Reconstruction of a semi-arid late Pleistocene paleocatena from the Lake Victoria region, Kenya

2015 ◽  
Vol 84 (3) ◽  
pp. 368-381 ◽  
Author(s):  
Emily J. Beverly ◽  
Steven G. Driese ◽  
Daniel J. Peppe ◽  
L. Nicole Arellano ◽  
Nick Blegen ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Homo Sapiens ◽  
Lake Victoria ◽  
Mean Annual Precipitation ◽  
Equatorial Africa ◽  
Lake Victoria Region ◽  
Rainfall Reduction ◽  
Few Data ◽  
Volcaniclastic Deposits ◽  
The Last Glacial

The effect of changing environment on the evolution of Homo sapiens is heavily debated, but few data are available from equatorial Africa prior to the last glacial maximum. The Karungu deposits on the northeast coast of Lake Victoria are ideal for paleoenvironmental reconstructions and are best studied at the Kisaaka site near Karunga in Kenya (94 to > 33 ka) where paleosols, fluvial deposits, tufa, and volcaniclastic deposits (tuffs) are exposed over a ~ 2 km transect. Three well-exposed and laterally continuous paleosols with intercalated tuffs allow for reconstruction of a succession of paleocatenas. The oldest paleosol is a smectitic paleo-Vertisol with saline and sodic properties. Higher in the section, the paleosols are tuffaceous paleo-Inceptisols with Alfisol-like soil characteristics (illuviated clay). Mean annual precipitation (MAP) proxies indicate little change through time, with an average of 764 ± 108 mm yr− 1 for Vertisols (CALMAG) and 813 ± 182 to 963 ± 182 mm yr− 1 for all paleosols (CIA-K). Field observations and MAP proxies suggest that Karungu was significantly drier than today, consistent with the associated faunal assemblage, and likely resulted in a significantly smaller Lake Victoria during the late Pleistocene. Rainfall reduction and associated grassland expansion may have facilitated human and faunal dispersals across equatorial East Africa.

scholarly journals Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

2017 ◽  
Vol 5 ◽  
Author(s):  
Emily J. Beverly ◽  
Daniel J. Peppe ◽  
Steven G. Driese ◽  
Nick Blegen ◽  
J. Tyler Faith ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Lake Victoria ◽  
Lake Victoria Region

scholarly journals Simulated effects of a seasonal precipitation change on the vegetation in tropical Africa

2009 ◽  
Vol 5 (2) ◽  
pp. 853-878
Author(s):  
C. Cassignat ◽  
E. S. Gritti ◽  
O. Flores ◽  
R. Bonnefille ◽  
F. Chalié ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Deciduous Forest ◽  
Lake Victoria ◽  
Potential Effect ◽  
Mean Annual Precipitation ◽  
Pollen Data ◽  
Temperature And Precipitation ◽  
Equatorial Africa ◽  
Precipitation Seasonality ◽  
Climatic Scenarios

Abstract. Pollen data collected in Africa at high (Kuruyange, valley swamp, Burundi) and low altitude (Lake Victoria; Ngamakala, pond, Congo) showed that after 6 ky Before Present (BP), pollen of deciduous trees increase their relative percentage, thus suggesting the beginning of a drier climate and/or an increase of the dry season length. Until now, pollen-climate transfer functions only investigated mean annual precipitation, hence omitting the potential effect of a change in precipitation seasonality. In the present study, we use an equilibrium biosphere model (i.e. BIOME3.5) to estimate the sensitivity of equatorial African vegetation to such changes, at specific sites. Climatic scenarios, differing only by the monthly distribution of the current annual amount of precipitations, are tested at the above three locations in equatorial Africa. Soil nature, monthly temperatures and cloudiness are kept constant at their present day values. A good agreement is shown between model simulations and current biomes assemblages, as reconstructed from pollen data. To date, the increase of the deciduous forest component in the palaeodata around 6 ky has been interpreted as the beginning of the drier climate period. However, our results demonstrate that a seasonal change of the precipitation distribution should likely induce such reconstructed changes toward drier vegetation types. This study confirms the necessity of taking into account seasonal changes in the hydrological balance when palaeoecologists wish to reconstruct vegetation composition or to infer quantitative climate parameters, such as temperature and precipitation, from pollen or vegetation proxy.

