IN THE KERGUELEN PLATEAU: GEOPHYSICAL EVIDENCE FOR A PREVIOUSLY UNEXPLORED SHALLOWER MOHO BETWEEN THE SOUTHERN AND NORTHERN-CENTRAL PLATEAU

The Kerguelen Plateau is located in the Southern Ocean and is considered the second largest oceanic large igneous province (LIP) on earth emplaced above oceanic crust. The plateau is divided into discrete domains, primarily by age and morphological differences: the southern Kerguelen Plateau formed at 110 Ma, the central Kerguelen Plateau at around 90 Ma, and the northern Kerguelen Plateau at 40 Ma. These domains also exhibit geochemical characteristics that indicate varying degrees of contamination by continental crust and plume-asthenosphere interaction.

We used the seismic crustal thickness model CRUST1.0 and the World Gravity Model (WGM) 2012 to determine the degree to which these distinct domains are reflected in the thickness of the crust along the length of the plateau. Crustal thickness is represented with a resolution of ~ 1⁰ by 1⁰ in the CRUST1.0 model, and the Bouguer gravity anomaly with ~ 1’ by 1’ resolution in the WGM2012 model. We upward continued the gravity anomaly to 5 km in order to attenuate the high-frequency and shallow tectonic features.

Our results reveal Moho depths of ~ 25 km underneath the central and southern Kerguelen Plateau indicating a strongly thickened crust. This observation is consistent with previous studies on the Kerguelen Plateau and other LIPs, and may have resulted from magmatic underplating associated with plume impingement. We also observed a previously unexplored significantly shallower Moho depth (~10 km) beneath the plateau coincident with the boundary between the northern-central and southern Kerguelen Plateau. This is accompanied by a Bouguer anomaly map showing a gravity high between the southern Kerguelen Plateau and the northern-central Kerguelen Plateau. The implication of these observations is currently unknown. We plan to conduct a combined forward modeling of the gravity and seismic data, providing a detailed understanding of the boundary area’s crustal structure.