San Rafael Group

San Rafael Group strata exposed east of the San Rafael Swell, north of Hanksville. Sequence from orange cliff in foreground to cliff top in background Entrada Formation, Curtis Formation, Summerville Formation, capped by the (pink) Tidwell Member of the Morrison Formation.

San Rafael Group on the east side of the San Rafael Swell. Entrada at the base, overlain by the Curtis, then Summerville, and capped by the Morrison (Tidwell and Salt Wash Members).

The San Rafael Group is a geologic group or collection of related rock formations that is spread across the U.S. states of New Mexico, Arizona, Utah and Colorado. As part of the Colorado Plateau, this group of formations was laid down in the Middle Jurassic during the Bajocian, Bathonian and Callovian stages.^[1]

Asterisks (*) indicate usage by the U.S. Geological Survey.

Subunits[]

Subunits (alphabetical):^[1]

• Bell Ranch Formation (NM),
• Bluff Sandstone (AZ, NM),
• Carmel Formation (AZ*, CO*, NM*, UT*, WY*),
• Cow Springs Sandstone (AZ),
• Curtis Formation (CO*, UT*),
• Entrada Sandstone (AZ*, CO*, NM*, UT*),
• (UT),
• Page Sandstone (AZ*, UT*, WY*),
• (AZ*, UT*),
• Summerville Formation (AZ, CO, NM, UT),
• (UT*) or Temple Cap Formation (UT),
• (NM),
• (AZ, CO*, UT*) or Todilto Formation (AZ, CO, NM, UT),
• Wanakah Formation (AZ*, CO*, NM*, UT*).

History of investigation[]

There is no designated type locality for the group. It was named for exposures in the San Rafael Swell in Emery County, Utah by Gilluly and Reeside in 1928. That same year they divided the group into (ascending): Carmel Formation, Entrada Sandstone (new), Curtis Formation (new), and Summerville Formation (new). Areal extent limits were established by Gregory and Moore in 1931. Smith in 1954 revised and divided the group into Entrada, Todilto, and Thoreau (new) formations in the San Juan Basin. In 1959 another revision, this time by Griggs and Read, divided it into Entrada and Bell Ranch (new) formations in the and . The Carmel-Navajo contact was revised by Wright and others in 1962 and the Carmel-Entrada contact was revised by Phoenix in 1963. Thompson and Stokes created an overview and named the Henrieville Sandstone in 1970. The Temple Cap Sandstone was revised and the Page Sandstone added (new) by Peterson and Pipiringos in 1979. A revision by O'Sullivan in 1980 divided the group into Carmel, Entrada, and Wanakah formations in Paradox Basin. O'Sullivan revised the upper contact in 1984. In 1988 Peterson revised earlier work and divided the group into Page, Carmel, and Entrada formations in the Black Mesa Basin; divided it into Page, Carmel, Entrada and Romana (new) formations in the Plateau Sedimentary Province; and divided it into Page, Carmel, Entrada, Curtis, and Summerville formations in Paradox Basin. Condon in 1989 revised the group in San Juan Basin and divided it into Entrada and Wanakah formations in southeastern area; divided it into Entrada, Wanakah, and Cow Springs formations in south-central area; and divided it into Entrada and Cow Springs Sandstones in southwestern area.^[2]

Places found[]

Geologic Province:^[1]

• Black Mesa Basin*
• Great Basin province*
• *
• Paradox Basin*
• Piceance Basin*
• Plateau Sedimentary Province*
• San Juan Basin*
• *

Parklands (incomplete list):

• Canyonlands National Park - see geology of the Canyonlands area
• Capitol Reef National Park - see geology of the Capitol Reef area

References[]

Works cited[]

• GEOLEX database entry for San Rafael Group, USGS (viewed 20 March 2006)
• GEOLEX database Bibliographic References for Glen Canyon, USGS (viewed 20 March 2006)

Notes[]