Sedimentary Rocks Ch. 6

What is the pH of rainwater?

<7

Which of the following is not true about clast/grain size in a sedimentary rock: A. Larger clasts are always rounded due to abrasion during transport B. Larger clasts are deposited closer to the source of the sediment C. Smaller grain sizes are indicative of low energy depositional environments D. Larger clasts are indicative of high energy depositional environments E. Smaller grains are transported greater distances than larger grains

A. Larger clasts are always rounded due to abrasion during transport

Why is rainwater acidic?

Because sulfur and nitrogen emitted by coal fire power plants & Because there is CO2 in the atmosphere

Which of the following is not an environment where shale would form? A. Lakes B. River flood plains C. Deep ocean D. Alluvial fans E. Lagoons

D. Alluvial fans

Not an agent of erosion

Fire

Which of the following statements is TRUE?

Pieces of broken rock are collectively called clasts or detritus

Describe how a clastic sedimentary rock forms from its unweathered parent rock

Weathering Erosion Transportation Deposition Lithification

The structure that may form where a stream enters a lake is called

a delta

Which statement is FALSE? a. Chemical sedimentary rocks are crystalline in texture. b. Dolostone and limestone are polymorphs—they have the same chemical composition. c. Both chert and limestone may have either chemical or biochemical origin. d. Gypsum and halite are evaporite minerals.

b. Dolostone and limestone are polymorphs-they have the same chemical composition

Because the velocity of sediment settling (deposition) is positively related to grain size for waterborne sediments, fluvial deposits are more likely than glacial deposits to ________.

be well sorted

Rocks formed dominantly from the calcium carbonate shells of marine organisms are classified as _____ and called _____.

biochemical;limestone

A clastic sedimentary rock composed of angular pebble-sized fragments surrounded by matrix is

breccia

Lithification, the process by which sediments are turned into sedimentary rocks, includes ________.

compaction and cementation

Ripple marks, dunes, and cross bedding are useful indicators of

current direction

Which of the following rock types does not contain the mineral calcite? a. chalk b. micrite c. fossiliferous limestone d. chert

d. chert

Which of the following lists accurately describes grain size increasing from smallest to largest? a. silt, clay, sand Incorrect b. sand, cobbles, pebbles c. sand, silt, pebbles d. clay, silt, sand

d. clay, silt, sand

Which of the following features is a bed-surface marker, meaning it appears on the surface of a bed due to events during or soon after sediment deposition? a. slumps b. cross beds c. laminations d. mud cracks e. graded bedding

mud cracks

Which of the following sedimentary features is the surest indicator that the past environment was subaerial (under air), not submarine (underwater)? a. mud cracks b. turbidites c. scour marks d. fossil marine clam shell imprints e. ripple marks

mud cracks

The organic sedimentary rock that is composed of mud-sized particles and partially decayed organic matter (kerogen) derived from plankton and algae remains is

oil shale

If you find quartz sandstone in the place where it formed, you know you are looking at an ancient

sand dune

What is the most logical ancient environment to have produced a deposit consisting of layers of well-sorted sandstone with cross beds several meters high? a. glacial valley b. rivers c. shallow-water carbonate area d. sand dunes e. alluvial fan along a mountain front

sand dunes

Formation of a clastic sedimentary rock involves five stages. Which of the following describes erosion? a. process by which particles settle out of transport medium b. compaction and cementation of loose particles to form solid rock c. disintegration of bedrock into separate particles d. separation of rock or regolith from its substrate

separation of rock or regolith from its substrate

A clastic sedimentary rock with clay- and silt-sized grains that breaks in thin sheets is called

shale

As sediment is transported downstream, away from its point of origin, the particles become

smaller

Sedimentary rocks can form by each of the following processes EXCEPT

solidification from a melt

As compared with metamorphism, diagenesis ________.

takes place at lower temperatures and pressures

If water is the transport mechanism of sediment, the grain size of sedimentary deposits most closely indicates the ________.

velocity of the water at the moment the sediment settled to the bottom

The breakdown of exposed rock into small fragments and dissolved ions is termed _________.

weathering