Development of a Training Set of Contemporary Salt-Marsh Foraminifera for Late Holocene Sea- Level Reconstructions in southeastern Australia

Abstract

We collected contemporary foraminiferal training sets from two salt marshes to enable more precise and accurate proxy historical sea-level reconstructions from southeastern Australia. Combined with an existing training set from Tasmania, this new regional set consists of 112 samples and 16 species of foraminifera, of which 13 are agglutinated. Cluster analyses group the regional training set into a highelevation cluster, dominated by Trochamminita salsa, a mid-elevation cluster, dominated by Entzia macrescens and Trochammina inflata, and a mid-low elevation cluster dominated by Miliammina fusca and tidal-flat species. We develop transfer functions using local and regional training sets and assess their performance. Our resulting site-specific and chosen regional models are capable of predicting sea level with decimetre-scale precision (95% confidence intervals of 0.12-0.22 m). These results are comparable to other examples from around the world. When developing regional training sets, we advocate that the similarity in the environmental settings (particularly salinity) should be assessed as an alternative way of grouping sites, rather than simply using spatial proximity. We compare our findings with global results and conclude that salt marshes along microtidal coasts yield models with the lowest vertical uncertainties. Studies with the lowest uncertainties are located in the western Pacific and the western Atlantic, whereas those from the eastern Atlantic generally have larger tidal ranges and carry larger vertical uncertainties. Our models expand the existing region available for sea-level reconstruction and can be used to generate new late Holocene sea-level reconstructions across southeastern Australia.

Drivers of 20th century sea‐level change in southern New Zealand determined from proxy and instrumental records

“…In keeping with other similar studies (e.g. Gehrels, 2000; Edwards et al ., 2004; Williams et al ., 2021), we focus on the upper half of the intertidal zone as we seek to develop a training set suitable for high‐resolution sea‐level reconstructions from organic salt‐marsh sediments. Elevation is a surrogate variable, exerting no direct influence on species distributions.…”

“…A comprehensive understanding of the elevation‐dependent zonation of microfossils, e.g. foraminifera in intertidal environments, underpins quantitative proxy RSL reconstructions (Scott and Medioli, 1978; Birks, 1995; Hayward et al ., 1999; Gehrels, 2000; Kemp and Telford, 2015; Williams et al ., 2021). In recognition of the need for the development of more comprehensive training sets of modern samples, we enhance an existing foraminiferal dataset from Pounawea (Southall et al ., 2006) with the addition of new samples from Mokomoko Inlet.…”

Relative sea‐level changes in southeastern Australia during the 19th and 20th centuries

“…S3.1). Species encountered are similar to those at Lutregala & Wapengo (Williams et al, 2021) including: Trochamminita salsa, Haplophragmoides wilberti, Polysacammina ipohalina, Trochammina irregularis, Entzia macrescens, Trochammina inflata, Siphotrochammina lobata, Miliammina fusca and Ammobaculites exiguus, as well as Ammotium fragile (not previously encountered at either site). There is little vertical zonation of foraminifera and T. inflata dominates across the majority of the vertical gradient (average 65% abundance, maximum 97% abundance).…”

“…Transfer functions developed by Williams et al (2021) were used to generate PMSE estimates at Lutregala and Wapengo (Table 1). For Tarra, a screened local training set (36 samples) of foraminifera was generated from the two transects, which, when combined, have a vertical range of 0.6 m (see Supporting Information Fig.…”

Resolving Uncertainties in Foraminifera-Based Relative Sea-Level Reconstruction: a Case Study from Southern New Zealand

“…We use these samples in this paper, alongside a novel set of co-located subsurface samples. Each surface sample consisted of the uppermost 1 cm of sediment, following a strategy widely employed in the sea-level literature (e.g., Scott & Medioli, 1978;Horton & Edwards, 2003;Williams et al, 2021). This sampling strategy seeks to minimize the impact of seasonal fluctuations in assemblages, whilst also ensuring that significant changes in sea-level have not occurred during sample accumulation.…”