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Glaciers & Gold


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The earth has been warming and glaciers retreating for over 15,000 years. Almost everything in the part of Alaska I lived in was recently exposed by glaciers and been prospected the last couple hundred years. Glaciers are nature's bulldozers and they destroy and mix. The gold distribution in glacial material is generally random and sparse. Where water has had time to work glacial deposits new placers can form, but the short geologic time spans we are talking about usually mean small erratic deposits. The good news is that also means you can maybe find a gold nugget just about anywhere in glacial material.

If you watch the video a second time and pay attention to the area that becomes Alaska you will see that Anchorage, on the southern coast, was buried under 3000 feet of ice not too long ago. The interesting part is northern Alaska is largely ice free. This is extremely important. The placers are much older and more extensive in Interior Alaska than in the southern coastal areas.

The northern US was heavily glaciated and much of the material was pushed down from out of the north in Canada. I find glacial terrain interesting because glaciers have melt water running under them and along the edges, which form small oddball placers in the strangest places, and other placers are possible in the large outwash areas.

I am discovering there was a lot more glacial activity in the Sierras than I would have imagined and so this is still very relevant for me prospecting in California.

These links may not be for your exact area but all contain good information about glacial geology and prospecting.

Great freebie article Gold in Kansas

And a small related article at the ICMJ Undiscovered Placer Deposits in Alaska

Really good stuff starting page 117 on Gold Placers of Colorado

Placer Deposits of the Yukon

Geology of Tertiary and Quaternary Gold-Bearing Placers in the Cariboo Region, BC

Here is some really technical stuff for those so inclined Glacial Geology & Prospecting

Glaciers of California

A much more prospector friendly version can be had in an excellent but pricey book by Chuck Lassiter, Midwest Gold Prospecting at http://www.midwestprospector.com/book.html

I have a copy in my library of the best of the best. It is a high quality book with color maps and illustrations and a no-brainer at about half the cost. For $29.95 you have to just love books as much as me as that is as much as the Chris Ralph encyclopedia and this book would be a chapter in Chris book. That said, I have never seen the particular subject of glacial region prospecting covered better and more understandably anywhere else. It would be the go to primer for anyone interested in the subject.

 

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  Two very important geologic features to recognize while prospecting the Sierra Nevada are glacial activity and indications of ancient river channel. Time periods need to be more open to question/ debate as there are many non conforming discoveries that don't match assigned ages.

 In Plumas Co. there are Palm tree fossils and glacial scars almost within sight of each other. This ol' planet refuses to behave.

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I love observational geology. Most of the best stuff was people just like us looking at it all and applying common sense to what we see around us. It is still all a work in progress and some stuff changes as new information comes to light. Here is a newer report with lots of references that applies directly to my new backyard.

Late Pleistocene Glaciations in the Northwestern Sierra Nevada http://people.cas.sc.edu/ajames/Research/Pubs/03.INQUA.Log.pdf

I take a practical approach. Ages do not matter much, I just need practical information that I can use to find gold. Knowing an area was recently scoured by glaciers has a big impact on the likelihood of finding placers deposits of any sort there, even just residual placers. Those of us with detectors in particular prefer old land surfaces. But glacial deposits can hold small hidden placers, and those are very high on my interest list at the moment, which is what got me Googling away on this.

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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.

Lots of people have asked me about detecting around receding glaciers in Alaska. Given the number of people who have asked me about this over the years I think it must be the idea of never before seen ground that attracts people. Other than that there is nothing in particular to recommend glacial terrain. Gold placers relay on stream action sorting and concentrating material over millennia. Glaciers are more like bulldozers pushing and stirring everything up. Gold may be there but is more likely scattered. In the case where streams have been running under or next to a glacier and in streams issuing from glaciers there can be some shorter term concentration resulting in lean placers. Ultimately it depends on there being a gold source under or in the immediate vicinity of the glacier. Lacking these there will be no gold. Since glaciers have been receding for thousands of years they have of course been prospected already, and it is not likely that simply receding another mile will all of the sudden reveal gold that was not apparent before. The long story short is prospecting glacial material might produce some gold but due to the scattered poorly sorted material such gold tends to be sparse at best.

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Yeah, I like his stuff. Chris is more skeptical of portions of this one but still many good tips to be gleaned in the text and maps http://www.detectorprospector.com/forum/topic/227-free-book-the-upper-reaches-of-the-sierra-nevada-auriferous-gold-channels-california-and-nevada/

The thing is to not get bogged down the theory parts and just dig for the mentions of bits of geology here and there that might be worth prospecting.

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  No one knows exactly what went on thousands or millions of years ago, its all theory based on what each person believes and see's in their findings. I love hearing about them all, and come to my own conclusions of what may have transpired years ago.

Its all very interesting to me.

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I have read a lot about the subject. It is very apparent as Steve said around the Anchorage area. I have claims on the Willow side of hatchers pass and you can see all kinds of glacial features. You can see where as the glaciers retreated they paused for some time to build up intermediate moraines. The earth does warm up and cool down but I am not getting into the debate. Back home in wyoming most of the lakes on the south side of the Wind River mountains are morainal lakes

Any way I read mid west prospecting and though it was a interesting and great book.

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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...

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