Gold Mining On The Yuba River The Ancient American River, Ancient Yuba River, Ancient Calaveras River, Ancient Mokelumne River, Ancient Tuolumne River, Ancient Magalia Channel, Ancient Intervolcanic Cateract Channel, Ancient Intervolcanic American River and the Ancient Jura River (from the Jurassic Period), are plotted in detail on Big Tens California Gold Map 5. The present-day rivers bearing the same names as their ancient rivers are also shown. The Ancient Rivers of Gold in northern California are from the Tertiary Period. The Tertiary rivers existed millions of years ago and many of them had large quantities of gold within their gravels. Because of that, they are known as the “Ancient Rivers of Gold.” Each ancient river is discussed below. Information on this page is based on the classic work of Waldemar Lindgren of the United States Geological Survey and by study of Big Tens California Gold Map 5, which shows the relationship of the ancient rivers to landmarks, such as roads, creeks and towns in the region. These now-dry Tertiary rivers are thought to be a prime source of the gold found in many of the rivers and streams of the Mother Lode region of northern California. The ancient rivers are discontinuous and sometimes follow tortuous routes. They have been altered by volcanic activity, erosion, and in some instances portions of the rivers have been covered by lava. Much of the region underwent extreme volcanic eruptions. Volcanic flows have been found up to 4000 …