Sedimentary Environments and Lithogenesis GEOL-4046 University of Puerto Rico Mayagüez Campus Department of Geology Sedimentary Environments and Lithogenesis GEOL-4046 Dr. Hernán SantosOffice: F-412, ext Office Hours: Monday and Wednesday 8:35-11:35 AM Sec-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 Schwab Edit. House: Freeman 1st ExamSeptember 28 Sedimentary Rocks: An Introduction Chapter 2- Weathering Chapter 3- Clastic Transport and Fluid Flow Chapter 5- Sandstones and Conglomerates Chapter 6- Mudrocks 2nd ExamNovember 2 Chapter 8- Terrestial Sedentary Environments Chapter 9- Coastal Environments Chapter 10- Silisiclastic Marine and Pelagic Env. 3rd ExamDay 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: 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 Report Topics: (examples) Topics: (examples) –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 Sept 15 Topic of report and 3 references 7 to 15 pages including figures and 3 references 3-7 references Should include: –title page –Index –Introduction –body –references –numbered pages

Sedimentary Rocks: an Introduction Sedimentology- the study of the processes that erode, transport, and deposit sediments. Sedimentology- the study of the processes that erode, transport, and deposit sediments. Sedimentary petrology- the characteristics and origins of sedimentary rocks. Sedimentary petrology- the characteristics and origins of sedimentary rocks.

Analysis of sedimentary rocks involves “description” and “interpretation” We will learn to describe sedimentary rocks We will learn to describe sedimentary rocks Look for characteristics that will help us to determine the environment of deposition. Look for characteristics that will help us to determine the environment of deposition.

Conglomerate 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. Clastic- composed of individual fragments that were transported and deposited as particles. Crystalline- results from the in situ precipitation of solid mineral crystals. Crystalline- results from the in situ precipitation of solid mineral crystals.

Texture- refers to the size, shape, arrangement of the grains the make up the rock. Grain size- grain diameter (boulders, pebbles, cobbles, sand, silt, or clay). Grain size- grain diameter (boulders, pebbles, cobbles, sand, silt, or clay). Shape- is described in terms of sphericity Shape- is described in terms of sphericity Roundness or (angularity) refers to the sharpness or smoothness of their corners. 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 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. 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. Ripple marks, raindrop imprints, mud cracks, cross-bedding, ripple marks.

Fossil content 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 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 do we really want to know about any sedimentary rock? What information can be inferred from each of the physical characteristics? What information can be inferred from each of the physical characteristics? We seek the answer to rather simple questions. We seek the answer to rather simple questions.

We seek the answer to rather simple questions. 1. When was the sedimentary rock unit deposited, and over how broad a region? 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? 2. With what other rock units is the sedimentary rock contemporaneous? 3. From what kinds of source rocks were the sediments derived? 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? 4. Where was that source located? Was it near or far from the depositional site, and in what direction?

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

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