CPG Stratigraphic Analysis & Sedimentology 3

Question 1

Eustasy, as used in sequence stratigraphy, refers to:

Accepted Answer

Worldwide changes in absolute sea level independent of local tectonics

Answer

Local changes in sea level caused by tectonic subsidence

Answer

Changes in sediment supply that shift shoreline position

Answer

Vertical oscillations of the continental lithosphere due to ice loading

Question 2

A lowstand submarine fan in sequence stratigraphy develops when:

Accepted Answer

Falling sea level exposes the shelf, forcing rivers to incise to the shelf edge and deliver sediment directly to deep water

Answer

A carbonate platform is flooded during maximum sea-level highstand

Answer

A coastal plain fan is deposited during tectonic uplift of the hinterland

Answer

A delta progrades rapidly during maximum marine flooding

Question 3

Evaporite minerals such as halite and anhydrite most commonly form in which depositional setting?

Accepted Answer

Restricted marine basins or coastal sabkhas with evaporation exceeding water input

Answer

Deep marine abyssal plains with high productivity

Answer

Glacial outwash plains in polar climates

Answer

Alluvial fans in humid tropical climates

Question 4

What is the key distinction between a stratigraphic trap and a structural trap in petroleum geology?

Accepted Answer

Structural traps depend on rock deformation geometry while stratigraphic traps rely on lateral changes in lithology or porosity

Answer

Stratigraphic traps require faulting while structural traps require folding

Answer

Stratigraphic traps occur only in carbonates while structural traps occur only in clastics

Answer

Structural traps cannot be identified on seismic data

Question 5

Accommodation space in sequence stratigraphy is controlled primarily by the interplay of:

Accepted Answer

Relative sea-level change (eustasy plus subsidence or uplift)

Answer

Sediment supply volume and grain size

Answer

Lateral extent of parasequences and systems tracts

Answer

Water depth above the seafloor at any given time

Question 6

Primary controls on the development of carbonate reef facies in a petroleum system include:

Accepted Answer

Water depth, temperature, light penetration, and nutrient levels

Answer

Proximity to a large river delta supplying nutrients

Answer

Proximity to evaporite basins providing concentrated brines

Answer

Rate of clastic sediment input from adjacent uplifts

Question 7

A wave-ravinement surface in coastal stratigraphy is best described as:

Accepted Answer

An erosional surface cut by shoreface wave action during transgression that truncates underlying coastal sediments

Answer

The base of a turbidite system marking deep-water deposition

Answer

A subaerial exposure surface formed during sea-level lowstand

Answer

The boundary between marine and non-marine sediments at the delta plain