Tuesday, April 6th, 1999

Announcements: The third writing assignment is now optional; anyone can drop the lowest of their writing assignment grades. If you choose to drop the third writing assignment, e-mail Professor Furman telling her this is your option.

Lecture notes:

I. Geologic time
    A. The earth is roughly 4.5 billion years old (this is on the basis of meteorites)
            1. Where did this number come from?
                    a. Radiometric dating
                    b. Fossil records
                    c. Heat flow from earth's interior
                    d. General terms: superposition--unraveling the sequence of geological events

    B. Uniformitarianism--"present is key to the past"; processes happen slowly, at constant rate through time

    C. Superposition
            1. Sedimentary rocks form on flat surfaces; continental shelf--margin of the continent; is most well represented
            sedimentary environment (globally)

            2. Young sediments are deposited on old sediments

            3. Environments change in predictable ways (uniformitarianism)
                    ex. braided stream ---> meandering stream
                          beach ----> estuaries
                          eroding mountains  (sediments in grain size) coarse --->  fine grain

    D. Paleoenvironmental information
              1.     deltas
                              ------> continental margin sediments
                      beaches
 
               2.
                                shallow water (oxygen)
                                plant growth                ----->  fossils
                                animal community