Geomorphic indicators of Holocene winds in Egypt’s Western Desert

Geomorphic mapping of Egypt’s Western Desert from LANDSAT-MSS images reveals oriented aeolian landforms that record, in part, Holocene winds. Wind directions reconstructed from these landforms indicate the dominance of N–S airflow from 30jN to 20jN, turning clockwise southward to NE–SW, conformable with modern circulation. A second direction appears over western Egypt, W between 30jN and 26jN, NW between 26jN and 20jN. Cross-cutting aeolian landforms show that W/ NW winds are older than the N/NE winds. Geomorphic evidence, abundant south to 26jN and less abundant to 20jN, also indicates that W and NW winds were early Holocene ‘palaeowesterlies’. Some evidence also indicates that they extended eastward to at least 30jE, perhaps to the Red Sea. These winds steered moist Atlantic/Mediterranean air masses to Egypt, sustaining early Holocene lakes and playas north of the limit of tropical monsoonal rainfall at 20jN. Upon aridification, beginning after 5 kyr BP, yardangs oriented west to east were eroded in early Holocene basinal sediments in western Egypt, indicating that these winds continued there for 1–2 kyr, until 3–4 kyr BP. Optically stimulated luminescence (OSL) ages of surface sand sheet in southern Egypt indicate that the present north–south winds were established ca. 3–4 kyr BP, at the same time as the northern savanna boundary was stabilized at its present position. D 2003 Elsevier Science B.V. All rights reserved.