Historical Geology, Chapter 5
Learning Objectives and Study Questions
1. Infer a reasonable weathering and transport history for a body of clastic sediment from its
shape and observations of the sediment's rounding, sorting, and compositional maturity.
2. Recognize a variety of common sedimentary structures, including different types of bedding
and ripple marks as well as mud cracks and biogenic structures, and use them to infer a
sedimentary rock's likely conditions of deposition.
3. Identify the likely depositional environment of a sequence of sedimentary rocks formed in a
common continental setting (e.g., glacial, desert, river, or lake), and explain your decision.
4. Identify the likely depositional environment of a sequence of sedimentary rocks formed in a
common transitional setting (e.g., delta, barrier island, or tidal flat), and explain your
decision.
5. Identify the likely depositional environment of a sequence of sedimentary rocks formed in a
common marine setting (e.g., contintental shelf, continental slope and rise, deep-ocean
basin, reef, or carbonate platform), and explain your decision.
6. Apply the concept of a sedimentary facies to determine whether a sequence of continental
shelf sediments was deposited during marine transgression or regression.
1. Oxisols, soils rich in insoluble iron and aluminum oxides, typically form in _____.
A. polar regions
B. high-latitude forests
C. mid-latitude forests
D. deserts
E. tropics
2. Caliche, a deposit of calcium carbonate that is formed by the evaporation of rising
groundwater, is typically formed in _____.
A. polar regions
B. high-latitude forests
C. mid-latitude forests
D. desert regions
E. tropical regions
3. Typically, sediments deposited in freshwater lakes become ____ farther from shore.
A. coarser
B. finer
C. more abundant
D. less abundant
E. nicer
4. In glacial lake sediments with varves, one set of dark and light layers record deposition
during one _____.
A. day
B. week
C. month
D. year
E. century
5. Meter-scale cross-bedding of well-sorted sands that are associated with ancient playa lake
deposits are likely to record _____.
A. alluvial fans
B. dunes
C. meandering streams
D. braided streams
E. beaches
6. Poorly-sorted and rounded sediments deposited by debris flows at the bases of mountain
canyons in arid regions form _____.
A. dunes
B. playas
C. deltas
D. point bars
E. alluvial fans
7. Typically, meandering streams produce meter-scale deposits that fine upward from sand to
clay and record the transition from _____.
A. rainy season to dry season
B. dry season to rainy season
C. channel to floodplain
D. floodplain to channel
E. here to there
8. Walther’s law says that sedimentary facies that form next to one another in environments
that migrate laterally tend to lie _____ in the rock record.
A. next to one another
B. at widely separated sites
C. on top of one another
D. at variable locations
E. through their teeth
9. A typical delta deposit grades upward from prodelta clays, through delta-front silts and
sands, to channel sands and, finally, _____.
A. tills
B. dune sands
C. point bar deposits
D. marsh deposits
E. alluvial fans
10. As sea level rises and barrier island-lagoon complexes migrate inland, barrier island sands
are deposited directly on top of _____.
A. shallow marine sediments
B. lagoonal silts and muds
C. marsh deposits
D. river floodplain deposits
E. none of these
11. As the ocean transgresses, continental shelf sediment sequences tend to _____.
A. coarsen upwards
B. have uniform grain sizes
C. fine upwards
D. become thicker
E. contain more treasure
12. The coarsest sediments associated with reefs tend to be on their _____.
A. seaward sides
B. landward sides
C. tops
D. bottoms
E. central parts
13. The coral reef show below is best described as a/an _____.
A. atoll
B. barrier reef
C. fossil reef
D. fringing reef
E. patch reef
14. Turbidity currents that sweep down continental slopes
deposit sediments with _____ bedding on the adjoining seafloor.
A. cross
B. graded
C. planar
D. bioturbated
E. comfortable
15. Because of the increased solubility of CO2 with depth in seawater, _____ are not deposited
below the carbonate compensation depth.
A. calcareous oozes
B. cosmogenous sediments
C. hydrogenous sediments
D. siliceous oozes
E. terrigenous sediments
16. Siliceous oozes are common on the deep ocean floor beneath areas where upwelling brings
_____ to the surface.
A. fish
B. other plankton
C. dissolved CO2
D. nutrients
E. lost treasure