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GEOLOGY 3430 - INTERPRETATION OF SOURCE AREA PROJECT Introduction This exercise is based on a study of the Pass Peak Formation in the northern Green River Basin by J.R. Steidtmann (under whom I did my MS thesis). The exercise involves interpretation of source areas and is meant to give you a real example that shows the kinds of data sedimentologists use to interpret the direction of sediment transport and the nature of source rocks. You will focus on making interpretations about the source area on the basis of grain size data and mineralogic data. This exercise will be divided into three parts with separate due dates : 1. You will determine how to take a sedimentary rock and determine its grain size and sorting quantitatively . 2. Now that you have determined grain size for several locations in the Green River Basin, you will be given size information for additional localities and learn how to construct a map that shows the spatial distribution of grain size (a contour map of grain size). You will use this to make interpretations about where sediment source areas were located. 3. In a third homework assignment, you will be given compositional data for 46 locations in the Green River Basin. From those data, and from the grain size data, you will make a comprehensive interpretation about sediment dispersal patterns and lithologic nature of the source rocks. 4. Later in the semester, you will return to this exercise to construct an isopach map and interpret depositional setting for the Pass Peak Formation. The Pass Peak Formation was deposited in the Hoback Basin of western Wyoming during Eocene time. The mountain belts that you see on the map (Gros Ventre and Wind River Ranges) were rising at the time of deposition. To the west of the basin is the Wyoming thrust belt; however, tectonic activity there appears to have predated deposition of the Pass Peak Formation. Part 1: Determining quantitative parameters of grain size and sorting Learning goals - by the end of this exercise, students should be able to: 1. Explain the methodology behind determining quantitative parameters of grain size and sorting. 2. Given data on the weight of sediment of various grain sizes determined by sieving a bulk sample, calculate percent of total weight, cumulative weight, and cumulative weight percent of each grain size class. 3. Use data to construct frequency curves, arithmetic cumulative curves, and probability cumulative curves. 4. Use constructed curves to calculate average size parameters (mode, median, graphic mean) and sorting (graphic standard deviation). 5.
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This note was uploaded on 02/04/2010 for the course GEOL 3430 taught by Professor Kraus during the Spring '10 term at Colorado.

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