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Seafloor Sediment workshop ppt


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Seafloor Sed guiding ppt

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Seafloor Sediment workshop ppt

  1. 1. Seafloor Sediments Investigation (Ch 2 p. 27)Goal: To explores marine sediments using cores,photos, and smear slide data.Objectives: After this exercise, you (your students)should be able to:•Describe the physical characteristics of sediment cores.•Identify major sediment components and their origin.•Make smear slides, and use composition and texture datafrom smear slide samples to determine the lithologicnames of the marine sediments.•Make a map showing the distribution of the primarysediment lithologies of the Pacific and North AtlanticOceans.•Explain the distribution of marine sediments on their map.•Predict what the sediment lithologies are at otherlocations on the sea floor (e.g., in the Indian Ocean).
  2. 2. Pedagogy• Student Inquiry• Real Data• Constructivist approachdo-talk-do-talk-do….To Do: form teams
  3. 3. Part 2.1. Predict (individually and then in yourteam):1. What kinds of materials might you expect to find onWhat kinds of materials might you expect to find onthe seafloor?the seafloor?2.2. Is there any geographic pattern to the distribution ofIs there any geographic pattern to the distribution ofthese materials?these materials?You will investigate these questions using empirical data andteamwork. And then hypothesize why the sediments aredistributed the way they are.Goal for you to learn both WHAT we know about seafloorsediments and HOW we know it.p. 27
  4. 4. Initial Inquiry into Seafloor Sediments:Core ObservationPart 2.2 Q1: Find your team’s assigned cores in:• Core Photos (p.60-79; or access high resolution photos at:• Table 2.1 (p. 28-29)• On the base map (p. 32-33).Make a list of observations and questions.[Follow with whole group discussion.]p. 28-33
  5. 5. Scientific ocean drilling site locations, from: Unique Identification Codes to Scientific Samples
  6. 6. Example of sample nomenclature and core photo.The standard labeling for ocean drilling samples.From ODP Leg [i.e., Expedition] 199 Initial Reports Volume, Explanatory Notes:
  7. 7. TO DO in your group:Q2 (p.30): Design a way toorganize and record your visualobservations that could be usedby all of the students in the classfor all of the cores. [Follow withwhole group discussion.]Q3 (p. 31): Using the agreedupon approach, describe yourcore. [Follow with grouppresentations of cores.]Q4 (p. 34): Explain why asystematic, complete, andconsistent method of recordingobservations is important.
  8. 8. Sediment Composition (think back to your predictions)• Composition (minerals & microfossils) and texture are the primarydata used to “name” the sediment:TO DO:Part 2.3 Q1 (p. 37): Match smearslide data for your core’s sampleslisted Table 2.2 (p. 42-51) to mineraland fossil images in Fig 2.3.p. 35-51Extension Lab: Make a sample request from IODP ( make your own smear slides. Try to identify the components, using the followingresources:•Images in Fig 2.3, p. 35-36.••Rothwell, Minerals and Mineraloids in the Marine Sediments.
  9. 9. Sediment Classification….Name that Sediment!TO DO: Q2, (p. 37) For your assigned core(s), determine thedominant sediment types in the samples.HOW?–Use the smear slide data (Table 2.2, p. 42-51).–Look at the core photos p. 60-79, or access high res digitalcore photos at–Use the Decision Tree p. 38-41.–Record your sediment names in Table 2.2 AND (Part 2.4,Q1, p. 52) plot on your map AND on “class” map usingcolors on p. 52.Do example together
