Synthesis • Depositional elements ranging from fluvial trunk river channels to distributary channels, with associated overbank deposits. • Large variations in form and sedimentology are recorded by the >20 km vs. around 3 km max channel belt width and grain size distribution. • Transition from a confined to an unconfined fluvial system as the alluvial plain merges with the deltaic plain of the Triassic Barents Sea. • Three distinct phases of delta progradation with subsequent transgression. • Variability in floodplain and fluvial sedimentology, both planform seismic and core/wireline. • Anastamosing rivers and increase in coal deposits indicate a humid environment for the Carnian interval. Acknowledgements References Bridge, J.S. (2003) Rivers and floodplains: forms, processes, and sedmentary record. Blackwell Publishing, Oxford, 491 s. pp. Henriksen, E., Ryseth, A.E., Larssen, G.B., Heide, T., Rønning, K., Sollid, K. and Stoupakova, A.V. (2011) Chapter 10 Tectonostratigraphy of the greater Barents Sea: implications for petroleum systems. Geological Society, London, Memoirs, 35, 163-195. Gibling, M.R. (2006) Width and Thickness of Fluvial Channel Bodies and Valley Fills in the Geological Record: A Literature Compilation and Classification. Journal of Sedimentary Research, 76, 731-770. Glørstad-Clark, E., Faleide, J.I., Lundschien, B.A. and Nystuen, J.P. (2010) Triassic seismic sequence stratigraphy and paleogeography of the western Barents Sea area. Marine and Petroleum Geology, 27, 1448-1475. Jakobsson, M., Macnab, R., Mayer, L., Anderson, R., Edwards, M., Hatzky, J., Schenke, H.-W., Johnson, P., 2008. An improved bathymetric portrayal of the Arctic Ocean: implications for ocean modeling and geological, geophysical and oceanographic analysis. Geophysical Research Letters 2. doi:10.1029/2008GL033520. Riis, F., Lundschien, B.A., Høy, T., Mørk, A. and Mørk, M.B.E. (2008) Evolution of the Triassic shelf in the northern Barents Sea region. Polar Research, 27, 318-338. Skjold, L.J., van Veen, P.M., Kristensen, S.-E. and Rasmussen, A.R. (1998) Triassic sequence stratigraphy of the southwestern Barents Sea. In: Mesozoic and Cenozoic Sequence Stratigraphy of European Basins (Eds P.-C. de Graciansky, J. Hardenbol, T. Jacquin and P.J. Vail), pp. 651-666. Society for Sedimentary Geology (SEPM), Tulsa. Stølum, H.-H. (1998) Planform geometry and dynamics of meandering rivers. Geological Society of America Bulletin, 110, 1485-1498. 1 2 4 3 100 km N 600 800 1000 1200 1400 1600 1800 0 500 1000 1500 2000 2500 3000 3500 Depth TWT (ms) Max channelbelt width (m) 600 800 1000 1200 1400 1600 1800 0 500 1000 1500 2000 2500 3000 3500 Depth TWT (ms) Max channelbelt width (m) 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 0 5000 10000 15000 20000 25000 Depth TWT (ms) Max channelbelt width (m) L1 L1 L1 1. Obesum 2. Caurus 3. Guovca C1-2 C3-N1 C1-2 C1-2 C3-N1 C3 Top: Channel width against stratigraphic depth. Three sequences are highlighted. In the westernmost datasets there is a trend of two distinct channel-widening phases within a thick fluvial sequence. Yellow: Ladinian (L1); Purple: Early Carnian (C1-C2); Blue: Late Carnian-Norian (C3-N1). Top: The modern Niger Delta. A reasonable analogue for the Snadd Formation. Image from Google Earth. Top: Rose diagrams plotted against their datasets. Westward, distal, increased dispersal in palaeocurrent trends. Top: Block diagram of the Lower Snadd Fm showing the gradual transition between the main depositional elements, and differences between these. Channel bodies become more isolated down depositional dip, due to more accomodation and a higher frequency of channel avulsion. Vegetated floodplain Vegetated point bar Active point bar and mid-channel bar Active, fluvial channel Mangrove/swamp Active, tidal channel Lake Floodplain deposits Lateral accreted fluvial sandstone deposits Amalgamated fluvial sandstone deposits Tidal deposits Tidal channel deposits Abandoned channel fill Sandstone sheets 3. 2. 1. 4. Distal Proximal Hundreds of kilometers 20 km 10 km 3 km