This document summarizes Jean Reyes' field observations of rocks near Camp Roberts Military Training Center in central California. The rocks were chosen based on color, shape, crystal structure and geographic location from the coastal area near San Miguel. Most of the rocks are consistent with the metamorphic and igneous rock families common to the Santa Lucia Mountains geology, which is dominated by the granitic Salinian Block. Specific rock samples identified include granite, quartzite and an igneous rock that is possibly basaltic gabbro. The document also briefly describes nearby geographic features like the Salinas River and Nacimiento Dam and how erosion shapes the local landscape.

1. Field Lab PT 1/Rock IdentificationBy: Jean Reyes

2. Location and backgroundI have chosen a certain number of rock types that I have found near my job location. I have chosen these rocks by color, shape, crystal structure and, geographic location.Although these rocks are different, most should have similar historical background as they are from the same area.The rocks I have chosen are from a coastal area located near San Miguel, C.A. at Camp Roberts Military Training Center near the Santa Lucia Mountains, where I am currently employed.

3. Location/Background continued…Camp Roberts is located near the Salinas River between Monterey and San Luis Obispo Counties.It is named after Harold W. Roberts, a World War 2 medal of honor recipient.It’s surrounded by the unincorporated communities of San Miguel, Heritage Ranch (Lake Nacimiento), and Bradley. Its closest incorporated city is Paso Robles, 12 miles south on HWY 101.

4. Location/background continued..

5. Santa lucia mountainsThe rock of the Santa Lucia's is dominated by the granitic basement of the Salinian Block, between the San Andreas Fault and Sur-Nacimiento Fault. According to plate-tectonic theory, the core of the Salinian block formed as part of the same batholiths which forms the core of the Sierra Nevada Mountains and the Peninsular ranges of Baja California. It was broken off the North American plate and transported north by the action of the San Andreas fault from an original position. It is predominantly Mesozoic granitic and pre-Cretaceous metamorphic rock. There is some Cretaceous sedimentary rock of the Great Valley Sequence, considerable Miocene marine sediments, and some other Tertiary sediments. Units west of the Sur-Nacimiento fault are dominated by rocks of the Franciscan Assemblage.

6. Granite/granitic-Identified to be of igneous origin-Phaneritic in texture-Large crystal structure-Felsic composition-Intrusive (because of the coarse-grained texture).-presumed to be light in silicates as granite contains only 10% dark silicates.

7. Quartz/quartzite MetamorphicIdentified to be of metamorphic origin. white with reddish/pinkish stains.Non-foliated/Porphyritic textureMedium-coarse grainFelsic compositionParent rock-Quartz sandstone

8. Igneous/graniteIdentified as Igneous in originLooks to be Pyroclastic in texture Intrusive (coarse grain)Pink/reddish in colorMafic (Basaltic)/Gabbro composition

9. Other Rock variances

10. Possibilities/conclusion…. Much of the outlying rock families in this immediate area seem to be very consistent with the Metamorphic/Igneous families.A solid amount of this area does contain sediment and sedimentary rock.Most of my findings and rock samples are not consistent with the sedimentary history that is suggested through out this area.Perhaps Metamorphism and the metamorphic rock cyclic processes has taken over within this area over the past century or longer.

11. Field Lab pt: 2Field Observationsby: Jean Reyes

12. Salinas riverLocated in central San Luis Obispo CountyFlows parallel to the Santa Lucia MountainsElevation-2,400 ftMouth-Monterey BayLength-175 Miles (282 km)Basin-4,160 sq miles

13. ErosionBecause of its periodic dry climate and dry river bottom at times during the summer, the Salinas river bed endures harsh erosion.During the summer months the Salinas river dries up. In the winter, during rain and flood seasons, heavy water and strong currents break down the river bottom.-this picture shows a prime example of erosion and the weathering process that occurs.

14. Bridges/railroadBuilt and developed during WW2 to transport troops to and from Camp Roberts Military Training Center.Operated by Southern Pacific Railroad TransportNo longer in operation (derailed after the Korean war)

15. Nacimiento Dam SpillwayNacimiento River Dam was constructed in 1961.Built by the Monterey County Water Authority for flood control and water irrigation.Created Lake Nacimiento which is now used by people for recreational purposes.It is a 210 ft earth fill dam.

16. Nacimiento continued…NacimientoNacimiento Dam Spillway has been undergoing extensive repair and modification operations since 2008.Purpose of modifications is to ensure safety regulations and to improve release maneuvers incase of large floods.