Key Elements:
- The outcropping at this point represents what the ground looks like under the topsoil in this region.
- This area prospered due to a wealth of minerals close to the surface as well as an expansive and stable aquifer.
Logging Requirements: (send me your answers)
- Why is basic geological knowledge of this area important?
- What are the principle mineral resources in the area?
- What do you think this material could be used for?
- Take a close look at the outcropping at the posted coordinates.
- Approximately how long is the visible outcropping?
- Examine the horizontal fractures at the posted coordinates
- What may have caused these fractures?
- Do these fractures improve or degrade the aquifer?
- Examine the vertical striations at the posted coordinates.
- In your opinion what caused these striations?
- Are they naturally occurring or man-made?
- Provide photographic evidence that you physically visited this site.
- You can be in the picture but are not required to be.
- Please post you picture with your log.
The Freeport Quadrangle is characterized by gentle hills, except for a few localities where steep- sided canyons were produced by glacial diversion of streams . The area is in the physiographic region called the Rock River Hill Country (Leighton, Ekblaw, and Herberg, 1948) . Surface elevations range from 1, 0 8 0 feet to 7 4 7 feet above sea level . The lowest point on the bed rock surface, in the Pecatonica River Valley,. is about 572 feet above sea level but is covered by 1 7 8 feet of alluvium . The Pecatonica River, which flows east ward to the Rock River and then south-westward to the Mississippi River, is the major drainage of the area . All streams are tributary to it.
(ref: Geology of the Freeport Quadrangle)
The two bedrock formations found in Freeport are further divided into seven lithologic units, all of which are enumerated as potential bedrock aquifers. The bedrock units are described as follows.
Medium dark gray salt-and pepper-textured quartz-plagioclase-biotite hornblende granofels with sporadic thin interbeds of medium greenish gray hornblende-diopside calc-silicate granofels.
(ref: Town of BCD "Rock Aquifer S
A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane.[1] Fractures can provide permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or hydrocarbon reservoirs, since they may possess both significant permeability and fracture porosity.
(ref: Fracture (geology))
The Freeport Quadrangle is in northwestern Illinois on the south slope of the Wisconsin Arch. The exposed bed rock consists of the Platteville and Galena Dolomites of the Champlainian Series of Ordovician age. The underlying St. Peter and Glenwood Formations are covered by Recent allu vium along the major valleys.
(ref: Geology of the Freeport Quadrangle)
Knowledge of the basic geology of the area is important to development and conservation of the mineral resources, to the design of foundations for buildings, bridges, and highways, and to interpretation of soil variations and agricultural productivity . The principal mineral resources in the area are dolomite and sand and gravel, which are used mainly for road metal and concrete aggregate.
(ref: Geology of the Freeport Quadrangle)
Further reading: