Late Quaternary micromammals and the precipitation history of the southern Cape, South Africa

Abstract

The southern Cape of South Africa is important to understanding regional climate because it straddles the transition between the winter and summer rainfall zones. We examine late Quaternary changes in rainfall seasonality and aridity through analysis of micromammal assemblages from three sites: Boomplaas Cave and Nelson Bay Cave in the aseasonal rainfall zone and Byneskranskop 1 in the winter rainfall zone. Our interpretation is based on analysis of 123 modern micromammal assemblages accumulated by barn owls (Tyto alba), which empirically links species composition to climate. The Pleistocene record (∼65 to 12 ka) from Boomplaas Cave, together with the last glacial maximum (LGM) samples from Nelson Bay Cave, indicates enhanced winter rainfall, especially during the LGM. Boomplaas Cave documents progressive aridification from the LGM to the earliest Holocene, followed by a return to moderately humid conditions through the Holocene. Byneskranskop 1 indicates a dominance of winter rains over the last 17 ka and a shift from an arid middle Holocene to a humid later Holocene. Agreement between the micromammal record and other local and regional proxies reinforces the potential of southern African micromammal assemblages as paleoclimate indicators.

High-resolution record of Holocene climate change dynamics from southern Africa's temperate-tropical boundary, Baviaanskloof, South Africa

“…Subsequent work and the application of evolving analytical techniques has further contributed to the wealth of data obtained from these sites (e.g. Avery, 2003;Cohen and Tyson, 1995;Faith, 2011;Faith, 2013;Faith et al, 2018;Loftus et al, 2016;Sealy et al, 2016;Sealy and Thackeray, 1998), but as anthropogenic deposits they are often fundamentally constrained in terms of both their taphonomy and their continuity.…”

Late Quaternary micromammals and the precipitation history of the southern Cape, South Africa — comment on the published paper by Faith et al., Quaternary Research (2019), Vol. 91, 848–860

“…GWA is the name for a layer at Boomplaas representing the period between 22,000 and 20,000 cal yr BP (Deacon, 1979). An important point that Faith et al (2019) do not explore in detail in their study relates to the identification of modern samples that are close to the fossil assemblage from this layer, dating to the time of the LGM. Three such samples can be identified from the results shown in their Figure 5.…”

“…The question has a long history in the context of palaeoenvironmental studies in South Africa; see, for example, Chase and Meadows (2007), Faith (2013), Sealy et al (2016), and Chase et al (2018). This brief study serves to re-examine the results obtained by ordination (Faith et al, 2019) regarding an aridity index. Special attention is given to Boomplaas Cave, which has one of the best late Quaternary sequences in southern Africa with material that can be used as proxies for palaeoclimate.…”

“…Faith et al (2019) have recently undertaken an impressive envirometric study of the relative abundances of modern and fossil mammalian microfauna from various regions in southern Africa in an attempt to obtain an aridity index that correlates strongly with mean annual precipitation. They do so under the assumption that variability in relative abundances and distributions of microfauna is affected indirectly, if not directly, by climatic factors that influence habitats in which the mammalian taxa are situated.…”

“…Faith et al (2019) make a controversial conclusion regarding palaeoclimates during the time of the last glacial maximum (LGM) when mean annual temperatures were about 5°C lower than present-day conditions (Thackeray, 1987). Notably, they infer that palaeoenvironments adjacent the Boomplaas Cave in the LGM were associated with winter rainfall in “humid” (relatively high rainfall) conditions.…”