Sedimentary rock forms from bits of rocks deposited over time by wind and/or water. Rocks occur in all sizes. The tiny amounts of mud, pebbles, sand grains, and smaller rock particles can form sedimentary rock. Sediment can also contain the remains of once living things. This may be bones, shells, droppings, leaves or stems. Wind and water carry sediments and deposit them in layers usually in a lake or ocean bottom. The processes that turn sediments into solid rock are compaction and cementation. The processes of compaction and cementation together are known as sedimentation.
Compaction
At first, the fragments of rock lie loosely together. But gradually, over many, many years these thick layers build up. This build up becomes heavy and presses down on the layers beneath it. Compaction is the pressing down of layers forcing the sediments to fit closer together. Over millions of years, this process can squeeze fragments tightly together. The layers often remain visible in the rock and may be used to identify sedimentary rock.
Cementation
During the process of compaction, the minerals in the rock are dissolving. These dissolved minerals fill in the spaces between sediment particles. Cementation is the process of sediments being glued tightly together. The processes of erosion, deposition, compaction, and cementation may occur over millions of years transforming rock fragments into solid rock.
The surface area structures of this area are divided into 3 time periods: 1. Pre-Mississippian 2. Late -Mississippian to early Pennsylvanian, and 3. Post -early Pennsylvanian. These form bands of outcrops radiating outward to the north and northeast from the Arbuckle mountains of Oklahoma. This fan – like array is called the Prairie Plains Homocline. This Homocline as a west facing dip of about 14 feet per mile of it’s course.
The surface rocks are arranged as a series of younger plates stacked upon each other. This road cut is a excellent example of these layers.
The Mississippian (also known as Lower Carboniferous or Early Carboniferous) is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earliest/lowermost of two subperiods of the Carboniferous period lasting from roughly 358.9 to 323.2 million years ago.
The Pennsylvanian (also known as Upper Carboniferous or Late Carboniferous) is in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly 323.2 million years ago to 298.9 million years ago Ma (million years ago).
The Mississippian consisted of an environment similar to what we see in today’s Kansas.
The following Material were used for Reference:
- AZGS.AZ.GOV and UCSB Geology Department
- U.S. Department of the Interior, Professional papers and Geological surveys
- California Institute of Technology
- www.kgs.ku.edu
- Universities Space Research Association
Logging Requirements: Please E-Mail me the answers, don't post any pictures of the site itself.
1. Type in GC7BV5B I-70, Hwy-40 Sediment in Kansas .
2. How many big layers do you count ?
3. What are the main colors in these layers?
4. Can you see a tilt? or is it somewhat flat?