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dc.contributor.advisorGorman, Andrew
dc.contributor.advisorRiesselman, Christina
dc.contributor.authorRees, Oliver William
dc.date.available2020-10-28T19:09:49Z
dc.date.copyright2020
dc.identifier.citationRees, O. W. (2020). Characterising the Quaternary stratigraphy of the paleovalley underlying Dunedin and Otago Harbour (Thesis, Master of Science). University of Otago. Retrieved from http://hdl.handle.net/10523/10473en
dc.identifier.urihttp://hdl.handle.net/10523/10473
dc.description.abstractBeneath the surface of the low-lying densely populated suburbs of Dunedin and the adjacent Otago Harbour is an extensive record of past sea level change over the Quaternary. Prior research into the Quaternary stratigraphy of Dunedin and Otago Harbour is limited with only recent work including seismic lines collected in the harbour and gravity measurements and modelling only being completed in recent years. In this investigation, I use a combination of seismic and sedimentological techniques to identify and constrain paleo sea levels within the subsurface geology of Dunedin and Otago Harbour. This research aims to build a better understanding of near coast highstand environments in this uniquely preserved setting and using this knowledge to better understand the effects of future sea level rise. Seismic imaging of sediments within Otago Harbour was used to track sea level highstand sedimentary units throughout the subsurface, identified by contrasts in the physical properties of the sediment, causing strong visible reflections. 42 seismic lines were collected in the harbour adjacent to Port Chalmers, imaging to a maximum of 140 m. The seismic images were used to propose and track representative sedimentary horizons, allowing comparison with the CE17/0106 sediment core which reached a depth of 20.7 m collected as part of the New Zealand SeaRise programme in early 2019 and from the Edgar Centre which reached a depth of 45.5 m in South Dunedin in 2016. This work maps five distinct horizontal sedimentary reflections observed within the paleovalley sediments, that coincide with observed changes in lithology within both the CE17/0106 and Edgar Centre cores. Elemental ratios such as Ca/Ti and Br/Inc produced from XRF measurements from core CE17/0106 are used to infer changes in the depositional environment as well as provenance. Radiocarbon ages from the CE17/0106 core provide an age model for the upper 12.4 m constraining it to the last 9 ka. The dated sediments can be tied to the shallowest horizon observed within the seismic record with similarities in the sediments between the CE17/0106 and Edgar Centre Cores. Below the horizon recovered in core CE17/0106, several more distinctive horizontal sedimentary reflections were observed. These horizons were deposited during sea level highstand events, infilled from the initial erosion of the paleovalley. These horizons lack any signs of past tectonics; however, the deeper horizons show evidence of erosion between highstands, cutting channels through the Quaternary sediments.
dc.language.isoen
dc.publisherUniversity of Otago
dc.rightsAll items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectGeophysics
dc.subjectQuaternary
dc.subjectStratigraphy
dc.subjectRadiocarbon
dc.titleCharacterising the Quaternary stratigraphy of the paleovalley underlying Dunedin and Otago Harbour
dc.typeThesis
dc.date.updated2020-10-28T07:52:08Z
dc.language.rfc3066en
thesis.degree.disciplineGeology
thesis.degree.nameMaster of Science
thesis.degree.grantorUniversity of Otago
thesis.degree.levelMasters
otago.interloanno
otago.openaccessAbstract Only
otago.evidence.presentYes
otago.abstractonly.term26w
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