  10. 10. Important information about using the Decision Tree (p.38-41):The decision tree aims to capture the most distinctive (i.e., end-member, dominant)sediment types:• Calcareous ooze: biogenic sediments composed of calcareous nannofossils and/orforaminifers.• Siliceous ooze: biogenic sediments composed of diatoms, radiolarians, spongespicules, and/or silicoflagellates.• Red clays: very fine terrigenous sediment that often contains siliceous microfossils,fish teeth, Mn-Fe micronodules, and/or volcanic glass.• Terrigenous sediment: siliclastics; sediment from the weathering of continents orvolcanic islands.• Glaciomarine sediment: sediment containing terrigenous sand, pebbles, or cobblestransported to the sea by icebergs.Note, while the above 5 sediment types are the most distinctive sediment types, mixedsediment types are common. In addition, the sediment type can also change within acore. For example the sediment could alternate between two or more sediment types orgradually change from one to another.In any of the sediment types, but especially in biogenic oozes and deep sea red clays,layers of volcanic ash may be distinguishable.
  11. 11. TO DO: Q2 & Q3 (p. 52-54). Analyze class map. Develophypotheses for what controls the distribution of each of theprimary sediment types in the modern ocean.
  12. 12. How does this distribution compare to your initial predictions?
  13. 13. Distribution of the primary sediment types on the seafloor (from Davies and Gorsline, 1976; Rothwell, 1989)Distribution of Marine Sediments– there is a rhyme and reason!YOU derived this sediment type map from core data!Q4 (p.54): How does your map compare to this one?
  14. 14. Idea for extension: Interpret the rest of map (draw boundaries betweendifferent primary sediment types)
  15. 15. Follow-Up Exercise with Lectureon Marine SedimentsTerrigenous Sediment• derived from the weathering& erosion of rocks on land:sand & mud• accumulates alongcontinental margins• masks other sediment typesbecause of highsedimentation ratesGlaciomarine Sediment• Terrigenous – but a specialtype that indicate glacialconditions on land.• Can accumulate far fromland via iceberg rafting.• Best recognized bydropstones in cores.
  16. 16. What are the requirementsfor biogenic ooze toaccumulate ?Biogenic Rich Sediment = Ooze1. Productivity in the surface waters2. Preservation (i.e., not dissolved) assettle through the water column3. High relative abundance (i.e.,avoid dilution by other sedimenttypes)
  17. 17. Key points for Lecture on MarineSedimentsCalcareous Ooze• composed of carbonateshells of plankton (CaCO3)• accumulates onbathymetric highs (aboveCCD) & beyond thecontinental marginsSiliceous Ooze• composed of the siliceousshells of plankton (SiO2)• accumulates under areas ofhigh productivity
  18. 18. Follow-Up Exercise with Lectureon Marine SedimentsDeep Sea Red Clay• wind-blown dust & currenttransported clays• accumulates on the abyssalplains (deep broad seafloor)• mixed with minerals thatprecipitate on the sea floorand some siliceousmicrofossils• very slow sedimentationrates
  19. 19. Exploring Further:Q5b (p. 55): Is calcareous ooze in the N Atlantic found at the same depth, shallowerdepths, or deeper depths than in the N. Pacific? Why?Q6 (p. 55): The map you constructed represents the modern distribution of sedimenttypes in the Pacific Ocean. Do you think this map would also represent sediment typedistribution in the geologic past and in the geologic future? What factors might vary (inthe past and in the future) that could change the distribution of sediment types?
  20. 20. Exploring The Instructor Guide See handout formost of theinstructor guide;For full guide goto DROPBOX.
  21. 21. Exploring Scientific Data Collected from Marine ExpeditionsTo Do: See Scientific Ocean Drilling Initial Results Volume(s) (online: or get a hard copy). ExploreInitial Results Vol overall.Idea for extension: Write (type, single spaced) a 1-page summary of thetypes of scientific data collected from cores, how it is reported andorganized, and your comments and questions on it.
  22. 22. Ideas for Extension: Refine Your Core Descriptionand Sediment Classification• Find the core description online (IR volumes) for your core.Compare your core description to the published description.Write a reflection on: the strengths and weakness of yourdescription, how you would modify your approach in the future.• Refine based on Explanatory Notes section of an Initial Results(IR) volume:-methodologies and symbols used in descriptions lithostratigraphy: naming the sediments (and then defininglithostratigraphic units)-