The Carmel Formation

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**Note: Formation descriptions are under heavy construction.**

(MID-JURASSIC)

SOUTHWEST UTAH


In the Carmel formation the predominant rock in the formation is limestone of various shades of gray in massive beds 3 inches to 2 feet thick, but more commonly in hard, brittle beds, many of them thin as cardboard, and that on weathering break into hard angular chips suitable for road material. At an outcrop in Coal Canyon near Rocky Hollow the basal strata are calcareous, argillaceous and gypsiferous shales, 5 to 8 feet thick. Some of the limestone beds are sandy, others slightly argillaceous and some are beautifully ripple marked. In places the whole formation is included in a cliff or, where tilted, stands as a ridge, but generally the exposures constitute a series of low cliffs and steep slopes that reflect the position and relative thickness of groups of hard and soft beds. In the topography at the heads of Kanarra and Murie Creeks and to a less extent farther north, the Carmel is the resistant cap that slows up the erosion of the underlying softer Navajo sandstone.

The stratigraphic limits of the Carmel formation are well defined. At the top of the formation compact resistant limestone directly underlies friable gypsiferous sand (Entrada sandstone) and in places the contact is further marked by an erosional unconformity. At its bottom the Carmel formation is conspicuously discordant with the underlying Navajo sandstone: fossiliferous marine limestone rests on the eroded surface of massive cross-bedded sandstone that was deposited by streams and winds.

So far as identified, the fossils gathered from the Carmel in Southwest Utah are listed below. According to Reeside, they fix the age of the formation as "early Upper Jurassic."

    1. Camptonectes extenuatus (Meek and Hayden)
    2. Camptonectes stygius White
    3. Lima n. sp.
    4. Nucula n. sp.
    5. Ostrea engelmanni (Meek)
    6. Ostrea strigilecula White
    7. Pentacrinus asteriscus Meek and Hayden
    8. Trigona montanensis Meek

These forms are included in the much larger fauna in the Carmel formation at its type in the Parunuweap Valley near Mount Carmel, Utah, to which point the outcrops in Southwest Utah have been traced.


SOURCE
-from Geology of Eastern Iron County, Utah by Herbert E. Gregory




SOUTHEAST UTAH

As its type locality in Parunuweap . Valley, near Mount Carmel village, the Carmel formation measures 222 to 269 feet, of which about 100 feet is limestone that contains a marine fauna of Upper Jurassic age. Northeastward from Mount Carmel the formation maintains its thickness and stratigraphic features at places as far distant as the San Rafael Swell, but southeastward across the Paria River and along the base of the Kaiparowits Plateau it thins gradually and loses its limestone, until near the mouth of Rock Creek it is represented by some 50 feet of calcareous sandstone with which is interbedded 2 inches of unfossiliferous hard, brittle limestone. As represented in the San Juan country the Carmel consists of red and white earthy, lumpy, unevenly bedded sandstones and earthy red mud shales that range in total thickness from 107 feet to the vanishing point.

Near the mouth of Allen Canyon the formation embraces 10 to 40 feet of friable red imbricated shales that weather into chips. At the head of Butler Wash it consists of 24 feet of red thin-bedded slabby sandstone. Southward along the wash the formation is thicker and includes not only sandstone and shales of various shades of red and wide range in bedding and composition, but also beds of. white sandstone. On Wilson Mesa the highest bed is a knobby arenaceous limestone that weathers like caliche.

In the San Juan country as elsewhere in the plateau province, the Carmel where present rests uncomfortably on the Navajo sandstone. The top surface of the Navajo is uneven and in most places is coated with particles of lenticular, nodular, even conglomeratic red shale?, and sandstone. In the Allen Canyon country masses of lumpy red, gray, and yellow shale occupy depressions and channels in the Navajo as much as 25 feet deep. In places the curved laminae in the Navajo were truncated before the lowest bed of Carmel was deposited. Though this unconformity may mark the division between the Lower or Middle Jurassic and the Upper Jurassic, it probably does not indicate a long interval of erosion.


SOURCE
-from The San Juan Country - A Geographic and Reconnaissance of Southeastern Utah by Herbert E. Gregory