CPG Sedimentology & Stratigraphy 2

Question 1

Graded bedding, with coarser grains at the base grading upward to finer grains at the top, is most commonly associated with which depositional process?

Accepted Answer

Turbidity current deceleration

Answer

Aeolian dune migration

Answer

Beach swash and backwash

Answer

Evaporite precipitation from brines

Question 2

Flute casts found on the base of a turbidite sandstone bed are most useful for paleoflow analysis because:

Accepted Answer

The deepest, closed (upstream) end of the scoop points into the paleoflow direction

Answer

Their long axes are always perpendicular to the current direction

Answer

They form only in aeolian environments, indicating wind direction

Answer

Their symmetric shape indicates oscillatory flow rather than unidirectional flow

Question 3

In sequence stratigraphy, a parasequence is formally defined as:

Accepted Answer

A relatively conformable succession of genetically related beds and bedsets bounded by marine flooding surfaces and their correlative surfaces

Answer

Any set of strata bounded above and below by sequence boundaries (unconformities)

Answer

A complete sedimentary cycle deposited during one glacial-interglacial oscillation

Answer

A succession of beds deposited by a single catastrophic storm event

Question 4

Lithostratigraphy differs fundamentally from biostratigraphy in that lithostratigraphy classifies and correlates rock units based on:

Accepted Answer

Observable physical and compositional characteristics of the rocks themselves

Answer

Fossil content and biozonal schemes tied to evolutionary first and last appearances

Answer

Absolute radiometric ages determined from isotopic systems

Answer

Geochemical anomalies such as stable-isotope excursions

Question 5

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

Accepted Answer

Symmetrical (in-phase) ripple marks

Answer

Tabular planar cross-bedding

Answer

Flute casts on bed bases

Answer

Asymmetrical ripple marks with steep lee faces

Question 6

In sequence stratigraphy, the maximum flooding surface (MFS) represents:

Accepted Answer

The stratigraphic surface marking the maximum landward extent of marine transgression, above which progradation begins

Answer

The basal erosional surface of the lowstand systems tract cut during sea-level fall

Answer

The contact between continental red beds and the first marine limestone

Answer

The sequence boundary formed at the onset of forced regression

Question 7

A nonconformity is the type of unconformity that occurs where:

Accepted Answer

Sedimentary rocks overlie intrusive igneous or metamorphic basement rocks

Answer

Sedimentary strata are tilted below the erosional surface and horizontal above it

Answer

Parallel sedimentary beds are separated by an irregular erosional surface

Answer

Sedimentation was interrupted so briefly that the time gap is cryptic in the rock record