Synthesis of late Paleozoic and Mesozoic eolian deposits of the ...

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east into the Central Colorado trough. The eolian
tongue grades into and is enclosed by arkose of
the upper Maroon Formation. Sparse subsurface
data (Irwin, 1976) suggests that to the south of the
Uinta Mountains the upper Weber Sandstone
grades into the arkose along the flank of the
Ancestral Uncompahgre Range and eolian sand
spilled southwest around the uplift into the Cedar
Mesa erg.
The Cedar Mesa complex, which includes parts
of the Queantoweap Sandstone to the west and
Esplanade Sandstone to the south, is a broad sheet
that thickens to over 400 m thick in south-central
and southwestern Utah (Fig. 7D and E). Strati-
graphic and sedimentologic framework for this
complex body has been provided by Blakey (1980),
Johansen (1981), McKee (1982) and Loope (1984),
although it should be pointed out that McKee did
not recognize eolian deposits in the Esplanade
Sandstone. The present configuration of the
eolian-bearing sandstone describes a parabolic
trough whose axis trends N60 °E across southern
Utah and thins rapidly on the northeast and
southeast flanks. The erg deposits also undergo
major facies changes along all of their margins. To
the northeast and east the Cedar Mesa grades
abruptly into the Cutler Formation (Baars, 1962:
Campbell, 1979; Mack, 1979); southward along
the Sedona arch the Esplanade Sandstone grades
eastward into continental redbeds of the Hermit
and Organ Rock Formations (Blakey, 1979, 1980);
westward along the Cordilleran hingeline eolian
deposits grade rapidly into Wolfcampian marine
carbonate of the Pakoon and Elephant Canyon
Formations (Baars, 1962; Irwin, 1976; McKee,
1982). Near the junction of the Green and Col-
orado rivers, the Elephant Canyon also contains
eolian strata. The Cedar Mesa Sandstone thins
across the Emery arch in central Utah to less than
30 m (Irwin, 1976) and should not be confused
(Fig. 7D) with thick younger eolian sandstone of
the overlying White Rim Sandstone (D. Baars,
pers. commun., 1985). The Cedar Mesa Sandstone
probably connects directly with the upper Weber
Sandstone across and to the north of the Emery
arch.
The Wolfcampian ergs were probably once con-
tinuous and are now separated geographically and
structurally into three bodies (Fig. 8). Wolf-
campian eolian deposits are confined to a trend
defined by parallel northeast-trending lines, the
western one running from southwest Utah to
north-central Wyoming and the eastern one run-
ning from central Arizona to northeast Wyoming.
The Casper Sandstone formed as a coastal and
inland sand sea adjacent to marine deposits of the
Lusk embayment and north of the Ancestral
Rockies. Episodic changes in sea level caused the
interdigitation of marine and eolian deposits across
much of east-central Wyoming (Steidtmann, 1974;
Fryberger, 1984). In the Laramie-Fort Collins
area, narrow facies belts and abrupt facies changes
reflect the complex interactions between uplift to
the southwest, coastal dunes, and marine trans-
gressive-regressive events to the east (Steidtmann,
1974).
The eolian deposits of the upper Weber Sand-
stone were sandwiched between the Ancestral
Uncompahgre and Front Ranges and the Oquirrh
Basin and Cordilleran miogeocline. As such, it
was a triangular deposit that responded to uplift
to the east and sea level changes to the west.
The Cedar Mesa Sandstone accumulated dur-
ing a time of rapid subsidence accompanied by
numerous sea-level changes and uplift in the
Ancestral Uncompahgre Range. The southern
Cordilleran miogeocline and Circle Cliffs trough
were strongly negative but the influx of eolian
sand was strong enough to keep the sea to the
west much of the time. The rather straight margins
of this complex unit suggest long-ranging tectonic
controls on the erg margins (see Blakey, this
volume).
Leonardian I eolian deposits
Ergs deposited during the lower Leonardian are
restricted to the southern Colorado Plateau and
are represented by major unconformity to the
north (Figs. 2 and 7). The eolian sedimentology is
provided by Blakey and Middleton (1983) and
Vonderharr (1986) and the stratigraphic frame-
work by Blakey (1979, 1980), and Blakey and
Knepp (in press). The eolian deposit comprises
parts of the Schnebly Hill and Yeso Formations
and De Chelly Sandstone. It forms a broad