IdahoAl Posted February 4, 2015 Share Posted February 4, 2015 Hey Steve, About 30 years ago I lived about 35 miles NW of Gerlach Nev. and my Dad was raised in that country. When I was a youngun about 60 some years ago I was with my Dad traveling from Herlong Ca. to Gerlach and my dad pointed out a dry lake between Nixon and Gerlach and said that when he was a kid he rode on a commercial fishing boat on that lake. He told me what the lake was called but I can not recall. So there have been some drastic changes within the last hundred years... Link to comment Share on other sites More sharing options...
doc holiday Posted February 5, 2015 Share Posted February 5, 2015 Steve please continue to post info such as this because the geological changes on the earth are indisputiable ---the rub with a lot of folks is that the pols try to take natural occurances and place a tax on them.The REASON I read your site is for real and scientific information. 1 Link to comment Share on other sites More sharing options...
calgeologist Posted February 5, 2015 Share Posted February 5, 2015 On 2/4/2015 at 11:58 AM, Steve Herschbach said: I have to admit I have a heck of a time deciding what is old glacial material and what might be old stream material or even ancient beach deposits at times. They can grade imperceptibly from one into the other. Good news with a detector is, well, just detect the darn stuff and see what happens. Just a quick way to check (by no means always the case) is to look for any sort of bedding within the gravels. Most stream conglomerates show a high level of stratification, fining upwards as is the case with inside bends (point bars). A FANTASTIC place to see this is at the Gold Run rest stop on the westbound side of highway 80. You can get up and close with the big tertiary channel and stick your nose right on it from a safe location. Its incredible the amount of scouring, bedding, and grading that you can see. Now if you are working in a intervolcanic channel like are common in the motherlode, then things get a little more challenging. (Picture 1) This shows the base of the channel where there is no bedding at all. Look at the chaotic nature of the boulders and smaller cobbles. The matrix of the conglomerate is also clay produced from the weathering of the volcanic material. Compare this chaos to nice bedding (Picture 2). Where it gets really tricky is comparing intervolcanic conglomerates with glacial deposits. Since the defining characteristic of both is that there is almost no sorting of the stream load you need to inspect the rocks a little more closely. The first thing I look for is a change in boulder type. In the Sierras this is very easy to see. The rocks that dominate the tertiary channels are largely metamorphic and in my area lots of blue lead (serpentine). The rocks that make up the glacial deposits are dominated by granites eroded from the batholith to the east. Picture 3 and 4 show what some recent Sierra glacial deposits look like. Picture three is till, while picture four is deposition of glacial outwash sediments above modern day river deposits. Now a lot of the generalities that I have mentioned apply to the Sierra, but the biggest thing that is a dead giveaway for glacial sediments is a change in rock type (provenance) and the utter chaotic nature to the material. If you have examples of glacial material that is bedded I would love to see them just out of curiosity. Hope this helps a little, at least in the general sense. 5 1 Link to comment Share on other sites More sharing options...
Rick K - First Member Posted February 5, 2015 Share Posted February 5, 2015 Great thread. Here in the UAE there are a lot of ancient sand dunes buried under new ones, along comes a road cut and the cross bedded layers are revealed. No gold of course, excep on the Bedouin ladies' wrists. Link to comment Share on other sites More sharing options...
wwace Posted April 20, 2021 Share Posted April 20, 2021 I have been up close with some glaciers and am familiar with the moraines from the last Ice Age. I think there could be quite the difference as a mile thick ice sheet does quite a number on terrain compared to a receding glacier, which I thought could expose pre glacier placer or a new lode and its associated placer. Glacial till I see leaves stream rocks exposed far away and above current drainages and hundreds of feet to bedrock, without a visible clay layer I wouldn't bother looking for gold even in a rich area under that condition. Link to comment Share on other sites More sharing options...
Steve Herschbach Posted April 22, 2021 Author Share Posted April 22, 2021 On 4/19/2021 at 8:25 PM, wwace said: without a visible clay layer I wouldn't bother looking for gold even in a rich area under that condition. Spent most of my life where ice was a mile thick, and nearly all the gold I’ve ever found was related to glacial action. Most glacial action is more recent than the massive ice sheets, with most small Alaskan glaciers being Pleistocene age, for example. Nobody not interested should waste their time in glacial terrain. I’m just the opposite. I’ll run a detector over anything just to see. I’ll never forget a patch I walked past for a decade because “gold can’t be there”, until a novice who was not as smart as I dug there and found out there was. Glacial terrain can be exciting as gold can literally be anywhere or nowhere. Glaciers also bury and preserve pre-glacial placer that can be very rich. Crow Creek Mine near Anchorage is a perfect example. 2 Link to comment Share on other sites More sharing options...
HardPack Posted November 19, 2023 Share Posted November 19, 2023 Steve, Any current follow up updates regarding Sierra Nevada glacial deposits. Great post. Link to comment Share on other sites More sharing options...
Steve Herschbach Posted November 19, 2023 Author Share Posted November 19, 2023 Well, no, everything posted is just as valid now as it was two years ago. But thanks for the kudos. Link to comment Share on other sites More sharing options...
HardPack Posted November 19, 2023 Share Posted November 19, 2023 Steve, You may find the articles on the Sierra Geology Org. site interesting. https://sierrageology.org Link to comment Share on other sites More sharing options...
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