Sed & Strat exam 2

What is longshore transport and how does it occur?

Longshore transport is the shore-parallel movement of sediment along coastlines that is generated by longshore currents that result from the refraction of waves that approach a coastline at an oblique angle.

Would a prograding nearshore sequence coarsen or fine upward? Why?

A prograding shoreface will coarsen-upward. The highest energy transport conditions (and coarsest materials) are found nearest the coast, and the lowest energy transport conditions (and finest materials) are found at offshore positions. As the shoreline progrades, it would deposit beach sediments on top of offshore sediments, resulting in coarse sediments on top of fine sediments, coarsening-upward.

Distinguish the effects of storms vs. average waves on nearshore process & strata.

Average wave conditions result in longshore currents that are large relative to onshore- offshore currents. As a result, they are responsible for longshore transport that serves to build and prograde the barrier island. In contrast, storm waves (e.g., from hurricanes) cause much greater onshore-offshore transport and cause erosion, and can make large washover fans into back barrier lagoons.

Describe 2 sedimentary structures that you might expect to find in tidal deposits.

Tidal environments consist of tidal flats and tidal channels. In tidal flats, it is expected that the primary sediment is mud and that the mud is highly bioturbated. In tidal channels, the primary sediment is sand and is moved like in rivers. However, because tides reverse flow direction twice daily, they make two unique structures. Herrinbone cross-stratification looks like unidirectional cross-stratification except that it alternates apparent transport direction in vertically stacked sets. Vertically aggrading oscillation ripples are also found in tidal channels.

What does k_sp mean?

Solubility product constant = product concentrations of both ions in solution in equilibrium with a solid