Palynological evidence for late quaternary warming episodes in Southern Africa

Abstract

Polleniferous sediments from southern Africa associated with past warm episodes before the Last Glacial Maximum, are rare. Interpretation of environmental conditions during these phases are complicated by difficulties of dating. In sediments from the northern areas, north of 28°S, the prominence of tropical woodland pollen suggests that the period between 7000 and 6500 yr B.P. was associated with optimal temperatures during the Holocene. Identifying the warmest phase in the southern high-lying grasslands and semi-arid Karoo shrublands south of 28°S is difficult, because unlike the savanna areas of the north, they do not yield good pollen indicators for changes in temperature such as those of frost sensitive trees. However, some pollen sequences from further south along the southern coast of Africa (34°S) and at Marion Island in the Southern Ocean (47°S), suggest that the Holocene temperature optimum occurred at about the same time in the sub-antarctic area in the south and the subtropical regions in the north. The advent of moister conditions in southern Africa during the early to middle Holocene, is generally recorded earlier (ca. 7500-6500 yr B.P.) in the north at ca. 26°S, than around 31°S, (ca. 5000 yr B.P.). This change is provisionally associated with a relative shift in seasonality from a predominance of all-season precipitation to a greater proportion of summer rainfall, which apparently reached the southern Karoo areas two thousand years later than the northern Bushveld region.