CPG Sedimentology & Stratigraphy

Question 1

According to Walther's Law, which statement correctly describes the relationship between vertical and lateral sedimentary facies?

Accepted Answer

Facies observed in vertical succession were deposited in laterally adjacent environments

Answer

Walther's Law states that facies found in conformable vertical succession once existed as laterally adjacent depositional environments, allowing vertical sections to be used to reconstruct lateral paleogeography.

Question 2

The Bouma sequence (divisions Ta through Te) is the diagnostic sedimentary structure package of which depositional environment?

Accepted Answer

Turbidite (deep-water submarine fan)

Answer

The Bouma sequence records the successive hydrodynamic stages of a turbidity current, from massive graded sand (Ta) through laminated, rippled, and fine-grained upper divisions, making it diagnostic of turbidite deposition.

Question 3

In the Wentworth grain-size classification, which size range defines 'sand'?

Accepted Answer

0.0625–2 mm

Answer

The Wentworth scale defines sand as particles ranging from 0.0625 mm (very fine sand lower limit) to 2 mm (granule boundary), spanning four sub-classes from very fine to very coarse sand.

Question 4

An angular unconformity is best described as a surface where:

Accepted Answer

Tilted or folded beds below are overlain by younger, more gently dipping or horizontal beds above, indicating intervening deformation and erosion

Answer

An angular unconformity records a sequence of deformation (tilting/folding), uplift, erosion, and subsequent deposition of horizontal strata, producing the characteristic angular discordance between lower and upper beds.

Question 5

In Dunham's classification of carbonate rocks, a 'wackestone' is defined as:

Accepted Answer

Mud-supported fabric containing more than 10% carbonate grains

Answer

Dunham's wackestone is mud-supported with more than 10% grains; it contrasts with mudstone (mud-supported, fewer than 10% grains) and packstone/grainstone (grain-supported).

CPG - Certified Professional Geologist Practice Test

CPG - Certified Professional Geologist Practice Test

CPG Sedimentology & Stratigraphy