The Lithospheric Architecture of Australia From Seismic Receiver Functions

In the past decade, mounting evidence has pointed to complex, layered structure within and at the base of the mantle lithosphere of tectonically quiescent continental interiors. Sometimes referred to as negative velocity gradients or midlithospheric discontinuities (MLDs), the origin of intralithospheric layering has prompted considerable discussion, particularly as to how they may result from continent formation and/or evolution. Previous Sp receiver function analysis in Australia (Ford et al., 2010, ) found evidence for complex lithospheric layering beneath permanent stations located within the North, South, and West Australian Cratons and characterized these as MLDs. This study provides an update to the original study by Ford et al. (2010, ). Sp receiver function results are presented for 34 permanent, broadband stations. We observe the lithosphere-asthenosphere boundary (LAB) on the eastern margin of the continent, at depths of 75-85 km. The cratonic core of Australia has discontinuities within the lithosphere, with no observable LAB. On the western margin of the continent, we observe several stations with an ambiguous phase that may correspond to an MLD or the LAB. We also observe multiple negative phases at most stations, suggesting a complex and heterogeneous lithosphere. Australian MLDs are likely linked to the presence of hydrous minerals in the midlithosphere and may result from ancient processes such as subduction, plume interaction, or melt infiltration from the paleo-LAB.