From Introduction: "Uranium has been discovered in fluvial quartz-pebble conglomerates in most of the Precambrian shield areas of the world, including the Canadian, African, South America, Indian, Baltic, and Australian shields. Occurrences in these and other areas are shown in Figure 1.1. Two of these occurrences, the Huronian supergroup of Canada and the Witwatersrand deposit of South Africa contain 20-30 percent of the planet's known uranium reserves (Nininger, 1974). Thus it is critical that we understand the origin of these deposits and develop exploration models that can aid in finding new deposits."