Sunday, September 7, 2003

Visit to Green Valley

Green Valley is near Dutch Flat and Alta on the North Fork American, just where the weak serpentine of the Melones Fault Zone crosses the river, and the canyon widens, the walls recede, and large glacial outwash terraces of multiple ages cloak many slopes. Two thousand people are said to have resided in Green Valley in 1851-52. Saturday, Gay Wiseman, Neil Gerjuoy, his friend Cindy, and I, walked down the old mule trail by which Green Valley was provisioned in the old days. In some places it is worn and eroded into a narrow trench. Mule trains came up from Illinoistown (~Colfax) to many mining camps, such as Little York, Dutch Flat, Cold Springs (now Gold Run), and Green Valley.

Later in the 1850s wagon roads reached Dutch Flat itself, and the pack trains to Green Valley and the other remote or canyon-bound mining camps left from Dutch Flat, Gold Run, and Towle.

Helicopters thundered constantly across the canyon to the south, filling their water buckets at Sugar Pine Reservoir, and then zooming east and south to the Codfish Fire, near Deadwood Ridge. The day was sunny and clear, tho a pall of smoke had lifted out of the canyons near the fire, and drifted slowly across the main North Fork canyon to the east, as the upslope winds increased in strength.

We took the High West Trail and threaded our way down to the very end, below the bluffs of the Green Valley Blue Gravel mine, and near the site of the old suspension bridge, torn out by a flood several decades ago. I have two old photographs showing one incarnation that bridge, ca. 1940. This bridge is mistakenly shown very far upstream to the east, on the USGS 7.5 minute "Dutch Flat" quadrangle.

At the river a fresh strong breeze stirred the trees and ruffled the river and we could no longer hear the helicopters.

After a lunch break, Gay and Cindy swam the huge deep pool at the end of the trail, a spot also notable for its fine view of Lovers Leap, rising 2300` above the river, just to the west. Neil and I went upstream to the bridge site, forded the North Fork, admiring the masses of cemented glacial outwash, and took the trail climbing west to the Gold Ring Mine. We continued right past the old, Depression-era log cabin, following the trail across the meadow, and into Giant Gap Gulch, where the path plunged right down to the river. Somehow I had missed the correct trail, which stays high, so we climbed steep slopes adorned with poison oak to this true trail, and continued west.

The trail passes a number of mining areas which involve patches of glacial outwash. Apparently the glacial outwash in general, and the cemented outwash in particular, was rich with gold, and stamp mills were dragged down here in the olden days to pound it up so it could be run through sluice boxes.

The trail narrowed drastically as it approached the North Fork, and crossed some rather steep slopes, just where one would wish it broadest, but soon enough we were on the sparkling clear stream again, just upriver from the Gate Post, a remarkable column of rock which rises right from the water, where the river leaves the shattered serpentine of Green Valley for the massive metavolcanic rocks of Giant Gap. The faulted contact between the Melones serpentine and the Calaveras Complex metavolcanics is very near the Gate Post, and an especially fine pool is just downstream. The last significant deposits of Green Valley's glacial outwash sediments, including some cemented gravels, on the south bank, are just here, just at the contact. Farther downstream, in Giant Gap, the slopes are too steep to have preserved such sediments. Springs likely associated with the more fractured rock in the fault zone, which zone forms a near-vertical plane crossing the canyon obliquely, are on both sides of the river, that on the south bank still flowing nicely.

Fording the river again, we climbed up to the line of the Giant Gap Survey on the north canyon wall, 150 feet above the river, but did not follow it very far. On the way to the river from the Gold Ring Mine I had looked across and seen two major sections of the Survey, where a narrow bench cut had been blasted from the cliffs a century ago, part of a scheme to divert the waters of the North Fork and deliver those waters to San Francisco. However, these sections of the Survey were on very steep cliffs, and the bench cuts did not look to be properly continuous, in fact, it looked difficult to impossible for someone to really hold the line of the Survey, over there, just upstream from the Gate Post. These sections were the last crossing the serpentine, before the Survey entered the tough Calaveras Complex rock of Giant Gap.

Dropping back to the river, we swam the fine pool below the Gate Post, admired the wildflowers, especially the purple asters, and the fine views of the Pinnacles, to the southwest, and then made the pure scramble up the north bank of the river back to the West Trail Pool. After some more snacking in the shade of a big alder tree, we started a long slow slog up the trail, reaching the top about 7 p.m.

Such was a fine day in Green Valley and at the eastern entrance to Giant Gap.

No comments: