ASBOG Sedimentology and Stratigraphy 2

Question 1

Which sedimentary structure indicates oscillatory (wave) flow rather than unidirectional current flow?

Accepted Answer

Symmetrical ripple marks

Answer

Symmetrical ripple marks have crests of equal slope on both sides, forming under oscillatory (wave) motion rather than unidirectional currents.

Question 2

The Bouma sequence (ABCDE) in turbidites begins with which division at the base?

Accepted Answer

Massive or graded sand

Answer

Division A (Ta) at the base of the Bouma sequence consists of massive or normally graded sand deposited from the high-density head of the turbidity current.

Question 3

Which diagenetic process involves the replacement of original minerals by silica (SiO₂)?

Accepted Answer

Silicification

Answer

Silicification is the replacement of original minerals or fossil material by silica, commonly producing chert or silicified fossils.

Question 4

What does a 'fining-upward' sequence in fluvial deposits typically indicate?

Accepted Answer

Migration of a meander loop and point bar accretion

Answer

Fining-upward cycles in fluvial settings record lateral accretion on a point bar as the meander migrates, with coarse channel lag at the base grading to fine overbank muds.

Question 5

The principle that allows geologists to date rock layers by the fossils they contain is called:

Accepted Answer

Faunal succession

Answer

The law of faunal succession states that fossil assemblages succeed each other in a definite, recognizable order that can be used to correlate strata globally.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG Sedimentology and Stratigraphy 2