Sedimentation is derived from an Italian “Sedimentum” which refers to “Settling”. It’s commonly used to refer to solid materials settling out of fluid. (Tarbuck, 2000) This phenomenon is observed due to the differences in density between the fluid and the solid particles. “In geography sediments are derived from broken rock particles due to weathering.” Sediments are often deposited then undergo lithification process to form a new rock. “The resultant rock will depend on the original rock particles and the process it was subjected to.” This paper seeks to examine the overview of the role played by plate tectonics in the sedimentation process.
“Tectonics refers to a phenomenon whereby the earths crust is deformed leading to the formation of structural features.” (Tarbuck, 2000) Plate tectonics creates conditions that facilitate the deposition of sediments leading to the formation of sedimentary rocks. There are three main types of plate boundaries, the boundaries are named according to the process that leads to their formation. They include divergent boundaries, where plates move apart resulting in the upwelling of materials. The second form is convergent boundaries,” where plates move together resulting in consumption of oceanic lithosphere. The third form is Transform faults where plates grind past each other with no destruction to the lithosphere.” (Tarbuck, 2000) The divergent plate boundaries may lead to the formation of a rift valley on the continental margin bordering the ocean, the continental shelf may continue to subside leading to further accumulation of materials. Eventually, “the material thickens and lithification occurs as sediments are buried further.” (Tarbuck, 2000) The convergent plate boundaries may result from the collision of the plates or subduction, both processes result in the formation of faults or trenches. Collision of the plates often leads to mountain building. During this process of mountain building, troughs are formed as a result folding and faulting of rocks. Streams flowing from the formed mountains will deposit “sediments (sand, gravel and conglomerate) in the low lying areas” or troughs. Continuous erosion and deposition of material will lead to thickening, lithification, and formation of conglomerate rocks. (Tarbuck, 2000) The subduction process may lead to the formation of ocean trenches which will be filled with deposits initiating the process of sedimentary rock formation. Plate tectonics contributes to the formation of many physical features. These physical features play a role in the process of sedimentation. Plate tectonics mainly influences the sedimentation of clastic sediments through processes that result in the formation and deposition of sediments. Clastic sediments in most cases are produced by weathering and erosion and are normally deposited in low lands which may include trenches, troughs, and basins. Sediments are transported and deposited in the troughs and basins to facilitate sedimentation. “Sediments could be transported by water, force of gravity or ice”. (Tarbuck, 2000) They are deposited when the transporting mediums are weakened by other physical features such as the terrain. The deposition depends on the means of transport, “sediments transported by glacier ‘sat the glaciers base or released at the margin of the glacier as melting occurs.” Streams can deposit materials in a variety of places depending on the stream itself, nature of the sediments and speed of flow when deposited at the mouth they form deltas. Sand grains transported by wind can be deposited anywhere depending on the strength of the wind. Oceanic deposits are of different types depending on the location, they include shelves, where the materials are deposited at the river mouth in gorges left by erosion. “Turbidites, is another form of ocean deposits and are found at the foot of continental slopes at depths as great as 5km beneath the surface of the ocean. Carbonate platforms which consists calcium carbonate deposited in continental shelves” and finally, the seafloor which constitutes many different types of sediments derived from different sources.
Appendix
Week Five Lab Report: Relative and Absolute Geologic Time
Answer the lab questions for this week and summarize the lab experience using this form.
Carefully read pages 89-104 of Geoscience Laboratory.
Complete this week’s lab by filling in your responses to the questions from Geoscience Laboratory. Select answers are provided for you in red font to assist you with your lab work. Although you are only required to respond to the questions in this worksheet, you are encouraged to answer others from the text on your own.
Lab Questions
- Apart from the composition of the rock itself, what climate do you imagine is more conducive to physical weathering?
Arctic climate
- How about chemical weathering? Hint: Clues are evident in Figure 5.2.
Temperate climate
- Based on your life experiences, what’s your guess as to which of the four rocks listed in Figure 5.3 most resembles concrete?
Answer: conglomerate
- How about pottery?
Answer: claystone
Imagine that the gasoline that you are burning in your car this week was refined from petroleum that was produced from Jurassic-age rocks in Arkansas.
- What is the primary source of energy that has been reclaimed to power your car? Explain. Hint: What is the ‘heat engine’ that drives the origin of coal?
Answer: the primary source of the energy is the sun. The sun facilitates the manufacture of food by plants. The food is utilized by plants and animals for growth. When plants and animals die they release organic materials into the soil which is subjected to heat and pressure for long periods to form coal and petroleum
Progressive growth (upward from the seafloor) of the barrier sand bars in Figure 5.5.
- A should be recorded in lagoonal sediments by which vertical succession: salt on top of gypsum or gypsum on top of salt? Hint: Which succession reflects increasing salinity produced by the growing barrier effect of the sand bars (see the caption to Figure 5.5A)?
Answer: salt on top of gypsum
- Drawing on the first paragraph on the previous page 96, what kind of rock appears to underlie the sandstones that cap the hills in Figure 5.8?
Answer: shale
- 5.7. Judging from the orientation of the fin-like ridges in Figure 5.8, what is the approximate orientation of the joints that bound them—north-south or east-west?
Answer: East-west
Figure 5.12 shows the distribution of district councils controlled by two unlabeled parties. One party is the Labour Party—the party of labor unions and big government. The other party is the Conservative Party—the party of private ownership and minimal government intervention.
- Which party’s domain do you suppose is labeled Party X in Figure 5.12?
Labour Party—the party of labor unions and big government
- Which party’s domain do you suppose is labeled Party Y? Hint: Key terms are labor unions, big government, private ownership, minimal government intervention.
Conservative Party—the party of private ownership and minimal government intervention
Lab Summary
Address the following questions in a 100- to 200-word summary: Customer to answer (it’s about his / her experience with the lab)
- Summarize the general principles and purpose of the lab.
- Explain how this lab helped you better understand the topics and concepts addressed this week.
- Describe what you found challenging about this lab.
- Describe what you found interesting about this lab.
Write your summary here: ____________________________________________________
Appendix I
Sedimentary Rock Identification
Examine the images of the five rocks. Identify as many characteristics as possible and enter the information in the table below. Based upon the observed characteristics, identify each specimen in the last column of the table. You may want to refer to Table 5.1 in Geoscience Laboratory (p. 92). Submit the completed Appendix in the Individual forum.
Rock Specimen
Rock Identification
| Specimen number | Detrital – particle size? Organic – constituents? Chemical – minerals? | Descriptive Physical Properties | Rock Name |
Example | Organic, Fossils | Fossils ‘floating’ in opaque mud | fossiliferous limestone |
| 1. | calcite | Gray to brown, fine-textured: conchoidal fracture | micrite |
| 2. | sandy | Gray to brown, fine to coarse textured; finer texture appear sugary. | Dolostone |
| 3. | calcite | Yellow, red, brown: Color banded appearance | Travertine |
| 4. | Salt (sodium chloride) | Scratched with the nail, salty taste, cubic crystals | Rock Salt |
| 5. | Calcite | White, gray, beige ; millimeter size spherules | Oolite variety of limestone |
Reference
Tarbuck, L. (2000). Earth Science, Ninth Edition. New Jersey: Mcmillan Publishing Company.