Grand Castle Formation

Usage of Geologic Unit Name:
Grand Castle Formation

Age:
Tertiary*
Paleocene*
Geologic Province:
Great Basin province*
Colorado Plateau province*
Geologic Extent:
Utah* Nevada?

Type Locality: Composite type section; base of lower and middle units located on west side of Grand Castle, in NE/4, sec. 6, T. 35 S., R. 8 W.; base of upper unit located on south side of Grand Castle, in NW/4 NE/4 sec. 8, T. 35 S., R. 8 W., Parowan quadrangle, Iron Co., UT. Named from Grand Castle (Goldstrand and Mullett, 1997).

Dominant Lithology: conglomerate, sandstone
 
Unit Name History: Named for topographic feature southeast of Parowan, eastern Iron Co, UT, Great Basin province. Composite type section (measured): base of lower and middle members on west side of Grand Castle, NE/4 sec 6, T35S, R8W; base of upper member on south side of Grand Castle, NW/4 NE/4 sec 8, T35S, R8W. Exposed on Markagunt Plateau from south of Cedar Breaks National Monument northward to Paragonah area and west of Parowan in Parowan Gap area. Generalized geologic map. Had been considered lower part of Claron Formation (revised). Divided into three informal members. Upper and lower conglomerate members consist of boulder- to pebble-size clasts grading upward into sandstone; fossil plant fragments and petrified wood occur in upper member. Middle sandstone member consists of very fine- to fine-grained sandstone; log casts, carbonized wood debris, leaf impressions, and root traces; rare burrows. Thickness at type is 181.4 m; ranges up to 230 m. Isopach map. Lower conglomerate member forms gray hoodoos. Unit provides a tectonostratigraphic record between Sevier and Laramide orogenies for southwest UT. Unconformably overlies Iron Springs Formation. Age is not well constrained; correlative rocks to east in Table Cliff Plateau are probably lower Paleocene based on early Paleocene palynomorphs in overlying and underlying rocks; late Paleocene palynomorphs in basal part of Claron to southwest in Pine Valley Mountains.
Source: GNU records (USGS DDS-6; Denver GNULEX).

Unit undivided from underlying Cretaceous Wahweap Formation in Cedar Breaks National Monument area, lack of observed conclusive stratigraphic evidence does not separate Cretaceous and Paleocene units in the national monument area (Hatfield and others, 2003). See also: North Horn Formation

References:

Goldstrand, P.M., and Mullett, D.J., 1997, The Paleocene Grand Castle Formation; a new formation on the Markagunt Plateau of southwestern Utah, IN Maldonado, Florian, and Nealey, D.L., editors, Geologic studies in the Basin and Range-Colorado Plateau transition in southeastern Nevada, southwestern Utah, and northwestern Arizona, 1995: U.S. Geological Survey Bulletin, 2153, p. 59-77.

Hatfield, S.C., Rowley, P.D., Sable, E.G., Maxwell, D.J., Cox, B.V., McKell, M.D., and Kiel, D.E., 2003, Geology of Cedar Breaks National Monument: In Geology of Utah's Parks and Monuments, Sprinkel, D.A., Chidsey, T.C., and Anderson, P.B., editors, Utah Geological Association Publication 28.,p. 107-138. And, Hintze, L.F., 1988, Geologic History of Utah; A Field Guide to Utah's Rocks: Brigham Young University Geology Studies Special Publication 7, p. 139-154; chart, p. 143.

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The URL is: https://gotbooks.miracosta.edu/gonp/coloradoplateau/lexicon/grand_castle.htm
Last modified:10/25/2009