Diagenesis

Question 1

What is diagenesis?

Answer 1

Physical, chemical and biological processes that turn a sediment into a sedimentary rock

Question 2

Which seven processes belong to diagenesis?

Answer 2

• Compaction
• Recrystalllization
• Solution (eg. pressure solution)
• Cementation
• Neocrystallization
• Replacement
• Bioturbation

Question 3

Which processes are most relevant in siliciclastic sedimentary rocks?

Answer 3

Compaction, Neocrystallization and replacement

Question 4

How much can clay compact, as water is pressed out?

Answer 4

By a factor of up to ten

Question 5

What is differential sediment compaction?

Answer 5

Different sediments can compress by different amounts leading to cross sections that are warped after diagenesis.

Eg. clay vs carbonate

Question 6

How does the porosity of sandstone change during diagenesis?

Answer 6

Pre-lithification: 15-60 % porous
Post-lithification: < 15 % porous

Question 7

What are the main reasons for the change in porosity of sandstone during diagenesis?

Answer 7

Cementation, Neocrystallization, Replacement and pressure solution

Compaction is not the primary factor, but causes some of the other ones.

Question 8

Which cements are most common in siliciclastic sedimentary rocks?

Answer 8

Quartz
Calcite