Reconstruction of the original extent of the Tertiary pre-volcanic gravels in the northern Sierra Nevada (CA): Implications for the range's Paleotopography

Abstract

The ancient auriferous gravels that helped spawn the California Gold Rush have figured prominently in investigations of the Cenozoic history of the Sierra Nevada. These fluvial sediments, scattered throughout the northern half of the range, are the remnants of much larger deposits that accumulated throughout the Eocene and Early Oligocene. In this study, we present a reconstruction of the original extent of the gravels developed according to a few simple rules. This reconstruction suggests that large swaths of the northern Sierra Nevada were once buried under broad alluvial plains, a result consistent with previous work. The reconstruction also supports the hypothesis that the gravels accumulated behind high ridges along the Sierra Nevada foothills, with the Yuba River providing an important outlet. Moreover, gravel deposits on two high peaks indicate that the gravels may have buried the Feather River watershed up to the modern crest of the range. Finally, on the basis of our reconstruction, we estimate that the total volume of the gravels was, at a minimum, ∼200 km³.