Tracing Sand From Source to Sink Across Eastern North Island, New Zealand: Insights From the Shelf Segment of the System

Marsaglia, Kathleen M.¹, Shelby Dawson¹, Julie Parra¹, Kevin Rivera¹, Alissa DeVaughn¹, Dawn James¹, Steven Kuehl² (1) California State University Northridge, Northridge, CA (2) Virginia Institute of Marine Science, Gloucester Point, VA

The MARGINS Source-to-Sink paradigm is a holistic view of continental margins, looking at the production, erosion, transport and deposition of sediment from mountain highlands, across shelves and slopes, to abyssal fan sinks. Application of this paradigm to the stratigraphic record has important ramifications for hydrocarbon exploration in deep-water systems where reservoirs are generally sandy and reservoir quality is a direct function of sand composition. Our focus is the Waipaoa River Sedimentary System situated within the actively deforming forearc of North Island, New Zealand. We have characterized sand production within the subaerial part of the system, linking sand petrology to bedrock geology, with an historical perspective via the petrology of Quaternary fluvial terrace deposits within the drainage basin. During sealevel lowstands, Waipaoa River sediment may have been directly fed into deeper water canyons and funneled into the Hikurangi Trough. More recently, during interglacial highstand, sediment is at least in part, trapped on the shelf. We evaluate the likelihood of a Waipaoa River source of sandy sediments recovered in box, Kasten and piston cores from the Poverty Shelf using the provenance model developed from our Waipaoa River basin study. Alternate sources of sand are both intrabasinal (e.g., shoreline erosion) and extrabasinal (e.g., longshore input from the north and/or south); these have characteristic provenance signatures. Results from this study are applicable to other active margins where young sedimentary successions are the main sediment sources.