Environmental changes in the Central Sahara during the Holocene - The Mid-Holocene transition from freshwater lake into sebkha in the Segedim depression, NE Niger

Baumhauer, Roland; Schulz, E; Pomel, Simon

doi:10.1007/978-3-540-44930-0_3

Cited by 6 publications

(4 citation statements)

References 10 publications

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“…Two sedimentary basins of Quaternary age, the Oulliminden Basin to the west and the Niger Oriental Basin to the north and east, cover a large area of Niger. Southern and eastern areas, in particular, are covered by extensive areas of playa deposits which were laid down during periods of higher rainfall during the Quaternary and as late as the early mid Holocene [e.g., Gasse et al , 1987; Felix‐Henningsen , 2000; Baumhauer et al , 2004].…”

Section: Sampling Details and Physical Settingmentioning

confidence: 99%

Mineral magnetic properties of surface soils and sands across four North African transects and links to climatic gradients

Lyons

Oldfield

Williams

2010

Geochem Geophys Geosyst

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[1] In light of their earlier success in characterizing and differentiating soils, sediments and atmospheric particulates, magnetic measurements were carried out on samples of North African surface soils and sands. The main aims were to document spatial variations in magnetic properties, explore their possible links to climatic gradients and their likely basis, and thereby help to differentiate potential sources for Sahara/Sahel-derived dusts. Samples were collected along four broadly north-to-south orientated transects located in Egypt, Niger, Mali, and Benin and southern Togo. These transects cover major climatic gradients ranging from hyper-arid to tropical. Across the rainfall range spanned by the Niger and Mali Transects (<100 to >800 mm/yr) there are significant north-to-south gradients in magnetic mineral concentrations. This is seen most clearly in the concentrations of the finest ferrimagnetic minerals (magnetite/maghemite), which are strongly represented in the clay fraction. Concentrations of the imperfect antiferromagnetic minerals (predominantly haematite) also increase with increasing rainfall. By analogy with studies spanning a similar rainfall gradient in areas of more uniform lithology, we suggest that the most likely cause for these trends is increased chemical weathering linked to the progressively wetter climate across the Sahara/Sahel transition. Within the set of samples from Egypt (rainfall >100 to <5 mm/yr), there is a marked gradient in the coercivity of remanence in the antiferromagnetic minerals present, with coercivity increasing southwards, paralleling the trend toward increasing aridity. Given the strong spatial discrimination demonstrated, especially in the Niger and Mali transects, these potentially climate-linked gradients hold out the promise of discriminating between dust source regions.

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Section: Sampling Details and Physical Settingmentioning

confidence: 99%

Mineral magnetic properties of surface soils and sands across four North African transects and links to climatic gradients

Lyons

Oldfield

Williams

2010

Geochem Geophys Geosyst

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“…Surficial palaeo-lake sediments, formed during periods of heightened humidity during the Late Quaternary (e.g. Gasse et al, 1987;Grunert et al, 1991;Felix-Henningsen, 2000;Baumhauer et al, 2004) and dunes are common across much of Niger and form a significant source of atmospheric dust (Drees et al, 1993). In particular, the Bilma alluvial plain (18 N, 12 E) has been identified as an important area of dust production (Goudie and Middleton, 2001;Prospero et al, 2002;Washington et al, 2003), and one that contributes a significant component of dust infall in southern Niger (Kalu, 1979;McTainsh and Walker, 1982;Chappell, 1996).…”

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confidence: 99%

The possible role of magnetic measurements in the discrimination of Sahara/Sahel dust sources

Lyons

Oldfield

Williams

2011

Earth Surf Processes Landf

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The mineral magnetic properties of deposited dusts collected along a broadly north‐to‐south transect across Niger have been investigated on both a bulk and particle size‐specific basis. Dusts display a general north‐to‐south gradient in fine‐grained ferrimagnetic mineral (magnetite/maghemite) concentrations, with samples south of the Sahara/Sahel transition (south of ~15·5o N) generally containing greater concentrations than dusts from further north where the climate is much drier. This distinction is seen especially clearly in the clay (< 2 µm) fraction, which harbours the products of weathering and pedogenesis. This gradient in ferrimagnetic mineral concentrations broadly parallels that previously reported for surface soils/sands across a similar latitudinal range. We suggest that the regional distinction in both dust and surface soil/sand magnetic properties can be related to differences in weathering regime between the arid Saharan parts of the transect and the Sahel sites where higher rainfall has permitted stronger weathering and pedogenesis. Given that the weathering‐related magnetic signatures in the clays dominate the magnetic properties of the < 16 µm fractions in these samples, and that this particle size component is most likely to be involved in long‐range transport, magnetic measurements hold out the potential of discriminating Sahara and Sahel dusts deposited in remote areas. Copyright © 2011 John Wiley & Sons, Ltd.

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“…The evidence for fire across the Sahara is found throughout the Holocene (Baumhauer et al, 2004; Marlon et al, 2013) and likely extends deep into the Pleistocene (Hoag and Svenning, 2017). However, charcoal particles counted from an offshore sediment record adjacent to the western Sahara show high (>6 × 10 3 particles cm −3 ) levels of charcoal during the AHP, which significantly increases between 7 and 6 ka (10 × 10 3 particles cm −3 ) (Dupont and Schefuß, 2018).…”

Section: Neolithic Pastoral Ecologies Of Northern Africamentioning

confidence: 99%

Impact of farming on African landscapes

Wright

2022

The Anthropocene Review

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As the continent with the deepest record of human history, the relationship between landscape formation and human subsistence practices is inseparable. The activities that constitute ‘farming’ are open for some matter of discussion, but essentially speak to the co-evolution of human, plant and animal reproductive systems along a continuum of interdependence. This process is ever evolving, but has resulted in the formation of landscapes in which anthropogenic processes characterize ecosystem functionality in nearly all biomes on the continent. Practices of cultivation, broadly conceptualized, across Africa are varied in the ways in which they have transformed ecological systems and landscapes. The use of fire as a landscape management tool dates to the Pleistocene, and penning of wild sheep to the early Holocene. The alteration of the landscape of fear by these types of human activities had fundamentally restructured trophic systems in Africa prior to the introduction of agriculture. However, the introduction of animal herding and intensive forms of plant cultivation by the middle Holocene correlated to even more significant ecological changes. The creation of agricultural landscapes has had a negative impact on biodiversity in some locations, whereas other some practices at different points in time have positively affected biodiversity. It is now recognized that humans have long influenced the evolution of landscapes wherever they live, but the current research focuses on where, when and how socio-ecological processes become coupled in the palaeoecological record.

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Environmental changes in the Central Sahara during the Holocene - The Mid-Holocene transition from freshwater lake into sebkha in the Segedim depression, NE Niger

Cited by 6 publications

References 10 publications

Mineral magnetic properties of surface soils and sands across four North African transects and links to climatic gradients

Mineral magnetic properties of surface soils and sands across four North African transects and links to climatic gradients

The possible role of magnetic measurements in the discrimination of Sahara/Sahel dust sources

Impact of farming on African landscapes

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