Sedimentology and Stratigraphy Flashcards

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

Answer: Symmetrical ripple marks

Symmetrical ripple marks have crests of equal slope on both sides, forming under oscillatory (wave) motion rather than unidirectional currents.

The Bouma sequence (ABCDE) in turbidites begins with which division at the base?

Answer: Massive or graded sand

Division A (Ta) at the base of the Bouma sequence consists of massive or normally graded sand deposited from the high-density head of the turbidity current.

Which diagenetic process involves the replacement of original minerals by silica (SiO₂)?

Answer: Silicification

Silicification is the replacement of original minerals or fossil material by silica, commonly producing chert or silicified fossils.

What does a 'fining-upward' sequence in fluvial deposits typically indicate?

Answer: Migration of a meander loop and point bar accretion

Fining-upward cycles in fluvial settings record lateral accretion on a point bar as the meander migrates, with coarse channel lag at the base grading to fine overbank muds.

The principle that allows geologists to date rock layers by the fossils they contain is called:

Answer: Faunal succession

The law of faunal succession states that fossil assemblages succeed each other in a definite, recognizable order that can be used to correlate strata globally.

Which type of unconformity separates tilted or folded sedimentary rocks below from parallel sedimentary rocks above?

Answer: Angular unconformity

An angular unconformity forms when older tilted or folded strata are eroded and then overlain by younger, more gently dipping sedimentary rocks.

Carbonate rocks that form through the accumulation of coral reefs and associated organisms in a wave-resistant framework are called:

Answer: Bindstones

Bindstones are carbonate rocks in which sessile organisms bind the sediment in place, forming a rigid, wave-resistant reef framework.