GEOL 3700 Structure and Tectonics Laboratory Exercise One, M. Bunds Instructor page 1

GEOL 3700 STRUCTURE AND TECTONICS LABORATORY EXERCISE 1

Goals: 1. Learn the Rule of V's and apply it to interpreting and drawing geologic maps. 2. Learn to use basic trigonometry to calculate true bedding thickness, depth to beds and other

useful geologic information. 3. Learn to determine bedding strike and dip and thickness from map data using basic

trigonometry. 4. Improve your topographic map reading skills. 5. Draw an accurate and neat topographic profile. Tasks: a) Read and understand the Rule of V's. b) Read and understand the trigonometry handout. c) Complete Exercise 1, in which you a) utilize the rule of V's to sketch planar geologic features

across a topographic map and b) determine the strike and dip of thrust fault from its outcrop pattern.

d) Complete Exercise 2, in which you calculate bed thickness, depth to a bed, and apparent dip of a bed in a simple scenario (perfectly flat topography).

e) Complete Exercise 3, in which you calculate bed strike and dip, bed thickness, depth to a bed using the outcrop pattern of a mapped sedimentary bed.

This lab is due at the beginning of the next lab period.

Exercise 1: a) Sketch the outcrop traces of the veins that have the orientations listed below. Draw each vein so that it passes through point X. All of the veins are about 5 m thick. Label each vein on the map. Veins A, C, and D should be fairly straight forward to sketch, but vein B is tricky because its dip is so shallow. Here is a hint: calculate the slope of the stream (dash-dot-dash line on the map) in degrees before you sketch vein B, to see if it perhaps violates the Rule of V's.Vein A: N30E, 20NW Vein B: N30E, 10SE Vein C: N50E, 90 Vein D: N30E, 50SE

b) The figure below is a topographic map of a hill on which a thrust fault has been mapped. Determine the following: 1) The attitude (strike and dip) of the fault plane) 2) Draw a cross-section perpendicular to the strike of the fault plane. Show the topographic surface and the fault plane on your cross section.

32

X

YA

A'

Exercise 2.A coal seam oriented 000/32 is shown on the map above. Line A - A' represents a very high, vertical cliff that drops off to the south. The ground everywhere on the map is completely horixontal, with the exception of the cliff. Determine the following:a) The true thickness of the bed.b) The depth to the top of the mapped bed beneath point X.c) The vertical thickness of the bed beneath X (i.e., the difference between the depth to the top and bottom of the bed).d) The depth to the top of the bed beneath point Y.e) The apparent dip of the bed in the cliff face along line A - A'. M.Bunds, Dept. of Earth Science, Utah Valley State College

coal

sea

m

horizontal ground, elevation 100 m

horizontal ground, elevation 50 m

scale: 1cm = 10 m

0 50 100 m N

Tw

Tn

Kk

Qal Alluvium.Tn Tertiary Norwood Formation. Extrusives.Tw Tertiary Wasatch Formation. Sandstone and conglomerate.Kk Cretaceous Kelvin Formation. Shales.

EXPLANATION

Exercise 3. The company for which you work has been asked to make a bid on a well for a farm. As the company's structural geologist, you must estimate the depth and thickness of the local aquifer, the Wasatch formation, beneath the farm. Fortunately, the Wasatch formation crops out on a hill near the farm, where you mapped it as shown above. The land surrounding the farm is dead flat at 5000 feet elevation. Using your map information, determine the following: 1) the strike and dip of the Wasatch formation in the area; 2) the true thickness of the Wasatch formation in the area; 3) the depth to the top of the Wasatch formation beneath the spot, marked by an X, where the farmer would like to drill his well; 4) the thickness of Wasatch formation that a vertical well could penetrate through and draw water from beneath the X; and 5) make a recommendation for a different well location that would require less drilling and indicate the depth at which the Wasatch formation would be found at your preferred location. Include all your calculations and describe any assumptions you made about the geology in the area when making your calculations.

Qal

contour interval = 10 ft(1 meter = 3.28 feet)

5000

5050

Curly Tail Hog Farm

M.Bunds, Dept. of Earth Science, Utah Valley State College

Exercise 4The map above shows topography across a creek in New York. Note that north is not straight up on this map - see the north arrow on the right side of the map. Complete the following.a) Draw a section line from point D across the map following a trend of S60oE. Label the end of the line on the east side of the map D'.b) What is the contour interval of the map?c) What is the maximum relief crossed by section line D - D'?d) On a sheet of tracing paper construct a topographic profile with no vertical exaggeration along the line of section that you drew. e) What is the steepest slope crossed by your line of section? Express your answer in degrees and grade (gradient is the rise/run x 100%, which equals the tangent of the slope angle multiplied by 100%; note that the steepness of roads is commonly expressed as a grade).f) Sketch on the map the outcrop pattern of a bed that outcrops about 300 feet south of D is about 75 feet thick, and is oriented 090/45S.