George A. Brook’s research while affiliated with University of Georgia and other places

This chapter examines the Pleistocene archaeology of three sites in the Tsodilo Hills located in the Kalahari Desert, about 45 km west of the Okavango River in NW Botswana (Fig. 1). The sites are White Paintings Shelter (WPS; 18.769 S, 21.749 E), Depression Shelter (DS; 18.738 S, 21.745 E), and Rhino Cave (RC; 18.735 S, 21.731 E). Tsodilo is the only area in the Kalahari of Botswana that has dated rock shelter sequences containing Pleistocene archaeological deposits that can be related to regional and global-scale paleoclimatic events. New OSL and radiocarbon chronologies are presented for DS and WPS and the data from all three sites are re-examined to determine how paleoenvironmental factors may have influenced their occupation and use over the last 100 kyr. There are three main hills at Tsodilo known as Male, Female, and Child and another hill called North Hill (Campbell et al., 2010). White Paintings Shelter is located at the base of Male Hill, while the other two sites are on Female Hill (Fig. 2). Thus far, the oldest stone artifacts date to the Middle Stone Age (MSA). While Early Stone Age Acheulean artifacts have not yet been found at Tsodilo, they do occur elsewhere in Botswana (Robbins et al., 2016; Robbins & Murphy, 1998). The current inhabitants of Tsodilo include two communities; Ju/’hoansi San and Hambukushu, both of whom we gratefully acknowledge for their friendship and help. Oral traditions also indicate that another group of people known as the Ncaekhoe, lived at Tsodilo prior to the arrival of the current inhabitants in the mid-1800s (Taylor, 2010).

We report a previously unknown black obsidian outcrop located at the eastern end of the Deseado Massif, near the Atlantic Ocean and the town of Tres Cerros, in Patagonia. This obsidian is a subalkaline rhyolite glass with medium potassium content. It is of lower quality than the black obsidian from the Pampa del Asador source, located in the vicinity of the headwaters of the Chico River, in the northwest of Santa Cruz. The ICP-MS and INAA geochemical data obtained for 16 obsidian samples are comparable when measurement uncertainties are considered. However, these are significantly different from published ICP-MS data for samples from Pampa del Asador and 17 de Marzo, indicating that obsidian from Tres Cerros can be differentiated geochemically from these secondary sources. A black obsidian artifact from the Alero 4 site, located on the northeastern coast of Santa Cruz, was analyzed, showing macroscopic characteristics similar to those identified in the Tres Cerros samples. The results indicated that it was an obsidian from Pampa del Asador. Likewise, the geochemical trends obtained for the Tres Cerros samples were not compatible with those observed in artifacts from the Alero del Valle and Cueva Aristizábal sites, located close to the southeast coast of Santa Cruz. In this sense, we emphasize that no evidence has yet been recorded that indicates the exploitation of Tres Cerros source by human hunter-gatherer groups that occupied the Patagonian region in the past. In this framework, the geochemical characterization of the potential source presented here constitutes initial information which can be compared with the one obtained from artifacts in archaeological sites, providing information to understand human mobility and the criteria for raw material selection.

Fossil pollen and geochemical sequences from a series of hyrax dung deposits from rock shelters along the eastern margin of the central Namib Desert shed light on the Holocene environmental history of Namibia. Grassy pollen assemblages suggest relatively humid conditions during the early Holocene between ca. 9.6 and 7.7 ka. A series of stepwise changes follows, including the prominence of different pioneer plant communities of which changes in ratios between grassy and shrub pollen types suggests moisture oscillations. The development of more C4 plants around ca. 4.5 ka, as indicated by isotope concentrations and persistent grass pollen percentages, point to the development of a different climatic regime than that in the early Holocene, which extended the area of subtropical savanna towards the south at c. 24°S. This transition can in part be interpreted as a vegetation response to a shift in the rainfall distribution from an early even seasonal distribution to the current late Holocene summer rainfall regime. Climate changes may have been driven by variations in austral summer and winter solar insolation with changes in total solar irradiance (TSI) superimposed upon them. Through its link to Bond events in the North Atlantic, and thus Atlantic Meridional Overturning Circulation (AMOC), TSI may have affected SSTs in the SE Atlantic and SW Indian Ocean, which influence both summer and winter rainfall in southern Africa.

