Eolian sediment responses to late Quaternary climate changes: temporal and spatial patterns in the Sahara

Swezey, Christopher S.

doi:10.1016/s0031-0182(00)00235-2

Cited by 186 publications

(81 citation statements)

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“…The interpretation of this passage from high productivity and shallow pycno/nutricline to a more modern system dominated by less nutrient supply and a deeper pycno/nutricline is more difficult to explain with respect to the older event documented at Maya MV. Pollen records identify a progressive climatic aridity along the Mediterranean coasts between 6000 and 4000 years BP, roughly corresponding to the end of the African Humid Period at 5500 years BP, with dry conditions observed in the continental records (Barriendos and Martin-Vide, 1998;De Menocal et al, 2000;Swezey, 2001;Liu et al, 2007). At about 4000 years BP the progressive development of complex human society occurred along the Mediterranean coasts (Roberts, 1989) resulting in a drastic anthropogenic-related change in the natural vegetation in the Eastern Mediterranean Sea.…”

Section: Dhaka Mud Volcanomentioning

confidence: 97%

Growth and demise of cold-water coral ecosystems on mud volcanoes in the West Alboran Sea: The messages from the planktonic and benthic foraminifera

et al. 2011

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The Dhaka and Maya mud volcanoes (MVs), located in the Mud Diapir Province in the Western Alboran Basin along the Moroccan Coasts, were cored during the TTR-17, Leg 1 cruise. Cores were taken on the top of the volcanoes at a water depth of 370 m on the Dhaka MV (core TTR17-MS411G) and at 410 m water depth on the Maya MV (core TTR17-MS419G), respectively. On both mud volcanoes the extruded mud breccia provides the nucleation point for the colonization and development of cold-water corals and associated ecosystems. Two phases of cold-water coral growth are observed: (1) between slightly older than 4175± 62 years BP and around 2230± 59 years BP at Dhaka, and (2) between slightly older than 15583 ± 185 years BP and around 7613 ± 38 years BP at Maya MV. On the top of the Maya MV only a small patch reef and/or isolated corals proliferated, whereas a more extended patch reef colonized the top of the Dhaka MV. At both sites the cold-water coral development was triggered by the availability of a suitable substrate for initial coral settling, provided either as a firm ground or as single clasts. Subsequently coral growth was supported by enhanced nutrient flux possibly related to upwelling and/or strong currents. During the intervals of coral growth planktonic foraminiferal assemblages were dominated by Neogloboquadrina incompta. The decline of coral ecosystems on the mud volcanoes is accompanied at surface by a shift from the N. incompta dominated assemblage to a Globorotalia inflata dominated assemblage, possibly reflecting more oligotrophic conditions. This shift is coeval to the passage from wet to arid conditions at the end of the African Humid Period at Maya MV. It is interpreted as an effect of an early human impact on a fragile environment, which was already stressed by desiccation at the time of the development of complex human society along the Mediterranean coasts, at Dhaka MV.

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Section: Dhaka Mud Volcanomentioning

confidence: 97%

Growth and demise of cold-water coral ecosystems on mud volcanoes in the West Alboran Sea: The messages from the planktonic and benthic foraminifera

et al. 2011

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“…The results from the compilation of dune dates for the INQUA Quaternary Dune Atlas show that much progress has been made using luminescence dating to constrain the age of sand dunes in the Sahara since the review of Swezey (2001). However, optical dating of sand dunes in the southern Sahara dune systems can be described as patchy, or more probably spotty, and in many areas there are no data whatsoever, leaving large gaps in the coverage.…”

Section: Discussionmentioning

confidence: 99%

“…Field observations from other parts of the Sahara suggests that this is a widespread and relatively common occurrence where dunes that migrated into endorehic basins in dry periods became flooded during succeeding humid periods (Callot 1991, Swezey, 2001Armitage et al 2007). The ages of the dunes preserved beneath lake deposits in the southern Sahara range between 19 ± 2 and 4.7 ± 0.3 ka, and appear to represent at least three distinct lake transgressions.…”

Section: Discussionmentioning

confidence: 99%

“…Most recently, Shanahan et al (2015), suggest that the termination of the African humid period was locally abrupt, but occurred progressively later at lower latitudes accompanied by both declining rainfall intensity and gradual southward migration of the tropical rainbelt. Swezey (2001) provides a review of the Late Quaternary aeolian stratigraphy in the Sahara even though, at that time (2001), few aeolian sediments in the Sahara had been dated directly. As a consequence there were, and still are, numerous uncertainties regarding the timing of aeolian sediment mobilisation and stabilisation (Swezey 2001).…”

