Sedimentological and Stratigraphic study of glaciomarine clays and postglacial beach deposits exposed in a raised coastal section beyond the Tromsø Lyngen (Younger Dryas) end moraine at Spåkenes, Lyngen, northern Norway

Abstract

Thick succession of suspension settled muds, deposited from meltwater plumes, which are frequently interbedded with sandy mass flows deposits. Between conformable beds, discrete units have been in intensely deformed, often into large recumbent folds with complex structure. Suspension settled muds are observed in three distinct structural facies, namely massive clays, rhythmically banded muds and rhythmically laminated muds with sands or silts. The coarser grained deposits, attributed to mass flows, are indentified as complex structured turbidites and massive debrites. From detailed sedimentological analysis of grain size distributions and rhythmic bed structures it is interpreted multiple meltwater plumes were active in loading the water column with suspension settling sediments and that different meltwater sources were dominant in loading the water column under different facies regimes. Prevailing conditions of meltwater plume deposition, responsible for depositing thick successions of colour banded mud, are thought to have occurred under a weakly stratified water column where plume integrity was extremely low. Episodic high discharge events are thought to be responsible for the deposition of laminated facies. Sedimentation rates are interpreted to have been extremely high, such that it is postulated that the entire cliff section was deposited in less than one year and predominantly within one meltwater season.