Abstract
Abstract A total of one hundred ten samples of quartz grains, two-thirds of them from the southern and northeastern coastal regions and the lower Amazon valley, from sands and sandstones ranging in age from Precambrian to Recent have the same general characteristics found on other continents. Wind-worn grains are characteristic of the Devonian, Carboniferous, and Triassic. Water-worn grains are particularly abundant in the Tertiary of the Amazon basin. Grains in the Precambrian Minas Gerais series are unusally limpid and show relatively little wear. The tillite of the Carboniferous Itarare group in the southern coastal region contains abundant wind-worn grains of periglacial origin.
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