Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

During the Early and Middle Paleozoic, central Colorado was located in an eastwest-trending
trough or structural low (the Colorado Sag) in the northeast-trending
Trans-Continental Arch. The trough area received intermittent shallow marine
sedimentation which was periodically interrupted by epirogenic uplift and erosion
resulting in numerous unconformities between the various Lower and Middle Paleozoic
formations (Tweto, 1980a). Knepper (1974) documented evidence for at least five major
episodes of epirogenic uplift and suggested as many as nine may be present. On the basis
of his regional geology compilation and tectonic analysis study, Knepper (1974; p.50)
stated that no folds or faults of early or middle Paleozoic age have been identified in the
region.
The Mississippian-Pennsyvanian (Ancestral Rocky Mountains) orogeny was
characterized by development of three major, in part fault-bounded uplifts: the Front
Range, Uncompahgre-San Luis, and Apishapa Highlands (Tweto, 1980a). The northwesttrending
highlands were separated by a structural trough, the northwest-trending Central
Colorado trough which cut diagonally across the west-central part of Colorado (DeVeto,
1972) and includes the area of the Maysville quadrangle (fig. 3). The similar paleosedimentation
patterns for Upper Cambrian through Permian sedimentary rocks suggest
that the late Paleozoic orogenic highlands and the intervening Central Colorado trough
were modifications and enhancements of the early and middle Paleozoic epirogenic
positive areas and the intervening Colorado Sag. Tweto (1980a) characterized the late
Paleozoic highlands as asymmetric, having steep fault-bounded margins on one side and
moderate up warping on the other.
A long standing controversy in Colorado geology involves the nature and timing
of the Sawatch Uplift and whether or not a positive highland existed intermittently in this
area during the early to middle Paleozoic and especially during the late Paleozoic
orogeny. Early workers showed the area of the Laramide Sawatch uplift with the various
Paleozoic formations lapping the eastern and western margins, thus indicating uncertainty
in their paleo-continuity (Litsey, 1958). In contrast, some later workers proposed that an
Ancestral Sawatch uplift existed in the present area of the Sawatch Range and that it
divided the Central Colorado trough into two depositional sub-basins (DeVoto, 1972).
Tweto (1980a) did not support the view of an Ancestral Sawatch uplift and specifically
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