A Sequence Stratigraphical Approach to Ice-Marginal Deltas formed during hundred years, Swedish West Coast
Piret Plink and Lars Ronnert
Ice-marginal deltas, on the Swedish West Coast displayed very rapid accommodation changes and high sediment flux. These Late Weichselian ice-marginal deltas were deposited during approximately 100 years and exposed sections are 20-80m thick. Measured vertical sections contained recurrent cyclicity of different temporal and spatial scale. Furthermore, documented depositional events occurred at known water depth, during a restricted and known time period. The three studied deltas have similar facies and process distribution and contain a subaqueous fan covered by a tripartite Gilbert-type delta succession.
A generalised genetical model is suggested. Large-scale stratigraphy is controlled by interaction between accommodation and sediment flux. The accommodation variations are created by eustasy, glacio-isostatic uplift and ice-margin displacement. The sediment flux is changed by displacement of the inflow point (ice-margin position) and by actual changes in sediment supply. Small-scale variations may reflect flood and non-flood alternations, and slope instability. Local variations in accommodation changes and sediment flux cause differences between studied deltasets. The sediment supply influences, e.g. the character of the transgressive surface and the transgressive systems tracts, creating accretionary or non-accretionary situations. Facies distribution is confined to specific systems racts, as it depends on the rate of accommodation changes and sediment flux, in addition to water discharge, sediment load, slope. angle and length.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California