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- 1. John Fors Professor Lawler GEL 104, Summer 2011 July 10, 2011 Middle Fork of The American River Field Assignment
- 2. Content Background & Method Brief Geological History River Canyon Geology Gold Deposits Rock Examples Geological Features Plant Examples 2
- 3. Background and Research Methodology In late June I visited an area in the canyon of the Middle Fork of the American River The photos and rock samples included in this report are from this field trip 3D map images were prepared using Google Earth Identification of rocks done using: Geology of the Sierra Nevada, by Mary Hill (2006) Identification of plants done using: Trees and shrubs of California, by Stuart & Sawyer (2001) 3
- 4. Site Location Near Auburn, California Entry through Driver’s Flat Road, on dirt road down to bottom of river canyon Coordinates 38.962362, -120.929775 4
- 5. Deep Down in the River Canyon Googl e Earth View up the very deep canyon of Middle Fork of American River Valley has been carved by the flow of the river for last several million years 5
- 6. Quick Geological History and Overview Sierra Nevada is a tilted fault block 400 miles long, with rugged east face, and sloping west face 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 Volcanic eruptions filled ancient valleys with lava and mudflows Present river system formed by erosion during last 5 million years (Lindstrom, 2000; “North,” 2006; “North,” 2007) 6
- 7. Geology of Middle Fork River Canyon Undulating steep mountains, elevation 1,600 – 5,600 feet Foresthill Divide is a NE trending ridge system, separating North and Middle Forks of American River River has cut steep canyons 1000 ft below top of Foresthill Divide Significant surface erosion, especially on steep hill sides Mean annual precipitation between 30-40 inches Extremely low seismic activity 7 (“North,” 2006; “North,” 2007)
- 8. Gold Deposits Around Foresthill Area Streams flowing down western slopes carried Auriferous gravels Auriferous gravel <0.5 percent of soil types in the area Flows of lava later covered and protected many of these deposits Gold veins usually are 3-4 feet thick, in NW direction Gold discovered in Foresthill in 1850 Primarily placer mines, with extensive hydraulic mining In next 15 years more than $10 million was extracted (“Description,”1897; “Gold,” 1970; “North,” 2006; “North,” 2007) 8
- 9. Rock Sample: Periodotite / Serpentinite Serpentinite is derived from basic intrusive rock It is created through geological low- temperature metamorphic process involving heat in Description: some small presence grains, black/gray color, can be of water scratched, no layers, can be Peridotite is derived from fractured the Earth's mantle Identification: I believe this is Serpentinite, a plutonic igneous rock type (Hill, 2006) 9
- 10. Rock Sample: Greenstone /Green schist The rock is derived from basalt, gabbro or similar rocks containing sodium- rich plagioclase feldspar, chlorite, epidote and quartz Description: weathered Greenstone and green red/brown color, fine- schist belts are primarily grained, can be formed of fine-grained scratched, faint layering volcanic Identification: I believe this is rocks, dominated by Greenstone, a metamorphic basalt, with minor parts rock (Hill, 2006) sedimentary rocks 10
- 11. Sandstone Rock Outcropping Fragile grainy sand-colored sedimentary rock Appears to be sandstone or gritstone The outer layer, in part, is held together by a thin layer of vegetation Likely result of earlier deposits of sand, later put under high pressure from overlaying sediment or lava layers Tilted almost 90 degrees, by earlier rock folding process 11
- 12. Polished Bedrock Down at River Level Sections of the rock at river level has smooth appearance Polishing effect likely is from flowing silt-filled water 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 12
- 13. Erosion and Break Up of Larger Rocks Large boulders cracking and fragment into smaller blocks Process driven by heating/freezing cycles, as well as erosion from water, snow, and ice The large boulder may have come down by rock fall from higher up in the river canyon as part of ongoing erosion 13
- 14. Tilted Sedimentary Rocks Appears to be layered sedimentary rock Could be part of the earlier seabed Tilted between 60 to 90 degrees, mostly facing NE Covered by moss and other plants 14
- 15. Plant and Animal Life Ground around the river bed is mostly rocky and dry Mixed forest, oaks, and small shrubs; with habitat for diverse fauna No major animals seen, except one river otter (which quickly disappeared 15 under the
- 16. Madrone Tree • The madrone is a member of the Heath family (Ericaceae) of vascular green plants • Ericaceae is under the order Ericales, which evolved from Magnoliales, which in turn descended from I believe this tree is a angiosperms originating in Pacific Madrone (Arbutus the Mesozoic Era menziesii) • It has high tolerance to poor soil, drought, extreme (Stuart & Sawyer, 2001) temperature, shade, and 16 elevation; which enables it to thrive in many different
