Evolution paléohydrologique du marais Paurosa au centre du Gabon au cours des deux derniers millénaires : Contribution des diatomées

Kom, Meliphe Francis; Nguetsop, Victor François; Brémond, Laurent; Fonkou, Théophile; Noumsi, Bernadette; Sebag, David; Oslisly, Richard; Tsalefac, Maurice

doi:10.4314/cajeb.v12i1.8

Cited by 2 publications

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“…The interpretation of the δ 15 N signal is not obvious because we are not aware of any study that has attempted to interpret the signal in the same type of environmental context. However, when comparing variations in δ 15 N at Paurosa with diatom assemblages published by Kom et al (2018) it would appear that δ 15 N has the highest values when benthic diatoms dominate. Kom et al (2018) interpret the base of the sequence as a phase with shallow water depth, a nutrient-poor environment and marked dry seasons.…”

Section: Discussionmentioning

confidence: 95%

“…However, when comparing variations in δ 15 N at Paurosa with diatom assemblages published by Kom et al (2018) it would appear that δ 15 N has the highest values when benthic diatoms dominate. Kom et al (2018) interpret the base of the sequence as a phase with shallow water depth, a nutrient-poor environment and marked dry seasons. This is in agreement with Swap et al (2004) study showing a decrease of δ 15 N of southern African vegetation with precipitation increase.…”

Section: Discussionmentioning

confidence: 95%

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Establishment and functioning of the savanna marshes of the Lopé National Park in Gabon since the termination of the African humid period and the arrival of humans 2500 years ago

et al. 2021

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Holocene paleoecological studies in tropical Africa are rare because most lakes either dried out at the termination of the African Humid Period or have since filled up. However, tropical sedge marshes can be an alternative to perform long-term ecological studies. The Lopé National Park (LNP) in Gabon is a mosaic of forest and savanna enclosed in the equatorial forest, where open areas facilitated the development of peat marshes accumulating several-meter-thick sediment. In order to reconstruct the historical dynamic in these marshes through a local and regional point of view, we compared sedimentological, continuous X-ray fluorescence, and stable isotopic analyses on sediment cores from six herbaceous marshes in the LNP. A reliable chronological frame was based on 50 14C dates, over the last 2500 years in most sites, and reaching 9000 years in one marsh. We show that the origin of these marshes is a major hydrological change, 3450 and 2300 years ago, that affected the entire region, almost concomitantly with the diffusion of Iron Age population. The sedimentation within marshes is homogenous with low intra-site variability. In contrast, high inter-sites variability evidences that the functioning of the marsh itself exerts a much more significant influence than in lakes. However, a regional event is recorded between 1400 and 800 years ago, concurrently with an archeological trace hiatus throughout the forest hinterland of West Central Africa.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 95%

Establishment and functioning of the savanna marshes of the Lopé National Park in Gabon since the termination of the African humid period and the arrival of humans 2500 years ago

et al. 2021

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Holocene paleoenvironmental reconstruction based on the lacustrine evolution of three Cameroonian lakes (SW, Africa)

Bessa,

Kołaczek,

Ndjigui

et al. 2024

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Lakes are the most attractive and expressive characteristics of a landscape. Lacustrine sediments provide a historical record of the conditions of the surrounding catchment area. The aim of this study is to reconstruct the Holocene lacustrine evolution of 3 lakes located in Yaoundé, Dizangué and Ngaoundéré regions (Cameroon, SW-Africa) using a multiproxy approach including analysis of sediments, diatoms, pollen, with absolute chronologies based on radiocarbon dates. Sediment cores were recovered from a raft using polyvinyl chloride (PVC) pipe. Sediment grains are generally sub-rounded and rounded indicative of both aeolian and fluvial transportation. Pollen and diatom data revealed major hydrological changes and strong fluctuations between wet conditions during the "Medieval Warm Period" (1100 − 800 yrs BP), and dry conditions during the "Little Ice Age" (500 − 300 yrs BP). Four distinct paleoclimatic phases were identified from the diatom assemblage of lakes from Yaoundé and Dizangué (South) and Ngaoundéré (North). The diatom assemblages in Simbock Lake (southern Cameroon) indicate high water levels initially, followed by a transition marked by increased aerophilic species, potentially indicating episodic drying or reduced water supply. Furthermore, a pH and trophic inversion suggests eutrophication due to nutrient influx. In the Ossa Lake complex (southern Cameroon), four phases reveal changes from oligotrophic to eutrophic conditions, with Aulacoseira species dominating, and the evolution of acidic to clear waters. Lake Ngaoundaba in the Adamawa (northern Cameroon) exhibits three phases, indicating stable oligotrophic conditions, episodic drying, and a rise in lake level with increased tychoplanktonic species, particularly Aulacoseira distans. These hydrological changes have controlled the dynamics of tropical rainforests during the Little Ice Age (LIA) and the Medieval Warming (MW) in this part of Africa, resulting in their expansion during periods of heavy rainfall and contraction during periods of reduced rainfall.

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Evolution paléohydrologique du marais Paurosa au centre du Gabon au cours des deux derniers millénaires : Contribution des diatomées

Cited by 2 publications

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Establishment and functioning of the savanna marshes of the Lopé National Park in Gabon since the termination of the African humid period and the arrival of humans 2500 years ago

Establishment and functioning of the savanna marshes of the Lopé National Park in Gabon since the termination of the African humid period and the arrival of humans 2500 years ago

Holocene paleoenvironmental reconstruction based on the lacustrine evolution of three Cameroonian lakes (SW, Africa)

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