Synthesis3 AAPG ACE 2012...Synthesis • Depositional elements ranging from ˜uvial trunk river channels to distributary channels, with associated overbank deposits. • Large variations

Synthesis

• Depositional elements ranging from �uvial 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 con�ned to an uncon�ned �uvial 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 �oodplain and �uvial 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 �oodplains: 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 Classi�cation. 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 thewestern 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.

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1. Obesum 2. Caurus 3. Guovca

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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 �uvial sequence. Yellow: Ladinian (L1); Purple: Early Carnian (C1-C2); Blue: Late Carnian-Norian (C3-N1).

Top: The modern Niger Delta. A reasonable analogue for theSnadd 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 di�erences between these. Channel bodies becomemore isolated down depositional dip, due to more accomodation and a higher frequency of channel avulsion.

Vegetated �oodplain

Vegetated point bar

Active point bar and mid-channel bar

Active, �uvial channel

Mangrove/swamp

Active, tidal channel

Lake

Floodplain deposits

Lateral accreted �uvialsandstone deposits

Amalgamated �uvialsandstone deposits

Tidal deposits

Tidal channel deposits

Abandoned channel �ll

Sandstone sheets

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