Geology 15                                                                                          West Valley College

R. Lopez                                                                                             


Study Questions 7: Sedimentary Rocks


Read about sedimentary rocks in Harden, p. 26-31, p. 36-37 and see Table 2-3.


1)      What are the three reasons that sedimentary rocks are particularly important?

2)      Be able to briefly discuss the four main processes involved in turning parental solid rock into sediments and eventually sedimentary rock.

3)      What are the two kinds of weathering and give an example of each?

4)      Give three examples of agents that transport sediments.

5)      Be able to name at least three non-marine and three marine depositional environments.

6)      What is a sedimentary “fan”, and what does alluvium mean?

7)      Lithification involves commonly involves three steps, what are they?

8)      What are the two major groups of sedimentary rocks (see text, Table 2-3)?

9)      What does “clastic” mean?

10)  Define the following: conglomerate, breccia, sandstone, shale, and mudstone.

11)  What does the term “fissile” mean? And what rock does it best describe?

12)  What are the two subdivisions of the Biological/Chemical group (also known as the Chemical Precipitate group)?

13)  Define Limestone.

14)  Cite three examples of marine organisms that extract calcium carbonate from seawater, and whose skeletons may form limestone.  Is most limestone of inorganic or biological origin?  What is calcareous ooze?

15)  What are radiolaria (see Harden, fig. 3-10)?  What are their shells mad of? What are the deposits of radiolaria on the seafloor known as?, and what kind of rock do they eventually form?

16)  Chert is composed of what mineral?

17)  What are diatoms and what are their deposits called (read Harden, p.441, and note pictures on pp. 442-443)?

18)  What famous geological formation in California is a Diatomite?

19)  What principle do geologists use to interpret ancient depositional environments?

20)  What kinds of features in sedimentary rocks provide information on depositional environments?

21)  What is compositional maturity?

22)  What is textural maturity?

23)  What tectonic setting are quartz sandstones, arkose sandstones, and greywacke sandstones deposited in?

24)  Where is clay size sediment most likely to be deposited in the marine environment?

25)  In a bedded sequence of sedimentary rocks, what does each bed represent in terms of depositional environments?

26)  What are cross beds and how do they form?

27)  What are graded beds and how do they form? What is a Turbidite?

28)  What is the CCD?  What is the reaction involved to form carbonic acid?

29)  Be able to sketch a “trailing continental margin” showing the continental shelf, slope, rise, and deep ocean (abyssal plain).  Where would you expect reefs, turbidites, and oozes to be deposited?





Scenic Places to Visit to See Interesting Sedimentary Rocks:


Pigeon Point Lighthouse on Highway 1 between Santa Cruz and Half Moon Bay.  Conglomerates containing boulders and cobbles of volcanic rocks, granites, and fine sandstone are exposed along the beach north of the lighthouse.  Submarine landslides probably deposited these sediments.


Devil’s Slide on Highway 1 between Half Moon Bay and Pacifica.  It is too dangerous to stop you car here, but beautiful turbidites are exposed in the road cuts.  To the north San Pedro Rock can be seen in close to shore, and on a clear day the Farallon Islands can be seen far offshore.  The turbidites exposed at Devil’s Slide also crop out near San Pedro Rock, and you can safely examine them there.


San Pedro Rock.  Take the southern most exit in Pacifica, head towards the ocean, and ask someone how to get to Shelter Cove.  The latter is a small community on the beach, but the road to it was lost to landslides years ago and now you must walk in.  Great views of the Rock, and good exposures of turbidites.  Look for graded bedding.  The Rock is a hogback (see below).


Vasquez Rocks.  Off the Antelope Valley Freeway (Highway 14) between Los Angeles and Palmdale.  Exit at Agua Dulce Canyon and follow the signs to the County Park.  The landform here is a “hogback ridge” (a ridge formed by resistant layers within steeply tilted eroded strata) formed by erosion of resistant sandstone and fanglomerate layers (a special name for conglomerates found in alluvial fans).


Mormon Rocks.  See Harden plate 28.  These sandstone hogbacks have caught your eye if you have driven on Highway 138 between Palmdale and San Bernardino.


Pt. Lobos State Reserve.  The “Crown Jewel of the California State Park System”.  Located a few miles south of Carmel on Highway 1.  Only about an hour and a half drive from San Jose.  Beautiful conglomerates and sandstones with interesting sedimentary structures, all unconformably lying on Mesozoic Granite of the Salinian Block.