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California's Ancient River
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Home California's El Dorado -Secrets of Geology and finding gold treasure!
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This Google Earth screenshot shows limestone rock protruding through the soil on the east side of new Stanislaus and just above the old Pine Log gold camp located on the South Fork of the Stanislaus. The elevation here is 2150+/-. Pine Log town is gone for many years of course-destroyed by fire and repeating floods of the South Fork. But in it's short-lived heyday 1853, the town though small was as rich an rowdy as any California gold camp. This was placer gold eroded from the Eldorado located well above the South Fork riverbed as it exited from the overburden of volcanics underwhich it was buried. One of the few remaining placer claims in this area was here on the South Fork just beyond old Pine Log until flooded by the Melones reservoir.

Columbia represents the best evidence of the ancient Eldorado. The cemented river gravels here were rich gold placers for over 10 years of hydraulic blasting. The pay dirt lay welded in between huge boulders of Calaveras limestone. The old river course was confined in place by a geologic bowl as ice ages waxed and waned. As the ice, melting and freezing again, forced the great blocks apart, the wandering river, from time to time, cut down in deep channels and deposited ever more gold in the gaps wedged open by ice. When the hydraulic monitor could not be focused directly on the face of the gravel, miners hacked the hardened gravels and moved it to the water for processing in the rocker. The Boulder Range at Knapp's ranch near Columbia proper yielded a 50 pound gold nugget. An unknown number of huge nuggets were secreted away from the Columbia diggings without ever being recorded.

The area at Columbia known as the Boulder Range consists of large limestone blocks weathered by the slightly acid rainwater leaching down through the thin topsoil. It was discovered only shortly after the digging at Columbia started because the soil horizon was immediately apparent. The pay dirt between the boulders was the source of big gold nuggets. Ancient Eldorado flowed over the top of the limestone basement repeatedly depositing gold in the deep channels between blocks of stone. The region was buried by volcanic ash and mudflow that decayed to a thin soil that uniformly covered the boulders. Note in the above image that the distant terrain is absolutely flat with the tops of the boulders in the foreground at the same elevation. The native thin soil of 2-3 feet sits atop most of the boulders. The miners knew the gold lay at depth and simply did not process the top soil.
A gold explorer should look for large areas near 2150' along the path of Eldorado that are flat +/- 100' and do not have a complete horizon exposed. The post hole digger is handy to take samples at depth. If limestone formations are exposed, check if the rock has the characteristic appearance seen in the image; described as smooth and unusual distorted shapes. The geo-chemical action on the stones is the same as what happens to build caves. Any area with treeless and flat terrain should be checked. The slow etching of the stones by acidic percolation and tremendous force by ice created the "Boulder Range". The boulders set about 1/2 mile east and 100' higher than the Columbia township main street.
The Ancient Eldorado is much older than today's mighty Sierra rivers and somewhat older than the so called ancient tertiary rivers referred to by Lindgren's study. The Ancient Eldorado formed as the original Sierra Nevada range stopped it's growth and started to erode away some 50 million years ago. The tributaries of Eldorado and the entire river drainage system looked very similar to todays Sacramento system. A smaller coastal range kept Eldorado running north to south and parallel to the old Sierra. After millions of years the erosion had leveled the mountain chain to a low flat plain. Much of the gold of the entire old mountain chain was deposited in the riverbed of Ancient Eldorado. Some 5 million years ago, the Pacific and American plates once again collided and a new Sierra was born. In birthing the new, the earth buried the old river under the ash and mud of the new mountain chain. The quartz riddled plutons of the new mountains did penetrate the old river valley but insufficient time has elapsed for these quartz veins to have eroded to source all the gold in Eldorado. Eldorado gold looks the same as modern gold but is simply laid down millions of years before.

The secret of where to look for gold is in knowing the geology of the gold country. Very simple and straight forward. So simple in fact that most folks want to make it more complicated. Don't be tempted to make it harder than it should be. It'll be hard enough for the gold tracker to scramble over some of California's toughest terrain. So let's keep it simple and safe. From what is seen here, the key is sampling along the 2150' terrain line on the topographic map. To review the geology return to the previous gold pageHome Gold Page or continue on to more Southern Mines Sonora Gold Page or north to Murphys Murphys Gold Page
American Camp and French Camp are two additional Gold Camps in this area above the Italian Bar. As was described on the geology page, the valley of Ancient Eldorado was low, flat, and very wide. The elevation climbed very slowly away from the main channel(s). So many streams draining into Eldorado contained gold as well. These two are examples of that. The satellite view shows many flat areas with no or very sparse vegetation and located only slightly above the 2150' reference elevation. These are deeper stream channels that were filled with volcanics. When the face of these areas are exposed, look for white, grey, and pink clays. The bottoms of these clays should always be sampled. While the metal detector is a valuable tool, the comprehensive testing can only be done by extensive sampling. On a morning's walk along the 2150" line, samples are taken in low spots, tiny stream crossings, or inviting flat areas. Finding clay, always sample regardless of how the clay lies. The Google Earth provides another look at the terrain and whenever green grassy areas appear, as happens at both American and French camps, the prospector should take time to sample in and around the green grassy areas. These areas frequently mean seeps and springs. The eroded rock (clay) of the ancient river or stream bottom holds rainwater and releases it slowly to create springs. In 1870, well after the height of the gold rush, a prospector found a pocket of gold "among "the grass roots" in the American Camp area that sold for $8,200 dollars. At USD $20/oz that equal some 410 oz. At today's price of USD $1842 that would be over $700,000! Was that grass over a spring seep as discussed? Take at least several dozen samples, annotating the GPS position of each on the map. Plan for an easy exit to the vehicle as the backpack will be he heavy with the samples. Returned to camp and processed in the pan, the samples will tell where the gold is located on the map.
The red cross on the topographic map is the center of the 2150' limestone formation shown in the satellite image. While unlikely that this area has never been prospected, it is remote and may be undiscovered. Note how the area sits above the map curiosity of Elliot's cabin, a feature on many maps of the area since the 1945 editions of USGS topographic maps. Speculation would be that maybe Elliot had a claim in the area, as remote as the cabin is. An educated guess would say yes- a good chance that gold is here as Columbia sets not to distant across the South Fork at an elevation of 2140'. This area would naturally drain down Stoney Gulch to feed the Pine Log placers as well. If nothing else, it shows Eldorado passed this way at some point in the past. To get here Italian Bar: from Columbia take the Italian Bar road north out of town. Once at Italian Bar, go up Silver Gulch the top like going on to Rose Creek. At the top, turn left onto Forest Road NF3N15 (Ponderosa Way). Continue west past the old fire watch tower location to the intersection with Pine Log trail. Park and hike the (ridgeback) trail down to the the GPS location W120º 24' 08.5" N 38º 05' 4.6". This is a difficult hike out and only the experienced hiker should attempt this. Always prospect with another person and plan your prospect in advance. The National Forest personnel don't have hike plans per say, but you should leave a hand written hike plan that contains contact information at a NF field office in the area.