Matupi Cave, near the equator at 1.2°N in the northeastern Democratic Republic of the Congo, is in an inland region of equinoctial (March–May and August–November) rainfall distinct from summer rainfall to the north (e.g., in the Sahara) and to the south. Investigation of one entire stalagmite, parts of two others, and a core through a fourth from Matupi reveals stalagmite growth, and faster deposition, during two periods at ∼18.1 to ∼13.4 and ∼9.2 to 3.1 ka, with stalagmite deposition ending at 3.1 ka during a transition to drier conditions. The two periods of inferred wetter conditions at Matupi coincide with the two maxima in equatorial insolation over the most recent 25 kyr. The inferred periods of wetness extend earlier and later than the North African Humid Period, which resulted from a maximum in solstitial (June) insolation at 11–12 ka rather than equinoctial (March or September) insolation at 6 and 17 ka. Matupi's pattern of two wet periods that are coincident with maxima in equatorial insolation over the most recent 25,000 years is also seen in a paleoclimate record from inland equatorial South America (and earlier periods of wetness in that record coincide with earlier maxima in equatorial insolation). The two records combine to suggest the concept of insolation-driven Equatorial Humid Periods at ∼11-kyr intervals, analogous to – but distinct in long-term timing and in seasonality of rainfall from – the more familiar North African Humid Periods recognized across the Northern Hemisphere from roughly 10°N to 25°N.

The 4.2 ka Event has generally been regarded as a period of decades to at most a few centuries in which comparatively dry conditions existed in the Middle East and more broadly across the mid-latitude Northern Hemisphere. This paper presents new stable-isotopic and petrographic observations from two previously-unreported U-Th-dated stalagmites from Dante Cave in northeastern Namibia. The results are most compatible with wetter conditions during the 4.2 ka Event, and wetness during the 4.2 ka Event is the only inference supported by evidence. These new results add to observations previously reported from a third Dante Cave stalagmite suggesting a comparatively wet 4.2 ka Event in which Africa's Tropical Rain Belt migrated southward and rainfall increased along the Congo Air Boundary and/or Kalahari Discontinuity. The new results support findings from three other locations in Namibia and Botswana, from at least seven other locations in the Southern Hemisphere, and at least one in southern China, that suggest a wetter rather than drier 4.2 ka Event in those regions. The pattern emerging from these sites generally agrees with recent modeling results indicating increased moisture over broad areas (but not all) of the Southern Hemisphere. This in turn suggests a 4.2 ka Event that was not a global drought but was instead a set of latitudinally-dependent responses to global-scale southward migration of the Inter-Tropical Convergence Zone (ITCZ), and thus Africa's loosely linked Tropical Rain Belt, as a result of cooling of the Northern Hemisphere, which brought drier conditions to some areas and wetter conditions to others.

Geomorphological studies have been carried out in rapidly evolving salt caves related to small watersheds in the San Pedro de Atacama area, Chile. Radiocarbon ages of bones and wood from cave deposits, combined with the presence of large salt caves, geomorphological and sedimentological observations, and the results of micrometer measurements outside and in some of the caves, suggest a period of speleogenesis in the Cordillera de la Sal during the onset of the Holocene, during which the large halite cave systems developed, followed by an early Holocene hyperarid period. Most smaller caves (i.e. Lechuza del Campanario) most probably formed at the start of the wetter mid-Holocene period (5–4.4 ka), when precipitation was never intense enough to entrain large amounts of sediments, but enough to trigger cave development. A diamicton in Lechuza del Campanario Cave radiocarbon dated at ca. 4.4 ka shows that at least one high intensity rainfall event occurred in this recharge basin during the mid-Holocene wet interval. A wet period with lower intensity rainfall events followed between 4.0 and 2.5 ka, causing the 4.4 kyrs old diamicton in Lechuza del Campanario Cave to be entrenched, and the alluvial fan at the downstream end of Palacio del Sal Cave to be covered with windborne sediments dated by OSL at around 3.6 ka. At ca. 2 ka there was a high-intensity rainfall event documented by the age of a twig stuck in the ceiling of the Palacio del Sal Cave, followed by a period with lower intensity rain events until ca. 1.3 ka, when another intense flood produced a mudflow that deposited a second diamicton in Lechuza del Campanario Cave. From then on clustering of radiocarbon ages for wood and bone recovered from caves indicates increased rainfall intensity in the period ca. 0.9–0.5 ka, followed by no registered events until a minor flood at ca. 0.13 ka. The four-centuries long wetter time interval (0.9–0.5 ka), corresponding to the Medieval Climate Anomaly, has been an archaeologically important period in the Atacama Desert (Tiwanaku culture). The observations and a detailed review of paleoclimate literature from this key area have allowed the development of a landscape evolution model related to changing climate conditions during the Late Holocene.

