Sedimentary Provenance Analysis of the Giant Foresets Formation, Offshore Taranaki Basin, Aotearoa New Zealand

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records (Posters)

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Abstract:

Sediment input and dispersal in the Taranaki Basin, offshore New Zealand’s North Island was influenced by a complex interplay of ocean currents and sea level fluctuation over the late Neogene. This behavior is recorded in the Pliocene-Pleistocene Giant Foresets Formation (GFF) that records a rapid progradation of the western continental shelf into the basin. High sedimentation rates during this time were likely a major contributing factor for the emplacement of multiple, large-scale (up to ~3,500 km³) mass transport deposits (MTD), caused by shelf and slope collapse of similar scale to that of the well-studied Storegga slide, offshore Norway. With these events being investigated for reoccurrence potential and tsunami generation, it is imperative sediment origins and transport mechanisms be well understood. The Westland Current is predicted to have transported sediment ~600km northwards from the South Island into the Taranaki Basin during deposition of the GFF. However, it is currently unknown to what extent sediment sources from the central North Island, including volcanics associated with the Australia-Pacific plate boundary (i.e, the Hikurangi subduction margin) to the east of New Zealand, and (meta)sedimentary units, might have contributed to the GFF during formation of the large-scale MTDs. To determine sediment sources to the GFF over time, we use laser ablation U-Pb geochronology of detrital zircon from well cuttings acquired spatially from GFF clinoforms and stratigraphically equivalent outcrops in the Whanganui Basin. Preliminary U-Pb age dates suggest a distinct provenance signal from the Cretaceous Median and Devonian-Carboniferous Karamea batholiths, along with Mesozoic metasedimentary terranes of the Austral Superprovince such as the Torlesse Supergroup. Supplementing U-Pb dates, we conduct a petrographic provenance analysis from thin sections of equivalent strata in the adjacent Whanganui Basin. Along with providing the first detrital zircon U-Pb age data from the GFF, we stand to gain novel insights into the nature of a strongly progradational, strike-fed, shelf-to-deep basin system.