CPG Stratigraphic Analysis & Sedimentology 2

Question 1

A classic Bouma sequence (Ta-Te) deposited by a turbidity current shows which grading pattern?

Accepted Answer

Normal grading from coarse sand at base to mud at top

Answer

The Bouma sequence shows normal (fining-upward) grading, reflecting waning turbidity current energy from massive graded sand (Ta) through laminated divisions to hemipelagic mud (Te).

Question 2

In sequence stratigraphy, parasequences are bounded by:

Accepted Answer

Marine flooding surfaces

Answer

Parasequences are relatively conformable successions of genetically related beds bounded above and below by marine flooding surfaces and their correlative surfaces.

Question 3

What distinguishes a transgressive systems tract (TST) from a highstand systems tract (HST) in parasequence stacking patterns?

Accepted Answer

TST shows retrogradation (backstepping) while HST shows progradation

Answer

The TST is characterized by retrogradational (backstepping) parasequence sets during rising accommodation, while the HST shows progradational to aggradational stacking as accommodation rate decreases.

Question 4

Which diagenetic process most commonly destroys primary porosity in deeply buried sandstone reservoirs?

Accepted Answer

Quartz cementation and mechanical compaction

Answer

Quartz cementation precipitates silica overgrowths that occlude pore throats while mechanical compaction rearranges grains to reduce pore volume, both severely degrading primary porosity.

Question 5

In a fluvial depositional system, which facies represents the highest-energy deposition?

Accepted Answer

Channel-lag conglomerates and trough cross-bedded sands

Answer

Channel-lag conglomerates and trough cross-bedded sands deposited in the active channel represent the highest energy environment in a fluvial system.

(CPG) Certified Petroleum Geologist Practice Test

(CPG) Certified Petroleum Geologist Practice Test

CPG Stratigraphic Analysis & Sedimentology 2