A multi-proxy reconstruction of the late Holocene climate evolution in the Kapsabet Swamp, Kenya (East Africa)

Njagi, Dennis M; Routh, Joyanto; Olago, Daniel; Gayantha, Kasun

doi:10.1016/j.palaeo.2021.110475

Cited by 12 publications

(5 citation statements)

References 88 publications

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“…Moreover, there are higher total charcoal contents in all three cores at this time, probably due to burning, [56,57,84], which indicated a dry climate across the area associated with the late Holocene arid climate regime in East Africa [80,90]. This observation is accompanied by multiproxy records from the Kapsabet Swamp in Kenya, which shows a warm and dry climate stage from 280 to 1325 CE [91]. In addition, the abundance of charcoal fragments larger than 100 µm in size, around 635 CE in cores AUU1, BUU1 and CUU1 suggested that local fire regimes possibly represent anthropogenic rather than natural fires with fingerprints related to earliest human settlement on Unguja Ukuu [9,31].…”

Section: ~600-950 Ce (1350-1000 Cal Yr Bp)mentioning

confidence: 72%

High-Resolution Multiproxy Record of Environmental Changes and Anthropogenic Activities at Unguja Ukuu, Zanzibar, Tanzania during the Last 5000 Years

et al. 2023

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A high-resolution multiproxy sedimentary record comprising pollen, charcoal, trace element, stratigraphy and particle size data is used to reveal environmental changes from the mangrove ecosystem at Unguja Ukuu, Zanzibar, Tanzania, over the last 5000 years. Historical human–environment interactions over the last millennia are explored by a comparison of the stratigraphic and archaeological data. The area was characterised by a mixture of mangrove forest and beaches, indicating a low level of tidal inundation to at least 3300 BCE. From 2750 BCE, mangrove forest expanded as the area experienced sea-level rise. Further sea-level rise is recorded between 600 and 1100 CE, indicated by the pollen record, particle size analysis and the presence of shell fragments. After 1100 CE, mangrove forest decreased with back mangrove species increasing, indicating a falling sea level. Cocos nucifera decreased after 1900 CE, which reflects a recent sea-level rise and possibly a phase of exploitation. Cereal pollen shows a high presence at around 1500 CE, which coincided with the arrival of the Portuguese on Zanzibar and the transition to Omani colonisation. The sedimentation rate in the core top indicates that mangroves in Unguja Ukuu cannot keep pace with the current rate of sea-level rise.

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Section: ~600-950 Ce (1350-1000 Cal Yr Bp)mentioning

confidence: 72%

High-Resolution Multiproxy Record of Environmental Changes and Anthropogenic Activities at Unguja Ukuu, Zanzibar, Tanzania during the Last 5000 Years

et al. 2023

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“…This increasing trend is expected for peats composed almost entirely of organic matter. The presence of mineral-rich intervals such as clayey or sandy intervals or a steady input of a large amount of mineral matter will affect this trend (Baker et al, 2014;Njagi et al, 2021). Such records are therefore not ideal for the modeling presented in this study.…”

Section: Validation and Limits Of The Approachmentioning

confidence: 99%

“…If the mineral component is very low, the TOC will follow the trend of the organic matter and increase with depth and time (e.g., Upton et al, 2018). In mineral-rich peat, or when mineral fraction supply varies, the increasing trend will no longer be visible because the increasing proportion of the mineral fraction due to the decomposition of the organic matter will mask the evolution of the carbon in the organic matter (e.g., Baker et al, 2014;Njagi et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Modeling the Decomposition Signal and Correcting Bulk Organic Data from a Peat Deposit: a Case Study at Low Latitudes (Cameroon)

Schaaff,

Sebag,

Grossi

et al. 2023

Imog 2023

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Organic compounds are widely used for paleoclimatic and paleoenvironmental reconstructions. Bulk organic proxies, however, are more complicated to interpret due to the multiple causes of variation in climatic and environmental conditions and the degree of diagenetic alteration. As labile compounds, rich in easily degradable function and generally richer in heteroatoms such as oxygen and nitrogen, decompose, the remaining organic matter becomes progressively richer in refractory carbon and its carbon content increases. Thus, in a peat deposit composed almost entirely of organic matter, total organic carbon (TOC) is expected to increase with time and depth, which could mask the paleoclimatic signal. We propose a simple model for peat sediments to remove the decomposition signal based on a logarithmic function fitted with a partial dataset where decomposition is the main parameter. The subtraction of the obtained logarithmic function to the raw data (i.e., measured data) leads to "residual" data. We discuss the influence of different parameters (water table depth, vegetation, microbial community) on the "residual" data and their possible link to paleoclimatic and paleoenvironmental variations. This method is tested on bulk elemental and isotopic data obtained from a new peatcore from the Adamawa Plateau (North-East Cameroon) covering nearly 10 ka cal BP. Comparison with Rock-Eval® parameters highlights similar variations between the Hydrogen Index and residual TOC variations, supporting the interpretation based on residual TOC. Our approach allows to extract paleoenvironmental information from decomposition-prone bulk organic proxies and can be generalized to peat deposits where decomposition plays a major role in controlling bulk data.

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“…A significant change in material culture and subsistence occurs in the Later Holocene, as the climate approaches modern highly seasonal rainfall conditions and forest decline after c. 2 ka (Dale, 2007;Ssemmanda et al, 2002;Stager et al, 1997Stager et al, , 2003. Multi-proxy data from Kapsabet Swamp in the northwest of the Lake Victoria Basin indicate overall wetter conditions after 3 ka, but punctuated by arid episodes that highlight the increasing unpredictability and sub-regional variation of the Late Holocene that may have challenged Kansyore lifeways (Njagi et al, 2021). Responses to these conditions appears to have included greater commitment to delayed-return strategies, including acquiring livestock from surrounding herders before ultimately being integrated or replaced by pastoralists (Dale et al, 2004;Prendergast, 2010;Lane, 2004).…”

Section: Lake Victoria Fisher-foragersmentioning

confidence: 99%

Hunter-gatherer technological organization and responses to Holocene climate change in coastal, lakeshore, and grassland ecologies of eastern Africa

Goldstein

Shipton

Miller

et al. 2022

Quaternary Science Reviews

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A multi-proxy reconstruction of the late Holocene climate evolution in the Kapsabet Swamp, Kenya (East Africa)

Cited by 12 publications

References 88 publications

High-Resolution Multiproxy Record of Environmental Changes and Anthropogenic Activities at Unguja Ukuu, Zanzibar, Tanzania during the Last 5000 Years

High-Resolution Multiproxy Record of Environmental Changes and Anthropogenic Activities at Unguja Ukuu, Zanzibar, Tanzania during the Last 5000 Years

Modeling the Decomposition Signal and Correcting Bulk Organic Data from a Peat Deposit: a Case Study at Low Latitudes (Cameroon)

Hunter-gatherer technological organization and responses to Holocene climate change in coastal, lakeshore, and grassland ecologies of eastern Africa

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