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

Coarsening upward from mud to sand

Answer

Inverse grading from fine at base to coarse at top

Answer

Uniform grain size with no internal grading

Question 2

In sequence stratigraphy, parasequences are bounded by:

Accepted Answer

Marine flooding surfaces

Answer

Sequence boundaries

Answer

Maximum flooding surfaces

Answer

Transgressive surfaces of erosion

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

TST shows progradation while HST shows retrogradation

Answer

TST is always deposited in deeper water than HST

Answer

TST is bounded below by the maximum flooding surface

Question 4

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

Accepted Answer

Quartz cementation and mechanical compaction

Answer

Dissolution of feldspar grains creating secondary porosity

Answer

Dolomitization of calcareous cement

Answer

Formation of stylolites along clay laminae

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

Floodplain overbank muds

Answer

Oxbow lake organic-rich silts

Answer

Crevasse splay fine sands

Question 6

In seismic stratigraphy, reflections that terminate against an inclined surface in an updip direction (onlap) indicate:

Accepted Answer

Relative sea-level rise with sediment filling toward the basin margin

Answer

Progradation of sediment toward the basin margin

Answer

Regression and falling sea level

Answer

Sediment bypassing to deep water

Question 7

A fining-upward cycle in a fluvial deposit, from pebble lag at the base to overbank muds at the top, most likely represents:

Accepted Answer

Lateral migration and abandonment of a meandering river channel (point bar)

Answer

Progradation of a delta lobe into a lake

Answer

Transgression of a barrier island system

Answer

Deepening of a lacustrine basin