Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

Qpt Pinedale till, undivided (late Pleistocene) – Heterogeneous deposits of gravel,
sand, silt, and clay deposited by ice in terminal and lateral moraines in (from north to
south) Squaw Creek, North Fork, Cree Creek, South Arkansas River, and Green Creek.
May also include localized lenses of material transported by melt-water adjacent to ice
and post-glacial alluvium in stream courses too small to map. Deposits are light-olivegray,
poorly sorted, unstratified or poorly stratified, matrix-supported, boulder, pebble,
and cobble gravel in a silty sand matrix. Clasts are typically angular to rounded and
unweathered. Small kettle holes and hummocky topography are common. Soils
comprised of moderately well-developed A-horizon and weakly developed C-horizon.
Lack of clast weathering, limited soil development, and hummocky surface morphology
suggest a late Pleistocene age (Pinedale equivalent, 15-35 thousand years, ka).
Maximum thickness is unknown.
Qpty Pinedale till, younger (late Pleistocene) – Heterogeneous deposits of gravel,
sand, silt, and clay deposited by ice in terminal and lateral moraines. May also include
localized lenses of material transported by melt-water adjacent to ice. Deposits are lightolive-gray,
poorly sorted, unstratified or poorly stratified, matrix-supported, boulder,
pebble, and cobble gravel in a silty-sand matrix. Clasts are typically angular to rounded
and unweathered. Small kettle holes and hummocky topography are common. Soils
comprised of moderately well-developed A-horizon and weakly developed C-horizon.
Lack of clast weathering, lack of soil development, and very hummocky surface
morphology suggest a late Pinedale age (15-22 ka). Mapped only in the North Fork,
where unit forms a ground moraine. Maximum thickness is unknown, but roadcuts along
County Road 240 expose a thickness of at least 33 ft in places.
Qbt Bull Lake till, undivided (middle Pleistocene) – Heterogeneous deposits of
gravel, sand, silt, and clay deposited by ice in terminal and lateral moraines. Moraines lie
adjacent to and outside of Pinedale moraines at Squaw Creek, North Fork, Cree Creek,
and South Arkansas River. Deposits are yellowish-gray, poorly sorted, unstratified or
poorly stratified, matrix-supported, boulder, pebble, and cobble gravel in a silty sand
matrix (fig. 8). Most clasts are angular to subangular and little weathered, but Mount
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