Field Trip To Ione Basin--October 22, 2002

Western Foothills Of The Sierra Nevada

Amador County, California

The bushy shrubs in foreground and middleground are the Sticky white-leaf manzanita, Arctostaphylos viscida, observed near Lygodium Gulch, one of the great fossil leaf localities in the Middle Eocene Ione Formation, western foothills of the Sierra Nevada, Ione Basin, Amador County, California. In the background is a dramatic, striking geologic contact in the Ione Formation--where brilliant white, massive fluvial (river-deposited) sandstones (mined for the commercial grade content of silica elsewhere in the Ione Basin) underlie thinly bedded reddish-brown shales and sandtones that contain a higher percentage of biotite and feldspar than the white sandstones below. Such a shift in mineral content demonstrates that the reddish-brown shales accumulated under paleoconditions that were less humid and rainy than the white sandstones below. Image snapped on October 22, 2002.

Please note: All fossil localities in the Ione Formation of Amador County, California, presently occur on private property; explicit permission from the land owners must be secured before collecting fossils there.

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