University of Puerto Rico
Mayagüez Campus
Department of Geology
Sedimentary Environments and Lithogenesis
GEOL-4046
Sec-070
Room 201
Prerequisite: Geol 3056
Dr. Hernán Santos
Office: F-412, ext. 3583
Office Hours: Monday and Wednesday
8:35-11:35 AM
Objective of course:
This courses provide the students with the
knowledge to identify sedimentary rocks,
sedimentary structures, to understand the
processes of erosion, transportation, and
deposition, and to associate the rocks to
environments of deposition.
Description of the course:
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Introduction to the processes of sedimentary rock
formation, including the weathering of rocks, and the
transportation, deposition, and lithification of
sediments.
Emphasis on the field study of diverse modern
sedimentary environments and classification of
sedimentary rocks based on petrographic analysis.
Sedimentary Environments and Lithogenesis
($99.35, University Bookstore)
Text Book: Sedimentary Geology, 2nd Ed.
Author: Donald R. Prothero and Fred Schwab
Edit. House: Freeman
1st Exam
September 28
Sedimentary Rocks: An Introduction
Chapter 2- Weathering
Chapter 3- Clastic Transport and Fluid Flow
Chapter 5- Sandstones and Conglomerates
Chapter 6- Mudrocks
2nd Exam
November 2
Chapter 8- Terrestial Sedentary Environments
Chapter 9- Coastal Environments
Chapter 10- Silisiclastic Marine and Pelagic Env.
3rd Exam
Day of Final Exam
Chapter 11-Carbonates Rocks
Chapter 12- Carbonate Environments
Chapter 13-Other Biogenic Sedimentary Rocks
Chapter 14-Chemical and Non-Epiclastic Sedimentary Rocks
Grading:
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The final grade of the class will consist
of 60% class grade:
– 3 partial exams
– A Final Report
– A total of 400 points
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40% laboratory grade.
Final Report
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Topics: (examples)
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Microbial build-ups
Deltas
Eolian systems
Eruption processes and facies
Glaciers and glaciers deposits
Volcanic eruption processes
and facies
Deep water processes and
products
Shallow water carbonates
Lacustrine processes and
deposits
Reef structures and sediments
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Sept 15 Topic of report
and 3 references
7 to 15 pages including
figures and 3 references
3-7 references
Should include:
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title page
Index
Introduction
body
references
numbered pages
Sedimentary Rocks: an
Introduction
Sedimentology- the study of the processes
that erode, transport, and deposit sediments.
 Sedimentary petrology- the characteristics
and origins of sedimentary rocks.
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Analysis of sedimentary rocks involves
“description” and “interpretation”
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We will learn to
describe sedimentary
rocks
Look for
characteristics that
will help us to
determine the
environment of
deposition.
Conglomerate
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Composed of pebbles of
preexisting rocks and
minerals. Clasts-broken
fragments.
Color.
Composition of clasts of
rocks and minerals.
Texture- refers to the size,
shape, arrangement of the
grains the make up the
rock.
– Roundness
Texture
Clastic- composed of individual fragments
that were transported and deposited as
particles.
 Crystalline- results from the in situ
precipitation of solid mineral crystals.
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Texture- refers to the size, shape, arrangement
of the grains the make up the rock.
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Grain size- grain diameter
(boulders, pebbles,
cobbles, sand, silt, or
clay).
Shape- is described in
terms of sphericity
Roundness or (angularity)
refers to the sharpness or
smoothness of their
corners.
Sedimentary Structures
Large scale, three-dimensional features of
sedimentary rocks best studied in outcrops
 The most important is stratification- the
banding or layering exhibited by as
consequences of deposition of the clasts
grain by grain over time.
 Ripple marks, raindrop imprints, mud
cracks, cross-bedding, ripple marks.
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Fossil content
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Sedimentary rocks often contains organic
remains, either hard parts (shells, bones, or
their replacement) or trace of organism such
as tracks, trails, burrows (ichnofossils).
Sedimentary rock Interpretation: A case
study
What do we really want to know about any
sedimentary rock?
 What information can be inferred from each
of the physical characteristics?
 We seek the answer to rather simple
questions.
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We seek the answer to rather
simple questions.
1. When was the sedimentary rock unit
deposited, and over how broad a region?
 2. With what other rock units is the
sedimentary rock contemporaneous?
 3. From what kinds of source rocks were the
sediments derived?
 4. Where was that source located? Was it
near or far from the depositional site, and in
what direction?
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5. Was the source a mountainous highland or an
area of low relief?
6. How was the material transported to the
depositional site from the area where it was
weathered and eroded? Was it blown by the wind,
bounced along the channel of flowing river,
moved by the surf and longshore currents, or
carried by a sheet of slow-moving glacial-ice?
7. In what kind of physical setting did the
sedimentary rock form? Was it deposited by an
ancient river delta system? Is it a lithified desert
dune complex?
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8. How have the color, composition, texture,
and other physical properties of the
sedimentary rock been modified in the time
since deposition?
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Answering these questions helps us
understand the genesis of a sedimentary
rock. Answers to such questions are
formally embodied as stratigraphy,
provenance, dispersal, transporting agent,
depositional setting, paleo-geography,
sedimentary tectonics, and diagenesis.