Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

(1969). Thickness possibly as much as 80 ft.
Qna1 Nebraskan () alluvium, older (early Pleistocene) – Light-brown to gray,
poorly sorted, poorly stratified, deeply weathered, sandy bouldery gravel. Forms a small
part of the distal high pediment surfaces on the range-front piedmont, west of Walden
Gulch. Possibly includes outwash from pre-Bull Lake glaciers. Soil at top is strongly
developed. Partly equivalent to unit Qg2 of Van Alstine (1969). Thickness possibly as
much as 80 ft.
Qn Nussbaum () alluvium (early Pleistocene) – Brownish-gray to pale-brown,
crudely stratified, poorly sorted bouldery alluvium. Composition varies widely depending
on source. Deeply weathered; soil at top is very strongly developed. Forms the highest
pediment surface on the range-front piedmont; lies about 80 ft above the Nebraskan
(Qna) pediment surface. Mapped in only two locations, a large area of pediment between
Squaw Creek and Placer Creek, and a narrow pediment surface north of Squaw Creek
near the eastern quadrangle boundary. Equivalent to unit Qg1 of Van Alstine (1969).
Thickness probably as much as 20 ft.
COLLUVIAL DEPOSITS – Silt, sand, and gravel on valley sides and floors. Material
mobilized, transported, and deposited primarily by gravity, but movement commonly
assisted by sheetwash, rillwash, freeze-thaw action, and debris flows resulting in units too
small to map.
Qc Colluvium (late Pleistocene and Holocene) – Ranges from unsorted, clastsupported,
pebble to boulder gravel in a sandy silt matrix to matrix-supported gravelly,
clayey, sandy silt. Generally unsorted to poorly sorted and contains angular to
subangular clasts. Includes weathered bedrock fragments that have been transported
downslope primarily by gravity. Mapped mainly in small areas at the base of steep
slopes in major canyons but also above timberline south of Mount Shavano. Deposits
derived from glacial or alluvial deposits contain rounded to subrounded clasts. Clast
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