Lab 2

Geology 435 Laboratory Exercise #2: Due Sept. 17
Unconsolidated Sediments and Rocks: Hand Samples; Binocular Microscope and Hand Lens
References: Fichter and Poche, p32-56; Nichols, Ch2, p.10-24;
I. Unconsolidated sediments.
1. Follow the instructions on p. 39-41, Fichter and Poche, Part one Level one (omit acid reaction)
and also the questions on this sheet for the 4 unconsolidated samples, listed below
2. Citronelle Formation, Miocene, Florida.
a. Give a complete name. (Folk, Andrews & Lewis, 1970; see attached)
1. ______________________________________________.
b. Does any relationship exist between grain size and grain roundness? Explain.
c. What is the sorting value? (Estimate with sorting comparison charts)
1. ________________________________________________.
3. Guatemala; recent. (Samala River, B-2)
a. Give a complete name: __________________________________.
b. What is the sorting value? (estimate):___________________________.
c. What is the average roundness? (estimate):______________________.
4. Tecolutla, Mexico; Recent.
a. Give a complete name: ___________________________________.
b. What is the range of roundness present?
c. Is there any relationship between grain roundness and grain type? Explain.
5. Treasure Is., Florida, Recent.
a. Give a complete name: ______________________________.
b. What is the sorting value? _____________________________.
c. What is the average roundness present? ___________________.
6. Analysis
a. Which sample(s) (#1 - 4) are the most mineralogically mature?
b. ____________________________________
c. Which sample (#1 - 4) had undergone the least amount of mechanical abrasion:
___________________________________.

II.
Rocks
1. Follow the instructions starting on p. 47 but especially p. 49-51 in Fichter and Poche for at least
6 samples from the core material available to you, AND the brown hand sample marked CH-CGL.
You should choose as varied a selection of samples as possible from the cores that are available
(at least one each of “conglomerate/breccia”, “sandstone”, “siltstone”, “mudstone”, and
“claystone/shale”).
2. You should write your observations on the “Type 2 - Siliciclastic Data Sheet” and give each rock a
complete name using the procedures in the attached summary (Folk and others, 1970). Note
that this naming procedure is a little different from the Lab text procedures. The attached
approach is preferable.
III. Thin Sections
1. For the two samples with thin sections, draw a simple picture representing the texture of the
rock (more than one picture if the texture is different within the thin section). Be sure to
indicate the primary framework grains, matrix, cement (secondary minerals) and pores.
Remember that sand typically is deposited with 25%-40% pore space. Have these rocks been
altered especially with respect to original, primary porosity? What is the nature of that
alteration, if any?