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

Younger sediments always contain finer grain sizes than underlying older sediments

Answer

Facies transitions across stratigraphic boundaries always indicate unconformities

Answer

Lateral facies changes are always more abrupt than vertical facies changes

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

Prograding river delta front

Answer

Intertidal flat

Answer

Alluvial fan

Question 3

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

Accepted Answer

0.0625–2 mm

Answer

0.004–0.0625 mm

Answer

2–64 mm

Answer

64–256 mm

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

Parallel sedimentary beds are separated by an erosional gap with no angular discordance

Answer

Sedimentary rocks overlie intrusive igneous or metamorphic rocks

Answer

Sedimentation paused briefly but beds above and below remain conformable

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

Grain-supported fabric with carbonate mud present between grains

Answer

Grain-supported fabric lacking carbonate mud matrix

Answer

Mud-supported fabric with less than 10% carbonate grains

Question 6

Tabular and trough cross-bedding dipping in the direction of paleoflow is most commonly formed by:

Accepted Answer

Migration of bedforms (dunes and ripples) downstream under unidirectional wind or water currents

Answer

Tectonic tilting of originally horizontal sedimentary beds

Answer

Bioturbation and reworking by burrowing organisms

Answer

Chemical precipitation of minerals from pore fluids

Question 7

Which systems tract in sequence stratigraphy is deposited during a relative sea-level fall, before the lowstand is reached?

Accepted Answer

Falling-stage systems tract (FSST)

Answer

Transgressive systems tract (TST)

Answer

Highstand systems tract (HST)

Answer

Lowstand systems tract (LST)