ISLAND-ENCAPSULATING EOLIAN SEDIMENTARY SYSTEMS OF THE CANARY AND CAPE VERDE ARCHIPELAGOS

摘要

Eolian dunes are generally absent or poorly developed on oceanic islands. Yet, large-scale eolian sedimentary systems characterize the oceanic islands of the Canary and Cape Verde archipelagos. These islandencapsulating sedimentary systems extend around or across entire islands and comprise upwind source areas, eolian transport corridors, and downwind sediment depocenters, each of which is characterized by distinctive dune forms. Upwind beaches are denuded of sand, while downwind locations exhibit progressive shoreline accretion. Cross-island transport corridors developed in topographic lows on the island surface are characterized by a variety of landforms including sandsheets, barchanoid dunes, and transverse dunefields, depending on topography and local sediment volume and supply. Circum-island transport corridors develop when the island topography is high and sediment transport takes place on the island margins, alternating between headlandbypass dunes and longshore transport in the littoral zone in the intervening embayments. Depocenters comprise extensive eolian dunefields, prograding beaches, or beach ridges depending on local topography. Recognition of the interconnected nature of the components of these contemporary systems has important management implications.