Field Lab PT 1/Rock Identification<br />By: Jean Reyes<br />
Location and background<br />I 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.<br />Although these rocks are different, most should have similar historical background as they are from the same area.<br />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.<br />
Location/Background continued…<br />Camp Roberts is located near the Salinas River between Monterey and San Luis Obispo Counties.<br />It is named after Harold W. Roberts, a World War 2 medal of honor recipient.<br />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.<br />
Santa lucia mountains<br />The 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.<br />
Granite/granitic<br />-Identified to be of igneous origin<br />-Phaneritic in texture<br />-Large crystal structure<br />-Felsic composition<br />-Intrusive (because of the coarse-grained texture).<br />-presumed to be light in silicates as granite contains only 10% dark silicates.<br />
Quartz/quartzite Metamorphic<br />Identified to be of metamorphic origin.<br /> white with reddish/pinkish stains.<br />Non-foliated/Porphyritic texture<br />Medium-coarse grain<br />Felsic composition<br />Parent rock-Quartz sandstone<br />
Igneous/granite<br />Identified as Igneous in origin<br />Looks to be Pyroclastic in texture<br /> Intrusive (coarse grain)<br />Pink/reddish in color<br />Mafic (Basaltic)/Gabbro composition<br />
Possibilities/conclusion…. <br />Much of the outlying rock families in this immediate area seem to be very consistent with the Metamorphic/Igneous families.<br />A solid amount of this area does contain sediment and sedimentary rock.<br />Most of my findings and rock samples are not consistent with the sedimentary history that is suggested through out this area.<br />Perhaps Metamorphism and the metamorphic rock cyclic processes has taken over within this area over the past century or longer.<br />
Field Lab pt: 2Field Observations<br />by: Jean Reyes<br />
Salinas river<br />Located in central San Luis Obispo County<br />Flows parallel to the Santa Lucia Mountains<br />Elevation-2,400 ft<br />Mouth-Monterey Bay<br />Length-175 Miles (282 km)<br />Basin-4,160 sq miles<br />
Erosion<br />Because of its periodic dry climate and dry river bottom at times during the summer, the Salinas river bed endures harsh erosion.<br />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.<br />-this picture shows a prime example of erosion and the weathering process that occurs.<br />
Bridges/railroad<br />Built and developed during WW2 to transport troops to and from Camp Roberts Military Training Center.<br />Operated by Southern Pacific Railroad Transport<br />No longer in operation (derailed after the Korean war)<br />
Nacimiento Dam Spillway<br />Nacimiento River Dam was constructed in 1961.<br />Built by the Monterey County Water Authority for flood control and water irrigation.<br />Created Lake Nacimiento which is now used by people for recreational purposes.<br />It is a 210 ft earth fill dam.<br />
Nacimiento continued…<br />Nacimiento<br />Nacimiento Dam Spillway has been undergoing extensive repair and modification operations since 2008.<br />Purpose of modifications is to ensure safety regulations and to improve release maneuvers incase of large floods.<br />
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