Depositional processes and internal architecture of Late Weichselian ice-margin submarine fan and delta settings, Swedish west coast

Three, genetically distinct elastic bodies are defined from facies-architec tural analyses of Late-Weichselian ice-margin deposits in outcrops at Lysen garden, Skollunga west and Skollunga east, Swedish west coast. These clasti c bodies formed seaward of the retreating ice-margin, in the lee of topogra phic highs of a high relief bedrock erosion surface. Each elastic wedge, 20 -80 m thick with areal extents of 12 000-25 000 m(2), was deposited over a period of about 100 years and is composed of a lower division which records deposition on a submarine fan, and an upper division which represents a Gi lbert-type delta system. The submarine fan and delta successions record a large variety of depositio nal processes, and involve: (a.) diffusely laminated gravelly beds deposite d by steady turbidites; (b) overall normally graded gravelly, sandy and sil ty-clayey beds deposited by surge-type turbidites; (c) inversely graded bed s deposited by cohesionless grain flows; (d) inversely to normally coarse-t ail graded beds of matrix-strength modified grain flows; (e) deformed beds of slump and slide deposits from the upper slope; (f) deformed diamictons f rom the glacier-front environment; (g) trough-cross stratified and plane-pa rallel laminated gravelly beds deposited as fluvial bedload on braid plains . A depositional model records six genetically related facies associations ch aracterized by specific depositional regimes. The submarine fans register d eposition at (1) continuous discharge regime in proximal portions on the lo wer slope regions, (2) surge-type discharge in middle-portions of the fans on the basin floor, and (3) surge-type non-continuous discharge in upper po rtions of the fans on the basin floor. The Gilbert-type deltas document (1) glaciofluvially discharged braid plains in topsets, (2) avalanche regime i n steep foresets, and (3) surge-type discharge in bottomsets on the basin f loor. Deposition was generally episodic and flood controlled, and upward fi ning depositional units record hood-events. The sedimentary facies and depo sitional architecture of the studied ice-margin settings resemble those of non-glacial submarine fan and Gilbert-type deltas, except for the depositio n of slumps and slides of glacial debris.