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Holocene pollen spectra from Oyo, northwestern Sudan: problems of interpretation in a hyperarid environment

(Scarborough College, University of Toronto, Scarborough, Ontario, Canada M1C 1A4)

The Oyo site is in the hyperarid core of the eastern Sahara. A 3.4 m core of lake sediment yielded a continuous pollen record for the period 9 to 4.5 ka BP. The lower, regularly-laminated carbonate sediments (9-6 ka) show a pollen assemblage with the tropical taxa dominated by plants of Sudanian and Sahelian affinity, and the local taxa dominated by grass and Typha. The upper sediments (6-4.5 ka), grading from laminated carbonates to coarsely bedded and massive layers with aeolian sands, have reduced frequencies of Sudanian pollen taxa, and increases in Saharan types and sedge-dominated local pollen spectra. A possible vegetational reconstruction is a mosaic of savanna woodlands associated with groundwater-supported lakes and marshes between 9 and 6 ka BP, and sparser cover of steppe and semidesert communities between 6 and 4.5 ka BP as water tables dropped and hyperarid conditions were restored.

Key Words: pollen analysis • lake core • desert • savanna • palaeoclimate • groundwater • Sahara • Holocene.

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