Name: Class day and time:
7.
Web extras: Where to find basic geologic maps of your state.
There are several places to look for geologic maps of your state. The simplest is to visit http://geology.about.com/od/stategeologicmaps/ . Many state geologic surveys offer much more information, so you may want to visit the California Geological Survey
( www.consrv.ca.gov/cgs/index.htm
) and click on Other State Surveys to see a complete list of web pages of the state surveys.
For this exercise, we will use a simplified geologic map of Oklahoma and two cross sections to answer the following questions. You can get the map and cross-sections by visiting http://ogs.ou.edu/level2-earthscied.php
and scrolling down to EP-9 Earth Science and Mineral Resources in Oklahoma. The map and cross-section are on pages 6 and 7 of this publication. Note: Your instructor may specify a different state and a different set of questions for you to complete. a.
Is Oklahoma mostly covered by igneous, sedimentary, or metamorphic rocks? Where did you find this information? b.
What is the age (give the name of the period) of the youngest units, and what caused their deposition as long streaks across the state? c.
The state is dominated by a series of rock units mapped in broad swaths of orange, blue, and green. i.
Give the ages of these units going from oldest to youngest. Pay attention to the letters indicating the ages of these units (P, J, K, etc.) because green, for example, indicates two very different ages on the map. ii.
From the map pattern, do you infer that these units are nearly horizontal or tightly folded and steeply dipping? iii.
Check out cross-section A-A’, which follows the red line A-A’ across northern Oklahoma, to see if you were right. This section is at the top of page 7. d.
The map of the geomorphic provinces of Oklahoma (p. 8) shows the location of the Wichita, Arbuckle, and
Ouachita mountains (in green letters on the map) as well as the Ozark Plateau (northeast corner). The geologic map indicates that these areas host the oldest rocks in the state. Are these rocks generally near horizontal, or are they extensively faulted and folded? e.
Examine cross-section E-E’, which runs north-south along the eastern edge of the state. All cross-sections have a 10x vertical exaggeration, which makes the faults look much steeper and the layers much thicker than they actually are. i.
Which type of fault is common within the Ouachita Mountains? ii.
Did these faults form from compression, extension, or shear (Chapter 14)? iii.
Were the rocks caught up in these faults moved from the south to the north or from the north to the south?
Web Extras for the Laboratory Manual for Physical Geology by Jones and Jones (McGraw-Hill).

iv.
What type of fault is found between the Arkoma Basin and the Ozark Uplift? Did these faults form from compression, extension, or shear? v.
The rocks of the Ouachita Mountains were deformed when South America ran into the southern edge of North America. We can figure out when this deformation ended by examining the geologic map south of Latimer and LeFlore counties. What is the age of the youngest rocks clearly impacted by faulting and faulting?
What is the age of the oldest rocks that are part of the suite of nearly undeformed rocks that drape much of the rest of the state?
Now you know when the folding and faulting stopped. f.
What type of contact (see Chapter 14) separates the Precambrian and Cambrian igneous and metamorphic rocks from the Cambrian sedimentary rocks in the Anadarko Basin (cross-sections B-B’ and C-C’)? g.
How old are the oldest rocks in Oklahoma?
Where to find detailed maps of any part of the United States: The United States Geological Survey features a National Geologic Map Database ( http://ngmdb.usgs.gov/ ) that allows you to find all maps at a variety of scales that include a given town or other geographic feature. You’ll have to play with the site a bit to figure it out, but you can find a gold mine of maps available on-line as well as on paper. (The paper maps you would have to find in a library or order from the USGS or state survey.)
Web Extras for the Laboratory Manual for Physical Geology by Jones and Jones (McGraw-Hill).