Fan deposits

What the map says

Mostly unsorted and unstratified, matrix- supported bouldery debris-flow deposits that consist of granule- to boulder-size clasts in a sandy, silty sand, or finer-grained matrix. Unit locally includes poorly to moderately well sorted, crudely stratified, clast-supported, stream-deposited sand and gravel. These mass-movement and alluvial deposits commonly form fan-shaped landforms at the mouths of small tributaries streams. Locally these deposits coalesce to form a broad, relatively gently sloping apron. Clasts are mostly subangular to subrounded; some are as long as about 2 m, but most are much smaller. Unit Qf is commonly graded to levels at or slightly above present stream level. Depositional processes were periodically active during the Holocene, but probably were most active during Pinedale deglaciation. Surface is locally veneered by unmapped deposits of sheetwash alluvium and probably by hyperconcentrated-flow deposits. Fan deposits on the east side of the Arkansas River, in the southern part of the map area, are locally mantled by unmapped deposits of eolian sediments and alluvium undivided (Qes). Estimated thickness is as much as 15 m

1:100,000 sheet: Kellogg and others, 2017, U.S. Geological Survey Scientific Investigations Map 3382 (2 crags). A contact line at that scale is about 100 m wide on the ground.

Mostly poorly sorted, slightly bouldery pebble and cobble gravel and locally pebbly and cobbly silty sand. Deposited chiefly by streams and debris flows in fan-shaped accumulations near base of moderate to steep slopes. Unit locally includes sheetwash de

1:100,000 sheet: Kellogg and others, 2008, USGS Geologic Investigations Series 3000 (8 crags). A contact line at that scale is about 100 m wide on the ground.

Served by Macrostrat (CC BY 4.0). The wording is the map's own, quoted as a fact about the mapped unit, not about any one wall.