Late glacial (17,060-13,400 cal yr BP) sedimentary and paleoenvironmental evolution of the Sekhokong Range (Drakensberg), southern Africa.

Malin E Kylander,Elin Norström,Richard Bindler,Antonio Martinez Cortizas,Mikaela Holm,Stefan Grab,Jennifer Fitchett,Walter Finsinger

doi:10.1371/journal.pone.0246821

Abstract

Southern Africa sits at the junction of tropical and temperate systems, leading to the formation of seasonal precipitation zones. Understanding late Quaternary paleoclimatic change in this vulnerable region is hampered by a lack of available, reliably-dated records. Here we present a sequence from a well-stratified sedimentary infill occupying a lower slope basin which covers 17,060 to 13,400 cal yr BP with the aim to reconstruct paleoclimatic variability in the high Drakensberg during the Late Glacial. We use a combination of pollen, total organic carbon and nitrogen, δ13C, Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR) spectral and elemental data on contiguous samples with high temporal resolution (10 to 80 years per sample). Our data support a relatively humid environment with considerable cold season precipitation during what might have been the final stage of niche-glaciation on the adjoining southern aspects around 17,000 cal yr BP. Then, after an initial warmer and drier period starting ~15,600 cal yr BP, we identify a return to colder and drier conditions with more winter precipitation starting ~14,380 cal yr BP, which represents the first local evidence for the Antarctic Cold Reversal (ACR) in this region. On decadal to centennial timescales, the Late Glacial period was one marked by considerable climatic fluctuation and bi-directional environmental change, which has not been identified in previous studies for this region. Our study shows complex changes in both moisture and thermal conditions providing a more nuanced picture of the Late Glacial for the high Drakensburg.

Highlights

Southern Africa sits at the interface of tropical and temperate systems, generating a dynamic climate and a heterogeneous landscape
Paler layers are located at 356–353 cm and 349–345 cm while stark red laminations are found at 330–320 cm
A similar approach can be taken using the squared loadings of each rotated components (RC) plotted against time, which shows the importance of each RC for an individual sample (Fig 5)

Summary

Introduction

Southern Africa sits at the interface of tropical and temperate systems, generating a dynamic climate and a heterogeneous landscape. The spatial extent and precipitation intensity of these rainfall zones is linked to changes in global climate systems. During the Last Glacial Maximum (LGM), when mountain glaciers reached their maximum ice extent in the mid-latitude southern hemisphere (23,000 and 19,000 cal yr BP) [4,5,6], it is suggested that an equatorward shift of the SWW extended the WRZ, generating humid conditions over much of southern Africa [e.g., 7–11]. A number of open questions related to climate development from the LGM to present still exist. This is in part because high-resolution, continuous, long-term environmental reconstructions are rare and available records are unevenly distributed geographically [12]. While an increasing number of paleorecords from southern Africa are available for the Holocene, the LGM and the Late Glacial (or Last Glacial Transition, ~18,000 to 11,700 cal yr BP [13]) are less frequently represented

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