Depositional environments at a Palaeoproterozoic continental margin, Vastervik Basin, SE Sweden

This study documents: (1) the sedimentary environments and depositional processes and (2) the temporal and spatial relationships of sedimentary environments within well-preserved areas in the Palaeoproterozoic Vastervik metamorphic siliciclastics in southeastern Sweden. Based on lateral and vertical facies transitions, seven facies associations were documented: fluvial deposits (Facies Association 1), tidal flat deposits (FA 2), tidal channel deposits (FA 3), upper-flow-regime tidal flat deposits (FA 4), tidal bar deposits (FA 5), shoreface deposits (FA 6) and turbidite deposits (FA 7). The documented facies associations reflect deposition on a Palaeoproterozoic continental margin, where rivers drained the continent to the present north/northwest and carried sediment southeastwards. The rivers became tidally influenced further seawards. Sediments accumulated in tide-dominated estuaries, river-dominated deltas and in wave-dominated shallow-water environments. The documented tide-dominated estuary suggests that the coastline at least during some periods was macrotidal (> 4 m). The metasediments of the Vastervik succession are locally strongly altered by tectonic deformation and metamorphism, and detailed vertical and lateral correlation was possible only in restricted separate areas. Vertical facies transitions show transgressive to regressive deposition in two of the in detail studied areas as indicated by the vertical change from riverine to a shallow marine and back to river deposition in Area 1. In Area 3 the transition occurs from river-dominated deltas into tide-dominated estuaries, succeeded above by river deposition. In the two remaining areas the deposition was overall transgressive as river deposits are succeeded above by deltaic turbidites. Despite the somewhat "fragmentized" character of the Vastervik succession this work enabled to recognize general character of the Vastervik Palaeoproterozoic continental margin. (c) 2006 Elsevier B.V. All rights reserved.