- 17. Evolution of Pacific Madrone (Arbutus menziesii) Plantae => Angiosperms => Eudicots => Asterids => Ericales => Ericaceae => Arbutus => A. menziesii 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 This species dates to the Miocene Epoch of 12 to 26 million years ago The species composition and flora is similar to oak-madrone forests in California today Current madrone-related flora is believed to have originated in southwestern North America (Axelrod, 1958;Tappeiner & McDonald, n.d.) 17
- 18. Oak Tree An evergreen oak that is found in the southwestern part of North America, especially in California Coast Ranges Often found near creeks and drainages, growing in moist cool microhabitats I believe this tree is a It is part of order Fagales, Canyon Live Oak (Quercus also descendant from chrysolepis) angiosperms May live for up to 300 yrs (Stuart & Sawyer, 2001) 18
- 19. Evolution of Canyon Live Oak (Quercus chrysolepis) Plantae => Angiosperms => Eudicots => Rosids => Fagales => Fagaceae => Quercus => Protobalanus => Q. chrysolepis Early fossil evidence of family Fagaceae found in western Tennessee, dated to Paleocene/Eocene boundary (Crepet & Nixon,1989) Quercus forms swarms of hybrids making precise analysis of lineage difficult More than 200 different species of Quercus across every continent of the world, including 89 in the US, and 20 in California Quercus in general are wind-pollinated, however, Lithocarpus and Chrysolepis are insect-pollinated, thus causes major differences in their flowers Chrysolepis the most common member of Protobalanus group in (Crepet & Nixon,1989; Nixon, 2002) California 19
- 20. Flowering Manzanita Shrub About 60 species of Arctostaphylos, ranging from ground-hugging arctic, coastal, and mountain species to small trees up to 6 m tall Believed to have come I believe this shrub is a from subtropical to warm Mexican Manzanita temperate groups and (Arctostaphylos pungens) then evolved in response to the expansion of a Belong to order Ericales new adaptive zone: dry (Axelrod, 1958; Stuart & Sawyer, 2001) climate 20 Also from angiosperms
- 21. Evolution of Mexican Manzanita (Arctostaphylos pungens) Plantae => Angiosperms => Eudicots => Asterids => Ericales => Ericaceae => Arctostaphylos => A. pungens Shares evolutionary history with Pacific Madrone (Arbutus menziesii) as described on earlier pages Rich fossil record, and considered to be of Miocene origin, approx 15 million years ago Radiation of genus occurred 1.5 million years ago during the Pleistocene Oldest remains of Arctostaphylos from lower Pliocene Texas (Adams,1935) Southern California thought to have been a major Pleistocene center of distribution and variation, which then shifted northward (Adams, 1935) 21 (Adams, 1935; Markos,1995)
- 22. Evolutionary Tree of Angiosperms 22
- 23. References Adams, J. E. (1935). A systematic study of the genus Arctostaphylos. Berkeley Press: Berkeley. Axelrod, D. (1958). Evolution of the madro-tertiary geoflora. The Botanical Review. 24(7) 433-509. Crepet, W., Nixon, K. (1989). Earliest megafossil evidence of Fagaceae: phylogenetic and biogeographic implications. American Journal of Botany. 76: 842-855. Description of the Gold Belt. (1897). pubs.usgs.gov. Retrieved July 7, 2011, from pubs.usgs.gov/gf/041/text.pdf Gold Districts of California. (1970). Oakland Museum of California. Retrieved July 8, 2011, from http://museumca.org/goldrush/dist-foresthill.html Hill, M. (2006). Geology of the Sierra Nevada (Rev. ed.). Berkeley: University of California Press. Lindstrom, S. (2000, July 15). FORESTHILL DIVIDE COMMUNITY PLAN (FDCP) HERITAGE RESOURCE ELEMENT. Appendix B.1. Retrieved July 7, 2011, from http://www.placer.ca.gov/Departments/CommunityDevelopment/Planning/CommPlans/FDCP/~/media/cdr/Planning/CommPlans/ FDCP/RDEIR/Appendices/deir%20rfdcp%20appendix%20b%201.ashx Nixon, K. (2002). The Oak (Quercus) Biodiversity of California and Adjacent Regions1. US Forest Service. Retrieved July 10, 2011, from www.fs.fed.us/psw/publications/documents/psw_gtr184/psw_gtr184_001_Nixon.pdf North Fork American River Trail. (2006, June 1). Welcome to Beautiful Placer County California. The official website.. Retrieved July 8, 2011, from http://www.placer.ca.gov/Departments/CommunityDevelopment/EnvCoordSvcs/EIR/NorthForkTrail.aspx North Fork/Middle Fork American River Sediment Study. (2007, April 1). USDA. Retrieved July 7, 2011, from www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5275882.pdf Stuart, J. D., & Sawyer, J. O. (2001). Trees and shrubs of California . Berkeley: University of California Press. Tappeiner, J. C., & McDonald, P. M. (n.d.). Arbutusmenz. Northeastern Area State & Private Forestry - USDA Forest Service. Retrieved July 10, 2011, from http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/arbutus/menziesii.htm 23