Resolving uncertainties in foraminifera-based relative sea-level reconstruction: a case study from southern new zealand

Since the pioneering work of David Scott and others in the 1970s and 1980s, foraminifera have been used to develop pre-cise 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-20(th )century. Here, we test whether infaunality, taphonomy, and sediment com-paction 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 assem-blage zones is consistent with recent sea-level rise and trans-gression. 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.