Complete Lab 6 answer sheetreal
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Georgia State University *
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Apr 3, 2024
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Lab 6- Depositional Sedimentary Structures Answer Sheet
1.
The table below contains descriptions of actual sedimentary rocks and suites of associated rocks. Use the three sedimentary environment tables (Tables 6.1, 6.2, and 6.3) to identify all possible sedimentary
environments for each sample. For some of these, you will have to list several possible environments. Certain sedimentary structures (or other features) may be present in the environment but might not be
in a particular sample (perhaps because of small sample size). By examining other features, such as sedimentary structures or fossils, you may be able to increase the certainty of your interpretation. Use Laboratory 10: Invertebrate Macrofossils and Classification of Organisms or a fossil identification book if
you are unfamiliar with any fossils listed here (such as brachiopods, bryozoans, or molluscs).
Sampl
e
Rock Type
Sedimentary
Structures
Chemical Characterist
ics
Biological Characterist
ics
List All Possible Sedimentary Environments
1
Quartz sandstone
None visible
in this sample
Quartz grains and cement, white to tan
color
Brachiopo
d fossil molds
Barrier Beach
2
Fossiliferou
s limestone: very coarse, no mud
None visible
in this sample
All calcium carbonate, white to gray color
Rock is dominated by
very coarse coral pieces
reef
3
Fossiliferous limestone (fossils in
a lime mud matrix)
Vague layerin
g
All
calcium
carbonat
e, gray
color
Rock is filled with whole and broken brachiopo
d shells and branching bryozoan colonies
Continental shelf
Sampl
e
Rock Type
Sedimentary
Structures
Chemical Characterist
ics
Biological Characterist
ics
List All Possible Sedimentary Environments
4
Gypsum with very thin laminations
of calcium carbonate
Laminations
Evaporit
e minerals
White color (due to gypsum), with gray calcium carbonate laminations
No fossils
Dunes, Tidal Flat, Lakes
5
Breccia
Poorly sorted, some clasts up to 6 inches (15 cm) in diameter
Silty matrix
None visible
in this sample
Red color due to iron oxide cement
Grains
are
fragment
s of
various
types of
metamorph
ic rocks
No fossils
Fluvial-
Alluvial Fan
6
Limestone and dolostone, interlayered
Irregular layers and burrows
Carbonat
e minerals
Burrows
Tidal Flat.
7
Black shale Chert Chalk
Very fine grained
Lamination
s in shale
Organic-
rich
black
shale
Gray to
black chert
White
to
gray chalk
(calcium
carbonate)
Microfossils probably present in the chalk although they were
too small to
identify in lab
Abyssal Plain.
8
Limestone Fossiliferous shale Graywacke
Lamination
s, graded bedding
Gray limestone and shale, greenish gray graywacke
Fossils in shale and limestone, primarily molds of brachiopod
s
Continental Rise-Slope.
9
Quartz sandstone (some are pebbly and poorly sorted) Micaceous Pebbly sandstone
is poorly layered Quartz sandstone
is Reddish brown color due to iron oxides
Quartz, muscovite, No fossils
Dunes, Rivers
siltstone
laminated and
cross
bedded No
structures
in siltstone
clay minerals
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