Climate and archaeology

Vegetation and climate development of South Africa are interesting in particular because the archaeology of the region substantially contributed to the understanding of human origins.

Continuous vegetation record of the Greater Cape Floristic Region (South Africa) covering the past 300 thousand years (IODP U1479)
Dupont LM, Zhao X, Charles C, Faith JT, Braun, D
Climate of the Past Discussions (in review)
https://doi.org/10.5194/cp-2021-93

A two million year hydroclimatic context for hominin evolution in southeastern Africa
Caley T, Extier T, Collins JA, Schefuß E, Dupont L, Malaizé B, Rossignol L, Souron A, McClymont EL, Jimenez-Espejo FJ, Garcia-Comas C, Eynaud F, Martinez P, Jorry SJ, Charlier K, Wary M, Gourves P-Y, Billy I, Giraudeau J
Nature 560 (2018) 76-79
https:doi:10.1038/s41586-018-0309-6

We com­bined very dif­fer­ent kinds of ana­lyses and investigated hy­dro­gen and car­bon iso­topes of mo­lecu­lar plant waxes and com­pared them with the res­ults of pol­len ana­lyses and ele­ment com­pos­i­tions. (Figure 2 from Caley et al. 2018)

Hydrological changes in the Limpopo catchment compared to sea surface temperatures of the southwestern Indian Ocean over the last 2.14 Ma.

Bottom up. a) δ¹⁸O of benthic foraminifera compared to the reference LR04 curve (Lisiecki & Raymo, 2004) providing the stratigraphy and age model. MPT denotes the Mid Pleistocene Transition. b) Sea surface temperatures estimated after foram assemblages and Mg/Ca measurements. c) ln(Fe/Ca) XRF ratios indicating the terrestrial contribution to the marine sediments. Arrow indicates the long-term trend toward less Limpopo River discharge. Grey frames represent events of hydrological cycle intensification. d) Pollen percentages of Cyperaceae. e) δ¹³C of the n-C₃₁ alkane of plant waxes (from Castaneda et al., 2016 in light green and this study in dark green) indicating the relative abundance of C4 plants in the vegetation. Note the correspondence with the Cyperaceae pollen percentages suggesting that a substantial part of the C4 signal comes from large tropical sedges (for instance papyrus) in the Limpopo catchment area during wet phases. f) δD of the n-C₃₁ alkane of plant waxes, in this region indicative of the amount of rainfall.

NB: time scale runs from right (old) to left (young)

The roles of climate and human land-use in the late Holocene rainforest crisis of Central Africa
Bayon G, Schefuß E, Dupont L, Borges AV, Deenielou B, Lambert T, Mollenhauer G, Monin L, Ponzevera E, Skonieczny C, André L
Earth and Planetary Science Letters 505 (2019) 30–41
doi:10.1016/j.epsl.2018.10.016

Early anthropogenic impact on Western Central African rainforests 2600y ago
Garcin Y, Deschamps P, Ménot G, De Saulieu G, Schefuß E, Sebag D, Duont LM, Oslisly R, Brademann B, Mbusnum KG, Onana J-M, Ako AA, Epp LS, Tjallingii RT, Strecker MR, Brauer AB, Sachse D
PNAS 115 (2018) 3261-3266
doi:10.1073/pnas.1715336115

The Cent­ral African rain forest has long been re­garded as primeval and largely without hu­man im­pact, climate being considered as the sole cause of the dis­ap­pear­ance of the rain forest around Lake Barombi in Cameroon ca. 2600 years ago and its reappearrance roughly 600 years later. The study published in the Pro­ceed­ings of the Na­tional Academy of Sci­ences (PNAS) shows that climate cannot have been the reason.

Carbon and hydrogen isotopes of higher plant waxes stored in the lake sediments provide a record of C₄ vs C₃ vegetation (in this case roughly savannah vs forest) and an estimate of rainfall, respectively, both measured on n-alkanes. Pollen analysis confirms that grasses are the main source of C₄ plant material.

Records of environmental change from Lake Barombi over the past 10,500 y and comparison with local summer insolation.

In red the long-term insolation changes at 5°N for June–July–August. In green stable carbon isotopes of n-alkane C₃₁ and in blue hydrogen isotopes measured on the same n-alkane. More negative Deuterium values indicate wetter conditions, while less negative carbon isotopes indicate more C₄ vegetation. The upper blue curve shows the Deuterium values corrected for C₄ material indicating no sudden drop in rainfall between 2600 and 2000 BP.

NB: time scale runs from right (old) to left (young)