Vegetation and climate dynamics in a 16,600-year marine sequence offshore Mozambique in Delagoa Bight, south-eastern Africa

Abstract

Few records of long-term vegetation dynamics and climate variability exist from coastal southeastern Africa. This study presents a new high-resolution marine pollen record (GeoB20615-2) from southern Mozambique, spanning the past c. 16,600 years. The chronology is based on a Bayesian age-depth model constructed using twelve radiocarbon dates on marine and terrestrial remains. Prior to c. 15,000 cal BP, pollen from ericaceous shrubs was prevalent, indicating low temperatures, while forest or woodland pollen taxa were minimal or absent. From c. 13,000 cal BP onwards, the record shows a gradual increase in savanna pollen taxa such as Spirostachys and Burkea, suggesting climatic warming. Pollen of Spirostachys, a woodland tree thriving in dry, warm regions, continues to increase into the early Holocene, between c. 11,200 and 9200 cal BP. After c. 9200 cal BP, a decline in Spirostachys pollen corresponds with a rise in Podocarpus pollen during a phase of high sea levels, indicating a potential expansion in coastal and/or montane forests, possibly reflecting increased moisture availability. From c. 3500 cal BP, Podocarpus pollen declines, likely due to more arid conditions, as indicated by a concomitant increase in Chenopodiaceae/Amaranthaceae, Asteraceae, and Spirostachys pollen. The youngest section of the profile is potentially affected by sediment mixing from c. 250 cal BP onwards. The section reveals the impact of European colonialists, with the appearance of neophytic pine pollen, and an increase in indigenous Alchornea, a disturbance indicator. The pollen results are in good agreement with terrestrial palynological records from the Indian Ocean Coastal Belt Biome such as Lake Eteza in northeastern South Africa. The GeoB20615-2 record contributes greater understanding of long-term vegetation dynamics and associated climatic shifts in the Indian Ocean Coastal Belt Biome.