ORCID Profile
0000-0002-6031-4170
Current Organisation
The University of Auckland
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Publisher: Authorea, Inc.
Date: 05-10-2023
Publisher: American Geophysical Union (AGU)
Date: 07-10-2021
DOI: 10.1029/2021GL094543
Abstract: Holocene marine terraces occur globally and record information about the timing and magnitude of past coseismic events. Staircased terraces develop through repetitive coseismic uplift of shore platforms, but are also subject to destruction from subsequent wave erosion and rock weathering. In this study we calibrate a rock coast evolution model using terrace field data from Mahia Peninsula, New Zealand, and use it to investigate how relative sea level (RSL) change influences Holocene terrace development. Analyses of 10,002 simulations reveal time periods of extremely rapid terrace creation and destruction as a result of shore platform development processes that are modulated both by episodic and gradual RSL change scenarios. Subtle differences in these scenarios give rise to completely different terrace sequences, even if coseismic event timing is held constant. Improved interpretation of Holocene terrace sequences require higher resolution paleo RSL data and chronological data on shore platform development.
Publisher: Wiley
Date: 24-07-2022
DOI: 10.1002/ESP.5440
Abstract: Flights of Holocene marine terraces are useful for reconstructing past earthquakes, but coastal erosion can remove terraces from the landscape, potentially leading to incorrect estimates of earthquake magnitude and frequency. Relatively little effort has been afforded to studying terrace erosion processes, and this paper presents the first field evidence that we are aware of documenting terrace erosion rates. Two case studies from New Zealand provide a unique opportunity to observe the beginning and end phases of terrace development. We present downwear and backwear erosion measurements, showing that both sets of processes are important. Micro‐erosion meter measurements from Kaikōura Peninsula, South Island, confirm that downwear processes are modifying new marine terraces that were created when the peninsula was uplifted about 1 m during the 2016 earthquake. Erosion rates were high immediately following uplift as the relatively barren intertidal rock shore platform rapidly transformed into an incipient marine terrace with cover deposits. However, the Kaikōura earthquake uplifted shore platforms only a small distance above the upper tidal limit and ongoing downwear and backwear erosion may begin to remove parts of this terrace in future decades. We explored this prospect with a case study at Māhia Peninsula, North Island, where 100–300 years have elapsed since the last terrace‐forming earthquake. Historical photographs were used to document about 80 years of backwear erosion. Terrace erosion rates have been nearly constant through this period, and extrapolation implies that the terrace will be removed in places by 2030. The erosion data in this paper provide new insights into how terraces can be removed from the landscape, but there are many complicating factors. To help understand these factors we present a new conceptual model of marine terrace creation and destruction for soft‐rock coasts.
Publisher: Wiley
Date: 08-07-2022
DOI: 10.1002/ESP.5438
Abstract: Co‐seismic uplift of Kaikōura Peninsula in 2016 has substantially reduced the number of wetting and drying cycles that occur on the shore platforms and the newly uplifted incipient marine terraces. A simple empirical model incorporating field and laboratory measurements was used to determine the number and frequency of wetting and drying cycles. The mudstone supratidal terraces are vulnerable to material disintegration and slaking through sustained drying, and occasional sweeping by storm waves. Overall, wetting and drying cycles have decreased on six of eight field transects, between −8% and −148%, resulting in prolonged drying of the supratidal terraces following uplift (upwards of a 29% increase in annual drying hours). We conclude that accelerated rates of denudation due to enhanced drying post‐uplift are likely to return sections of the incipient mudstone terraces to their former intertidal pre‐uplift state, potentially removing evidence of the co‐seismic uplift event. Terrace preservation, however, will likely be highly variable between locations depending on its inherited morphology, lithological vulnerability, and the timing of any future tectonism.
Start Date: 2019
End Date: 2022
Funder: Marsden Fund
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