University of Puerto RicoMayagüez Campus

Department of Geology

Sedimentary Environments and LithogenesisSedimentary Environments and Lithogenesis GEOL-4046 GEOL-4046

Dr. Hernán Santos Office: F-412, ext. 3583Office Hours: Monday and Wednesday

8:35-11:35 AM

Sec-070 Room 201Sec-070 Room 201

Prerequisite: Geol 3056

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:

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 SchwabEdit. House: Freeman

1st Exam September 28Sedimentary Rocks: An IntroductionChapter 2- WeatheringChapter 3- Clastic Transport and Fluid FlowChapter 5- Sandstones and ConglomeratesChapter 6- Mudrocks

2nd Exam November 2

Chapter 8- Terrestial Sedentary EnvironmentsChapter 9- Coastal EnvironmentsChapter 10- Silisiclastic Marine and Pelagic Env.

3rd Exam Day of Final ExamChapter 11-Carbonates RocksChapter 12- Carbonate EnvironmentsChapter 13-Other Biogenic Sedimentary RocksChapter 14-Chemical and Non-Epiclastic Sedimentary Rocks

Grading:

The final grade of the class will consist of 60% class grade:– 3 partial exams– A Final Report – A total of 400 points

40% laboratory grade.

Final ReportFinal Report

Topics: (examples)Topics: (examples)– Microbial build-upsMicrobial build-ups– DeltasDeltas– Eolian systemsEolian systems– Eruption processes and facies Eruption processes and facies – Glaciers and glaciers depositsGlaciers and glaciers deposits– Volcanic eruption processes Volcanic eruption processes

and faciesand facies– Deep water processes and Deep water processes and

productsproducts– Shallow water carbonatesShallow water carbonates– Lacustrine processes and Lacustrine processes and

depositsdeposits– Reef structures and sedimentsReef structures and sediments

Sept 15 Topic of report Sept 15 Topic of report and 3 referencesand 3 references

7 to 15 pages including 7 to 15 pages including figures and 3 referencesfigures and 3 references

3-7 references 3-7 references Should include: Should include:

– title pagetitle page– IndexIndex– IntroductionIntroduction– bodybody– referencesreferences– numbered pagesnumbered pages

Sedimentary Rocks: an Sedimentary Rocks: an IntroductionIntroduction

SedimentologySedimentology- the study of the processes - the study of the processes that erode, transport, and deposit sediments.that erode, transport, and deposit sediments.

Sedimentary petrologySedimentary petrology- the characteristics - the characteristics and origins of sedimentary rocks.and origins of sedimentary rocks.

Analysis of sedimentary rocks involvesAnalysis of sedimentary rocks involves““descriptiondescription” and “” and “interpretationinterpretation””

We will learn to We will learn to describe sedimentary describe sedimentary rocksrocks

Look for Look for characteristics that characteristics that will help us to will help us to determine the determine the environment of environment of deposition.deposition.

ConglomerateConglomerate

Composed of pebbles of Composed of pebbles of preexisting rocks and preexisting rocks and minerals. Clasts-broken minerals. Clasts-broken fragments.fragments.

Color.Color. Composition of clasts of Composition of clasts of

rocks and minerals.rocks and minerals. Texture- refers to the size, Texture- refers to the size,

shape, arrangement of the shape, arrangement of the grains the make up the grains the make up the rock.rock.– RoundnessRoundness

TextureTexture

Clastic- composed of individual fragments Clastic- composed of individual fragments that were transported and deposited as that were transported and deposited as particles.particles.

Crystalline- results from the in situ Crystalline- results from the in situ precipitation of solid mineral crystals.precipitation of solid mineral crystals.

Texture- refers to the size, shape, arrangement Texture- refers to the size, shape, arrangement

of the grains the make up the rock.of the grains the make up the rock.

Grain size- grain diameter Grain size- grain diameter (boulders, pebbles, (boulders, pebbles, cobbles, sand, silt, or cobbles, sand, silt, or clay).clay).

Shape- is described in Shape- is described in terms of sphericityterms of sphericity

Roundness or (angularity) Roundness or (angularity) refers to the sharpness or refers to the sharpness or smoothness of their smoothness of their corners.corners.

Sedimentary StructuresSedimentary Structures

Large scale, three-dimensional features of Large scale, three-dimensional features of sedimentary rocks best studied in outcropssedimentary rocks best studied in outcrops

The most important is stratification- the The most important is stratification- the banding or layering exhibited by as banding or layering exhibited by as consequences of deposition of the clasts consequences of deposition of the clasts grain by grain over time.grain by grain over time.

Ripple marks, raindrop imprints, mud Ripple marks, raindrop imprints, mud cracks, cross-bedding, ripple marks.cracks, cross-bedding, ripple marks.

Fossil contentFossil content

Sedimentary rocks often contains organic Sedimentary rocks often contains organic remains, either hard parts (shells, bones, or remains, either hard parts (shells, bones, or their replacement) or trace of organism such their replacement) or trace of organism such as tracks, trails, burrows (ichnofossils).as tracks, trails, burrows (ichnofossils).

Sedimentary rock Interpretation: A case Sedimentary rock Interpretation: A case studystudy

What do we really want to know about any What do we really want to know about any sedimentary rock?sedimentary rock?

What information can be inferred from each What information can be inferred from each of the physical characteristics?of the physical characteristics?

We seek the answer to rather simple We seek the answer to rather simple questions.questions.

We seek the answer to rather We seek the answer to rather simple questions.simple questions. 1. When was the sedimentary rock unit 1. When was the sedimentary rock unit

deposited, and over how broad a region?deposited, and over how broad a region? 2. With what other rock units is the 2. With what other rock units is the

sedimentary rock contemporaneous?sedimentary rock contemporaneous? 3. From what kinds of source rocks were 3. From what kinds of source rocks were

the sediments derived?the sediments derived? 4. Where was that source located? Was it 4. Where was that source located? Was it

near or far from the depositional site, and in near or far from the depositional site, and in what direction?what direction?

5. Was the source a mountainous highland or an 5. Was the source a mountainous highland or an area of low relief?area of low relief?

6. How was the material transported to the 6. How was the material transported to the depositional site from the area where it was depositional site from the area where it was weathered and eroded? Was it blown by the wind, weathered and eroded? Was it blown by the wind, bounced along the channel of flowing river, bounced along the channel of flowing river, moved by the surf and longshore currents, or moved by the surf and longshore currents, or carried by a sheet of slow-moving glacial-ice?carried by a sheet of slow-moving glacial-ice?

7. In what kind of physical setting did the 7. In what kind of physical setting did the sedimentary rock form? Was it deposited by an sedimentary rock form? Was it deposited by an ancient river delta system? Is it a lithified desert ancient river delta system? Is it a lithified desert dune complex?dune complex?

8. How have the color, composition, 8. How have the color, composition, texture, and other physical properties of the texture, and other physical properties of the sedimentary rock been modified in the time sedimentary rock been modified in the time since deposition?since deposition?

Answering these questions helps us Answering these questions helps us understand the genesis of a sedimentary understand the genesis of a sedimentary rock. Answers to such questions are rock. Answers to such questions are formally embodied as formally embodied as stratigraphy, stratigraphy, provenance, dispersal, transporting agent, provenance, dispersal, transporting agent, depositional setting, paleo-geography, depositional setting, paleo-geography, sedimentary tectonics, and diagenesissedimentary tectonics, and diagenesis ..