| Abstrakt: |
Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be "magma‐poor" despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time. Plain Language Summary: Numerous investigations into the evolution of continental rift systems have advanced understanding of how the Earth's crust stretches and may eventually result in the formation of new ocean basins. However, these studies have not considered the case of thick mafic crust, sometimes including continental fragments. Here we focus on William's Ridge (Kerguelen Plateau) and Broken Ridge, formed as a single feature, in the Southern Indian Ocean. We investigate how these features rifted, broke apart, and separated in the current conceptual framework of deformation migration. We use multichannel seismic reflection data, multibeam bathymetry data, drilling results, and magnetics data to interpret their structure, stratigraphy, and tectonics with the goal of explaining how the features evolved in time and space. Surprisingly, we find evidence for relatively weak magmatism despite the features being located near a mantle hotspot. Nevertheless, we suggest that the mantle hotspot influenced how the crust broke apart along different segments of the features' conjugate margins. We also find that the Australia and Antarctic tectonic plates, on which the features are now located, were moving laterally with respect to each other while rifting and breaking apart. Key Points: The first consistent tectono‐stratigraphic framework across the Kerguelen Plateau‐Broken Ridge rifted margins is presentedWilliam's Ridge‐Broken Ridge rifted margins are defined as "magma‐poor" and classified following the deformation migration modelThe Kerguelen mantle plume controls along‐strike segmentation and promotes syn‐rift transform motion in William's Ridge‐Broken Ridge [ABSTRACT FROM AUTHOR] |
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