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April 1999 Field Trip Review

Trip Log: (These notes were taken on the trip and supplemented from the field trip guide. Extra copies of the field trip guide are available from Ray Crowe.) Start -- We met at Shari's at the 10th Street/West Linn exit on 205 and started by turning left on 10th out of the Shari's parking lot. We then turned right on Willamette Falls Drive and continued to 14th Street.

Stop 1 -- Corner of 14th Street and Willamette Falls Drive by the Willamette United Methodist Church. Here lies a replica of the Willamette meteorite. The meteorite, discovered in 1902, currently is in the Hayden Planetarium in New York. The meteorite is believed to have been rafted into the area in an iceberg during the Missoula floods. The lack of an impact crater and the nearby granite erratics prove that the meteorite is itself an erratic. (Dick Pugh and John Allen wrote a report on the site in Oregon Geology about 1989?). The meteorite is composed of nickel and iron and is the sixth largest in the world. It was found in 1902 by Alex Hughes.

Back on Willamette Falls Drive go north about 2 miles to Sunset Avenue. Turn left on Sunset Ave and then left on Chestnut and right to Walnut Street. At the end of Walnut Street is the Camassia Nature Preserve.

Stop 2 -- Camassia Nature Preserve. The preserve shows outcrops of basalt and has kolk lakes -- areas scoured by the Missoula floods. Kolk lakes are potholes with no inflow or outflow of water. An erratic is evidently in the quarry that is part of the preserve. At the time of the floods this area was under about 100 feet of water. The hills of the surrounding area are covered by Portland Hills Silt. The silt is a light brown color and ranges from 25 to 100 feet thick. The silt was deposited by strong winds during the Pleistocene. Three soil horizons separate four distinct layers of silt. This represents the interglacial warm intervals.

Return to Willamette Falls Drive and go back to 10th to 205. Take 205 south around to Tualitin. Turn north on I-5 and then immediately take the Sherwood-Tualitin Road exit. Watch for the library sign on the right. Follow to the Tualitin Library next to the Safeway store.

Stop 3 -- In the library's lobby is the skeleton of the body of a Mastodon found nearby in April 1962. "Tu Tu Tuala" is the name given to the female mastodon. Radiocarbon dating puts the age of the skeleton at 11,300 years. Growth rings on her tusk indicate the mastodon was 27 or 28 years old at the time of death. (The Missoula-Bretz floods occurred between 12,000 and 16,000 years ago.)

Stop 4 -- Just a drive by the place of the Mastodon's discovery -- the parking lot of the Tualitin Fred Meyer just across the Sherwood-Tualitin Road.

Back on the Sherwood Tualitin Road head west through Tualitin and on to Sherwood. At the intersection of Sherwood Tualitin Road and 99W. Turn south on 99W. About 4 miles down the road you will see a sign indicating Parrott Mountain on left. Parrott Mountain at the westernmost edge end of the Columbia River Plateau, lavas coming from northeast Oregon down the Columbia River during the Miocene.

Continue on 99W through Newberg and on to Dundee. Note the red soils in the Dundee area. "The red soils are the Eola surface of old Columbia River basalt that has weathered and decomposed. The soil is great for grape growing." (Field trip guide.)

Continue on 99W to hwy 18 bypassing McMinnville. On out Hwy 18 several miles (don't give up) go past the first small brown glacial rock sign, to the geology marker.

Stop 5 -- Geology Marker -- is a description of the flood and how the glacial erratics arrived. You can see the large glacial rock from here.

Continuing on Hwy 18 for about .5 to 1 mile is the second turn off for the Erratic State Park. Follow the signs.

Stop 6 -- Erratic State Park. The rock is called the Belleview erratic and is the largest such erratic found in the Willamette Valley so far. It is at an elevation of 306 feet. In 1950, the rock was found to weigh about 160 tons. Over the years, people have taken souveniers from the rocks amounting to about 70 tons. (Cataclysms on the Columbia, J.E. Allen and M.Burns)

Stop 7 - "Terraces along Hy. 18 in the Yamhill Valley and west, past Erratic Rock Wayside, dip to the next flat surface where the current flood plain exists. North and west of McMinnville is seafloor basalt which crops out past the Willaminia-Salem intersection. Prior to Willamina, watch for seafloor sandstones. A roadcut at the Sheridan exit has exposures of basalt pillows." (field trip guide)

Stop 8 -- Spirit Mountain Casino for lunch. Grand Ronde. "To the south are shale, sandstones, and basalts. During the Pliocene, continued subduction of the Juan de Fuca plate and growth of an offshore accretionary wedge has renewed the uplift and tilting of the Coast Rnage and folding of Willamette Valley rocks." (field trip guide)

Stop 9 - Stewart-Grenfell County Park. "North of here a low rise of 500 feet may have let some of the flood waters spill over to the ocean via the Little Nestucca River." At this stop, people looked for cobbles containing fossils and for cobbles composed of quartzite.

Members on this field trip: Ray Crowe, Leader, Carol Hasenberg, Lyle Groves, Michael Stuart-Champion, Frank Poundstone, John Schriever, David Schriever, Dick Cheadle, John Hawthorne, Jeralynne Hawthorne.


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