Hi this is a fundamental course and I need help with this lab file is attached.
GEOL 104
Lab 3: Facies Mapping
Name______________________________
Materials: Samples (provided), grain-size card (provided), colored pencils, hand lens
Learning Objectives:
● Practice identification of sedimentary rock types and fossils
● Generate interpretation of depositional setting from sedimentary data
● Map distribution and pattern of facies to reconstruct an ancient depositional environment
Background:
The goal of this activity is to create a paleogeographic reconstruction using rock samples and
fossil information. Paleogeographic reconstructions produce a map of past environments, such
as the location of ancient rivers or shorelines. For example, the famous beaches of Florida have
only been at their present location for under 12,000 years; they formed at their current position
as result of a 70-meter rise in sea level due to melting of the northern hemisphere ice sheet.
Underneath the sandy sediment of the beach and nearshore environment you will find deposits
of soils and swamps.
Paleogeographic reconstructions use a variety of information (i.e., data) regarding past
environments, including data from sedimentary rocks and the fossils they contain.
Reconstruction also relies on our understanding of modern depositional environments in order
to produce a realistic model of ancient environments. This information was information
discussed in the previous lab to aid you in producing a realistic paleogeographic reconstruction.
A facies is a rock with a suite of identifying characteristics. Sedimentary facies have
characteristics that indicate a particular depositional environment. Because the distribution of
depositional environments, and thus sedimentary facies, is not random, you can use facies at
one location to predict the types of rocks that will be present in other locations.
Instructions:
For this project you have a set of samples listed in the table shown on the following page. The
samples were acquired from the corresponding locations shown on the map. Your task for this
lab includes:
First,
examine each rock or set of rocks/fossils to fill in the table.
o Map spot: this refers to the position of the sample on the map
o Lithology: determine the rock type; all rocks will be sedimentary rocks
o Texture: assess grain-size, using a grain-size card if appropriate, and sorting
o Sed. structures: if you see sedimentary structures, identify them here
o Accessories/Other features: This includes fossils and trace fossils and other attributes
of the samples found at each spot. if you notice something else about the sample, or if
other specimens are provided, note that here
You
have been given the depositional environments for each location fill in
the rest of the table based on what you have learned about the environments
from the power point and complete the maps.
Possible Depositional Environments:
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Offshore/Deep Marine
Nearshore (area that is underwater between beach and offshore/deep marine)
Beach
Delta channel
River channel
Floodplain/overbank
Once you have determined the facies represented by each sample, you will use this
information to reconstruct the paleogeography of the map area. To do this, draw lines on the
map to delineate facies tracts. A facies tract is a contiguous region of sedimentary deposits
produced by similar environmental conditions; since the conditions of deposition are similar,
the rocks may have features that are similar but the rocks may not necessarily be identical.
o Think carefully about how environments are associated laterally with one
another in modern depositional environments. Some geometries of facies
tracts make more sense for certain environments compared to others.
For example, deltas tend to have a triangular-shaped distribution, with a
broad area toward the ocean basin that tapers in the direction of the
source area; it generally does not form a long, ribbon-like tract of facies
that stretches for long distances like a river channel might. Use models of
the depositional environments to guide your delineation of facies tracts.
Color
in your facies tracts and include a legend/explanation at the bottom of the page that
reflects the depositional environment that each color represents. Congrats- you have created
a paleogeographic reconstruction!
After creating your paleogeographic reconstruction map, you will be given 2 more blank
maps(Attached at the end ignore points on the second two maps) theses maps do not need
to be exact just show you have the idea of what it will look like when it changees.:
o On the second map, draw facies tracts as they would likely appear due to a rise in sea
level that shifted the shoreline 2 miles (3.2 km) toward the ocean. Use the same
colors for facies tracts as you did in your first map.
o On the third map, map, draw facies tracts as they would likely appear due to a drop in
sea level that shifted the shoreline 2 miles (3.2 km) toward the land. Use the same
colors for facies tracts as you did in your first map.
Turn in:
●
Sample identification table
Offshore
Near shore
Beach
Flood Plain
Ignore Point
3
Delta
Map of your paleogeographic reconstruction showing facies tracts, fully colored and
including an explanation of symbols/colors
Fluvial/ River
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