Transport Pressure Mark Mechanisms in the Late Cretaceous-Early Eocene Conglomerates, Northwestern Wyoming

Abstract

In spite of rather intensive investigation into the origin of the Harebell (Late Cretaceous), Pinyon (Paleocene) and Pass Peak (Early Eocene) conglomerates in Jackson Hole and adjacent areas certain critical questions remain unanswered. The great thickness, coarseness and lateral extent imply an ancient source of considerable size and relief relatively near to present day Jackson Hole. Evidence for such a source is, however, equivocal and previous workers do not agree on its location. An even more perplexing question concerns the mechanisms by which such a huge volume of cobbles and boulders was transported from the source, wherever it was, to its depositional site. Such a system implies the existence of ancient alluvial fans on a scale unknown in modern environments.