La Croix, Andrew D.Carvalho, RafaelRackham, Bailey2025-12-152025-12-152025https://hdl.handle.net/10289/17824The Rangitāiki Plains is a tectonically active alluvial plain in the Eastern Bay of Plenty, New Zealand. Throughout the mid-late Holocene (8 ka to present), the Rangitāiki Plains have undergone substantial geomorphological change, with the coastline prograding approximately 10 km over the past 6.5 ka, leaving relic shoreline features known as beach ridges. Previous studies of the Rangitāiki Plains have utilised tephrochronology and radiocarbon dating to determine the ages of several palaeoshorelines. These dates provided minimum ages for beach ridges and resulted in aging constraints; furthermore, limited textural and geochemical characterisation of beach ridges has hampered understanding of sediment provenance and reworking changes. Addressing these research gaps is important as this knowledge is especially relevant in coastal management, modern climate change, and increasing anthropogenic impacts on the coastline. Optically Stimulated Luminescence (OSL) dating on the Rangitāiki Plains produced older beach ridge ages than those derived via tephrochronology. OSL dating also showed that beach ridge ages coincided with volcanic eruption events. The OSL progradation rates extend to much older time frames than those based on tephrochronology, starting at 7.6 ka rather than 5.5 ka. New data concludes a prominent progradation peak up to 43.03 m yr⁻¹ between 5.202±0.368 ka and 5.187±0.447 ka, around the time of the Whakatāne eruption. By 4 ka, progradation had slowed to only 1.14 m yr⁻¹, suggesting that longshore drift occurred earlier than previously calculated (2 ka), or that progradation slowed before longshore drift commenced. XRF and XRD analysis of sediments from Rangitāiki Plains confirms that beach ridge sediments comprise of intermediate igneous sediments that have been tephra fingerprinted to the Taupō Volcanic Zone.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Rangitaiki PlainsBeach RidgesGround penetrating radarLight detection and rangingProgradationOptically stimulated luminescenceThesis