Hominin transition to Upper Pliocene

2017 ◽  
Author(s):  
Francisco J. Ayala ◽  
Camilo J. Cela-Conde
Keyword(s):  
Brain Development ◽  
Late Pleistocene ◽  
Technological Progress ◽  
Homo Sapiens ◽  
Middle Pleistocene ◽  
Evolutionary Significance ◽  
Australopithecus Afarensis ◽  
Phylogenetic Significance ◽  
Homo Neanderthalensis ◽  
Surprising Discovery

This chapter analyzes the transition of the hominins from the Middle Pleistocene to the Late Pleistocene. Two alternative models are explored, the “Multiregional Hypothesis” (MH) and the “Replacement Hypothesis,” and how each model evaluates the existing relationships between the taxa Homo neanderthalensis and Homo sapiens. Next is the investigation of the transitional (or “archaic,” if this grade is taken into account) exemplars found in Europe, Africa, and Asia and their evolutionary significance. In particular, the comparison between H. erectus and H. sapiens in China and Java is investigated, as the main foundation of the MH. The chapter ends with the surprising discovery of Homo floresiensis and its description and interpretations concerning its taxonomic and phylogenetic significance. The correlation between brain development and technological progress is at odds with the attribution of perforators, microblades, and fishing hooks to a hominin with a small cranial volume, similar to that of Australopithecus afarensis.

Late Pleistocene Vegetation of Kings Canyon, Sierra Nevada, California

1983 ◽  
Vol 19 (1) ◽  
pp. 117-129 ◽  
Author(s):  
Kenneth Cole
Keyword(s):  
Plant Community ◽  
Sierra Nevada ◽  
Late Pleistocene ◽  
Coniferous Forest ◽  
Pollen Grains ◽  
Mean Annual Precipitation ◽  
Juniperus Occidentalis ◽  
Sequoiadendron Giganteum ◽  
Western Side ◽  
Modern Sample

AbstractSeven packrat midden samples make possible a comparison between the modern and late Pleistocene vegetation in Kings Canyon on the western side of the southern Sierra Nevada. One modern sample contains macrofossils and pollen derived from the present-day oak-chaparral vegetation. Macrofossils from the six late Pleistocene samples record a mixed coniferous forest dominated by the xerophytic conifers Juniperus occidentalis, Pinus cf. ponderosa, and P. monophylla. The pollen spectra of these Pleistocene middens are dominated by Pinus sp., Taxodiaceae-Cupressaceae-Taxaceae (TCT), and Artemisia sp. Mesophytic conifers are represented by low macrofossil concentrations. Sequoiadendron giganteum is represented by a few pollen grains in the full glacial. Edaphic control and snow dispersal are the most likely causes of these mixed assemblages.The dominant macrofossils record a more xeric plant community than those that now occur on similar substrates at higher elevations or latitudes in the Sierra Nevada. These assemblages suggest that late Wisconsin climates were cold with mean annual precipitation not necessarily greater than modern values. This conclusion supports a model of low summer ablation allowing for the persistence of the glaciers at higher elevations during the late Wisconsin. The records in these middens also suggest that S. giganteum grew at lower elevations along the western side of the range and that P. monophylla was more widely distributed in cismontane California during the Pleistocene.

Eolian and fluvial sedimentation in the southwestern Sinai Mountains, Egypt: a record of flash floods during the late Pleistocene

2012 ◽  
Vol 44 (2) ◽  
pp. 281-299
Author(s):  
Jörg Völkel ◽  
Jörg Grunert ◽  
Matthias Leopold ◽  
Kerstin Hürkamp ◽  
Juliane Huber ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Arid Environment ◽  
Alluvial Fan ◽  
Luminescence Dating ◽  
Alluvial Fans ◽  
Extreme Floods ◽  
Optically Stimulated Luminescence Dating ◽  
Fluvial Sedimentation ◽  
Southwestern Sinai ◽  
The Last Glacial

