The capital letter(s) that label a rock unit (e.g., KJk) on a geologic map represents the rock unit's
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age or geologic time period.
To determine the age of a rock unit on a geologic map, you can follow these steps:
1. Obtain a geologic map: Geologic maps are detailed representations of the types, distribution, and age relationships of rocks in a specific area. These maps can be obtained from geological survey organizations, universities, or online resources.
2. Locate the rock unit of interest: Look for the specific rock unit you want to determine the age of on the geologic map. The rock units are typically represented by different colors or patterns on the map.
3. Identify the capital letter(s): Once you have located the rock unit, look for the capital letter(s) associated with it. These letters are usually printed adjacent to the boundary lines that define the extent of the rock unit.
4. Refer to the map legend: The map legend provides a key to understanding the symbols and abbreviations used on the geologic map. In the legend, you should find an explanation of the capital letter(s) used to represent the age of the rock unit.
5. Consult additional resources: If the map legend does not provide a direct explanation of the capital letter(s), you may need to consult additional resources. Geologic reports, textbooks, or online sources specific to the region in question can provide further information on the age representation conventions used in that area.
By following these steps and interpreting the geologic map legend, you can determine the age or geologic time period associated with the capital letter(s) on a geologic map.