Abstract

South Africa’s extensive and topographically diverse coastline lends itself to interpreting and understanding
 sea-level fluctuations through a range of geomorphological and biological proxies. In this paper, we present
 a high-resolution record of sea-level change for the past ~1200 years derived from foraminiferal analysis of
 a salt-marsh peat sequence at Kariega Estuary, South Africa. A 0.94-m salt-marsh peat core was extracted
 using a gouge auger, and chronologically constrained using five radiocarbon age determinations
 by
 accelerator mass spectrometry, which places the record within the late Holocene period. Fossil foraminifera
 were analysed at a high downcore resolution, and a transfer function was applied to produce a relative sea-
 level reconstruction. The reconstructed sea-level curve depicts a transgression prior to 1100 cal years BP
 which correlates with existing palaeoenvironmental literature from southern Africa. From ~1100 to ~300
 cal years BP, sea levels oscillated (~0.5-m amplitudes) but remained consistently lower than present-day
 mean sea level. The lowest recorded sea level of −1±0.2 m was reached between 800 and 600 cal years
 BP. After 300 cal years BP, relative sea level has remained relatively stable. Based on the outcomes of this
 research, we suggest that intertidal salt-marsh foraminifera demonstrate potential for the high-resolution
 reconstruction of relative sea-level change along the southern African coastline.

Highlights

  • Understanding past patterns of sea-level change is impor tant on local, regional to national and global scales

  • Late Holocene Relative sea-level (RSL) curves were produced for New Zealand[11] and Tasmania[12], yet no such curve exists for South Africa

  • It is clear that the reconstruction encompasses the falling limb of rapid RSL decline out of the late Holocene highstand which is documented across South African coastlines.[17,19]

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Summary

Introduction

Understanding past patterns of sea-level change is impor tant on local (e.g. for coastal management and engineering), regional to national (e.g. national future sea-level predictions) and global scales (e.g. for understanding polar ice sheet history). Evidence of recent sea-level change can be derived from instrumental data such as tide gauges (for example see Douglas1) and satellite altimetry (for example see Nerem[2]) These records can be extended back into the Holocene by means of proxy data from archaeological sites, geomorphological features, isolation basin contacts and salt-marsh sediments.[3,4] Relative sea-level (RSL) curves have been constructed for a substantial portion of northern hemisphere coastlines[3,5,6,7,8]; to date, few curves have been presented for the southern hemisphere.[9,10] Recently, late Holocene RSL curves were produced for New Zealand[11] and Tasmania[12], yet no such curve exists for South Africa. The majority of proxy sea-level data from South Africa derive from sites on the western and southwestern coastlines (e.g. Langebaan, Knysna, Verlorenvlei and Bogenfel Pan)

Methods
Results
Discussion
Conclusion

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