7012

• UCREFRP Catalog Number: 7012
• Author: Cross, J. N.
• Title: Ecological Distribution of the Fishes of the Virgin River ‎(Utah, Arizona, Nevada)‎.
• USFW Year: 1975.
• USFW - Doc Type: University of Nevada,
• Copyright Material: NO

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TOPOGRAPHY
16
The Virgin River basin, lying .along the boundary {Grand Wash
Cliffs) between the Colorado Plateau and the Great Basin, is a land
of contrasting topography (Figure 1). The major structural feature
of the basin is the Hurricane fault ~rhich roughly divides the basin.
into tiro dissimilar topographic areas separated somewhat by the low-
lying St. George basin (Cook ]960). To the east of the St. George
basin and the Hurricane fault lie the strikingly colorful mesas and
plateaus of the Colorado Plateau region. The topography to the west
and north of the St. George basin is characteristic of the Basin and
Range province.
The Colorado Plateau is typified by strata-that lie more or less
horizontal and have been eroded .into plateaus, mesas and deep canyons.
The topography is due to differential uplift of segments of the earth's
crust along northward-trending faults producing a series of terrace-
]ike steps (Cook 1960, Ives 1947) that lead from the Grand Canyon
to the high plateaus of Utah 80 km to the north. A number.of faults
and monoclines roughly paralleling the Hurricane fault divide each
terrace step into a series of plateaus. One of these faults, the
Sevier fault, determines the eastern boundary of the Virgin River
basin along the East Fork. The regional dip of the plateaus is
northeasterly but averages about one degree in 160 km {Gardner 1941).