A Marine Reservoir Correction for the Houtman-Abrolhos Archipelago, East Indian Ocean, Western Australia

Abstract

ABSTRACT. High-precision analysis using accelerator mass spectrometry (AMS) was performed upon known-age Holocene and modern, pre-bomb coral samples to generate a marine reservoir age correction value (R) for the HoutmanAbrolhos Archipelago (28.7S, 113.8E) off the Western Australian coast. The mean R value calculated for the Abrolhos Islands, 54 ± 30 yr (1) agrees well with regional R values for Leeuwin Current source waters (N-NW Australia-Java) of 60 ± 38 yr. The Abrolhos Islands show little variation with R values of the northwestern and north Australian coast, underlining the dominance of the more equilibrated western Pacific-derived waters of the Leeuwin Current over local upwelling. The Abrolhos Islands R values have remained stable over the last 2896 cal yr BP, being also attributed to the Leeuwin Current and the El Niño Southern Oscillation (ENSO) signal during this period. Expected future trends will be a strengthening of the teleconnection of the Abrolhos Islands to the climatic patterns of the equatorial Pacific via enhanced ENSO and global warming activity strengthening the Leeuwin Current. The possible effect upon the trend of future R values may be to maintain similar values and an increase in stability. However, warming trends of global climate change may cause increasing dissimilarity of R values due to the effects of increasing heat stress upon lower-latitude coral communities. INTRODUCTIONSurface ocean radiocarbon levels are largely representative of the proportionate contributions of atmospheric CO 2 and 14 C-depleted subsurface water DIC, thus making them lower than atmospheric and terrestrial 14 C. The influence of the "older" 14 C-depleted carbon source incorporated by marine organisms creates a differential between the marine organism's 14 C age and the 14 C age of its terrestrial contemporary. The average offset between the marine and terrestrial 14 C age (~400 yr) is referred to as the marine reservoir age (R) and is described and accounted for by the application of atmospheric modeling. The marine reservoir age also has regional variation referred to as the marine reservoir correction or R value and represents the local influence of ocean and atmospheric mixing due to currents, gyres, upwelling and climatic variations, which vary on seasonal to multidecadal scales (Stuiver and Reimer 1986;Stuiver and Braziunas 1993;Reimer and Reimer 2001).Around the Australian coastline, especially towards the remote north and northwestern regions and along the East Indian Ocean, there are many gaps in the record of R values with low spatial resolution (Reimer and Reimer 2001;Southon et al. 2002;Ulm 2006). In addition, there are several factors that limit the range of existing R values available for any chosen analysis. To avoid potential errors when selecting R values (or material to sample) for calculating site or regional averages, one must consider beforehand criteria such as: the trophic level and particular feeding habits of sampled organisms; the physicochemical nature of the aquati...

Rapid, high-resolution 14C chronology of ooids

“…Instead, they were within uncertainty of each other for each size class. This is possible if the local reservoir age was closer to 0 yr BP than the nearest reported reservoir age (466 ± 31 yr), which was measured outside of Shark Bay (Squire et al, 2013). Therefore, concordance between lifespans and maximum 14 C ages implies that the smaller ooids began assimilating carbonates approximately 1470 ± 280 yr BP, and the larger ooids began approximately 1120 ± 210 yr BP.…”

“…In both classes, ages of the outermost layers were significantly (> 2 σ) younger than the nearest reported pre-bomb reservoir age (466 ± 31 yr, at 28.7°S, 113.8°E) from corals near the Western Australian coast (Squire et al, 2013 The implications of these chronologies can be further explored by applying growth models for individual grains. The simplest models are empirical and assume constant net growth (i.e., carbonate assimilation -abrasion) with respect to either ooid mass or radius.…”

Prograded foredunes of Western Australia's macro‐tidal coast – implications for Holocene sea‐level change and high‐energy wave impacts

“…Selected mollusc shells without erosion features and plant remains were dated by carbon-14 accelerator mass spectrometry ( 14 C-AMS) ( Table I). For marine carbonates, 14 C ages were corrected for a marine reservoir effect of ΔR = 58 ± 17 years (O'Connor et al, 2010), which appears to be rather uniform along the central and northern coastal sections of WA (Bowman, 1985;Squire et al, 2013). All datings were calibrated using CALIB 6.0 software (Reimer et al, 2009).…”

Australian Marine Radiocarbon Reservoir Effects: Δr Atlas and Δr Calculator for Australian Mainland Coasts and Near-Shore Islands

“…This review is restricted to mollusks, which are the most commonly 14 C-dated materials in Australian coastal archaeological and geomorphological studies. There are a small number of studies of recent marine radiocarbon reservoir effects based on coral records that are not included here Griffin 1993, 1999;Squire et al 2013;Hua et al 2015;Komugabe-Dixson et al 2016;Wu et al 2021). However, a comparison between the ΔR values based on mollusks reported here and those based on these corals within the time frame of our study is presented in Results and Discussion below.…”