The reason it has to do with that specific time frame of formation is it coincides with the laramide oregeny and all that gold rich rock was subducted, melted, and redeposited in vein structures of epithermal nature and in secondary enrichment zones in some cases via groundwater, theres also good gold in a different ore assemblage in the near pre-cambrian granites. Thats my first step before I ever touch any maps is dig up the USGS report outlining what formations the gold is known to occur in then connecting that with known geological events, it completely cuts out any guess work of where the gold is coming from, what rock type you find it in, given the age of the formation / resistance to weathering and annual climate of an area you can determine whether placering or lode will be the most efficient way to mine. I think a lot of people fail to make this connection and thats why they often are confused as to why the granites in AZ contain fantastic high grade veins and the Granite state has little but fly poop gold that which has zero to do with granite.
If you are looking for workers for next season inland mining I'd be interested. I work circles around 9.9/10 people I meet, am 26 with no kids nor any real commitments at this time, am a total gold junkie. Fairly good at prospecting new grounds as well. Shoot me an email if you want to chat more.