Section: Introductionmentioning

confidence: 99%

“…Swezey (2001) provides a review of the Late Quaternary aeolian stratigraphy in the Sahara even though, at that time (2001), few aeolian sediments in the Sahara had been dated directly. As a consequence there were, and still are, numerous uncertainties regarding the timing of aeolian sediment mobilisation and stabilisation (Swezey 2001). Despite these limitations, Swezey concluded that "although the data are relatively sparse, when viewed as a whole, they reveal a general pattern of widespread eolian sediment mobilisation during the Late Pleistocene, eolian sediment stabilisation during the early Holocene, and a return to widespread eolian sediment mobilisation in the later Holocene" (Swezey 2001, p.128).…”

Section: Introductionmentioning

confidence: 99%

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Dune ages in the sand deserts of the southern Sahara and Sahel

Bristow

Armitage

2016

Quaternary International

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In this paper we aim to document the history of aeolian processes within the southern Sahara as part of the INQUA Dune Atlas. We review available luminescence ages for sand dunes across the southern Sahara to develop an improved understanding of the dune chronology on a regional basis and attempt to correlate periods of sand accumulation. This was achieved by analysing dune age by country, as well as by latitude and longitude. The results show a very patchy spatial distribution of dune ages with large gaps that encompass some of the largest sand seas. Despite these gaps, some related patterns in dune morphology and stratigraphy appear to be consistent between northern Nigeria and southern Mali where older linear dunes are distinct from younger Late Holocene transverse and barchanoid dunes. Elsewhere in Mauretania linear dunes with different orientations appear to have accumulated at different times, most likely in response to changes in atmospheric circulation. Regional climatic changes are identified where dunes are transgressed by lake deposits within endorehic basins. We identify four locations where dune accumulation is terminated by lacustrine transgressions, two of which, in Lake Chad and the Bodélé Depression, occur shortly after the last glacial maximum (LGM). The third example at Gobiero in Niger occurred later, in the early Holocene, around 8.4 ka and a fourth marks a later transgression of Palaeolake MegaChad after 4.7 ka. Larger-scale latitudinal and longitudinal distributions in dune ages across the southern Sahara do not show any consistent patterns, though this may be due to the small sample size relative to the study area. In addition, local variations in external controls such as wind regime, rainfall, vegetation and sand supply need to be considered, sometimes on a site by site basis. Limiting the analysis to dune ages determined using the single-aliquot regenerative-dose (SAR) protocol indicates a lack of dune preservation during the LGM and the Younger Dryas, times associated with increased dust input to the oceans which is assumed to indicate increased aeolian activity. The SAR dune dates suggest that preservation of dunes at the onset of succeeding humid intervals is an important component of the dune record. The most striking examples of this phenomenon occur where dunes are preserved within endorehic basins by lacustrine transgressions.

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High‐Altitude Aeolian Research on the Tibetan Plateau

Dong

Qian

et al. 2017

Reviews of Geophysics

110

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Aeolian processes and their role in desertification have been studied extensively at low elevations but have been rarely studied at high elevations in areas such as the Tibetan Plateau, where aeolian processes were active in the geologic past and remain active today. In this review, we summarize research that improves our understanding of aeolian processes on the Tibetan Plateau, including the distribution, characteristics, and provenance of aeolian sediments; the history of aeolian activity; aeolian geomorphology; and wind‐driven land degradation. Contemporary aeolian processes primarily occur in dry basins, in wide river valleys, on lakeshores, on mountain slopes, and on gravel pavements. Sediment characteristics suggest a local origin and provide interesting contrasts with those of China's Loess Plateau. The history of aeolian activity and its paleoclimatic implications, reconstructed based on aeolian archives, is short (mostly since the Late Glacial) and shows wide regional differences. Aeolian geomorphology is simple and suggests short formation time. Wind‐driven land degradation is less severe than previously thought, driven by different factors in different areas, and exhibited complex interactions with freeze‐thaw processes. Aeolian research has been conducted within the general framework of aeolian science but addresses issues specific to the Tibetan Plateau that arise due to the low air temperature, low air density, and the presence of a cryosphere. We propose six priorities for future research: aeolian physics, the effect of freeze‐thaw cycles, comparisons with other areas, regional differences, effects of wind‐driven land degradation, and integrated observation and monitoring.

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Eolian sediment responses to late Quaternary climate changes: temporal and spatial patterns in the Sahara

Cited by 186 publications

References 93 publications

Growth and demise of cold-water coral ecosystems on mud volcanoes in the West Alboran Sea: The messages from the planktonic and benthic foraminifera

Growth and demise of cold-water coral ecosystems on mud volcanoes in the West Alboran Sea: The messages from the planktonic and benthic foraminifera

Dune ages in the sand deserts of the southern Sahara and Sahel

High‐Altitude Aeolian Research on the Tibetan Plateau

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