GEOG 1610: Structural geology and landforms of Dallas County.
For a printable answer sheet click here.
Introduction & Background.
Dallas County provides a good example of the relationship between geologic
structure (the geometry of rock layers below ground) and landforms (features of
the earth's surface, such as hills, valleys, ridges and plains). Fundamental
information gained from fieldwork includes identifying rock types, mapping
rock outcrops (a map of where a particular rock occurs at the surface) and
measurement of strike and dip (properties that describe
the orientation of rock layers).
This virtual field trip visits the
four major rock outcrops running through Dallas County:
1. Taylor Marl in eastern Dallas
County.
2. Austin Chalk in central Dallas County.
3. Eagle Ford Shale in western Dallas County.
4. Woodbine Sandstone on the Tarrant County border.
(river sediments, shown in yellow and orange on the map, are much more recent
than the Cretaceous bedrock).
Figure 1. Geology of Dallas County. Numbers refer to field trip sites.
As shown in figure 1, all four outcrops have an approximately north-south strike.
Virtual field trip:
1. Taylor Marl.
2. Austin Chalk.
3. Eagle Ford Shale.
4. Woodbine Sandstone.