Fig 1.
Location maps and images of Bulli Beach (New South Wales, Australia) showing key sites discussed in text.
(a) Large scale regional map of Australia, (b) New South Wales coast with early Holocene Kurnell and Minnamurra sites shown in relation to Bulli (maps produced with GMT [98]). (c) Ariel image of Bulli Beach, overlain in (d) with a Digital Elevation Model (DEM) derived from LiDAR (figures based on material sourced from Geoscience Australia, 2019 [99]). Note, in panel c the yellow square shows the location of the bench mark, while the yellow stars denote 14C sampling sites north and south of Slacky Creek proximal to locations dated by Jones et al., 1979 [56]. The DEM highlights the extent of the receded barrier (maroon and brown) backing the central portion of Bulli Beach and bisected by Slacky Creek. Also note the beach (green) and low-lying dune (yellow and orange) that has built since the 1978 storm, burying the estuarine mud. While the aerial photograph (c) displays an accreted beach, the LiDAR (d) captures a post-storm recovery bar.
Fig 2.
Photographs and GPR data of the estuarine mud deposit at Bulli Beach.
(a) Oblique photograph looking south across Slacky Creek of estuarine mud exposed along Bulli beach after the 1978 storm (courtesy of Bob and Ann Young). (b) Northern GPR transect across present-day Bulli Beach imaging the buried estuarine mud surface with a strong reflection surface around an elevation of 1 m above MSL, similar to that found in the southern GPR transect (c). (d) The three-dimensional model used to image the estuarine mud surface in 3D (e). By isolating and interpolating between the high amplitude reflections caused by the peat surface, the lower amplitude signature within the overlying sand is stripped away, remotely sensing the lateral extent of the estuarine mud surface (e) previously exposed in 1978 (a).
Fig 3.
Photographs of the exposed sediments sampled for this study at Bulli Beach (taken shortly after the June 2016 storm).
(a) Core location (white box) with limonite deposit marking the upper boundary of the estuarine sediments (white dashed lines). (b) Panorama of south-facing exposed estuarine sediment deposits (boundary with floodplain sediments marked by white dashed line). (c) North-facing view of the exposed estuarine sedimentary unit, with the dated wood (white box). Note, the keys used for scale in panels a and c.
Fig 4.
Lithostratigraphy and OxCal age-depth model for the Bulli Beach (Slacky Creek South, NSW) using SHCal13 [59].
The posterior and prior probability distributions are shown as dark and light respectively. The dark and light blue envelope provide the 1σ and 2σ calibrated age range respectively. Radiocarbon age laboratory numbers are denoted by the prefix ‘Wk’. The anomalously older charcoal sample is shown in red.
Table 1.
Radiocarbon ages for Bulli and McCauley’s beach estuarine sediments.
The Bulli ages (obtained on the south side of Slacky Creek) have been modelled using the P_sequence and Outlier analysis option in OxCal 4.2 [100, 101] with SHCal13 [59]. Amodel = 91.2; Aoverall = 83.
Fig 5.
Comparison between Bulli Beach (Slacky Creek; this study in red and blue) with the previously published Holocene sea-level curve for New South Wales in greyscale [42].
All of the oldest dates on the previously published sea-level curve are from Bulli (denoted by dashed circle), with the next two oldest dates from nearby sites labeled K for Kurnell and M for Minnamurra (see Fig 1 for locations). Anomalously older wood and charcoal samples from this study are plotted for comparison (in red).