| 1. |
- Holmgren, Karin, et al.
(författare)
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Water-level variations in Lake Nhauhache, Mozambique, during the last 2,300 years
- 2012
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Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 48:2, s. 311-322
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Tidskriftsartikel (refereegranskat)abstract
- Stratigraphic variations in diatom composition and phytolith abundance in a sediment core from a small, hydrologically isolated waterbody, Lake Nhauhache, Mozambique, provide evidence of water-level fluctuations over the past 2,300 years. Ten AMS radiocarbon dates on bulk sediment samples show that the lake came into existence about 2,300 years ago and that it has dried out since then, but only for brief time periods. Changes in the diatom assemblage composition indicate that lake level fluctuated in response to shifting humidity conditions. The changes reflect wetter conditions ca. 300 BC-AD 800, more variable conditions between AD 800 and 1150, a distinct dry phase within the time span AD 1150-1700 and a return thereafter to more humid conditions until present. There is general agreement between the Lake Nhauhache record and other records from the Southern Hemisphere summer rainfall region. This suggests that sediments from small interdunal lakes, which are abundant along the coast of southern Africa, provide reliable, regional paleoenvironmental information about an area from which more such data are needed.
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| 2. |
- Norström, Elin, et al.
(författare)
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Coastal paleo-environment and sea-level change at Macassa Bay, southern Mozambique, since c. 6600 cal BP
- 2012
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Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 260, s. 153-163
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Tidskriftsartikel (refereegranskat)abstract
- Changes in Holocene coastal paleo-environment and sea-level variations have been recorded in estuary sediments from Macassa Bay, southern Mozambique. Methods include analysis of fossil diatoms, sediment stratigraphy, mineral magnetic properties, stable carbon and nitrogen isotope composition and carbon and nitrogen content. The chronology, based on six AMS 14C dates, suggests a basal age of the sediment core of c 6600 cal BP (calibrated years Before Present). The multi-proxy dataset implies two phases when the site was experiencing marine conditions and tentative sea-level high-stands: 1) between c 6600–6300 cal BP which is contemporary with the last phase of the global transgression and the Holocene climatic optimum, and 2) between c 4700–1000 cal BP, a period when sea level curves from the region suggest occasional minor sea level high-stands. Between these phases (c 6300–4700 cal BP), the environment within the Macassa Bay estuary was less influenced by marine processes, and studied proxies indicate a freshwater phase associated with relatively low sea levels. After c 1000 cal BP, a terrestrial environment prevailed at the site, probably as a result of a combined effect of sea level lowering and high accumulation of organic peat within the estuary.
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| 3. |
- Raúl Sitoe, Sandra, 1979-, et al.
(författare)
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Paleo-environment and flooding of the Limpopo River-plain, Mozambique, between c. AD 1200-2000
- 2015
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Ingår i: Catena (Cremlingen. Print). - : Elsevier BV. - 0341-8162 .- 1872-6887. ; 126, s. 105-116
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Tidskriftsartikel (refereegranskat)abstract
- Multi-proxy analysis was performed on a radiocarbon-dated core, collected from a relic oxbow lake in theLimpopo River-plain, Mozambique, with the aim to reconstruct paleo-environment and past flooding of thelower river system over the past c. 800 years. An additional objective was to evaluate and investigate the potentialuse of different proxies as recorders of paleo-flooding events and paleo-environmental variability within thefloodplain. The proxies applied in this study were: mineral magnetic properties, grain-size distribution, organiccarbon content and diatom microfossil assemblages.We found that sediment grain-size and mineral magneticproperties of the minerogenic fraction were the most sensitive proxies in terms of detecting signals from highintensityriver-discharge events. In the 800 year long sequence, variations in sand content, magnetic susceptibilityand saturation isothermal remnant magnetization suggest at least four major flooding events at the siteduring the reconstructed period; in the mid-1200, late-1300, mid-1500 AD and during the last century. Thediatom proxy reflects the development of the site from an open oxbow lake to a mainly terrestrial area. Thediatom assemblage indicates that open lake conditions prevailed at the site between c. AD 1200–1400, withperiodic inundation by marine water, most likely due to late Holocene sea-level changes. From c. AD 1400 andonwards, diatoms were rarely deposited at the site, which indicates drier conditions. This was a result of soilformation and gradual in-filling of the lake, a processwhich possiblywas accentuated by a regionally dry climatesituation. Our study shows that oxbow lakes and the proxies used here have great potential for reconstructingflooding events, a knowledge that is crucial for potential prediction and mitigation of flooding events inMozambique in the future. Although chronological uncertainties limit comparisons to other paleoenvironmentalrecords, it seems that the flooding events recorded at our site occurred both during regionallywet and dry periods. Our data infer however, that flooding was probably more clearly recorded during thelake-stages than during infilled stage, probably as the terrestrial environment was more exposed to erosion.
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