Sedimentary Rocks: Formation, Classification, and Interpretation

All flashcards

What is geological detritus?

Mineral and rock fragments produced mainly by weathering and erosion of existing rocks, as well as by the breakdown of solidified volcanic material.

What is marine snow?

Dead aquatic organisms, their parts, and waste that settle through water and accumulate on the bottom.

How do biochemical sedimentary rocks form?

Organisms use dissolved materials to build tissues or hard parts; accumulated remains can later form rock, such as shell-derived limestone or coal from vegetation.

What distinguishes an arenite from a wacke?

An arenite has little muddy matrix between grains, while a wacke has abundant muddy matrix, generally more than 10%.

What is an evaporite rock?

A sedimentary rock containing minerals left behind as water evaporates, such as halite, gypsum, or anhydrite.

Quiz questions

1. What minimum proportion of silt- and clay-sized particles does mudrock contain?Answer: At least 50% of its particles are silt- and clay-sized.
2. What is the main difference between conglomerate and breccia?Answer: Conglomerate is dominated by rounded gravel, while breccia is dominated by angular gravel.
3. A sandstone has more than 90% quartz grains and little muddy matrix. Which description best fits it?Answer: Quartz arenite.
4. Which process most directly produces coal as a biochemical sedimentary rock?Answer: Vegetation accumulates, is buried, and is compressed and chemically altered.
5. A rock forms when dissolved halite precipitates as water evaporates. How is it classified by origin?Answer: Chemical sedimentary rock.