Objectives
Your first project will be to determine the most likely geological
environment of deposition indicated by the rocks
exposed at Lessors Quarry, our first field study area. Don't worry
if you don't know what that means yet, we will define some new
terms and develop problems we can solve while in the Quarry itself.
The place to begin determining the environment of deposition
is to learn how to observe geological features in outcrops. We
will start by learning how to observe the physical and chemical
aspects of the rocks
and the sedimentary features that characterize them. We will be
applying the scientific method to determine the geological evolution
of the rocks in the quarry. Here's a step-by-step approach:
click here for a keith's suggested outline
I. General Theory
Geological observations indicate that Earth processes are ordered and they have not originated in a random manner. We will apply the scientific method to the rocks at Lessor's Quarry in order to determine their environment of deposition.
II. Ask General Questions
If Earth processes are orderly then:
1. In what type of environment were the rocks deposited?
2. What were the processes of deposition, transportation, and erosion?
III. Observe the rocks and collect relevant Data
Observe and, if possible, measure the following
characteristics:
a. Rock types, mineral compositions
b. Bed thicknesses
c. Sedimentary structures (ripples, laminations etc.)
d. Fossils and/or fossil traces (worm tubes etc)
e. Architecture and configuration of rock bodies (continuous or discontinuous). These are usually provided by a geologic map, cross sections, and a stratigraphic column.
f. Stratigraphy
g. Sorting, particle sizes, roundness, percent matrix vs. grains etc.
IV. Develop Multiple Working Hypotheses as Possible Answers to your Questions
Were these rocks deposited in Fresh Water or Marine Water? How might you tell?
What type of depositional setting; River Systems, Delta, Coastal Environment, Glacial Environment, Tidal, Flats, Carbonate Bank, Deserts?
What were the characteristics of the source areas: tectonically active or quiescent?
V. Testing Hypotheses
Test hypotheses by studying and comparing modern environments. Remember the general theory : Earth processes are orderly so processes going on today operated during the geological past, although there may be some modifications. Use your observations and data to help narrow down and eliminate hypotheses.
VI. Interpret Process
Eliminate those alternative hypotheses that do not fit the data (science progresses by negation. A hypothesis can not be confirmed by a prediction. All we can do is say in such a situation is that the hypotheses is permissible. Science makes progress by disproving predictions made by various hypotheses. For the rocks at Lessor's Quarry we arrive at the probable environmental interpretation by eliminating hypotheses that do not fit the data or inferences (predictions) of the data.
I. Construct a representative measured stratigraphic section
of Lessor's quarry. You will need to determine which part of the
many possible sections are representative. The only way to do
this is to start observing the characteristics of the rocks in
different places and compare and contrast these features. Follow
closely the procedure listed above for the scientific method.mThe
purpose of a stratigraphic column is to present information that
reflects your observations,including the size, texture, composition,
and vertical distribution of
bioclastic limestone beds and clay-bearing, fossil-poor limestone
beds. Please read the notes on drafting and graphs below.
II. Write a 2-page, type-written summary of your interpretations. Include your sketches. Some hints are listed below. Please pay careful attention to the notes on maps, graphs and essays.
If you misplaced any of the figures, you can print them by clicking here:
-GENERAL NOTES ON DRAFTING MAPS, GRAPHS AND SECTIONS-
The main purpose of a figure (maps and diagrams) is that it
presents material and measurements that is difficult to express
in words. All figures should be neat, attractive, and well labeled.
Remember you are trying to communicate a great deal of information.
This must be clear. The major purpose of the stratigraphic columns,
for example, is to present information that reflects the size
and vertical distribution of bioclastic limestone beds and clay-bearing,
fossil-poor limestone beds.
1. The vertical scale must be an arithmetic scale in either meters or centimeters and evenly divided into subunits. The origin must be in the lower left corner of the graph. The horizontal scale should reflect grain size, increasing toward the right. You should locate the base of each bioclastic limestone at its appropriate position above the base of the section.
2. Symbols for various features such as fossils and sedimentary structures should be included. All graphs must have a key that explains all symbols used.
3. All figures should have a figure caption that explains what
the figure represents, its location, and other pertinent information.
For your first exercise, the figure caption would be something
like the
following:
Figure XX. Graph representing the sequence of bioclastic limestone
and fine grain micritic limestone beds exposed on the western
side of the northern wall at Lessor's Quarry, South Hero, Vermont.
The
thickness of the individual beds are shown on the horizontal axis
and the height above an arbitrary datum is shown in centimeters
on the vertical axis. The "x" symbol to the right on
some of the lines
indicates that the top of the bioclastic bed is graded.
You do not have to use the same wording that I have used above. In fact the thickness may not be correct and you may think of additional information that should be given.
4. Before preparing final copies of figures, you should construct a neat pencil sketch with color that shows the relations, labels, and all pertinent geological features. The sketch should have a horizontal scale and geographic directions (East-West etc.). The figure caption should show the direction that the observer is viewing the diagram. For example at Lessor's Quarry, the figure caption for the north wall should that the diagram is oriented so that the viewer is looking north. It is important that you have all the proper information on this preliminary sketch so that you make as few mistakes as possible when you ink a final copy.
5. Note on computer generated diagrams. Computer art is very
effective but it generally takes as much time as drafting by hand.
Formost diagrams you must still prepare a good sketch is then
scanned and
subsequently enhanced in such programs as Canvas, Adobe Illustrator.
We will learn how to do this later in the semester. Labeling can
be done with relative ease. The main advance is that the scale
can easily be changed and the original file saved for subsequent
revisions. Unless you are familiar with these programs you will
find that they take considerable time to complete.
6. Use of photographs. Photographs are very helpful in that
they provide a basis for A and B. They can be used in reports,
but they must be good quality and well labeled so that the reader
knows what you
are referring to when the elements in the photographs are discussed.
We will not accept figures for any of the reports in this course
that are solely photographs. You must have line work. Photographs
can be used to augment your reports
Your essays must be well organized and must be
type-written using any sort of word processor and software. No
hand written material
will be accepted. Remember, first present the facts and then discuss
the interpretation. Always refer to the graph or used it in the
discussion. The graph is the factual basis of your discussion.
You should tell the reader what it represents. This discussion
should not include information that you have in the figure caption
since the reader can read that for himself.
2. Use spell check. Always read what you wrote out loud. In this way you will pick up poor phrases, unclear descriptions, and misspellings that were not picked up by spell check.
3. Scientific reports are generally written in the third person.
For example, "The stratigraphy at Lessor's Quarry consists
of alternating beds of 2 to 6 cm bioclastic limestone inter layered
with very fine
grained, faintly laminated, calcareous lutite (mudstone). The
lower contact of each of the bioclastic limestones is sharp whereas
the upper
contact was gradation in most places. Based on the foregoing information,
three hypotheses are considered. They are: <<list them,if
you wish>.
Do not say "On Tuesday we studied the stratigraphy
of Lessor' Quarry. We saw that the rocks consisted of alternating
beds of bioclastic limestone and faintly laminated mudstone. We
discussed the
origin of these units and came up with 3 hypotheses"
Make sure that all the facts are first presented to the reader before you consider hypotheses.