Assessing the paleoenvironmental potential of Pliocene to Holocene tufa deposits along the Ghaap Plateau escarpment (South Africa) using stable isotopes

Abstract

a b s t r a c tThe tufa deposits of the Ghaap Plateau escarpment provide a rich, yet minimally explored, geological archive of climate and environmental history coincident with hominin evolution in South Africa. This study examines the sedimentary and geochemical records of ancient and modern tufas from Buxton-Norlim Limeworks, Groot Kloof, and Gorrokop, to assess the potential of these sediments for providing reliable chronologies of highresolution, paleoenvironmental information. Chronometric dating demonstrates that tufa formation has occurred from at least the terminal Pliocene through to the modern day. The stable isotope records show a trend toward higher, more variable δ 18 O and δ 13 C values with decreasing age from the end of the Pliocene onwards. The long-term increase in δ 18 O values corresponds to increasingly arid conditions, while increasing δ 13 C values reflect the changing proportion of C 3 /C 4 vegetation in the local environment. Analysis of the Thabaseek Tufa, in particular, provides valuable evidence for reconstructing the depositional and chronological context of the enigmatic Taung Child (Australopithecus africanus). Collectively, the results of the present study demonstrate the potential of these deposits for developing high-precision records of climate change and, ultimately, for understanding the causal processes relating climate and hominin evolution.

Tufas indicate prolonged periods of water availability linked to human occupation in the southern Kalahari

“…This adds to growing evidence that the wet/dry, interglacial/glacial dichotomy through which much of southern African palaeoclimates has traditionally been viewed is overly simplistic [ 67 – 71 ]. While tufas have typically been associated with warmer and more humid interglacial climate conditions [ 72 – 75 ], several studies report tufa occurrences during both glacial and interglacial periods [ 41 , 42 , 66 , 76 , 77 ]. This highlights that, across the globe, regional climates respond variably to these boundary conditions, and cautions against simplistic interpretations of tufa deposits.…”

“…simplistic [67][68][69][70][71]. While tufas have typically been associated with warmer and more humid interglacial climate conditions [72][73][74][75], several studies report tufa occurrences during both glacial and interglacial periods [41,42,66,76,77]. This highlights that, across the globe, regional climates respond variably to these boundary conditions, and cautions against simplistic interpretations of tufa deposits.…”

“…Stratified above are younger deposits dated by OSL to 31±1.8 ka and 15±0.8 ka [36]. The hillside has abundant tufa deposits which are direct evidence for the presence of water on the landscape and are amenable to radiometric dating methods, making them valuable archives of changes in environmental conditions [37][38][39][40][41][42].…”

Integrating palaeocaves into palaeolandscapes: An analysis of cave levels and karstification history across the Gauteng Malmani dolomite, South Africa

“…Further afield at the Makapansgat Limeworks, massive amounts of what is likely very old speleothem occurs that is consistent with the even wetter climates of the Miocene-Pliocene (Latham et al, 1999(Latham et al, , 2003. Moreover, large quantities of tufa also formed during the Pliocene at Taung (Hopley et al, 2013;Doran et al, 2015) and older tufa deposits also exist that could be earlier Pliocene in age, or earlier (Kuhn et al, 2016a,b). One possibility that has been suggested to explain the dominance of sediment infills younger than 2 Ma is that the caves had formed prior to this, but were simply not open to the surface until after 2 Ma because the dolomite was covered by older Karoo cover strata (Dirks and Berger, 2012).…”