Precise relative sea level (RSL) data are important for inferring regional ice sheet histories, as well as helping to validate numerical models of ice sheet evolution and glacial isostatic adjustment. Here we develop a new RSL curve for Fildes Peninsula, South Shetland Islands (SSIs), a sub-Antarctic archipelago peripheral to the northern Antarctic Peninsula ice sheet, by integrating sedimentary evidence from isolation basins with geomorphological evidence from raised beaches. This combined approach yields not only a Holocene RSL curve, but also the spatial pattern of how RSL change varied across the archipelago. The curve shows a mid-Holocene RSL highstand on Fildes Peninsula at 15.5 m above mean sea level between 8000 and 7000 cal a BP. Subsequently RSL gradually fell as a consequence of isostatic uplift in response to regional deglaciation. We propose that isostatic uplift occurred at a non-steady rate, with a temporary pause in ice retreat ca. 7200 cal a BP, leading to a short-lived RSL rise of ~1 m and forming a second peak to the mid-Holocene highstand. Two independent approaches were taken to constrain the long-term tectonic uplift rate of the SSIs at 0.22-0.48 m/ka, placing the tectonic contribution to the reconstructed RSL highstand between 1.4 and 2.9 m. Finally, we make comparisons to predictions from three global sea level models.
14C ages have been normalized to -25 per mil PDB d13C using the d13C values shown.Dates on marine bulk sediment have been corrected using a local marine reservoir correction of 1064 ± 10 years (Milliken et al., 2009); errors on the original date and DR value were combined in quadrature. Sediments were interpreted as being of marine origin on the basis of diatom analysis, as d13C values are too wide ranging to allow discrimination of marine and freshwater sediments.Dates were calibrated using Calib (version 5.0.1, Stuiver and Reimer, 1993) using the SHCal04 calibration curve for terrestrial dates (McCormac et al., 2004) and the Marine04 calibration curve for marine dates (Hughen et al., 2004) with a DR value of 664 years (marine reservoir correction of 1064 years minus the global ocean reservoir correction of 400 years, Stuiver and Braziunas, 1993; Reimer, 2009, http://www.calib.qub.ac.uk/marine/). Where more than one calibrated range is given, the relative percentage area under the probability distribution is indicated in brackets; all other ranges constitute 100% of the probability distribution. Median ages are rounded to the nearest 10 years in all later discussions.
Supplement to: Watcham, Emma P; Bentley, Michael J; Hodgson, Dominic A; Roberts, Stephen J; Fretwell, Peter; Lloyd, Jerry M; Larter, Robert D; Whitehouse, Pippa L; Leng, Melanie J; Monien, Patrick; Moreton, Steven Grahame (2011): A new Holocene relative sea level curve for the South Shetland Islands, Antarctica. Quaternary Science Reviews, 30(21-22), 3152-3170