This document summarizes a field trip taken by the author to the Middle Fork of the American River near Auburn, California. The author provides background on the geological history of the area, describing the sedimentary and metamorphic rocks present such as sandstone, greenstone, and serpentinite. Samples of these rocks are photographed. Plant and tree species observed along the river include Pacific madrone, canyon live oak, and Mexican manzanita. Brief evolutionary histories are provided for these plant species.

1. John Fors Professor Lawler GEL 104, Summer 2011 July 10, 2011 Middle Fork of The American RiverField 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 Google 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 (“North,” 2006; “North,” 2007) 7

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

10. Identification: I believe this is Serpentinite, a plutonic igneous rock type(Hill, 2006) 9

12. Greenstone and green schist belts are primarily formed of fine-grained volcanic rocks, dominated by basalt, with minor parts sedimentary rocksDescription: weathered red/brown color, fine-grained, can be scratched, faint layering Identification: I believe this is Greenstone, a metamorphic rock (Hill, 2006) 10

13. 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

15. Process driven by heating/freezing cycles, as well as erosion from water, snow, and ice

16. The large boulder mayhave come down by rock fall from higher up in the river canyon as part of ongoing erosion13

17. 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

18. 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 under the surface) 15

20. Ericaceae is under the order Ericales, which evolved from Magnoliales, which in turn descended from angiosperms originating in the Mesozoic Era

21. It has high tolerance to poor soil, drought, extreme temperature, shade, and elevation; which enables it to thrive in many different habitatsI believe this tree is a Pacific Madrone(Arbutus menziesii) (Stuart & Sawyer, 2001) 16

22. Evolution of Pacific Madrone(Arbutus menziesii) 17 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.)

23. 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 It is part of order Fagales, also descendant from angiosperms May live for up to 300 yrs I believe this tree is a Canyon Live Oak (Quercuschrysolepis) (Stuart & Sawyer, 2001) 18

24. Evolution of Canyon Live Oak (Quercuschrysolepis) 19 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, LithocarpusandChrysolepis are insect-pollinated, thus causes major differences in their flowers Chrysolepis the most common member of Protobalanus group in California (Crepet & Nixon,1989; Nixon, 2002)

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. Also from angiospermsI believe this shrub is a Mexican Manzanita (Arctostaphylospungens) Belong to order Ericales (Axelrod, 1958; Stuart & Sawyer, 2001) 20

28. Evolution of Mexican Manzanita (Arctostaphylospungens) 21 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) (Adams, 1935; Markos,1995)

29. Evolutionary Tree of Angiosperms 22

30. 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