The path of Ancient Eldorado as it leaves the Matelot Gulch just above Columbia township at the 2150' elevation is marked in gold. The path is cut away by the erosion of present day South Fork of the Stanislaus. The eroded ancient riverbed is the source of the gold at Pine Log camp. The river, flowing north to south, created an oxbow and oxbow lake on the left hand (north) side of the valley. During a long period of time, this created a cavern below, which eventually collapsed some time later. The interior of the depression is scored by numerous fault blocks in the limestone. Within these cracks and openings is the obvious place to sample with the post hole digger. These rocks are large and the crevices are dangerous places. Only the experienced prospecting company should enter this area. Use caution.

While not as large a river as the current day Mississippi, the meander and cutoff oxbows of Ancient Eldorado were similar.

Another example of the assured path of Eldorado is the famous event at Shaw's Flat just south of Columbia. In 1855 Shaw's Flat was throughly depleted of gold bearing pay dirt after 4 years of intense surface mining. But in that year the richest channel of gold bearing gravel in California history was found at depth on the Western side of the flat. The olivine glass top of volcanic and perfectly flat Table Mountain towered above. The placer was so rich that small operations yielded 10 pounds of gold per day. Mine operations soon swarmed the area and worked under the conviction that the gold channel must somehow be connected to the Table Mountain and the old river bottom beneath it. Dozens of shafts and tunnels penetrated the mountain at great effort and expense- all to no avail. The scanty gold was not enough to keep the water pumps running and within a decade the entire effort foundered and was abandoned.
Millions of years ago Eldorado wandered about in this area and on one or more of the excursions away from the main flow, an oxbow developed far to the right side of it's ancient valley. Before retreating back towards the center of the valley, it dug a deep channel which resulted in an oxbow lake. The rainwater in the lake percolated through the limestone and carried the dissolved calcium carbonate away to create a large cavern beneath. Some time later, the cavern collapsed creating a large sunken channel. Later still, Eldorado returned to fill the deep hole with gold laden gravels. Very much later in time, the old Stanislaus passed very nearly upon the route of the Ancient Eldorado. The hard volcanics of todays mountain building episode entombed the old Stanislaus riverbed.
The miners of Shaw's Flat had found this ancient cavity filled with gold bearing gravel not realizing the real source. The rich pay dirt of the sinkhole was soon panned out, making a few lucky miners rich for life. They cleaned out the inside track of the ancient oxbow and the gold simply ended at the termination of the oxbow. So finding such a sinkhole in the path of Eldorado certainly requires investigation. One such area exists north of Columbia above the Pine Log and is labeled "Cave Country" on USGS terrain maps. A large anomaly on the map is the circular and steeply descending terrain immediately to the left of the "Cave Country" label. The center of the sink at 2150' features large irregular cracks in the jumble of calcareous boulders.This could be a large sinkhole created by Eldorado and could be the source of gold found at Pine Log, hundreds of feet below on the South Fork of the Stanislaus.

Striated blocks of limestone penetrate the soil in another flat region above the South Fork of the Stanislaus above Pine Log. Located at N 38degrees 05' 06.5" and W 120degrees 24' 10.45". This area could be accessed by the previous route described : have a support boat on the South Fork Stanislaus in advance; from Ponderosa Way hike down the ridgeback to the area. This area is BLM property subject to claim. After the prospect is completed, continue down to the boat. This will be much easier than hiking back up as the sample packs will be full.
The use of barbed wire in the West introduced the clam shell post hole digger in the 1870's. The 49ers did not have use of the post hole digger; using pick and shovel, jack knives, and even spoons to scoop and pry the easy gold from the crevices of the stream bottoms. So many gold reserves remained because the prospect sample(s) did not go "down" to the bottom of soil to reach country rock in the terrain well above the stream courses. This area of the image shown is the ideal place to utilize the post hole digger between the exposed limestone rock. The shadows of the protruding rocks indicate they could be standing several feet above the soil line and the crevices between boulders also several feet deep. That would indicate a long period of weathering and perhaps ancient stream flow. Be reminded the surface can be barren of gold but hidden 4' below is a bonanza of gold.