RESOLVING UNCERTAINTIES IN FORAMINIFERA-BASED RELATIVE SEA-LEVEL RECONSTRUCTION: A CASE STUDY FROM SOUTHERN NEW ZEALAND

Ed Garrett, M.J. Brain, B.W. Hayward, Rewi M. Newnham, Craig J. Morey, Willem Roland Gehrels

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Abstract

Since the pioneering work of David Scott and others in the 1970s and 1980s, foraminifera have been used to develop precise sea-level reconstructions from salt marshes around the world. In New Zealand, reconstructions feature rapid rates of sea-level rise during the early to mid-20th century. Here, we test whether infaunality, taphonomy, and sediment compaction influence these reconstructions. We find that surface (0–1 cm) and subsurface (3–4 cm) foraminiferal assemblages show a high degree of similarity. A landward shift in assemblage zones is consistent with recent sea-level rise and transgression. Changes associated with infaunality and taphonomy do not affect transfer function-based sea-level reconstructions. Applying a geotechnical modelling approach to the core from which sea-level changes were reconstructed, we demonstrate compaction is also negligible, resulting in maximum post-depositional lowering of 2.5 mm. We conclude that salt-marsh foraminifera are indeed highly accurate and precise indicators of past sea levels.
Original languageEnglish
Number of pages13
JournalJournal of Foraminiferal Research
Volume53
Issue number1
Publication statusPublished - 1 Jan 2023

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