DELTAS, SPITS AND LITTORAL TERRACES ASSOCIATED WITH RISING SEA-LEVEL - LATE QUATERNARY EXAMPLES FROM NORTHERN ICELAND

Boomer records from Eyjafjordur, northern Iceland, reveal a major fossil delta with associated wave-built littoral terraces which formed when comtemporary sea level was at about 40 m below the modern level and which post-date Late Weichselian glaciation of the site. The structure of these units, and a sequence of similar submerged deltas and spits which lie higher on the fjord side, are very instructive examples of the evolution of the structure of shallow-water sediment units formed on a rising sea level, and permit the nature of the transgression to modern sea level to be reconstructed. Simple approaches to the reconstruction of sea-level change from limited evidence are set out. In order to produce a sea level of -40 m in Eyjafjordur, it is necessary that the isostatic component of sea level change should have decayed before early Holocene eustatic sea levels rose above -40 m at 9000-10,000 yrs B.P. This may be explained either by a substantial early reduction in the local glacier load on the crust and associated early decay of the isostatic component of relative sea-level change, or by a low asthenosphere viscosity beneath Iceland permitting an anomalously rapid decay of the isostatic component.