Presenter: Rebekah Bradshaw (University of Sydney)

Description:
The Kenn Seamount is a 24 x 127 km edifice located in the northern end of the Tasmantid Seamount Chain, a north-south trending, age-progressive series of extinct volcanoes. While most of the seamounts in the hotspot track formed over the oceanic lithosphere of the Tasman and Cato Basins, Kenn Seamount is situated on the western margin of the Kenn Plateau and is thought to have a magma plumbing system through the thinned and extended continental crust of northern Zealandia. There has been a paucity of data surrounding Kenn Seamount until recently. A 2019 R/V Investigator voyage mapped and recovered 44 rocks from three dredge sites around Kenn Seamount, including basalt and trachy-basalt volcaniclastic rocks and carbonates hosting corals, algae, larger benthic foraminifera and other fossils. 21 of these rocks were studied alongside a newly compiled bathymetry grid, including bathymetric data from two recent R/V Falkor voyages. Petrological description, geochemical analysis and biostratigraphic investigation provide ground-truthing for features identified in the bathymetry data including reef and erosional terraces, fault scarps, and lava flow features. This new data provides valuable insight into the geologic and geomorphic history of the Kenn Seamount. The morphology of Kenn Seamount is different compared to the southern Tasmantids. Its southern end consists of a terraced guyot hosting a carbonate platform and extant reefs, whist its northern end is a roughly NE-SW aligned plateau with a 17 x 12 km secondary volcanic edifice at ~800 m depth, and a 17.5 km fault scarp on its south-east margin. Constraining the processes that influenced Kenn Seamount’s morphology, and how this compares to adjacent seamounts that have formed on oceanic crust, is important for understanding crustal controls on the geological and geomorphological evolution of seamounts.