Sedimentology Assessment 1 Due: Tuesday Feb 1, at midnight (Use your lecture slides and the text book) Instructions: Use text boxes to place your answers on the slides in the space beneath the question. Save your.ppt as a.pdf and drop it in your personal google folder. Include the excel sheet showing your work. Name them both in the following format: Assessment_1_FirstName_LastName. Place it in your google drive folder. If you have trouble figuring out how to drag and drop to your google folder, check with your class mates or Lindsey. If you need help with operating Excel, use a tutorial or ask Lindsey or ask myself, in that order. Feel free to check with me if you are having trouble with the science associated with ANY of the questions. All the best! Have fun. Anjali

Q. 1. (1 point) The accompanying excel sheet provides grain-size data of a sand sample taken from close to the water surface in a channel on the Mississippi Delta that is 8m deep, where depth averaged velocity is 1.7m/s. The samples was taken with a sediment net built to allow particles finer then 63microns to pass through. Please plot a histogram of the grain size distribution with particle size (microns) on the X-axis and frequency % (% retained) on the Y axis. Please plot a histogram of the grain size distribution with particle size (microns) on the X-axis and cumulative frequency % (% passing) on the Y axis. Paste your plots on the next slide and then answer the following questions.

Place your plots here 1. a. What is the d50 and d95?

1. b. Please quantify the following i. Sorting ii. Skewness iii. Kurtosis

Q. 1. c. The ratio of the long axis (a) to short axis (c) is approximately 1:0.85. How would you characterize roundness? d. The sample contained approximately 50% quartz and 50% organic carbon particles by volume. What is the QFR classification? e. Why is quartz sand the only mineral found in Holocene deposits on the Mississippi Delta? (explain in 5 sentences or less)

Q. 2. (2 points) Please use your excel sheet to compute the parameters below. Label the columns in your excel sheet as “Q. 2. a.” etc. and include the excel sheet with your submission. Write out the answers in words on the slides. a. shear velocity of the transporting fluid (u*) b. The hydraulic drag coefficient for the channel (Cd) c. Use a kinematic viscosity of Computer Reynolds number and Froude number of the flow. d. If I tossed a pebble into the water of this channel, which way would the expanding ripples travel. e. What handy Law can I use to approximate the velocity profile in this channel? f. What is the boundary shear stress that this fluid can apply?

Q.2. Based on the information you have, please predict what particle sizes could be transported in each mode. g. fully suspended load h. incipiently suspended load i. pure bedload j. When you took a sample of bed material with a grab sampler (it looks like a big jaw which takes a bite out of the bed) you pulled up consolidated laminated mud but no sand. Why? (5 sentences or less) k. Assuming a bed roughness ks associated with a particle size of 150microns, can you estimate the largest particle (quartz) that this flow is capable f transporting? (extra credit)

Q. 3. Three building stones have been labelled on the outside of Beach Hall. Approximate locations are marked on the map. Please photograph and present your images with annotations marking approximate flow direction and stratigraphic “up” on the next three slides. If one or the other cannot be determined from the available exposure please explain why. Do not forget to include one uninterpreted image plus all the elements of good geological figure presentation. Please stay true to the true paatern and geometry of laminations. Please place each exposure on a Rubin diagram indicating what face you think you are looking at. If multiple faces are available on the rock, indicate which face is represented on which part of Rubin’s diagram. (1 point) 1. (Blue) 2. (Pink) 3. (Yellow)

Tabular Cross-Strata produced by straight- crested bedforms Trough Cross-Strata produced by curved bedforms 1. (Blue)

2. (Pink) Tabular Cross-Strata produced by straight- crested bedforms Trough Cross-Strata produced by curved bedforms

Tabular Cross-Strata produced by straight- crested bedforms Trough Cross-Strata produced by curved bedforms 3. (Yellow)

Q This is a 3-D photograph of the Triassic Otter Sandstone exposed in Ladram Bay in Devon. Exposure is approximately 2m tall. Explore the outcrop and answer the following questions. Use this link: i. Are these straight crested or 3-D curved dunes? ii. Take a screen grab, annotate the figure and present them on the next slide. iii. Use Rubin’s diagram to indicate to me which face you are looking at. If none of the accompanying figures present the correct angle, use the USGS animations to find the right angle ( to orient your cross section on the Rubin diagram. Tabular Cross-Strata produced by straight-crested bedforms Trough Cross-Strata produced by curved bedforms

Q Present your figures here

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