Diagenesis

Question 1

What is Diagenesis?

Answer 1

Diagenesis is the physical, chemical, and biological processes that occur in sediments after they’ve been deposited and during and after lithification (been turned into a rock)

Question 2

What are the different stages of Diagenesis?

Answer 2

Eogenesis: early diagenesis - occurs between deposition and burial
Mesogenesis: middle-stage diagenesis - occurs after burial
Telogenesis: late-stage diagenesis - occurs after reexposure of formler buried rocks

Question 3

What does physical compaction mean?

Answer 3

As sediment layers accumulate, the weight of overlying material compresses lower layers, reducing pore space. Lots of water will be “squeezed” out.

Question 4

What do they mean with chemical changes?

Answer 4

Dissolution, precipitation, and mineral transformations occur due to interactions with pore fluids.

Question 5

What’s up with biological activity?

Answer 5

Microorganisms can alter the chemistry of sediments, often influencing mineral composition (e.g., organic matter decomposition).

Question 6

What are some common products of Diagenesis?

Answer 6

Cementation:
Minerals precipitate in pore spaces, binding sediment grains together.

Recrystallization:
Minerals reorganize into more stable forms (aragonite to calcite).

Dissolution:
Pore fluids dissolve unstable minerals, creating secondary porosity.

Question 7

Name frequent carbonate cements

Answer 7

Calcite
Aragonite
Dolomite

Question 8

Name frequent silicate cements

Answer 8

Quartz and clay

Question 9

What is a hardground?

Answer 9

Lithified sea floor
Often gives a great image of ancient marine environments