Geology tour of the Yuba River’s Buttermilk Bend Trail |

Geology tour of the Yuba River’s Buttermilk Bend Trail

A view of the South Yuba River from the Buttermilk Bend trail. Docents wil be leading a geology tour along the trail at 1 p.m. on Saturday.
Submitted by John Field |

South Yuba River State Park docents will lead a geology tour on the Buttermilk Bend Trail at 1 p.m. on March 17. The tour will include a lecture to provide background on the park’s complicated geologic history and then a walk to observe some of these geologic features on the trail. Participants will also receive a tour guide, entitled, “Geology of the South Yuba State Park — A Self-Guided Tour on Buttermilk Bend Trail.” This guide is available on the Park Association’s website at and will also be available in hard copy in the visitor center.

The objective of the Geology Tour is for participants to learn a little bit about the complex geologic history of the area and about the rock types along the Bridgeport portion of the South Yuba River. There will be a general geology review at the beginning of the tour to provide background for the geologic terms and concepts that will be discussed while walking the Buttermilk Bend Trail. The review will also give participants some information on the park’s regional geologic setting. The area bounded by South Yuba River State Park was an important gold-bearing site during the California Gold Rush in the 1850’s and again in the 1930’s during the Great Depression. The geologic history of these gold deposits will also be touched on in the tour.

The South Yuba River within the state park cuts through four major tectonic belts (assemblage of rocks of any origin that have been folded or mixed together). Like a surgeon, the 20-mile long scenic river canyon within the park has cut an incision across these belts. This has provided geologists with a cross-section of the ancient oceanic-continental tectonic plate boundaries within the park during Jurassic (about 160 million years ago) and older times. Participants will learn details about these relationships and more specifically about the rocks exposed within the South Yuba River State Park at Bridgeport.

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