Flux of Siliciclastic Grains in Sediments

Abstract

In the interval between their birth from crystalline rocks and their death by metamorphism, detrital silicate fragments suffer two major types of indignities: size reduction and selective destruction of their less stable comrades. The fact of size reduction is well established but its amount is not because of the confounding effects of sorting of grains by wind and water during grain transport and later dissolution of grains during diagenesis. A significant proportion of grains, particularly the more stable ones, may resist diminution, even unto death. The quartz content of primary source rocks of sediments averages only about 20 percent, but the percentage is quickly increased by soil-forming processes in the humid temperate and tropical climates that have dominated during most of Phanerozoic time. The average detrital rock (75 percent mudrock, 25 percent sandstone) contains nearly 40 percent quartz and 45 percent clay minerals, testifying to the effectiveness of surface weathering, although dissolution ...