Field assignment final


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Field assignment final

  1. 1. John Fors<br />Professor Lawler<br />GEL 104, Summer 2011<br />July 10, 2011<br />Middle Fork of The American RiverField Assignment<br />
  2. 2. Content<br />Background & Method<br />Brief Geological History<br />River Canyon Geology<br />Gold Deposits<br />Rock Examples<br />Geological Features<br />Plant Examples<br />2<br />
  3. 3. Background and Research Methodology<br />In late June I visited an area in the canyon of the Middle Fork of the American River<br />The photos and rock samples included in this report are from this field trip<br />3D map images were prepared using Google Earth<br />Identification of rocks done using: Geology of the Sierra Nevada, by Mary Hill (2006)<br />Identification of plants done using: Trees and shrubs of California, by Stuart & Sawyer (2001)<br />3<br />
  4. 4. Site Location<br />Near Auburn, California<br />Entry through Driver’s Flat Road, on dirt road down to bottom of river canyon<br />Coordinates 38.962362,-120.929775<br />4<br />
  5. 5. Deep Down in the River Canyon<br />Google Earth<br />View up the very deep canyon of Middle Fork of American River<br />Valley has been carved by the flow of the river for last several million years<br />5<br />
  6. 6. Quick Geological History and Overview<br />Sierra Nevada is a tilted fault block 400 miles long, with rugged east face, and sloping west face <br />West side has metamorphic rock formed by plate tectonics in Early Paleozoic to Late Jurassic (400-120 million years ago) – with portions of ancient seafloor<br />Volcanic eruptions filled ancient valleys with lava and mudflows<br />Present river system formed by erosion during last 5 million years<br />(Lindstrom, 2000; “North,” 2006; “North,” 2007)<br />6<br />
  7. 7. Geology of Middle Fork River Canyon<br />Undulating steep mountains, elevation 1,600 – 5,600 feet<br />Foresthill Divide is a NE trending ridge system, separating North and Middle Forks of American River<br />River has cut steep canyons 1000 ft below top of Foresthill Divide<br />Significant surface erosion, especially on steep hill sides<br />Mean annual precipitation between 30-40 inches<br />Extremely low seismic activity<br />(“North,” 2006; “North,” 2007)<br />7<br />
  8. 8. Gold Deposits Around Foresthill Area<br />Streams flowing down western slopes carried Auriferous gravels<br />Auriferous gravel <0.5 percent of soil types in the area<br />Flows of lava later covered and protected many of these deposits<br />Gold veins usually are 3-4 feet thick, in NW direction<br />Gold discovered in Foresthill in 1850<br />Primarily placer mines, with extensive hydraulic mining<br />In next 15 years more than $10 million was extracted<br />(“Description,”1897; “Gold,” 1970; “North,” 2006; “North,” 2007)<br />8<br />
  9. 9. Rock Sample: Periodotite / Serpentinite<br />Serpentinite is derived from basic intrusive rock<br />It is created through geological low-temperature metamorphic process involving heat in presence of water<br />Peridotite is derived from the Earth's mantle<br /><ul><li>Description: some small grains, black/gray color, can be scratched, no layers, can be fractured
  10. 10. Identification: I believe this is Serpentinite, a plutonic igneous rock type</li></ul>(Hill, 2006)<br />9<br />
  11. 11. Rock Sample: Greenstone /Green schist<br /><ul><li>The rock is derived from basalt, gabbro or similar rocks containing sodium-rich plagioclase feldspar, chlorite, epidote and quartz
  12. 12. Greenstone and green schist belts are primarily formed of fine-grained volcanic rocks, dominated by basalt, with minor parts sedimentary rocks</li></ul>Description: weathered red/brown color, fine-grained, can be scratched, faint layering<br />Identification: I believe this is Greenstone, a metamorphic rock <br />(Hill, 2006)<br />10<br />
  13. 13. Sandstone Rock Outcropping<br />Fragile grainy sand-colored sedimentary rock <br />Appears to be sandstone or gritstone<br />The outer layer, in part, is held together by a thin layer of vegetation<br />Likely result of earlier deposits of sand, later put under high pressure from overlaying sediment or lava layers<br />Tilted almost 90 degrees, by earlier rock folding process<br />11<br />
  14. 14. Polished Bedrock Down at River Level<br />Sections of the rock at river level has smooth appearance<br />Polishing effect likely is from flowing silt-filled water<br />12<br /><ul><li>It is difficult to see what the rock type is since the surface is so changed. It could either be the from the intruding plutonic rocks, or from the older sedimentary rocks from older sea bottom</li></li></ul><li>Erosion and Break Up of Larger Rocks<br /><ul><li>Large boulders cracking and fragment into smaller blocks
  15. 15. Process driven by heating/freezing cycles, as well as erosion from water, snow, and ice
  16. 16. The large boulder mayhave come down by rock fall from higher up in the river canyon as part of ongoing erosion</li></ul>13<br />
  17. 17. Tilted Sedimentary Rocks<br />Appears to be layered sedimentary rock<br />Could be part of the earlier seabed<br />Tilted between 60 to 90 degrees, mostly facing NE<br />Covered by moss and other plants<br />14<br />
  18. 18. Plant and Animal Life<br />Ground around the river bed is mostly rocky and dry<br />Mixed forest, oaks, and small shrubs; with habitat for diverse fauna<br />No major animals seen, except one river otter (which quickly disappeared under the surface)<br />15<br />
