Climatic and Paleoenvironmental Changes in Central Africa over the Last 300,000 Years: Evidence from the Rhizophora/Podocarpus Pollen Ratio in a Marine Core from the Gulf of Guinea
This high-resolution study expands on the initial analysis of the KW 23 core, which only covered the last 135,000 years, going back up to 300,000 years, extracted off the coast of Congo in the Gulf of Guinea, to reconstruct climatic and paleoenvironmental fluctuations in Central Africa. Fifty-eight samples were analyzed, allowing the identification of more than 150 pollen taxa. Particular attention was paid to the bioindicator taxa Rhizophora and Podocarpus, whose ecological requirements are respectively associated with warm and humid littoral conditions and cooler montane environments. Pollen diagrams were constructed using two datasets, including or excluding spores, which are often dominant in the assemblages. Variations in the Rhizophora/Podocarpus pollen ratio reveal a marked alternation between warm and cold climatic phases. This curve shows strong correspondence with the benthic foraminiferal δ1？O record of Melonis barleeanum, as well as with Milankovitch orbital curves and isotopic and temperature reconstructions derived from the Vostok ice core. Nine climatic zones corresponding to marine isotope stages (MIS 1 to 9) were identified. Odd-numbered stages are characterized by a high abundance of Rhizophora, reflecting warm and humid conditions favorable to mangrove development, whereas even-numbered stages are dominated by Podocarpus, indicating cooler climates and a downslope expansion of montane vegetation. These results demonstrate that the Rhizophora/Podocarpus pollen ratio is a reliable proxy for reconstructing Quaternary climatic variations in Central Africa and provide new insights into the regional expression of major global climatic oscillations.
References
[1]
Ericson, D.B. and Wollin, G. (1968) Pleistocene Climates and Chronology in Deep-Sea Sediments. Science, 162, 1227-1234. https://doi.org/10.1126/science.162.3859.1227
[2]
Shackleton, N.J. and Opdyke, N.D. (1976) Oxygen-Isotope and Paleomagnetic Stratigraphy of Pacific Core V28-239 Late Pliocene to Latest Pleistocene. Geological Society of America Memoirs, 162, 449-464. https://doi.org/10.1130/mem145-p449
[3]
lmbrie, J., Hays, J.D., Martinson, D.G., Mclntyre, A., Mix, A.C., Morley, J.J., Pisias, N.G., Prell, W.L. and Shackleton, N.J. (1984) The Orbital Theory of Pleistocene Climate: Support from a Revised Chronology of the Marine 61aO Record. In: Berger, A.L., Imbrie, J., et al., Eds., Milankovitch and Climate, Reidel, 269-305.
[4]
Dupont, L.M. and Agwu, C.O.C. (1991) Environmental Control of Pollen Grain Distribution Patterns in the Gulf of Guinea and Offshore NW-Africa. Geologische Rundschau, 80, 567-589. https://doi.org/10.1007/bf01803687
[5]
Lezine, A. and Cazet, J. (2005) High-Resolution Pollen Record from Core KW31, Gulf of Guinea, Documents the History of the Lowland Forests of West Equatorial Africa since 40,000 Yr Ago. Quaternary Research, 64, 432-443. https://doi.org/10.1016/j.yqres.2005.08.007
[6]
Bengo, M.D. and Maley, J. (1991) Analyses des flux polliniques sur la marge sud du Golfe de Guinée depuis 135 000 ans. Comptes Rendus de l’Académie des Sciences de Paris, Série II, 313, 843-849.
[7]
Dupont, L.M., Marret, F. and Winn, K. (1998) Land-sea Correlation by Means of Terrestrial and Marine Palynomorphs from the Equatorial East Atlantic: Phasing of SE Trade Winds and the Oceanic Productivity. Palaeogeography, Palaeoclimatology, Palaeoecology, 142, 51-84. https://doi.org/10.1016/s0031-0182(97)00146-6
[8]
Bengo, M.D., Gomat, H., Giresse, P., Maley, J. and Nganga, D.M. (2025) Implications of Marine Hydrodynamism in the Dispersal and Modern Distribution of Pollen on the Cameroonian Continental Shelf. Open Journal of Geology, 15, 716-734. https://doi.org/10.4236/ojg.2025.1510035
[9]
Bengo, M.D., Gomat, H., Ifo, S.A., Maley, J. and Giresse, P. (2025) Late Quaternary Paleoenvironmental Dynamics on the Cameroonian Continental Shelf (Gulf of Guinea): Palynological and Sedimentary Insights. Journal of Geoscience and Environment Protection, 13, 92-115. https://doi.org/10.4236/gep.2025.1312006
[10]
Bengo, M.D., Gomat, H., Bita, A.M., Ifo, S.A., Maley, J. and Giresse, P. (2026) High-resolution Study of the Late Holocene from Pollen of a Marine Core in the Gulf of Guinea (Cameroon): Paleoenvironmental and Ecological Dynamics in Central Africa during the Last 2,500 Years. Open Journal of Forestry, 16, 83-105. https://doi.org/10.4236/ojf.2026.161006
[11]
Bonifay, D. (1987) Interaction des accumulations terrig6nes et oc6aniques dans le Quaternaire moyen et sup6rieur des marges profondes du Gabon et de la ride m6dio-guin6enne. Ph.D. Thesis, University of Perpignan, 185 p.
