CPG Sedimentology & Stratigraphy 3

Question 1

In Folk's (1954) textural classification of sandstones, a rock with more than 25% feldspar and feldspar exceeding rock fragments is classified as:

Accepted Answer

Arkose

Answer

Quartz arenite

Answer

Litharenite

Answer

Graywacke

Question 2

Diagenesis encompasses which set of processes?

Accepted Answer

Physical and chemical changes in sediments occurring after deposition but prior to metamorphism, including compaction, cementation, and dissolution

Answer

Erosion, transport, and deposition of sedimentary particles at or near Earth's surface

Answer

The primary depositional processes that determine original sedimentary texture and structure

Answer

Folding, faulting, and recrystallization driven by elevated temperature and pressure in the crust

Question 3

A stratigraphic cyclothem, as classically defined in Pennsylvanian coal-bearing sequences of the U.S. midcontinent, represents:

Accepted Answer

A repetitive cycle of marine and non-marine deposits linked to glacioeustatic sea-level fluctuations

Answer

A single turbidite event layer deposited by one submarine flow

Answer

A set of beds bounded by two volcanic ash (tonstein) horizons

Answer

A sequence of strata deposited during a single glacial advance and retreat

Question 4

The principle of superposition, foundational to stratigraphy, states that:

Accepted Answer

In an undisturbed sequence of sedimentary rocks, older layers lie below younger layers

Answer

Igneous intrusions are invariably younger than the host rocks they cross-cut

Answer

Sedimentary rocks are always deposited in horizontal layers parallel to the paleosurface

Answer

Fossils in older rocks are morphologically simpler than those in younger rocks

Question 5

Which stratigraphic correlation method is generally regarded as the most powerful tool for global time correlation across widely separated basins?

Accepted Answer

Biostratigraphic correlation using index fossils with short stratigraphic ranges

Answer

Lithostratigraphic correlation using distinctive marker beds

Answer

Magnetostratigraphic correlation tied to the geomagnetic polarity timescale

Answer

Chemostratigraphic correlation using carbon-isotope excursions

Question 6

Transgressive depositional sequences are typically characterized by which stratigraphic pattern?

Accepted Answer

Fining-upward successions reflecting landward shoreline retreat as relative sea level rises

Answer

Coarsening-upward successions reflecting delta or shoreline progradation

Answer

Alternating coarse and fine beds of equal thickness deposited by tidal fluctuations

Answer

Massive, structureless beds emplaced instantaneously by mass-wasting flows

Question 7

In sequence stratigraphy, a sequence boundary is formally defined by:

Accepted Answer

A subaerial unconformity formed during relative sea-level fall and its correlative conformity in the basin

Answer

A marine flooding surface marking the turnaround from transgression to regression within a depositional sequence

Answer

The lithostratigraphic contact between two formations of contrasting rock type

Answer

A paleosol horizon indicating prolonged subaerial exposure without significant erosion