Creek bed layers

[Prospector B]

So I found myself a little creak which has a few flakes of gold in it which Im happy about and being new to prospecting I decided to dig a hole where I found the gold, the theory is that gold sinks because its heavy. What I found was this, there was nothing in the first 10cm, the next 10cm contained a few flakes and the start of a loose gritty clay layer and then the next 30cm had nothing in it. That last 30cm was also made up of gravel, rocks and the loose gritty clay that I would have thought the gold would have passed through or at least been in.

Can someone tell me why the gold is on top and not also underneath the first layer of clay? I would have thought that the gold would have been deposited in layers after floods or work its way lower but that is not what I am seeing here. BTW the clay was very decomposed and full of gravel, it was very easy to wash out in the pan and was nothing like what I would assume to be a false bedrock layer made of clay.

 

[HeadsUp]

visualise a flood , the clay gets deposited as silt during small floods that wont move the gold

the clay goes hard then a medium sized flood comes along that has enough power to carry gold and deposit it on top of the clay / gravel layers

a flood could have washed away a layer of topsoil or eroded a layer of rock before eventually exposing the reef that contained that gold

then the gold gets washed downstream

then more floods come and more layers

the gold could have come from 200 metres upstream and the layers of silt that became clay could have come from 10 metres away , 400 metres away , or 50 kilometres away

all depends how heavy the rains were that brought them to a creek near you

another scenario is that your bedrock could have contained gold underneath the clay in the past but it has been scoured by extra heavy rain and floods ( " 100 year floods for example" )

big floods could have washed away everything , gold , clay , gravels etc and that could have occurred many times over and over again over hundreds of thousands of years

---

the above are some scenarios but there are a million different permutations of weather cycles as well as freak occurrences where light rain might trigger a landslide that has been building up for release over hundreds of years and you could get a sudden dumping of 3000 tonnes of gravel into the river , including your gold with it.

hope that doesnt cause too much confusification

 

[Prospector B]

Thanks HeadsUp, that's a great reply. I had to read your response a few times to understand it, but I think I get it now

At least the gold is close to the top, makes life a little easier Ill have to dig around some more to figure out what is going on but I will certainly be keeping what you said in mind.

 

[TenOunce Tone]

Great response HeadsUp.

Cheers, Tone

 

[richo966]

very good information mate worth checking deeper for older deposits maybe you may hit rich pay level if it has happened once it could have happened in the past

 

[Prospector B]

Thanks Richo, a rich pay level would be nice I gave up digging because I only carry one of those portable shovels and I had hit a large rock which I could not move. Ill have to find a better spot to dig!

 

[Ramjet]

Great explanation headsup.

 

[dezman]

Interesting as this happened to me today! I kept digging down hill into a smooth bedrock hole in front of a rock bar and after yesterday's show in the pan I was excited. Big rocks amongst gravel and soft clay it looked like it had Been there for some time. But no good at all! I'm guessing the Chinese cleaned it out well long ago and my good show yesterday was from flood gold on top. Tomorrow I'm thinking of taking 6" off the top across the heavy gravel and see how that goes.

 

[richo966]

we have big history of Chinese miners in the highlands good workers they cleaned creek after creek one is named after them I had a go in that creek in 1997 found nothing and it was locked up the next year

 

[HeadsUp]

Thanks HeadsUp, that's a great reply. I had to read your response a few times to understand it, but I think I get it now

At least the gold is close to the top, makes life a little easier Ill have to dig around some more to figure out what is going on but I will certainly be keeping what you said in mind.

i could have worded that post better but i was squinting to see through a haze of porridge brain at the time from doing 95 hours + at work each week for longer than i can remember

i must get my azz out for a dig and some fresh air

 

[G0lddigg@]

headsup nailed it, i still reckon dig till you hit bedrock

 

[HeadsUp]

headsup nailed it, i still reckon dig till you hit bedrock

i do that in test patches and test dig at different strata levels too but sometimes where the gold is found doesnt equate with logic.

as per the OP , i have dug in places that look perfect in every way , perfect looking crevices and holes etc and yet they have no gold while halfway up another strata the gold is found so there are still plenty of mysteries in nature that i have yet to understand.

i just thought of another scenario that i missed above.
You could have stratified gold and gravel sitting on bedrock in the structure we would expect it to be in , but the right sized flood comes along to move the whole lot as a slurry which tumbles downstream , when it does settle it could be in the mixed and unstratified form as mentioned.

You could also have what appears to be an inverted strata where multiple layers of deposits have been formed through numerous mini and medium flood cycles.

One thing i am mindful of when i do dig down to bedrock , is that the bedrock could have been formed from compacted silt or clay and there might be other layers of gravel and bedrock underneath it dating back 100,000's - millions of years old . i carry a 6 foot pry bar and pick for the days when i do feel energetic and inspired enough to try although as yet i didn't discover an occurrence like it.

cheers people

 

[Prospector B]

Wow, I have heaps to learn 8) But strangely thats one thing I like about prospecting, its the figuring out the why so you can get more.

I think I will have to start a new sample hole, somewhere where I can gauge how deep the bedrock might be so I am not digging for ever. I will probably need some bigger tools too

Thanks again for all the great replies, there is some very useful information here that I will be digesting for awhile.