Mineral composition of Mississippi River sands

Abstract

INTRODUCTION Plausible hypotheses often become established as generally accepted facts by the mere passage of time and the lack of a direct challenge. Geology has afforded, and still affords, numerous examples of this principle. The particular case to which the writer wishes to call attention is the hypothesis that certain minerals, particularly the pyroxenes, amphiboles, and feldspars, are rapidly eliminated during transportation, and hence, that their presence in sediments indicates proximity to source rocks. Conversely, from this hypothesis, their absence indicates (1) deep weathering of the source rocks, or (2) derivation from pre-existing sediments, or (3) transportation for a considerable distance from the source area. To most students of sediments, a “considerable distance” apparently means, in this instance, only a few hundred miles. The literature dealing with clastic sediments is so full of cases in which this hypothesis has been treated as accepted fact and used as a basis for . . .