El objetivo de este trabajo es presentar los nuevos resultados obtenidos en torno a las ocupaciones tempranas en el sitio La Gruta 1, área de La Gruta, extremo sur del Macizo del Deseado, Patagonia argentina. Éstos se refieren tanto a la transición Pleistoceno-Holoceno como al Holoceno temprano y abarcan aspectos paleoambientales, nuevos fechados radiocarbónicos, además de la disponibilidad y utilización de materias primas. Se presentan los resultados de los nuevos análisis polínicos, realizados en un mallín del área ubicado en la meseta central, cerca de la localidad arqueológica Viuda Quenzana, con una edad basal de ca. 12.500 años A.P. (14.500 cal AP). Por otra parte, a partir de los resultados obtenidos se infiere una vegetación similar a la reconstruida por otros registros polínicos del área que sugieren condiciones húmedas durante el segundo período de ocupación humana del sitio arqueológico La Gruta 1, comprendido entre ca. 11.000 y 8000 cal AP Las evidencias procedentes de la ampliación de las excavaciones en este sitio muestran la falta de continuidad entre los fechados correspondientes a la transición Pleistoceno-Holoceno y los del Holoceno temprano. En ambos períodos existe evidencia de transporte de materias primas desde otros espacios, que incluyen artefactos bifaciales, lo que es consistente con la información obtenida previamente.

Stalagmite ANJ94-2 from Anjohibe Cave in northwestern Madagascar provides an exceptionally detailed and precisely dated record of changing environmental conditions that, combined with previously published data from stalagmites, wetland deposits, and archaeological sites, allows insights into past climate change, human environmental impact, and megafaunal extinction. Proxies of past conditions recovered from Stalagmite ANJ94-2 include ratios of carbon and oxygen stable isotopes (δ¹³C and δ¹⁸O), mineralogy (calcite and aragonite), layer-bounding surfaces, layer-specific width, and detrital material. Those proxies suggest that the natural environment changed in response to changes in rainfall at time scales of a few decades to multiple centuries; comparison with distant proxies suggests that wetter conditions in northwestern Madagascar may have been linked to cooling in the Northern Hemisphere. Carbon isotope data nonetheless suggest that the greatest environmental change in the area coincided with human introduction of swidden (tavy) agriculture about 1200 years ago, during a time not of drought but perhaps of slightly increasing wetness. The timing and extent of environmental change 1200 to 600 years ago seen in stalagmite and wetland data suggest that human modification of the landscape had a causal role in the extinction of Madagascar’s megafauna. On the other hand, the results combine with other recent research to indicate that drought was not the cause of the megafaunal extinction.

RESUMEN El objetivo de este trabajo es informar sobre la recuperación de seis tiestos en el área ubicada entre el extremo sur del Macizo del Deseado y el río Santa Cruz. Si bien se trata de un registro arqueológico poco abundante, constituye un aporte significativo al conocimiento sobre el uso de esta tecnología entre grupos cazadores-recolectores en estas latitudes y en espacios intermedios entre la costa y la cordillera. Se presenta la información cronológica (AMS) e isotópica (δ 13 C y δ 15 N) generada a partir de la datación y análisis de las sustancias adheridas a las superficies planas de dos fragmentos cerámicos. Asimismo, se exhiben los resultados de los análisis macroscópicos de los tiestos y microscópicos de las pastas. Sobre esta base se indaga acerca de las características de la cerámica, su posible función y el marco cronológico de uso de esta tecnología. Los resultados alcanzados son consistentes con aquéllos obtenidos en la región y apuntan a un uso tardío de la cerámica, a la utilización de recursos de estepa y a la posible obtención y transporte de recipientes por grupos indígenas con alta movilidad desde otros espacios.

Dating by the ²³⁰Th method indicates that Stalagmite DANf from Dante Cave in northern Namibia, in the Summer Rainfall Zone (SRZ) of southern Africa, formed about 92 ka, at the boundary of Marine Isotope Stages (MIS) 5b and 5c. In this dominantly semiarid zone, stalagmite growth may be evidence of a relatively wetter period, and trends in DANf's mineralogy and its C, O, and U isotope ratios further support formation in a period wetter than those before or after its formation. DANf's time of formation at 92 ka, like other wet periods in the SRZ of southern Africa over the most recent 100 kyr, coincides with a maximum in January insolation at 30°S that brought the SRZ, and more generally the tropical rain belt, farther south than before or after.