[12]
Bonifay, D. and Giresse, P. (1992) Middle to Late Quaternary Sediment Flux and Post-Depositional Processes between the Continental Slope off Gabon and the Mid-Guinean Margin. Marine Geology, 106, 107-129. https://doi.org/10.1016/0025-3227(92)90057-o
[13]
Fredoux, A. (1994) Paléoenvironnements enregistres dans une carotte marine du golfe de Guinée depuis 225 000 ans: Analyse pollinique. In: Maire, R., Pomel, S. and Salomon, J.N., Eds., Enregistreurs et indicateurs de l’évolution de l’environnement en zone tropicale, Presses Universitaires de Bordeaux, 85-102. https://doi.org/10.4000/books.pub.9929
[14]
Jahns, S. (1996) Vegetation History and Climate Changes in West Equatorial Africa during the Late Pleistocene and Holocene, Based on a Marine Pollen Diagram from the Congo Fan. Vegetation History and Archaeobotany, 5, 207-213. https://doi.org/10.1007/bf00217498
[15]
Ning, S. and Dupont, L.M. (1997) Vegetation and Climatic History of Southwest Africa: A Marine Palynological Record of the Last 300,000 Years. Vegetation History and Archaeobotany, 6, 117-131. https://doi.org/10.1007/bf01261959
[16]
Le Pichon, X. and Hayes, D.E. (1971) Marginal Offsets, Fracture Zones, and the Early Opening of the South Atlantic. Journal of Geophysical Research, 76, 6283-6293. https://doi.org/10.1029/jb076i026p06283
[17]
Larson, R.L. and Ladd, J.W. (1973) Evidence for the Opening of the South Atlantic in the Early Cretaceous. Nature, 246, 209-212. https://doi.org/10.1038/246209a0
[18]
Giresse, P. and Tchikaya, C. (1975) Contribution à la carte géologique de la plate-forme sous-marine congolaise (Mission N.O. Nizery de janvier 1974). Annales de l’Université de Brazzaville, 11, 23-34.
[19]
Giresse, P. (1980) Carte sédimentologique du plateau continental du Congo. ORSTOM, Notice Explicative No. 85, Editions ORSTOM.
[20]
Malounguila-Nganga, D. (1983) Les environnements sédimentaires des plateformes du nord-Congo et du sud-Gabon au quaternaire supérieur d’après les données de vibro-carottages. Ph.D. Thesis, Université de Toulouse, 169 p.
[21]
Kinga-Mouzeo (1986) Transport particulaire actuel du fleuve Congo et de quelques affluents; Enregistrements quaternaires dans l’éventail détritique profond (sédimentologie, minéralogie et géochimie). Ph.D. Thesis, University of Perpignan, 251 p.
[22]
Moguedet, G. (1988) Les relations entre le fleuve Congo et la sédimentation récente sur la marge continentale entre l’embouchure et le Sud du Gabon. Etude hydrologique, sédimentologique et g6ochimique. Doctoral Thesis, University of Angers, 185 p.
[23]
O!ivry, J.C., Bricquet, J.P., Thiebaux, J.P. and Sigha, N. (1988) Transport de matiere sur les grands fleuves des régions intertropicales: Les premiers resultats des mesures de flux particulaires sur le bassin du fleuve Congo. Proceeding of the Porto-Alegre Symposium, Porto Alegre, 11-15 December 1988, 509-521.
[24]
Nzila, J. D., Kimpouni, V., Watha-Ndoudy, N., Nanitelamio, M.M., Salisou, Y.M. and Nguila-Ntsoko, D.P. (2018) Soils Typology and Floristic Diversity of the Forest of the “Cité Scientifique” of Brazzaville, Congo. Open Journal of Ecology, 8, 286-304.
[25]
Wauthy, B. (1983) Introduction à la Climatologie du Golfe de Guinée. Océanogra-phie Tropicale, 18, 103-108.
[26]
Piton, B. and Kartavtseff, A. (1986) Utilisation de bouées dérivantes à positionnement par satellite pour une meilleure connaissance de I’hydrologie de surface du Ggolfe de Guinee. ORSTOM, 34, 41.
[27]
Leroux, M. (1983) Le climat de l’Afrique tropicale. Vols. 1-2. Champion.
