Recently this has become a pay to use parking lot.
So park on the road.....walk the 50 feet.....or .....?
1. Is the rock an orthoconglomerate or a paraconglomerate?
2. Is the rock intraformational or extraformational?
3. Is the rock oligomict, monomict or a polymict conglomerate?
4. Does the average clast size make it a granule, pebble, cobble or boulder conglomerate?
5. What material do you believe the clasts are composed of?
6. What material do you believe the matrix is composed of?
7. Are the clasts sorted or unsorted?
8. Is this rock a breccia or a conglomerate?
Basics:
In basic terms, conglomerates and breccias can be described as rocks consisting of individual stones that have become cemented together, forming an entirely new rock type. In truth there is nothing basic about the formation of these rocks. Formation occurs over very long periods of time, involving four seperate steps. Even though these "new" rocks are found in many different colors, shapes, textures and compositions, they are "all" formed from pieces of older rocks (clasts) and various minerals. By studying the composition of the boulder(s) at the coordinates, you will better understand some of the factors present during their formation.
Weathering:
Weathering is the break down of rocks, soils and minerals through contact with the Earth's atmosphere, biota and waters. Weathering occurs in situ, meaning "with no movement", and should not be confused with erosion.
Transportation:
Particles from weathered rocks are carried along with the aid of gravity, wind and water. By examining the shape and size of the pieces of weathered rock, one might tell the mode of transportation, and if they were acted upon by either a high energy, or a low energy source. If the rocks inside are well rounded and smooth, it generally shows that they were transported by a high energy source. If the rocks are more angular and rough, they were more than likely acted upon by low energy sources. If the clasts contained in the "new" rock are rounded and smooth, it is considered a conglomerate. If the clasts are sharp and angular it is considered a breccia. Shape of the clasts is basically the only thing seperating breccias from conglomerates. From this point on, when I use the word conglomerate, it is meant to cover both conglomerate and breccia.
Deposition:
As water and wind flows decrease (loss of transport energy) the particles carried within are dropped out of suspension and deposition begins. Normally these weathered bits and pieces are deposited into flat, horizontal layers, only to be covered by the next depositional layer. Successsive layers can be derived from a totally different rock type than the one deposited earlier.
Compaction and lithification:
As these sediments accumulate layer upon later, the added weight causes compaction and a temperature increase. In time this added pressure and heat, using silica, iron oxide and/or calcium carbonate (etc) as a glueing agent, compresses the sediments together and creates a new type of rock. A sedimentary conglomerate. The Matrix:
A matrix is defined as a finer grained mass of material (feldspar, mica, etc.) in which clasts, crystals or larger grains, are embedded. Conglomerates can be subdivided into paraconglomerates, which have more than 15% sand-grade matrix and orthoconglomerates, which have less than 15% sand-grade matrix. Basically, the matrix is the glue surrounding the pebbles or rocks within a conglomerate.
Clast Size:
To be categorized as a conglomerate, 50% of the fragments contained within must have a size larger than 2mm (5/64"). Anything below this size would be considered sandstone, another type of sedimentary rock. They are also sub-classified according to the dominant clast size. Granule conglomerates have clast sizes of 2-4 mm (.07 to .1"), pebble conglomerates have 4-64 mm (.1 to 2.5") clast size, cobble conglomerates are 64-256 mm (2.5 to 10") in size and boulder conglomerates have clast sizes above 256 mm (10").
Composition:
Classification also depends on the lithology (physical characteristics) of the clasts found within. A monomict conglomerate contains clasts with only a single lithology. oligomict conglomerates contain clasts of just a few different lithologies. polymict conglomerates contain clasts from a variety of different lithologies. They are further classified by the composition of the matrix. Intraformational conglomerates were eroded from the same sedimentary rock type that they are now deposited in. Extraformational conglomerates were formed from sources outside of the area of deposition. As a result, the clasts and matrix, are of different compositions than the rock found in the general area.
Rounding and Sorting:
The level of rounding and sorting of the clasts can also be used in classification.
At the posted coordinates you will find a large rock with a small plaque mounted on it. This is the rock to be used to answer the questions.
Email your answers to the questions, to me, using the link in my profile only. If your answers are not received by me, your log will be deleted. Photos are accepted and appreciated as long as the rock in question is not pictured. You do not have to wait for confirmation from me before logging this cache as completed. Most of all……learn……and enjoy the view.