Lynne J. Quick

Late glacial interhemispheric climate dynamics revealed in South African hyrax middens

Our ability to identify the timing and extent of past major climate fluctuations is central to understanding changes in the global climate system. Of the events that have occurred in recent geological time, the Younger Dryas (YD, 13–11.5 ka), an abrupt return to near-glacial conditions during the last glacial–interglacial transition (ca. 18–11.5 ka), is one of the most widely reported. While this event is apparent throughout the Northern Hemisphere ([Peteet, 1995][1]), evidence for its occurrence in the Southern Hemisphere remains equivocal due to a lack of well-dated terrestrial records. Here we report high-resolution stable carbon and nitrogen isotope records obtained from a rock hyrax midden, revealing the first unequivocal terrestrial manifestation of the YD from the southern African subtropics. These results provide key evidence for the relative influence of the YD, and suggest that a subtropical-temperate transition zone existed along the oceanic Subtropical Front (∼41°S) across the Southern Hemisphere, with the Northern Hemisphere exerting a strong influence on all but the higher latitudes of the Southern Hemisphere after the Heinrich Stadial 1 (15 ka). [1]: #ref-22

A 700‐year record on the effects of climate and human impact on the southern cape coast inferred from lake sediments of eilandvlei, wilderness embayment, south africa

Abstract The southern Cape coast, outh frica, is sensitive to climate fluctuations as it is influenced by different atmospheric and oceanic circulation systems. Palaeoecological evidence of Holocene climate variations in this region is presently limited. Here, we present a lake sediment record spanning approximately the last 670 years from ilandvlei, a brackish coastal lake situated mid‐way between Cape Town and Port lizabeth. The results from geochemical and sedimentological analyses point to an increase in minerogenic sediment input from the catchment starting around ad 1400. Changes in the seasonal distribution of rainfall during the Little Ice Age may have altered river discharge and increased erosion rates and fluvial sediment transport in pre‐colonial times. A rising mean lake level, possibly associated with an altered water balance or relative sea‐level rise, may offer an explanation for the deposition of finer sediments. After ad 1450, reduced burial flux of elements associated with autochthonous sediment formation may have resulted from ecological changes in ilandvlei. Enhanced sedimentation rates, increasing carbon, nitrogen, phosphorous and biogenic silica concentrations, as well as high concentrations of proxies for allochthonous sediment input (e.g. aluminium, titanium, zirconium) point to increasing sediment and nutrient flux into ilandvlei from the late nineteenth century onwards. The most likely factor involved in these recent changes is land‐use change and other forms of human impact.

The Cederberg: A Rugged Sandstone Topography

The Cederberg forms part of the western branch of the Cape Fold Belt , a mountain range that resulted from orogenic (mountain-building) processes in the Permo–Triassic (~300–230 Ma ago). After deposition, the Ordovician to Carboniferous sandstones and shales of the Cape Supergroup were subjected to faulting , folding and subsequent weathering which has produced a rugged mountainous terrain characterised by a sequence of elevated ridges and peaks (up to 2,027 m a.s.l.) separated by broad linear valleys. The geomorphology of the region is strongly controlled by these bedrock structures, which illustrates the close relationship between geologic and geomorphic patterns of landscape evolution over long timescales. The topography of the region has also exerted control on the Cederberg’s Mediterranean climate, with winter rains that support the Fynbos and Succulent Karoo biomes . The interlinked geology, geomorphology and ecology are protected as part of the Cederberg Wilderness Area , which is a significant geotourism and geoheritage region, rich in archaeological remains.