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Preparation Questions (Department of Geology, The College of Wooster) During the appropriate lecture, I will call on students to answer questions such as these. I will occasionally collect the papers of a particular day to be graded as quizzes. Feel free to use any sources of information to answer these questions, including books, articles, handouts or the Web.
1. What is the difference between the roundness and the sphericity of a sedimentary grain? 2. How can the surface texture of a sedimentary grain be more diagnostic of depositional environment than its form, roundness or sphericity? Please give an example. 3. Siliciclastic sedimentary rocks can be either grain-supported or matrix-supported. What is the difference between these two states, and what can they indicate about depositional conditions?
January 22, 2008 (Tuesday) 1. A classic hydrodynamics question: What is Stokes’ Law of Settling? 2. Please list the limitations on the application of Stokes’ Law to grains descending through a fluid. (In other words, what makes the use of Stokes’ Law only an estimation in natural systems?)
January 24, 2008 (Thursday) 1. For the following questions, imagine a stream 6.0 meters wide, 2.0 meters deep and flowing at 0.02 meters per second. Please show your work for each section. (Please note the “useful equations” on the back.)
January 29, 2008 (Tuesday) 1. We will continue our introduction to stratigraphy on Tuesday. Please briefly describe the kinds of unconformity below. We’ll fly through them in class. Little diagrams are always helpful. 2. How do we define a desert? You’ll find at least two definitions out there. So beautiful, deserts are.
January 31, 2008 (Thursday) 1. What is loess? Where would you expect to find loess deposits? You’ll get special bonus points if you can pronounce it correctly. 2. In a windblown sand deposit we often see grains “creep” along the surface, not saltating, but moving downwind. What drives these grains? 3. What are the sedimentological differences between humid alluvial fan deposits (through which water flows often if not constantly) and those of arid alluvial fans (where water flows through quickly, episodically, and rarely)? Think first about composition, assuming for both a similar source (a granite), and then think in terms of sorting.
February 5, 2008 (Super Tuesday) 1. How does a stream become “overloaded” with sediment? What happens to the channel when a stream is thus overloaded? A diagram will be useful here. 2. How does a natural levee form? These natural levees (and, of course, the artificial ones) were an issue during the Hurricane Katrina devastation in New Orleans. Please draw a cross-sectional diagram (perpendicular to stream flow) of a stream with natural levees.
February 7, 2008 (Thursday) 1. What are crevasse splay deposits? How would you recognize them? 2. What is a sedimentary delta? Why, by the way, is it called a “delta”? What is your favorite delta?
February 12, 2008 (Tuesday) 1. Deltas turn out to be really good places to find oil and natural gas. Why? Think broadly here about what we need to form petroleum and its byproducts, as well as what is needed to trap it for later exploitation.
February 19, 2008 (Tuesday) 1. What controls the tides? Yes, time to make a little set of drawings with the Earth, Moon and Sun showing how the tides are managed. Be sure to show the difference between a spring tide and a neap tide. 2. Why does a wave break when it reaches the shore?
February 21, 2008 (Thursday) 1. On this blustery and gray Ohio day, I want you to imagine yourself in a lagoon behind a barrier bar off the coast of North Carolina. What sort of sediments would you expect in this lagoon? How would these sediments differ from those on the other side of that barrier bar? What kind of sedimentary structures do you see in this lagoon? 2. What kind of sediments would you expect to see on the seaward side of that North Carolina barrier bar?
February 26, 2008 (Tuesday) 1. I love carbonates! We always start with the basics. What are the mineralogical and stability differences between the calcium carbonate minerals calcite and aragonite? 2. Calcium carbonate is inorganically precipitated in the following equations: CaCO3 + H2CO3 <=> Ca++ + 2HCO3- and H2O + CO2 <=> H2CO3 The driving mechanism of carbonate precipitation is the removal of CO2 from the water. What factors in a marine environment can thus produce carbonate precipitation?
March 4, 2008 (Tuesday) 1. In what depositional environment would you expect a biosparite/grainstone to have been deposited? Why? 2. Look up these three kinds of carbonate cement: isopachous, pendant and meniscus. Please draw a labeled diagram of each as they would appear in thin-section and briefly describe the conditions under which each forms.
March 6, 2008 (Thursday) 1. Dolomite is both a rock and a mineral. How are they defined? 2. Please describe with a labeled diagram the seepage reflux model for dolomitization of carbonate sediments. In what sort of depositional environments would you expect this to happen?
March 27, 2008 (Thursday) 1. As we approach carbonate sedimentary environments, tell me first how carbonate sediments differ from siliciclastic sediments in terms of sources, transportation and deposition. (These questions for today are thought experiments – you won’t get all the details.) 2. Imagine a modern coral reef system. (Nice ….) Now think of the sedimentary dynamics in and around a coral reef. What types of sedimentary patterns do you expect to see?
April 1, 2008 (Tuesday) 1. What are the differences between marine and nonmarine evaporite deposits? 2. Some evaporite units are more than 2 km thick. How can such enormous amounts of evaporative minerals accumulate? Note that evaporating the entire Mediterranean Sea right now will produce only 60 m of salt deposits. Please describe one possible depositional model.
April 8 & 10, 2008 (Tuesday & Thursday) 1. What is the difference between ferric and ferrous iron? Under what environmental conditions is each stable? 2. Pyrite is a common sedimentary mineral which can tell us a lot about a depositional environment. What is the chemical formula of pyrite? Under what conditions does it form in sediments?
April 10 & 15, 2008 (Thursday & Tuesday) 1. Chert is a siliceous rock which has many varieties with different names. Please list some of the names below, along with their distinguishing characteristics. 2. Why was chert and its rock relatives so popular with Stone Age cultures? What is it about this rock type that makes it so good for stone tools?
April 17, 2008 (Thursday) 1. Please list below the major coal deposits in the United States including locality and age. 2. Under what environmental conditions does a typical oil shale form? (I’ll show you a very atypical one from the Ordovician of Estonia which doesn’t fit the usual model.)
April 22, 2008 (Tuesday) 1. On Tuesday we will discuss the Snowball Earth Hypothesis, which is riddled with extraordinary observations and delicious debates. Tell me first in general what this hypothesis is. 2. Pick out one line of evidence which you find compelling either for or against the Snowball Earth Hypothesis and please describe it below.
April 24, 2008 (Thursday) Remember: Field trip leaves Scovel Hall at 7:00 a.m. on Sunday. You snooze, you lose. 1. A rift valley develops in the middle of a granitic continent. What sort of sediment (composition, grain size, etc.) would you expect to accumulate in this valley? Why? There will be more than one type, so imagine a sequence of sediments as the valley widens. 2. The Old Red Sandstone formed under what tectonic conditions? When was it deposited? (Use the Web!)
April 29, 2008 (Tuesday) 1. Next week we will begin to look at stratigraphy in detail. We’ll start with a review of terms. Please have definitions and/or examples ready for the following -- Formation Group Disconformity Walther’s Law of Facies Progradation Transgression Coarsening-upward sequence
May 1, 2008 (Thursday) 1. Sequence stratigraphy! This topic has produced needless fear in a generation of geology students. Fear not, though, because modern technology is making it more and more accessible through various visualization programs. This movie, for example, shows it all – http://strata.geol.sc.edu/movies/CLASTICSYSTEMTRACTS.MOV After watching the movie, go to the main University of South Carolina webpage – http://strata.geol.sc.edu/seqstrat.html and then define below for me a sequence: 2. What is a sequence boundary? After defining it, return to the movie and watch sequences and their boundaries develop. This is sure better than when I was in school …
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