Field Assignment Part 1

Christopher Sager

Geology 1

Dec 2011

Sampling Area

• My sampling area was the southern Sierra-Nevada mountain range in California. The majority of this area is formed by granite, which began to form as long ago as the Triassic period. When the oceanic plate began to dive under the north American plate, plumes began to form deep underground. These plumes helped cause extensive volcanism in the area prior to the ice age, pushing these large deposits to the surface. However limestone, marble and schist deposits can also be found in this area.

Sample 1

• I believe this sample to be granite, the igneous rock that forms the majority of the sampling area. The grain appears to be very coarse and has a black and white speckled pattern associated with high quartz and low feldspar content. High feldspar content in granite usually gives it a pinkish color.

Sample 2

• I believe this sample to be Schist (metamorphic) due to its smaller grain size (compare to the granite behind it) and its orange hue. The slight orange tint comes from a portion of iron oxides in the rock.

Sample 3

• I believe this sample to be Marble (metamorphic). Depending on mineral impurities Marble can be almost any color.

Sample 4

• I believe this to be Limestone (sedimentary). Limestone dissolves more easily than other rocks , as water can pick up small amounts of carbon dioxide forming a weak acid. This rock was probably in a stream or river at some point smoothing its edges.

Sample 5

• I believe this sample to be Quartzite (Metamorphic) due to its appearance of almost 100% quartz content and medium grain. Quartzite is formed from sandstone or chert recrystallizing under high pressure and temperature.

References

• Tarbucks, E., & Lutgens, F. (2011) Earth: An Introduction to Physical Geology. New Jersey. Pearson Education

• http://sequoia.virtualsierra.com/seqGeology.htm

• http://geology.about.com/library/bl/blrockident_tables.htm