Abrupt Climatic Changes Associated with the Arid Younger Dryas Interval in Africa

Kelts, Kerry; Stager, J. Curtis

doi:10.1007/978-94-017-1437-2_12

Cited by 11 publications

(5 citation statements)

References 25 publications

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“…The dD of terrestrial plant waxes, a proxy for water balance in the Congo basin, and surface water d 18 O, which at the core site is strongly influenced by the Congo River, both indicate the abrupt onset of drier conditions with reduced Congo River discharge during the YD, followed over the next 1500 years by a gradual transition to wetter conditions ( Figure 5). Pollen data from Lake Albert indicate an arid YD, and diatom evidence from Lake Victoria suggests lowered water levels over the same interval, but in both these cases there seems to have been a relatively rapid return to more humid conditions at the end of the YD [Beuning et al, 1998;Stager et al, 2002].…”

Section: Equatorial Regionsmentioning

confidence: 99%

“…The main period of transition may have occupied as little as 50 years [Alley et al, 1993;Björck et al, 1996;Severinghaus et al, 1998;Alley, 2000;Lotter et al, 2000]. It is now becoming clear that the YD event also had a significant impact on tropical Africa [e.g., Roberts et al, 1993;Beuning et al, 1998;Stager et al, 2002;Barker et al, 2004;Johnson et al, 2004;Schefuss et al, 2005;Weldeab et al, 2005;Garcin et al, 2006]. Here, using high-resolution (typically <100-to 300-year sample spacing) paleoenvironmental data from cores from African lakes, we show that within the limits of available dating methods, there was an apparently contemporaneous, abrupt change in the climate of tropical Africa at the end of the YD, a change that seems to have involved reorganization of monsoonal circulation across the continent and adjacent oceans.…”

Section: Introductionmentioning

confidence: 99%

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An abrupt change in the African monsoon at the end of the Younger Dryas

Talbot

Filippi

Jensen

et al. 2007

Geochem Geophys Geosyst

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[1] High-resolution studies of variations in the elemental and stable carbon-and nitrogen-isotope composition of organic matter in cores from Lakes Malawi, Tanganyika, and Bosumtwi (tropical Africa) indicate an abrupt change in the wind-driven circulation of these lakes that, within the limits of available chronologies, was contemporaneous with the end of the Younger Dryas in the northern hemisphere. The change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of Africa. A range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics. Africa south of 5°-10°S, on the other hand, initially suffered drought conditions. Together, the evidence suggests an abrupt northward translation of the African monsoon system at circa 11.5 ± 0.25 ka B.P. The data assembled here contribute to a growing body of work showing that the Younger Dryas was a major climatic excursion in tropical Africa. Furthermore, they add substance to recent suggestions that climatic events in the southern hemisphere may have played a significant role in the abrupt demise of the Younger Dryas.

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Section: Equatorial Regionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An abrupt change in the African monsoon at the end of the Younger Dryas

Talbot

Filippi

Jensen

et al. 2007

Geochem Geophys Geosyst

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“…Faunal evidence from Rusinga Island and Karungu also indicate drier conditions during the deposition of the Nyamita tufa than at present, possibly similar to the LGM (Tryon et al ., ; Faith et al ., in press b). A shift in δ 18 O caused by arid conditions, similar to that documented during the LGM (Beuning et al ., , ), may account for the more negative δ 18 O values at Nyamita during Late Pleistocene with enrichment of isotopically heavy 18 O due to evaporation at Kisaaka and Aringo.…”

Section: Discussionmentioning

confidence: 98%

“…The riverine tufas at Nyamita and Aringo provide a unique opportunity to reconstruct the palaeoclimate of the area. Evidence from cores indicates that the δ 18 O composition of palaeoprecipitation has varied in comparison to modern values (Beuning et al ., , ). Few modern temperature or isotopic data are available for the Lake Victoria region, but MAT for nearby Entebbe, Uganda, is 21·6 °C with an annual mean of −2·3‰ VSMOW for δ 18 O of precipitation and ranges from −7 to 3‰ (Rozanski et al ., , ).…”

Section: Discussionmentioning

confidence: 99%

“…This shift may be a result of changes in the moisture source, such as greater contribution of more negative monsoonal rains (Dansgard, ; McKenzie, ; Rozanski et al ., , ). Lake Victoria is very sensitive to changes in precipitation, and the loss of direct precipitation due to a decrease in lake size would greatly reduce the amount of more positive catchment rainfall (Beuning et al ., , ). Faunal evidence from Rusinga Island and Karungu also indicate drier conditions during the deposition of the Nyamita tufa than at present, possibly similar to the LGM (Tryon et al ., ; Faith et al ., in press b).…”

Section: Discussionmentioning

confidence: 99%

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Recurrent spring‐fed rivers in a Middle to Late Pleistocene semi‐arid grassland: Implications for environments of early humans in the Lake Victoria Basin, Kenya

et al. 2015

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The effect of changing palaeoclimate and palaeoenvironment on human evolution during the Pleistocene is debated, but hampered by few East African records directly associated with archaeological sites prior to the Last Glacial Maximum. Middle to Late Pleistocene deposits on the shoreline of eastern Lake Victoria preserve abundant vertebrate fossils and Middle Stone Age artefacts associated with riverine tufas at the base of the deposits, which are ideal for palaeoenvironmental reconstructions. New data from tufas identified on Rusinga Island and on the mainland near Karungu, Kenya are provided from outcrop, thin sections, mineralogical, stable isotopic and U-series dating analyses. Tufa is identified in four sites: Nyamita (94Á0 AE 3Á3 and 111Á4 AE 4Á2 ka); Kisaaka, Aringo (455 AE 45 ka); and Obware. The age ranges of these tufa deposits demonstrate that spring-fed rivers were a recurrent, variably preserved feature on the Pleistocene landscape for ca 360 kyr. Poor sorting of clastic facies from all sites indicates flashy, ephemeral discharge, but these facies are commonly associated with barrage tufas, paludal environments with d 13 C values of ca 10& indicative of C 3 plants and fossil Hippopotamus, all of which indicate a perennial water source. Other tufa deposits from Nyamita, Obware and Aringo have a mixed C 3 /C 4 signature consistent with a semi-arid C 4 grassland surrounding these spring-fed rivers. The d 18 O values of tufa from Nyamita are on average ca 1& more negative than calcite precipitated from modern rainfall in the region, suggesting greater contribution of depleted monsoonal input, similar to the Last Glacial Maximum. Microdebitage and surface-collected artefacts indicate that early modern humans were utilizing these spring-fed rivers. The presence of springÀfed rivers would have afforded animals a reliable water source, sustaining a diverse plant and animal community in an otherwise arid environment. 1611

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Planetary Machinery: The Dynamics of the Earth System Prior to Significant Human Influence

2005

Global Change and the Earth System

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Abrupt Climatic Changes Associated with the Arid Younger Dryas Interval in Africa

Cited by 11 publications

References 25 publications

An abrupt change in the African monsoon at the end of the Younger Dryas

An abrupt change in the African monsoon at the end of the Younger Dryas

Recurrent spring‐fed rivers in a Middle to Late Pleistocene semi‐arid grassland: Implications for environments of early humans in the Lake Victoria Basin, Kenya

Planetary Machinery: The Dynamics of the Earth System Prior to Significant Human Influence

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