Pollen analysis and age model of sediment core GIK-16856-2@en

Pollen and spores from a deep-sea core located west of the Niger Delta record an uninterrupted area of lowland rain forest in West Africa from Guinea to Cameroon during the last Interglacial and the early Holocene. During other periods of the last 150 ka, a savanna corridor between the western -- Guinean -- and the eastern -- Congolian -- part of the African lowland rain forest existed. This so-called Dahomey Gap had its largest extension during Glacial Stages 6, 4, 3, and 2. Reduced surface salinity in the eastern Gulf of Guinea as recorded by dinoflagellate cysts indicates sufficient precipitation for extensive forest growth during Stages 5 and 1. The large modern extension of dry forest and savanna in West Africa cannot be solely explained by climatic factors. Mangrove expansion in and west of the Niger Delta was largest during the phases of sea-level rise of Stages 5 and 1. During Stages 6, 4, 3, and 2, shelf areas were exposed and the area of the mangrove swamps was minimal.采自尼日尔三角洲（Niger Delta）以西深海岩芯（deep-sea core）的花粉与孢子记录表明，在末次间冰期（last Interglacial）与全新世早期（early Holocene），西非几内亚至喀麦隆一带分布着连续的低地雨林。在过去15万年的其他时段，非洲低地雨林的西部（几内亚片区）与东部（刚果片区）之间存在一条稀树草原廊道（savanna corridor）。这一被称为达荷美缺口（Dahomey Gap）的廊道在冰期阶段（Glacial Stages）6、4、3、2时规模达到最大。通过甲藻孢囊（dinoflagellate cysts）记录的几内亚湾（Gulf of Guinea）东部表层海水盐度降低现象显示，在第5、1冰期阶段时，当地降水充沛，足以支撑大面积森林生长。西非现今大面积分布的干燥森林与稀树草原，无法仅用气候因素解释。尼日尔三角洲及其以西海域的红树林扩张规模，在第5、1冰期阶段的海平面上升时段达到最大。在第6、4、3、2冰期阶段，大陆架区域裸露，红树林沼泽（mangrove swamps）的面积降至最低。