- Glacial, periglacial, fluvial, and mass-movement processes dominate in mountain environments.
- As the basin filled, or the rate of subsidence relative to the influx of material lessened, subaerial fluvial deposits were emplaced.
- The first cycle initiated in the early Paleocene and represents a transition from Cretaceous marine turbidites and shales to subaerial fluvial sandstones and conglomerates.
- These units are conformably overlain by fluvial and lacustrine volcaniclastic deposits, tuffs and hyaloclastites.
- It has been suggested that fluvial and lacustrine source rocks were locally deposited in grabens created along the transtensional edges of these rotating microcontinental blocks.