Chapter 9.4 Alluvial Fans

Question 1

Why and where do alluvial fans deposit from?

Answer 1

Alluvial fans form where there is a distinct break in topography between the high ground of the drainage basin and the flatter sedimentary basin floor

Question 2

Are alluvial fan deposits affected by climatic conditions?

Answer 2

Yes, precipitation and temperature can drive deposition influencing the amount of sediment and water.

Question 3

Are the slopes of alluvial fan deposits steep?

Answer 3

No

Question 4

are alluvial fan deposits typically uniform thickness?

Answer 4

No

Question 5

What variables control debris flow?

Answer 5

Poorly sorted
Matrix dominated

Question 6

What variables control sheetfloods

Answer 6

Form braided channels
Move from gradual lateral migration
cross-bedded sandstones

Question 7

What variables control stream channels (fluvial)

Answer 7

well sorted
normally graded

Question 8

Channel-fill succession in a braided system generally exhibits fining upward succession. Why and how?

Answer 8

Rejuvenation will supply the river with sediment and it will collect in bars. Water will travel towards the path of least resistance, so if the bar gets too large, the water will gradually migrate laterally one too much sediment has gathered in the bars to allow proper flow.

Question 9

Matrix dominated and poorly sorted would best describe what depo in an alluvial fan?

Answer 9

Debris flow

Question 10

Lateral accretion surfaces form in what depo environment?

Answer 10

Meandering streams