AN INVESTIGATION OF SANDUR DEPOSITS, NORTHERN ICELAND

Glacial landforms and sediments in Iceland record a complex deglaciation history, which lasted from the Late Weichselian glacial maximum ca. 18 ka BP to the Preboreal ca. 9.5 ka BP.  Early models proposing uninterrupted continuous deglaciation have been rejected in favour of single, double and finally multiple advance deglaciation models.  A recent trip to Iceland provided the author with an opportunity to investigate a small portion of this record.  Four sites, including valley and plain sandur examples, located between Skagafjörđur and the uplands of the Tröllaskagi Peninsula in Northern Iceland were examined. 

The exposed sediments are divided into seven facies, classified as glaciolacustrine (facies 1), type I non-jökulhlaup outwash (facies 2, 3, 6, and 7) and type II jökulhlaup outwash (facies 4, 5 and 6).  These facies are interpreted as:  1) rhythmites deposited in an ice-dammed lake, 2) low flow slough or active channel deposits, 3) active channel, slough channel or waning flow bar deposits, 4) debris flow deposits, 5) bar slipfaces, giant dune or delta deposits 6) bar cap or longitudinal bar deposits, and 7) longitudinal bars or active channel deposits.

The sediment record suggests the following sequence of events:  1) ponding of low flow meltwater by ice in Skagafjörđur, 2) glacial retreat from Skagafjörđur and the Tröllaskagi Peninsula recorded by deposition of type I non-jökulhlaup outwash, 3) catastrophic drainage of a sub-glacial lake recorded by deposition of type II jökulhlaup outwash, 4) return to lower flows recorded by the deposition of type I non-jökulhlaup outwash, 5) the final retreat of the Tröllaskagi ice-dome outlet glaciers and the shutting down of active sediment deposition, 6) modern re-working of deglaciation deposits.