[28]
Piton, B. (1987) Les anomalies océanographiques et climatiques de 1983 et 1984 dans le Golfe de Guinée. Veille Climatique Satellitaire, 16, 18-31.
[29]
Suchel, J.B. (1988) Les climats du Cameroun. Master’s Thesis, Université de Saint-Étienne.
[30]
Aubreville, A. (1948) Etude sur les forêts de l’Afrique équatoriale française et du Cameroun. Secteur Technique de l’Afrique Tropicale Bulletin Scientifique, No. 2, 132.
[31]
Letouzey, R. (1968) Étude phytogéographique du Cameroun. Lechevalier.
[32]
Boyé, M., Baltzer, F., Caratini, C., Hampartzoumian, A., Olivry, J.C., Plaziat, J.C. and Villiers, J.F. (1975) Mangrove of the Wouri Estuary, Cameroon. In: Walsh, G.E., Snedaker, S.C. and Teas, H.J., Eds., Proceedings of the International Symposium on Biology and Management of Mangroves, Institute of Food and Agricultural Sciences, University of Florida, 431-454.
[33]
Din, D. (1991) Contribution à l’étude botanique et écologique des mangroves de l’estuaire du Cameroun. Ph.D. Thesis, University of Yaoundé.
[34]
Elenga, H. and Vincens, A. (1987) Paléoenvironnements quaternaires d’après l’étude du sondage du Bois de Bilanko. Diplôme d’Études Approfondies (DEA), Université Aix-Marseille, 37 p.
[35]
Maley, J. (1991) The African Rain Forest Vegetation and Palaeoenvironments during Late Quaternary. Climatic Change, 19, 79-98. https://doi.org/10.1007/bf00142216
[36]
Thunell, R.C. (1976) Optimum Indices of Calcium Carbonate Dissolution, in Deep-Sea Sediments. Geology, 4, 525-528. https://doi.org/10.1130/0091-7613(1976)4<525:oioccd>2.0.co;2
[37]
Bengo, M.D. (1990) Analyses des flux polliniques sur la marge sud du Golfe de Guinée depuis 135.000 ans. Diplôme d’Études Supérieures (DES), Université Montpellier 2, 62 p.
[38]
Maley, J. and Brenac, P. (1998) Vegetation Dynamics, Palaeoenvironments and Climatic Changes in the Forests of Western Cameroon during the Last 28,000 Years B.P. Review of Palaeobotany and Palynology, 99, 157-187. https://doi.org/10.1016/s0034-6667(97)00047-x
[39]
Kimpouni, V., Loumeto, J. and Mizingou, J. (2015) Woody Flora and Dynamic of Aucoumea klaineana Forest in the Congolese Littoral. International Journal of Biological and Chemical Sciences, 8, 1393-1410. https://doi.org/10.4314/ijbcs.v8i4.4
[40]
Aubréville, A. (1962) Flore du Gabon, Volume 3. Muséum national d’Histoire naturelle.
[41]
Sowunmi, M.A. (1991) Late Quaternary Environments in Equatorial Africa: Palynological Evidence. Palaeoecology of Africa, 22, 213-238.
[42]
Sowunmi, M.A. (1987) Palynological Studies in the Niger Delta. In: Alagoa, E.J., Anozie, F.N. and Nzewunwa, N., Eds., The Early History of the Niger Delta, University of Port Harcourt, 29-64.
[43]
Malounguila-Nganga, D., Giresse, P., Boussafir, M. and Miyouna, T. (2017) Late Holocene Swampy Forest of Loango Bay (Congo). Sedimentary Environments and Organic Matter Deposition. Journal of African Earth Sciences, 134, 419-434. https://doi.org/10.1016/j.jafrearsci.2017.05.022
[44]
Bengo, M.D., Elenga, H., Maley, J. and Giresse, P. (2020) Evidence of Pollen Transport by the Sanaga River on the Cameroon Shelf. Comptes Rendus. Géoscience, 352, 59-72. https://doi.org/10.5802/crgeos.1
[45]
Elenga, H. and Vincens, A. (1990) Paléoenvironnements quaternaires récents des plateaux Bateke (Congo): Étude palynologique des dépôts de la dépression du bois de Bilanko. In: Lanfranchi, R. and Schwartz, D., Eds., Paysages quaternaires de l’Afrique centrale atlantique, ORSTOM, 271-282.
[46]
Vincens, A., Buchet, G., Elenga, H., Fournier, M., Martin, L., Namur, C., Schwartz, D., Servant, M. and Wirrmann, D. (1994) Changement majeur de la végétation du lac Sinnda (vallée du Niari, sud-Congo) consécutif à l’assèchement climatique holocène supérieur: Apport de la palynologie. Comptes Rendus de l’Académie des Sciences de Paris, 318, 1521-1526.
