ASBOG Sedimentology and Stratigraphy 5

Question 1

Which stratigraphic surface in sequence stratigraphy represents the deepest water conditions and maximum landward extent of marine flooding?

Accepted Answer

Maximum flooding surface (MFS)

Answer

The maximum flooding surface (MFS) marks the turnaround from transgression to regression, corresponding to the deepest water and most landward marine conditions.

Question 2

The conversion of smectite to illite during burial diagenesis is significant because it:

Accepted Answer

Releases silica and potassium that can alter reservoir quality

Answer

Smectite-to-illite conversion releases silica (which can precipitate as quartz cement) and consumes potassium, significantly reducing sandstone reservoir quality.

Question 3

What is the primary control on the preservation of sedimentary structures in tidal flat deposits?

Accepted Answer

Bioturbation intensity

Answer

High bioturbation by burrowing organisms in tidal flat environments can completely destroy primary sedimentary structures, so low bioturbation is essential for preservation.

Question 4

Which method of stratigraphic correlation relies on matching distinctive chemical signatures (e.g., carbon isotope excursions) across rock units?

Accepted Answer

Chemostratigraphy

Answer

Chemostratigraphy correlates rock units using geochemical signatures such as carbon, oxygen, or strontium isotope ratios that reflect global oceanographic or climatic events.

Question 5

A lacustrine (lake) deposit is most likely to be identified by which characteristic combination of features?

Accepted Answer

Varved laminae, non-marine fossils, and absence of tidal structures

Answer

Lacustrine deposits characteristically show finely varved (seasonally laminated) sediment, freshwater or brackish fossils, and lack marine or tidal indicators.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG Sedimentology and Stratigraphy 5