Metamorphic Rocks White marble. According to our text, marble is a ‘coarse, crystalline metamorphic rock whose parent was limestone or dolostone…. Marble can be pink, gray, green or even black’. (Tarbuck, Lutgens, Tasa, 240) I found this particular white marble sample in the Los Gatos Creek, which runs through Coalinga, California . The creek begins in the Santa Cruz mountains and meets the Guadalupe River. This rock was embedded in the creeks bank . Clearly, water erosion of the creek bed, exposed it. Many of the rocks found in this area are samples of sedimentary rocks which have been broken down from the anticline formations. They are ‘primarily from the Paleogene Epoch period (upper Oligocene and Lower Mioncene age from about 34 million to 23 million years before the present)’.
Igneous Rocks This is an example of serpentine. Serpentine is a igneous rock. Igneous (or crystallized from hot lava or magma) - examples: granite, basalt(Course lecture, chapter 4).This igneous rock , I found in the nearby hills of the town Parkfield. Serpentine is California's state rock because it is found in abundance. It is also found in areas where faulting occurs, and Parkfield is considered as the “Earthquake Capital of the World”. It is located on Little Cholame Creek, at an elevation of 1529 feet. In this particular region it is easy to find mudstones, sandstones, siltstones, and shale. The younger rocks of Tertiary and Quaternary age are in light tan and yellow.
Sedimentary Rocks My second rock sample is sandstone. This is actually a picture of a massive anticline sedimentary formation. I found this sample up in the hills of Coalinga, California, which is surrounded by such formations in a semicircle; from the west, around the north, and to the east. These formations contain accumulations of petroleum, from which oil has been withdrawn for more than a hundred years. These formations are primarily from the Paleogene Epoch period (upper Oligocene and Lower Mioncene age from about 34 million to 23 million years before the present).
This next sample, I believe, is a conglomerate Sedimentary Rock. Conglomerates are formed when large pebbles are glued together with small particle of sand and clay (Tarbuck, Lutgens, Tasa, 206). This particular rock has bone particles glue to it along with sand and clay. The color of conglomerates varies depending on the type of pebbles present. This sample I found near the oil fields in Coalinga. Most of the oil in the Coalinga field comes from a large-scale geologic formation known as the Kregenhagan-Temblor petroleum system. This region is surrounded by a body of Eocene-age (about 56 to 34 million years ago ) shales rich in organic sediments.
Igneous Rocks Granite is my fifth example. I am confident that it is a felsic granite rock. ‘Granite is perhaps the best known of all igneous rocks’ (Tarbuck, Lutgens, Tasa, 116). I found it on the shore of the Kaweah Lake in Visalia, California. This lake is actually a man made lake. ‘It was formed after the construction of the Terminus Dam in 1962. This lake is at is at an elevation of 694 feet in the foothills 17 miles east of Visalia. The lake has a surface area of 1,945 acres and 22 miles of oak and different colored granite rocks that outline the shoreline’.
1. Earth An Introduction To Physical Geology; Tenth Edition. Tarbuck, Lutgens, Tasa. Upper Saddle River, New Jersey, 2011. 2. The Sunnyside of the Valley.July 25, 2011 http://www.usacitiesonline.com/cacountycoalinga.htm
3. Parkfield, California: The Earthquake Capital of the World. http://www.parkfield.com/parkfield/ 4. Visit Visalia, California; Lake Kaweah. http://www.visitvisalia.org/Lake-Kaweah 5. http://www.google.com/search?aq=f&sourceid=chrome&ie=UTF-8&q=geological+background+of+west+hills+in+coalinga%2C+ca