Author ORCID Identifier:
Date of Graduation
5-2026
Document Type
Thesis
Degree Name
Master of Science in Geology (MS)
Degree Level
Graduate
Department
Geosciences
Advisor/Mentor
Sharman, Glenn
Committee Member
Dumond, Gregory
Second Committee Member
McGilvery, Mac
Keywords
Detrital Geochronology; New Zealand Geology; Offshore Sedimentary Basins; Sedimentary Basin Analysis; Sedimentary Provenance; Sedimentology
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 fluctuations over the late Neogene. This period of time was recorded in the Pliocene-Pleistocene Giant Foresets Formation (GFF) that represents a rapid progradation of the western continental shelf into the basin. High sedimentation rates during this time were likely a major contributing factor to the emplacement of multiple, large-scale (up to ~3,500 km3) mass-transport deposits (MTD) that were caused by shelf and slope collapse within the GFF of similar scale to that of the well-studied Storegga slide offshore Norway. With these MTDs being investigated for reoccurrence potential and tsunami generation, it is imperative that sediment origins and transport mechanisms be well understood. It remains currently unknown to what extent sediment sources from the western South Island and central North Island, the latter including Neogene volcanics associated with the Australia-Pacific plate boundary, might have contributed to the GFF during formation of the large-scale MTDs. To determine sediment sources to the GFF over time and space, we use laser ablation U-Pb geochronology and trace elements of detrital zircon from well cuttings acquired from GFF topsets, clinoforms, and bottomsets; the underlying Mangaa Formation; and stratigraphically equivalent outcrops. We utilize the Belousova et al. (2002) method in classifying the original igneous protolith of detrital zircon from trace element concentrations. U-Pb dates indicate significant zircon contributions from the Early Cretaceous Median and Devonian-Carboniferous Karamea batholiths, along with metasedimentary terranes of the Torlesse Supergroup. We find that the GFF is dominantly composed of sediment originating from South Island sources with spatial variations in detrital zircon U-Pb age indicating four probable modes of strike-fed sediment transport into the basin: (1) the Westland Surficial Current system carrying Permian- Triassic sediment affiliated with the Alpine Fault movement ~600 km northwards from central Westland into distal regions of the Taranaki Basin during deposition of the GFF, (2) a littoral drift system transporting sediment originating from erosion of the Median and Karamea Suite batholiths and Western Province metasedimentary terranes exposed in northern Westland into proximal regions of the basin, (3) a lowstand-driven exposure of the Farewell Rise channeling sediment originating from the Motueka Depression, including from erosion of the Median Batholith exposed in northwest Nelson, onto the shelf beginning in the mid-Pleistocene, and (4) sediment originating from North Island volcaniclastic sources transported southwards via the West Auckland Current or deposited into the basin via volcanic ash falls. Forward mixture modeling of zircon U-Pb ages identifies a distinct provenance shift in sediment sources to the proximal shelf vs distal shelf, slope, and basin floor fans with the latter being enriched in Permian – Triassic zircon derived from erosion of the Rakaia Terrane from the transpressional Alpine Fault boundary in central Westland. Proximal sources enriched in sediment derived from northern Westland granitoid intrusive suites implicate a long-distance longshore drift component of the Westland Current carrying sediment onto the shelf. North Island Neogene volcaniclastic zircon are rare (0.9%) with limited grains originating from the nearby Alexandra, South Auckland, and Coromandel volcanic zones and little evidence for Taupō Volcanic Zone input.
Citation
Kulkarrni, A. (2026). Sedimentary Provenance of the Pliocene – Pleistocene Giant Foresets Formation, Offshore Taranaki Basin, Aotearoa New Zealand. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6200
