Some two million years ago at the end of the tertiary era the mountain range system in the west of the United States had a tremendous amount of accidents and geological vibrations that changed its character to what they are nowadays. It was during this same period, when the current drainage network consisting in creeks, brooks and rivers was formed, which normally flows westward.
Previous to this period there was a vast and different system of rivers, which generally flow southbound. These were the ancient streambeds that existed during great part of the tertiary era, and that is why they are called tertiary channels or ancient rivers. The ancient rivers existed for millions of years, time in which they caused huge erosion, washing up considerable amounts of gold from the rich lodes deposits to the rivers.
The greatest changes happened at the end of this era, which rearranged the mountains forming the current drainage system, leaving some portions of the ancient channels adrift. Some portions were left on top of the current mountains. Others ended up I n deserts. And some of these portions were left next to or in the present drainage system.
Ancient channels which have been discovered and exploited have proven many times to be extremely rich in gold deposits. In fact, many of the most prosperous found in the present river system, have been discovered downstream in places in which many layers of gravel have crossed. Other areas in current system that have proven to be very rich have been located near ancient channels, where some two million years of erosion have caused that part of those channels and gold erode to current streambeds.
Ancient channels (benches) are recognized because of its very rich lower strata. This strata is sometimes of deep blue color, and truly, when one finds oneself with this rich deep blue color it is most surely an indication that there is an ancient gravel there. The lower strata of ancient gravel were known in the past as “blue lead” probably because ancient miners followed their way to the west to wherever it could get. Ancient blue gravel generally gets rusted and turns a rusty brownish-reddish color after being dug out and exposed to the atmosphere. It can be very hard and compact, but it is not always like that.