Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

stream-channel deposits of all perennial streams, adjacent flood-plain deposits, and lowterrace
alluvium that lie a maximum of 10 ft above modern stream level (fig. 10). The
largest mapped areas are in the channels and flood plains of perennial streams (South
Arkansas River and North Fork). Smaller areas lie in the channels of intermittent streams.
In the upper reaches of Squaw Creek and the other creeks draining the range front, the
deposits are very bouldery and display debris-flows levees and swales at the surface.
Deposits may be interbedded with colluvium or debris-fan deposits where the distal ends
of fans extend into modern river channels and flood plains. Maximum thickness about 33
ft. Areas mapped as alluvium may be prone to flooding and sediment deposition. The
unit is typically a good source of sand and gravel.
Qat Low stream terrace alluvium (Holocene) – Deposits are mostly clast-supported,
pebble, cobble, and locally boulder gravel in a sandy silt matrix. Mapped in South Sand
Creek, lower Squaw Creek, and an unnamed drainage in Section 19, T50N, R8E near the
central eastern map boundary. The deposits are locally interbedded with and commonly
overlain by sandy silt and silty sand. Clasts are subangular to well rounded, and their
varied lithologies reflects the diverse types of bedrock within their provenance. This unit
includes alluvium of low terraces above the modern flood plain, but below Pinedale
outwash terraces. Maximum thickness probably