  19. 19. Madrone Tree<br /><ul><li>The madrone is a member of the Heath family (Ericaceae) of vascular green plants
  20. 20. Ericaceae is under the order Ericales, which evolved from Magnoliales,  which in turn descended from angiosperms originating in the Mesozoic Era
  21. 21. It has high tolerance to poor soil, drought, extreme temperature, shade, and elevation; which enables it to thrive in many different habitats</li></ul>I believe this tree is a Pacific Madrone(Arbutus menziesii)<br />(Stuart & Sawyer, 2001)<br />16<br />
  22. 22. Evolution of Pacific Madrone(Arbutus menziesii)<br />17<br />Plantae => Angiosperms => Eudicots => Asterids => Ericales => Ericaceae => Arbutus => A. menziesii<br />Fossilized leaves of a species similar to modern day Pacific Madrone have been found in northwestern Nevada, the Blue Mountains of Oregon, and Tuolumne County, CA<br />This species dates to the Miocene Epoch of 12 to 26 million years ago<br />The species composition and flora is similar to oak-madrone forests in California today<br />Current madrone-related flora is believed to have originated in southwestern North America<br />(Axelrod, 1958;Tappeiner & McDonald, n.d.)<br />
  23. 23. Oak Tree<br />An evergreen oak that is found in the southwestern part of North America, especially in California Coast Ranges<br />Often found near creeks and drainages, growing in moist cool microhabitats<br />It is part of order Fagales, also descendant from angiosperms<br />May live for up to 300 yrs<br />I believe this tree is a Canyon Live Oak (Quercuschrysolepis)<br />(Stuart & Sawyer, 2001)<br />18<br />
  24. 24. Evolution of Canyon Live Oak (Quercuschrysolepis)<br />19<br />Plantae => Angiosperms => Eudicots => Rosids => Fagales => Fagaceae => Quercus => Protobalanus => Q. chrysolepis<br />Early fossil evidence of family Fagaceae found in western Tennessee, dated to Paleocene/Eocene boundary (Crepet & Nixon,1989)<br />Quercus forms swarms of hybrids making precise analysis of lineage difficult<br />More than 200 different species of Quercus across every continent of the world, including 89 in the US, and 20 in California<br />Quercus in general are wind-pollinated, however, LithocarpusandChrysolepis are insect-pollinated, thus causes major differences in their flowers <br />Chrysolepis the most common member of Protobalanus group in California<br />(Crepet & Nixon,1989; Nixon, 2002)<br />
  25. 25. Flowering Manzanita Shrub<br /><ul><li>About 60 species of Arctostaphylos, ranging from ground-hugging arctic, coastal, and mountain species to small trees up to 6 m tall
  26. 26. Believed to have come from subtropical to warm temperate groups and then evolved in response to the expansion of a new adaptive zone: dry climate
  27. 27. Also from angiosperms</li></ul>I believe this shrub is a Mexican Manzanita (Arctostaphylospungens)<br />Belong to order Ericales<br />(Axelrod, 1958; Stuart & Sawyer, 2001)<br />20<br />
  28. 28. Evolution of Mexican Manzanita (Arctostaphylospungens)<br />21<br />Plantae => Angiosperms => Eudicots => Asterids => Ericales => Ericaceae => Arctostaphylos=> A. pungens<br />Shares evolutionary history with Pacific Madrone(Arbutus menziesii) as described on earlier pages<br />Rich fossil record, and considered to be of Miocene origin, approx 15 million years ago<br />Radiation of genus occurred 1.5 million years ago during the Pleistocene <br />Oldest remains of Arctostaphylos from lower Pliocene Texas (Adams,1935)<br />Southern California thought to have been a major Pleistocene center of distribution and variation, which then shifted northward (Adams, 1935)<br />(Adams, 1935; Markos,1995)<br />
  29. 29. Evolutionary Tree of Angiosperms<br />22<br />
  30. 30. References<br />Adams, J. E. (1935). A systematic study of the genus Arctostaphylos. Berkeley Press: Berkeley. <br />Axelrod, D. (1958). Evolution of the madro-tertiary geoflora. The Botanical Review. 24(7) 433-509.<br />Crepet, W., Nixon, K. (1989). Earliest megafossil evidence of Fagaceae: phylogenetic and biogeographic implications. American Journal of Botany. 76: 842-855. <br />Description of the Gold Belt. (1897). Retrieved July 7, 2011, from <br />Gold Districts of California. (1970). Oakland Museum of California. Retrieved July 8, 2011, from <br />Hill, M. (2006). Geology of the Sierra Nevada (Rev. ed.). Berkeley: University of California Press. <br />Lindstrom, S. (2000, July 15). FORESTHILL DIVIDE COMMUNITY PLAN (FDCP) HERITAGE RESOURCE ELEMENT. Appendix B.1. Retrieved July 7, 2011, from<br />FDCP/RDEIR/Appendices/deir%20rfdcp%20appendix%20b%201.ashx <br />Nixon, K. (2002). The Oak (Quercus) Biodiversity of California and Adjacent Regions1. US Forest Service. Retrieved July 10, 2011, from <br />North Fork American River Trail. (2006, June 1). Welcome to Beautiful Placer County California. The official website.. Retrieved July 8, 2011, from<br />North Fork/Middle Fork American River Sediment Study. (2007, April 1). USDA. Retrieved July 7, 2011, from <br />Stuart, J. D., & Sawyer, J. O. (2001). Trees and shrubs of California . Berkeley: University of California Press. <br />Tappeiner, J. C., & McDonald, P. M. (n.d.). Arbutusmenz. Northeastern Area State & Private Forestry - USDA Forest Service. Retrieved July 10, 2011, from<br />23<br />