Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

feet below the Qboo terrace (fig. 11). Clasts are well rounded to subrounded, fairly well
sorted, poorly stratified, with a sand matrix. Composed of Tertiary igneous and
Proterozoic metamorphic and igneous rocks. All rock types are slightly weathered. Soil
at top is moderately well developed. Commercial source of gravel. Thickness less than 33
ft.
Qboo Bull Lake outwash deposits, older (middle Pleistocene) – Reddish-brown to
light-brown, sandy, cobbly alluvium. Mapped in two locations: (1) on the northern side of
the South Arkansas River, downstream from Maysville, where it forms a terrace about 20
ft above the Qboy terrace (fig. 11); and (2) on the western side of upper Walden Gulch,
where it was deposited by the eastern ice-marginal drainage of the Bull Lake glacier of
the North Fork. Clasts are well rounded to subrounded, fairly well sorted, poorly
stratified, with a sand matrix. Composed of Tertiary igneous and Proterozoic
metamorphic and igneous rocks. Clasts of Mount Princeton quartz monzonite are
disintegrated; other rock types are only slightly weathered. Soil at top is moderately well
developed. Forms the most continuous terrace on the north side of the South Arkansas
River, which lies 80 ft above (downstream) to 160 ft above (upstream, west of Maysville)
the modern stream. Commercial source of gravel. Thickness at least 33 ft.
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