Lecture 4: transport and deposition

Question 1

The settling velocity of material is useful knowledge when building dams/bridges and estimating ancient velocity. It is determined by the balance of what?

Answer 1

Uplift due to turbulence vs. gravity.

Question 2

What properties of rocks allow for palaeoenvironmental interpretation?

Answer 2

Colour, fossils, geometry

Question 3

What are terrigenous aka siliclastic grains?

Answer 3

Those formed from weathering of pre-existing material on land.

Question 4

Physical maturity of rocks indicated by what 3 characteristics?

Answer 4

• Same size grains
• Rounded
• Clast supported

Question 5

River flow can be laminar or turbulent depending on which three properties?

Answer 5

Velocity, Geometry and Viscosity.

Question 6

What is the competence of a river flow? How is this different from capacity?

Answer 6

Competence = ability to entrain material of a given size
Capacity = total sediment load

Question 7

Laminar flow carries clay sized particles in dissolved/suspended loads. How does turbulent flow differ?

Answer 7

Turbulent flows carry clay to boulder sized material, they have dissolved load, but also coarser suspended load and bed load.

Question 8

What do imbricated pebbles and fossil ripples show as forms of paleaoenvironmental interpretation?

Answer 8

Pebbles leaning in direction of flow due to high energy currents (Crossbedding = thin bedding plains where pebbles at angle to main bedding plane indicate flow changes direction frequently).
Symmetrical ripples show shallow, oscillating waves. Asymmetrical ripples are steeper on one side, showing direction of flow. Continuous straight ripples evolve to lingould ripples over time and at higher velocities.

Question 9

Wind is almost always turbulent and can deposit sediment as dunes or loess. What other products does wind transportation produce?

Answer 9

Sand, dust, pollen, bateria, ash, mineral fragments.

Question 10

Continental shelf deposition produces wave ripples and textural/compositional maturity. What controls these processes?

Answer 10

Waves, Tides, Longshore currents, tectonic uplift/subsidence and sea level change.

Question 11

By what transport and depositional process is a sub-marine fan formed?

Answer 11

Transported by turbidity currents slumping and deposited by waning flow.