Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

lithologies are variable and dependent upon types of rocks occurring within the
provenance area. Locally, this unit may include debris-fan deposits that are too small or
too indistinct on aerial photography to be mapped separately. Colluvium commonly
grades into and interfingers with alluvial, debris-fan, landslide, talus, glacial, and
sheetwash deposits. Maximum thickness probably about 30 ft; however, thickness may
vary. Areas mapped as colluvium are susceptible to future colluvial deposition and
locally are subject to debris flows, rockfall, and sheetwash. Colluvial deposits may be a
potential source of aggregate.
Qco Colluvium, older (middle to late Pleistocene) – Generally unsorted to poorly
sorted deposits containing rounded to subrounded clasts eroded from the moraine front.
Includes weathered bedrock fragments that have been transported downslope primarily
by gravity. Mapped only at the base of the younger Bull Lake terminal moraine (Qbty)
of Squaw Creek. Maximum thickness is about 33 ft.
Qls Landslide deposits, undivided (late Pleistocene to Holocene) – Chaotically
arranged debris ranging from clay to boulder size (diamicton). Mapped in three locations.
At the head of an unnamed drainage east of McClure Creek, long narrow landslides in a
gully are derived from highly fractured Proterozoic rock in the largest mega-slide block.
On the ridge between Cree Creek and Lost Creek, at the range-front fault north of Lost
Creek, landslide is derived from fractured Proterozoic rock of the Shavano fault zone. On
the west branch of Squaw Creek, two large landslides composed of till are derived from
the front of the Pinedale terminal moraine, where it overlies the Sawatch fault zone.
Surface is commonly hummocky, and source area of landsliding is generally identifiable
(on map, top of scarp area is indicated by thick dashed lines with ticks in direction of
sliding). Larger landslide deposits may be more than 50 ft thick.
Qlsy Landslide deposits, younger (late Pleistocene to Holocene) – Chaotically
arranged debris ranging from clay to boulder size (diamicton). Mapped only at the head
of an unnamed drainage east of McClure Creek. Surface is hummocky, and source area of
landsliding is easily identifiable (on map, top of scarp area indicated by thick dashed
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