GEOL 3000 Name_________________________ Lab Exercise 6 Structural Attributes of Tilted Lithostratigraphic Units Objective: With this lab exercise, we will learn how to determine various structural attributes of tilted lithostratigraphic units. These will include 1) determining the thickness of lithostratigraphic units on a geologic map, 2) defining structural contours and using them to project geologic contacts across a topographic map, and 3) determining the strike and dip of geologic contacts by the 3-Point Method. We will also evaluate geologic map patterns to define the locations of unconformities. 1) Thickness of Lithostratigraphic Units Use the information provided below to determine the thickness (T) of the units A, B, C and D on the following page. Show on a piece of graph paper how you arrived at your answers.2) Structural Contours and Projection of Geologic Contacts across Topography Structural Contours – lines of equal elevation for geologic planes (contacts, faults, unconformities) In the diagram on the next page, the structural contours for the top contact of Unit X are shown. From these contours, the trace of the contact across the map is drawn. The contact line basically connects the points where the structural contour of particular elevation crosses the topographic contour of the same elevation. Using a colored pencil, draw the structural contours on the map for the bottom contact of the unit (see lower cross section). Then draw the contact line for the bottom contact across the map. Now with the upper and lower contacts established, color the exposure area of the entire unit on the map. For a uniformly dipping contact, structural contours will be evenly spaced and parallel. X 3) Determining Strike and Dip of a Geologic Plane by the 3 Point Method On the topographic map (next page), determine the strike and dip for these three scenarios: A) Where a geologic plane passes through points A, B, and C. Strike ____________ Dip Direction __________ Dip Angle ___________ Draw the appropriate strike and dip symbol at Point C. B) Where a geologic plane passes through points A, B, and E. Strike ____________ Dip Direction __________ Dip Angle ___________ Draw the appropriate strike and dip symbol at Point E. C) Where a geologic plane passes through points B, C and D. Strike ____________ Dip Direction __________ Dip Angle ___________ Draw the appropriate strike and dip symbol at Point C. NOTE: The vertical margins of the map are N-S. Contour interval is 50 ft. Show your work on a piece of graph paper.With a colored pencil, draw the structural contours for the geologic plane in scenario A and then draw the trace of that plane across the map.