Radiocarbon ages for coatings on cupules ground in quartzite bedrock at Rhino Cave in the Kalahari Desert of Botswana, and their paleoclimatic significance

Abstract

This paper reports on the first AMS 14 C dating of coatings over wall depressions, or cupules, from an archaeological site in sub-Saharan Africa. Rhino Cave is primarily a Late and Middle Stone Age site located at the Tsodilo Hills in the northwestern Kalahari Desert of Botswana. A secondary precipitate up to 10 cm thick covers many of the 544 cupules engraved into one wall of the cave; this precipitate or coating was removed from two of these depressions. The coatings consisted of calcium phosphate, presumably derived from bat guano or bird droppings above the hollows, that was overlain by calcium carbonate and then silica. Organic material in this precipitate provided minimum calibrated AMS 14 C ages of 6443 to 6204 cal. yr B.P. (5580 Ϯ 60 14 C yr B.P.) for one depression, and 3000 to 2761 cal. yr B.P. (2830 Ϯ 50 14 C yr B.P.) for the other. The AMS 14 C ages and paleoclimatic data recovered from the cupules are in agreement with the regional paleoclimatic sequence for the Holocene. Specifically, comparison with data from Etosha Pan in Namibia and the Makgadikgadi Pans in Botswana suggests that deposition of the coatings and associated organic matter occurred preferentially during three periods of increased moisture in the region at around 6200, 3700, and 1200 cal. yr B.P. The gradual change from phosphate at the base of the coatings to carbonate and then to silica suggests that the wet intervals were superposed on a long-term trend toward a drier climate in the late Holocene.

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“…However, the southern wall of the cave, with its hundreds of carved grooves and depressions, remained "enigmatic in relation to age and function" (Robbins et al 2000a: 30). [Note: also see Brook et al (2011) for minimum dates of two cupules. ]…”

Arid geomorphology

“…Select examples include using: (1) CIA (e.g. 10 Be, 26 Al, 21 Ne) to infer histories and millennial-scale rates of surface process change along a Mojave Desert piedmont (Nichols et al, 2005(Nichols et al, , 2007 and to document spatial variations in erosion rates in a Namibian catchment (Codilean et al, 2008(Codilean et al, , 2010; (2) luminescence dating to investigate late Quaternary aeolian, lacustrine and fluvial interactions in the Nile valley, Sudan (Williams et al, 2010) and in central Australian (Cohen et al, 2010;Nanson et al, 2008), Namibian (Stone et al, 2010a) and Chinese (Yang and Scuderi, 2010) deserts; and (3) 14 C and/or Useries dating to assess groundwater recharge from Holocene interdune lakes in western China , the formation of tufa deposits in the semi-arid Naukluft Mountains, Namibia (Stone et al, 2010b), and the palaeoenvironmental significance of chemical precipitates and associated organic matter that coat cupules (wall depressions) in a Kalahari Desert cave (Brook et al, 2011).…”

Caracterização Espeleológica E Sedimentar De Uma Caverna Do Maciço Quartzítico Serra São José, Minas Gerais

“…Para cavernas quartzíticas, estudos tendem a focar mais em processos espeleogenéticos (Fabri et al, 2015, Sauro et al 2014Auler & Sauro, 2019), de modo que a sedimentologia acaba sendo muitas vezes negligenciada. A exemplo disso, a maior parte dos estudos sobre sedimentos em cavernas siliciclásticas foi realizada como parte de estudos arqueológicos (Butzer, 1973;Brook et al, 2011;Tribolo et al, 2016).…”

“…Quartzitic caves studies tend to focus on speleogenetic processes (Fabri et al, 2015, Sauro et al 2014Auler & Sauro, 2019), with sedimentology often being neglected. For example, most siliciclastic caves sediments studies have been conducted as part of archaeological studies (Butzer, 1973;Brook et al, 2011;Tribolo et al, 2016).…”