[47]
Brenac, P. (1988) Évolution de la végétation et du climat de l’Ouest-Cameroun entre 25 000 et 11 000 ans BP. Travaux de la Section Scientifique et Technique de l’Institut Français de Pondichéry, 25, 91-103.
[48]
Assi-Kaudjhis, C. (2012) Dynamique des écosystèmes et biodiversité des montagnes du Cameroun au cours des derniers 20 000 ans: Analyse palynologique d’une série sédimentaire du Lac Bambili. Ph.D. Thesis, Université de Liège and Université de Versailles Saint-Quentin-en-Yvelines.
[49]
Assi-Kaudjhis, C., Lézine, A.M. and Roche, E. (2008) Dynamique de la végétation d’altitude en Afrique centrale atlantique depuis 17 000 ans BP: Analyses préliminaires de la carotte de Bambili (Nord-Ouest du Cameroun). Geo-Eco-Trop, 32, 131-143.
[50]
Assi-Kaudjhis, C., Zéli Digbehi, B., Roche, E. and Lézine, A.M. (2010) Synthèse sur l’évolution des paléoenvironnements de l’Afrique occidentale atlantique depuis la fin de la dernière période glaciaire: Influences climatiques et anthropiques. Geo-Eco-Trop, 34, 1-28.
[51]
Zogning, A., Giresse, P., Maley, J. and Gadel, F. (1997) The Late Holocene Palaeoenvironment in the Lake Njupi Area, West Cameroon: Implications Regarding the History of Lake Nyos. Journal of African Earth Sciences, 24, 285-300. https://doi.org/10.1016/s0899-5362(97)00044-4
[52]
Vincens, A., Buchet, G. and Servant, M. (2010) Vegetation Response to the “African Humid Period” Termination in Central Cameroon (7° N)—New Pollen Insight from Lake Mbalang. Climate of the Past, 6, 281-294. https://doi.org/10.5194/cp-6-281-2010
[53]
Richards, K. (2021) A Holocene Pollen Record from Mboandong, a Crater Lake in Lowland Cameroon. In: Runge, J., Gosling, W., Lézine, A.M. and Scott, L., Eds., Quaternary Vegetation Dynamics—The African Pollen Database, CRC Press, 207-224. https://doi.org/10.1201/9781003162766-13
[54]
Reynaud-Farrera, I., Maley, J. and Wirrmann, D. (1996) Végétation et climat dans les forêts du Sud-Ouest camerounais depuis 4770 ans BP: Analyse pollinique des sédiments du lac Ossa. Comptes Rendus de l’Académie des Sciences de Paris, Série IIa, 322, 749-755.
[55]
Kerfoot, O. (1968) Mist Precipitation on Vegetation. Oxford Forestry Abstracts, 29, 8-20.
[56]
Maley, J. (1990) L’histoire récente de la forêt dense humide africaine: Essai sur le dynamisme de quelques formations forestières. In: Lanfranchi, R. and Schartz, D., Eds., Paysages quaternaires de l’Afrique Centrale Atlantique, ORSTOM, 367-382.
[57]
Levrard, B. (2005) Cycles de Milankovitch et variations climatiques: Dernières Nouvelles. Planet Terre. https://planet-terre.ens-lyon.fr/ressource/milankovitch-2005.xml
[58]
Petit, J.R., Jouzel, J., Raynaud, D., Barkov, N.I., Barnola, J., Basile, I., et al. (1999) Climate and Atmospheric History of the Past 420,000 Years from the Vostok Ice Core, Antarctica. Nature, 399, 429-436. https://doi.org/10.1038/20859
[59]
Vimeux, F., Cuffey, K.M. and Jouzel, J. (2002) New Insights into Southern Hemisphere Temperature Changes from Vostok Ice Cores Using Deuterium Excess Correction. Earth and Planetary Science Letters, 203, 829-843. https://doi.org/10.1016/s0012-821x(02)00950-0
[60]
Jahns, S., Hüls, M. and Sarnthein, M. (1998) Vegetation and Climate History of West Equatorial Africa Based on a Marine Pollen Record off Liberia (site GIK 16776) Covering the Last 400,000 Years. Review of Palaeobotany and Palynology, 102, 277-288. https://doi.org/10.1016/s0034-6667(98)80010-9
[61]
Lézine, A. and Vergnaud-Grazzini, C. (1993) Evidence of Forest Extension in West Africa since 22,000 BP: A Pollen Record from the Eastern Tropical Atlantic. Quaternary Science Reviews, 12, 203-210. https://doi.org/10.1016/0277-3791(93)90054-p
[62]
Dupont, L.M. and Weinelt, M. (1996) Vegetation History of the Savanna Corridor between the Guinean and the Congolian Rain Forest during the Last 150,000 Years. Vegetation History and Archaeobotany, 5, 273-292. https://doi.org/10.1007/bf00195296
