subenvironments Beach and shoreface Lagoon andor tidal flat Tidal inlet and tidal deltas Development and morphology of barrier islands depends on coastal gradient usually form on shallow slopes ID: 1021322
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1. Barrier Islands
2. Complex sedimentary systems with a variety of subenvironments Beach and shoreface Lagoon and/or tidal flat Tidal inlet and tidal deltas
3. Development and morphology of barrier islands depends on coastal gradient (usually form on shallow slopes) and tidal range/wave energy <2 m2-4 m>4 mTidal Range
4. Microtidal, wave-dominated barrier islands, TexasBarrier IslandBack-Barrier LagoonTidal InletTidal Inlet30 km
5. Mesotidal, tide-dominated barrier islands (Savannah, GA)Barrier IslandBarrier IslandBack-Barrier Tidal Flat10 km
6. Barrier IslandBack-Barrier Mangrove Swamp10 kmMeso- to macrotidal barrier islands (Brazil)
7. Prograding Barrier IslandArid Back-Barrier Tidal Flat5 kmPrograding barrier islands, Gulf of Carpentaria (Australia)
8. Microtidal barriers are rarely overtopped by high tides, so tidal channels rare; dominance by wave processes (washover lobes and flood tidal deltas) instead<2 m2-4 m>4 mTidal Range
9. Washover fans are common constituents of microtidal, storm-influenced barriersForm by storm surge deposition of sand in the back-barrier or lagoon
10. Mesotidal barriers are more frequently overtopped by high tides; have more numerous tidal inlets and dominance by tidal currents<2 m2-4 m>4 mTidal Range
11. Ebb tidal deltaFlood tidal deltaMigrating tidal inletTidal deltas and inlet are present in all barrier islands but more numerous (and more important in rock record) as tidal range increases
12. Tidal inletTidal inletIncoming (flood) current fastest on marginsOutgoing (ebb) current fastest in channel base
13. Rapid lateral migration due to erosion and longshore sediment driftDeep channels, slow lateral migration
14. In retrograding barrier islands, shoreface wave ravinement surface typically removes beach and dune faciesTidal inlet ravinement may erode flood tidal delta and lagoon sediments
15. A ravinement surface can be a sequence stratigraphic surface (Transgressive Ravinement Surface) if it separates systems tractsRavinement surfaces can occur within systems tracts (TST below, TST above) and are called “within-trend” wave or tidal ravinement surfaces