Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Jesse E. McNinch
A quantitative understanding of the processes controlling sediment transport and deposition across the land/sea interface is crucial to linking terrestrial and marine environments and understanding the formation of marine stratigraphy. The nature and distribution of terrestrial-derived sediment preserved in shelf stratigraphy in turn provides insight into the complex linkages inherent in source-to-sink sediment dynamics. Located inboard of an actively subducting plate boundary and characterized by one of the highest sediment yields in the world, the open-shelf setting off of the Waiapu River in New Zealand presents an excellent location to improve our understanding of the factors controlling the formation of continental shelf stratigraphy and associated sediment transport. Over 850km of high-resolution seismic and swath bathymetry data ground-truthed by cores show significant stratigraphic spatial variation preserved on the Waiapu continental shelf. This spatial variation is likely controlled by regionally-specific sediment deposition and resuspension processes as well as antecedent geology. Chronostratigraphic control obtained from black carbon analysis reveals that deforestation of the Waiapu catchment is preserved as a distinct event in the adjacent inner shelf stratigraphy, and further indicates that the inner shelf is currently capturing a significant ∼16-34% of the total Waiapu sediment budget. Shelf-wide stratigraphy shows that the thickest deposits of Holocene stratigraphy are found in tectonically-created accommodation spaces, highlighting the role of neotectonics in strata formation. The primary control on strata formation on the Waiapu continental shelf is presumed to be tectonically-steered, local sediment supply, which likely still influences modern-day sediment transport via the effects of small-scale bathymetric lows steering gravity-dependent sediment flows at the river mouth.
© The Author
Wadman, Heidi M., "Controls on continental shelf stratigraphy: Waiapu River, New Zealand" (2008). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1539616896.