Pliocene-Pleistocene stratigraphy and sea-level estimates, Republic of
South Africa with implications for a 400 ppmv CO2 world
Abstract
Hearty, P. J., Rovere, A., Sandstrom, M. R., O’Leary, M. J., Roberts,
D., & Raymo, M. E. (2020). Pliocene‐Pleistocene stratigraphy and
sea‐level estimates, Republic of South Africa with implications for a
400 ppmv CO2 world. Paleoceanography and Paleoclimatology, 35,
e2019PA003835. https://doi.org/10.1029/2019PA003835 The Mid-Pliocene
Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3
Ma) records, offers potential past analogues for our 400-ppmv world. The
coastal geology of western and southern coasts of the Republic of South
Africa expose an abundance of marine deposits of Pliocene and
Pleistocene age. In this study, we report differential GPS elevations,
detailed stratigraphic descriptions, standardized interpretations, and
dating of relative sea-level indicators measured across
~700 km from the western and southern coasts of the Cape
Provinces. Wave abrasion surfaces on bedrock, intertidal sedimentary
structures, and in situ marine invertebrates including oysters and
barnacles provide precise indicators of past sea levels. Multiple
sea-level highstands imprinted at different elevations along South
African coastlines were identified. Zone I sites average +32 ± 5 m (6
sites). A lower topographic Zone II of sea stands were measured at
several sites around +17 ± 5 m. Middle and late Pleistocene sites are
included in Zone III. Shoreline chronologies using 87Sr/86Sr ages on
shells from these zones yield ages from Zone I at 4.6 and 3.0 Ma, and
Zone II at 1.04 Ma. Our results show that polar ice sheets during the
Plio-Pleistocene were dynamic and subject to significant melting under
modestly warmer global temperatures. These processes occurred during a
period when CO2 concentrations were comparable to our current and
rapidly rising values above 400 ppmv.