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

his figures show suspiciously eolian-looking fea-
tures. Present data does not allow accurate iso-
paching of these eolian deposits but known strati-
graphic information suggests extremely complex
relations between eolian sandstone bodies and in-
tercalated marine carbonates and redbeds of un-
certain origin.
The Tensleep Sandstone and related units
covered the Wyoming shelf, which was bordered
to the east by a broad carbonate epicontinental
sea and to the west by marine basins of the
Cordilleran miogeocline (Fig. 4). The sand moved
southward from an uncertain source (see Johan-
sen, this volume) and abutted the edge of the
Ancestral Rockies, which shed coarse arkosic de-
bris into the southern edge of the ergs. Repeated
transgressions and repressions of the Penn-
sylvanian sea and episodic uplift of the Ancestral
Rockies caused the complex interfingering of
eolian and non-eolian deposits at the erg margins.
Some of the sand spilled southwestward along the
west edge of the Uncompahgre uplift and formed
dune fields or small ergs along the edge of the
Pardox basin. Some sand drifted southward across
the Piute platform of southern Utah into the
Grand Canyon embayment and accumulated as a
series of eolian deposits between marine strata
(Fig. 7). Eolian deposits in the Atokan Manakacha
Formation would be as old as or older than the
eolian deposits in the Tensleep Sandstone to the
north, the presumed direction of source.
Wolfcampian eolian deposits
Wolfcampian strata of the Western Interior
contain vast erg deposits that stretch from the
Mogollon Rim on the south to the Black Hills to
the north-east. Eolian deposits have been docu-
mented in the Esplanade Sandstone (Blakey, un-
published data), Queantoweap Sandstone (Johan-
sen, 1981), Cedar Mesa Sandstone and Elephant
Canyon Formation (Loope, 1984), upper Weber
Sandstone (Bissell and Childs, 1958), upper Casper
Formation (Steidtmann, 1974), and upper Min-
nelusa Formation (Fryberger, 1984). These units
likely once formed a single continuous sandstone
body, which probably formed by the amalgama-
tion of numerous ergs and dune fields. Each of the
stratigraphic units is known to intertongue with
fossiliferous Wolfcampian marine rocks (Fig. 7),
though the youngest age of some of the eolian
deposits is in doubt. For convenience, eolian de-
posits will be lumped into the Casper complex in
Wyoming and north-central Colorado, the upper
Weber Sandstone in the Uinta Mountains area,
and the Cedar Mesa complex on the Colorado
Plateau. Figure 8 is an isopach and facies map of
the eolian-bearing interval of Wolfcampian age.
The Casper complex is a horseshoe-shaped
sandstone body that wraps around the Lusk em-
bayment and abuts the Ancestral Front Range to
the south. Comprising parts of the upper Min-
nelusa Formation, upper Casper Formation, and
Ingleside Formation (Fig. 7A and B), the erg thins
from 100 m in thickness along the north-
northwest-trending Lusk embayment to an irregu-
lar-trending erosional edge across central Wyo-
ming. Steidtmann (1974) has described the eolian
characteristics and the relations with thin marine
carbonates in the southern portion of the erg
deposits; Fryberger (1984) has documented trans-
gressive-regressive events and eolian, sabkha and
marine relations for the northern portion of the
area. Agatston (1954) provided the stratigraphic
framework that documents the facies change to
Wolfcampian marine carbonates and clastics (up-
per Minnelusa Formation and related rocks) along
the western margin of the Lusk embayment. To
the south, the Casper and Ingleside grade into
coarse clastics of the upper Fountain Formation
(Hoyt, 1963). The relations of the Casper with
coeval Wolfcampian eolian deposits to the south-
west is uncertain due to lack of data in southwest
Wyoming. Most likely before post-Wolfcampian
erosion removed the erg deposits across western
Wyoming, a continuous eolian sheet spread across
the Uinta Mountains area into central Utah.
The upper Weber Sandstone (Fig. 7C) is pre-
served along the flanks of the Uinta Mountains
and eastward into northern Colorado (Fig. 8).
Bissell and Childs (1958) have documented the
eolian origin and stratigraphic framework of the
unit. They have delineated a northeast-trending
facies change through the central Uinta Moun-
tains to marine siliciclastics to the west and traced
a thin eolian tongue (Schoolhouse Tongue) south-
27