NORTH AMERICA
As a result of a series of microcontinental collisions, the Canadian Shield consisted of a series of high mountain ranges by the Proterozoic Eon. Throughout the Late Proterozoic and Early Cambrian, the Canadian Shield was uplifted and eroded. The uplifted and weathered Precambrian basement rocks (gneiss, granite) provided the source material for the generation of Cambrian sands. Early Cambrian sedimentary deposits consisted of mature quartz sandstones. "Mature" suggests that the sedimentary grains have been reworked over a long period of time such that those common minerals (feldspars, micas, amphiboles and pyroxenes) that break down (weather) will be transported away (eroded), leaving the most stable common mineral: quartz. Early Cambrian deposits in the United States display well-rounded, well-sorted, cross-bedded grains indicative of wind or water transport. These "basal" sandstones were deposited in shallow marine or coastal environments above Precambrian basement rocks. Examples of U.S. Cambrian formations include the Potsdam Sandstone of New York State, the Mt. Simon Sandstone of Wisconsin and the Tapeats Sandstone of Arizona. The transgression of the Sauk Seas and proliferation of marine invertebrates generated thick deposits of fossiliferous Middle to Late Cambrian shale, limestone and dolostone over the Early Cambrian sandstone.
Note i that much of the United States was flooded by the Sauk Seas and that North America straddled the equator. Wisconsin's Cambrian environment was more like Tahiti than the Northwoods. Coastal sediments from these warm shallow seas are preserved as erosional remnants in Central Wisconsin in the form of cross-bedded quartz sandstones. Also take note of the island arc identified as TAC (Taconic arc), located off the coast of what is now the eastern USA. At 440 Ma, the Taconic arc collided with eastern North America producing the first wave of the Appalachian Mountain development!