Wadis emerging from the southwestern Sinai Mountains (Egypt) westwards to the Gulf of Suez are filled by >40 m thick late Pleistocene sediments, which have been subsequently incised to bedrock after the Last Glacial Maximum (LGM). Sedimentation and erosion resulted from changes in the basin's hydrological conditions caused by climate variations. Sediment characteristics indicate distinct processes ranging from high to low energy flow regimes. Airborne material is important as a sediment source. The fills are associated with alluvial fans at wadi mouths at the mountain fronts. Each alluvial fan is associated and physically correlated with the respective sediment fill in its contributing wadi. The alluvial fans have steep gradients and are only a few kilometers long or wide. The alluvial fans converge as they emerge from the adjacent valleys. According to optically stimulated luminescence dating, the initial sediment has an age of ∼45 ka and the sedimentation ends ∼19 ka, i.e., happened mainly during marine isotope stage (MIS) 3 and early MIS 2 formation and initial incision sometime during LGM. As the delivery of sediments in such a hyper-arid environment is by extreme floods, this study indicates an interval of intense fluvial activity, probably related to increased frequency of extreme floods in Southern Sinai. This potentially indicates a paleoclimatic change in this hyper-arid environment.

scholarly journals Interactions between Natural Populations of Human and Rodent Schistosomes in the Lake Victoria Region of Kenya: A Molecular Epidemiological Approach

2008 ◽  
Vol 2 (4) ◽  
pp. e222 ◽  
Author(s):  
Michelle L. Steinauer ◽  
Ibrahim N. Mwangi ◽  
Geoffrey M. Maina ◽  
Joseph M. Kinuthia ◽  
Martin W. Mutuku ◽  
...  
Keyword(s):  
Lake Victoria ◽  
Natural Populations ◽  
Lake Victoria Region ◽  
Epidemiological Approach

Comparing a new paleomap of European loess landscapes to an atmospheric dust circulation model

2021 ◽  
Author(s):  
Janina J. (Bösken) Nett ◽  
Frank Lehmkuhl ◽  
Erik J. Schaffernicht ◽  
Stephan Pötter ◽  
Philipp Schulte ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Late Pleistocene ◽  
Circulation Model ◽  
Glacial Maximum ◽  
Source Areas ◽  
Last Glacial ◽  
Potential Source ◽  
Aeolian Sediments ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Loess is an important archive of environmental change covering approximately 10% of the Earth’s terrestrial surface. Numerous studies have analyzed loess deposits and in particular loess-paleosol sequences. To analyze these sequences, it is important to know the spatial distribution of aeolian sediments, their location relative to potential source areas, and the geomorphology of the sink area. We investigated these aspects by compiling a new map of aeolian sediments in Europe using highly resolved geodata from 27 countries (Lehmkuhl et al., in press). To determine the most relevant factors for the European loess distribution, we further mapped potential source areas and divided the map into different facies domains. We analyzed the geomorphological and paleoenvironmental effects on the deposition and preservation of Late Pleistocene loess. Finally, the geodata-based results were compared with results obtained from high-resolved regional numerical climate-dust experiments for the Last Glacial Maximum (LGM) in Europe, which were performed with the LGM-adapted Weather Research and Forecasting model coupled with Chemistry (WRF-Chem-LGM; Schaffernicht et al., 2020).  Complementing the mapping-based findings with the WRF-Chem-LGM experiments results in an improved understanding of the Late Pleistocene loess landscape in Europe.</p><p> </p><p>References:</p><p>Lehmkuhl, F., Nett, J.J., Pötter, S., Schulte, P., Sprafke, T., Jary, Z., Antoine, P., Wacha, L., Wolf, D., Zerboni, A., Hošek, J., Marković, S.B., Obreht, I., Sümegi, P., Veres, D., Zeeden, C., Boemke, B., Schaubert, V., Viehweger, J., Hambach, U. (in press). Loess landscapes of Europe – Mapping, geomorphology, and zonal differentiation. Earth-Science Reviews. Doi: https://doi.org/10.1016/j.earscirev.2020.103496</p><p>Schaffernicht, E.J., Ludwig, P., Shao, Y., 2020. Linkage between dust cycle and loess of the last Glacial Maximum in Europe. Atmospheric Chemistry and Physics 20, 4969–4986. Doi:10.5194/acp-20-4969-2020.</p>

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