1. Karrenfeld of Columbia, California From Andrew Alden, About.comAndrew Alden

2. Karrenfeld of Columbia, California A karrenfeld is a limestone or marble surface with wide fissures (karren) dissolved into it. Karrenfelds are typical of karst landscapes, where solution is the dominant means of erosion. A large karrenfeld underlies the town of Columbia, in the California gold country, and a neighboring area across the canyon of the Stanislaus River near Vallecito. Take a look at this distinctive geological feature and learn its significance in American history.

3. Columbia Park Machinery Many parks display Gold Rush mining equipment, but in the background, Columbia State Historic Park displays unusual rock formations as well.

4. Town Park Karrenfeld Picturesque, deeply carved outcrops of blue-gray marble (commonly called limestone) occur all over Columbia in its yards and parks. This landscape is a karst.

5. Grassy Karrenfeld These are not loose boulders, but little rounded knobs. Rooted in solid bedrock, they cannot be moved without being cut.

6. Stone Spires and Miner's Cabin Bedrock knobs can reach several meters in height as shown here in Columbia State Park, which commemorates the gold mining days of the 1850s. Miners excavated here, helping to expose the knobs.

7. Columbia Karrenfeld from the Air The Columbia Airport was built by filling in the rugged karrenfeld surface. Near it are large areas of exposed rock.

8. Karren Gone Wild Near the airport, the karrenfeld supports a low, dense scrub. In the 1850s, all of this land was dug down to bare rock by gold hunters.

9. Marble of the Calaveras Formation The stone itself is a tough, coarse-grained marble, part of the Calaveras Formation. Its age is poorly constrained but usually considered Paleozoic (most likely Devonian, ~350-400 Ma).

10. Karrenfeld Shapes The rock surfaces are heavily fluted and clean, as if polished in a riverbed. But groundwater did most of the work without much help from streams.

11. Karrenfeld Surface South of Columbia near Shaws Flat, a particularly rocky area of the karrenfeld displays a planar surface of clints and grikes. The terminology of karst is intricate, reflecting the great variety of forms produced by the interaction of water and lime rocks. Where a flat limerock surface is attacked by water, solution grooves may form along bedding planes or fractures (joints). The surfaces between the grooves are clints, and the grooves are grikes (or grykes). Generally a clint-and-grike karrenfeld is a fairly regular grid. At Columbia the surface is much more irregular, with wider grooves, and is better classified as a crevice karst. In any event, this wide, rugged hard-rock surface acted for millions of years as the riffles in the bed of an enormous sluicebox. Large deposits of gold-bearing gravel traveled over the Columbia area and heavy nuggets were left behind, in seemingly every hollow. The first miners pulled fist-sized nuggets from the ground here starting in 1850, and thousands of gold-seekers followed. Columbia had the richest gold placers ever discovered. Some $500 million worth of gold (at today's prices (~$280/oz c. 2005, or $2.68 billion in 2011 @ ~$1,500/oz)) was dug out by hand in less than 20 years. For a time it was the second- largest city in California. Now all that's left is a state historic park, a marble quarry north of town, and the ancient karrenfeld.a state historic park

12. Sluiceboxes A working replica of this mining tool sits in Columbia State Historic Park. Water washes sediment through the box, whose wooden riffles trap gold particles.

13. Calaveras Formation Marble The same marble crops out near Vallecito, across the Stanislaus River canyon north of Columbia. Erosion has removed any large karrenfeld here.

14. Dissolution Grooves A roadcut on Parrotts Ferry Road displays young solution features on a boulder of Calaveras Formation marble near Vallecito. This is how new karst forms.

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