A detrital record of lower oceanic crust exhumation within a Miocene slow-spreading ridge: Macquarie Island, Southern Ocean

Macquarie Island's sedimentary record reveals the exhumation of lower oceanic crust from a Miocene slow-spreading ridge, providing insights into tectonic processes in the Southern Ocean. The study identifies two distinct lithofacies: basal basaltic breccia and enriched mid-ocean-ridge basalt (E-MORB) with gabbroic intercalations. Basaltic detritus reflects upper oceanic crust metamorphism, while gabbroic detritus indicates deeper crustal sources. Geochemical analysis and zircon geochronology suggest the gabbroic material originated from Paleogene-aged tholeiitic MORB, likely sourced from the Southeast Indian Ridge via a long-offset transform fault. This research reconstructs the tectonic history of Macquarie Island, highlighting the role of transpression in shaping its geological features.

Portner, R. A., Murphy, M. J., & Daczko, N. R. (2010). A detrital record of lower oceanic crust exhumation within a Miocene slow-spreading ridge: Macquarie Island, Southern Ocean. Geological Society of America Bulletin, 123(1-2), 255–273. https://doi.org/10.1130/b30082.1