Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

Princeton quartz monzonite fragments are rounded and partly disintegrated. Some
boulders are more than 15 ft in diameter. Generally, exposed boulders are half or more
buried below surface of moraine. Moraine is only slightly hummocky and crest is
rounded. Soils are moderately developed and have a weakly developed argillic B-
horizon. Degree of clast weathering, soil development, and surface morphology suggest
a middle Pleistocene (Bull Lake, 130-160 ka) age. Maximum thickness is unknown but
may be as much as 200 ft in moraines at South Arkansas River.
Figure 8. Road-cut exposure of Bull Lake Till (Qbt).
Qbty Bull Lake till, younger (late middle Pleistocene) – Heterogeneous deposits of
gravel, sand, silt, and clay deposited by ice in terminal and lateral moraines. Mapped at
(1) Squaw Creek at the range front, where it lies downslope of Pinedale till; (2) North
Fork, where it lies outside the Pinedale moraines; and (3) Cree Creek, where it forms the
north lateral moraine from the South Arkansas River glacier. Deposits are yellowishgray,
poorly sorted, unstratified or poorly stratified, matrix-supported, boulder, pebble,
and cobble gravel in a silty sand matrix. Most clasts are angular to subangular and little
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