Late Pleistocene wetting and drying in the NW Kalahari: an integrated study from the Tsodilo Hills, Botswana

Thomas, David S.G.; Brook, George A.; Shaw, Paul; Bateman, Mark D.; Haberyan, Kurt A.; Appleton, C.C.; Nash, David J.; McLaren, Sue; Davies, Frances

doi:10.1016/s1040-6182(02)00135-0

Cited by 97 publications

(58 citation statements)

References 27 publications

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“…The Wadi Dana calcretes, on the other hand, show evidence of non-pedogenic evaporative pumping close to the upper surface. The Wadi Dana channel deposits are distinct from other forms of non-pedogenic calcretes such as the lacustrine calcretes studied by Thomas et al (2003) and the valley calcretes researched by Nash and McLaren (2003), which are both predominantly micritic with evidence of biotic activity.…”

Section: Impact Of Age Upon Calcrete Cementsmentioning

confidence: 85%

Characteristics, evolution and distribution of Quaternary channel calcretes, southern Jordan

McLaren

2004

Earth Surf Processes Landf

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Cemented and calcretized conglomerates of Quaternary age are found within ancient river channels exposed at various heights (between +1 and +125 m) above the current bed of the Wadi Dana in southern Jordan. In cross-section, the calcrete deposits are typically lensoid in shape and are found infilling palaeochannels cut into the bedrock. The fossilized channel sediments preserve evidence of past river conditions, sediment loads, source areas, phases of river down-cutting and sediment accretion, as well as post-depositional alteration processes.Samples have been analysed in thin section and under the scanning electron microscope in order to determine the calcrete micromorphology, cement types and crystal sizes. The results show that the river deposits have undergone significant displacement and replacement of the detrital grains by CaCO 3 , and this has resulted in the cementation in places of over 4 m of river material. The cements display an alpha-type fabric with no evidence of biogenic activity. The nature of the cement fabric within and between deposits differs as a function of two key variables: (i) the specific location within the channel and (ii) height above the modern wadi floor. Firstly, in many of the deposits cement crystal size varies, with sparite dominating at depth within impermeable palaeowadi channels, whereas on the flanks of the channels and near the top of the channels micrite is the main type of cement. These variations are thought to be a result of differences in the length of residence time of calcium carbonate-rich fluids in different parts of the channel and the spatially varying influence of evaporation. Secondly, distinct changes in cement fabric can be seen in channels of different ages with a reduction in the amount of micrite and an increase in the amount of secondary recrystallized pore-filling spar over time.

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Section: Impact Of Age Upon Calcrete Cementsmentioning

confidence: 85%

Characteristics, evolution and distribution of Quaternary channel calcretes, southern Jordan

McLaren

2004

Earth Surf Processes Landf

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“…1 and Fig. 9 d) (Munyikwa, 2005;Thomas et al, 2003;Thomas and Shaw, 2002;O'Connor and Thomas, 1999;Stokes et al, 1998;Stokes et al, 1997). According to these studies, dunes formed between 36 and 28 kyr BP, indicating that conditions were relatively arid at this time.…”

Section: Paleoclimatic Interpretationmentioning

confidence: 89%

“…Sediments from Lake Tsodilo (Thomas et al, 2003; K in Fig. 1) document lacustrine conditions 40-32 and 18-11 kyr BP, while the lake was dry 32-18 kyr BP.…”

Section: Paleoclimatic Interpretationmentioning

confidence: 99%

Hydrological changes in southern Africa over the last 200 Ka as recorded in lake sediments from the Tswaing impact crater

Kristen

Fuhrmann

Thorpe

et al. 2007

South African Journal of Geology

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Sediments from Lake Tswaing (25°24'30'' S, 28°04'59'' E) document hydrological changes in southern Africa over the last 200 kyr. Using high-resolution XRFscanning, basic geochemistry (TIC, TOC, TN), organic petrology and Rock-Eval pyrolysis, we identify intervals of decreased carbonate precipitation, increased detrital input, decreased salinity and decreased autochthonous (algal and bacterial) organic matter content that represent periods of less stable water column stratification and

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“…Unfortunately no organic matter was found to allow for any calibration of the OSL ages with radiocarbon techniques but this technique has been successfully applied elsewhere in similar arid environments (e.g. Moumani et al, 2003;Thomas et al, 2003;Eitel et al, 2006).…”

Section: Methodsmentioning

confidence: 99%

First evidence for episodic flooding events in the arid interior of central Saudi Arabia over the last 60 ka

McLaren

Al-Juaidi

Bateman

et al. 2008

J Quaternary Science

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2009. First evidence for episodic flooding events in the arid interior of central Saudi Arabia over the last 60 ka.ABSTRACT: Although evidence for Quaternary environmental changes in the Arabian Peninsula is now growing, research has mostly been conducted in the United Arab Emirates (UAE) and in the Sultanate of Oman. There have been virtually no recent studies in Saudi Arabia, especially in the central region such as around Al-Quwaiayh. In this area there are a series of outwash plains developed along the eastern edge of the Arabian Shield that formed in the late Quaternary. Four sedimentary sections, which are representative of the deposits that have accumulated, have been studied and five luminescence ages obtained. These are the first luminescence ages acquired from Quaternary sediments in central Saudi Arabia. The preserved fluvial deposits in the study area have formed during humid events at ca. 54 ka, ca. 39 ka and ca. 0.8 ka. In more recent times aeolian sands have been encroaching on to the distal parts of the outwash plains.

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Late Pleistocene wetting and drying in the NW Kalahari: an integrated study from the Tsodilo Hills, Botswana

Cited by 97 publications

References 27 publications

Characteristics, evolution and distribution of Quaternary channel calcretes, southern Jordan

Characteristics, evolution and distribution of Quaternary channel calcretes, southern Jordan

Hydrological changes in southern Africa over the last 200 Ka as recorded in lake sediments from the Tswaing impact crater

First evidence for episodic flooding events in the arid interior of central Saudi Arabia over the last 60 ka

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