The Middle Jurassic Entrada Sandstone near Gallup, New Mexico
Mountain Geologist
By: J. F. Robertson and R. B. O'Sullivan
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Abstract
Near Gallup, New Mexico, the Middle Jurassic Entrada Sandstone consists of, in ascending order, the Iyanbito Member, the Rehoboth Member, and an upper sandstone member. The Rehoboth Member is named herein to replace the middle siltstone member, with a type section located 26 km east of Gallup. The Iyanbito Member has been erroneously equated with the Wingate Sandstone of northeast Arizona, and the Rehoboth Member has been miscorrelated with the Dewey Bridge Member of the Entrada in Utah. The Dewey Bridge is an older unit that does not extend into New Mexico. The Iyanbito Member, east of Gallup, overlies the J-2 unconformity and the eroded tops of the Owl Rock and Petrified Forest Members of the Chinle Formation. The Wingate Sandstone of the Lower Jurassic Glen Canyon Group overlies the J-0 unconformity and the underlying Rock Point Member (topmost unit) of the Chinle Formation in northeast Arizona. Both the Wingate Sandstone and the Rock Point Member are missing east of Gallup below the J-2 unconformity. Similarly, the Wingate is missing southwest of Gallup, near Lupton, Arizona, but the Rock Point Member is present and underlies the Iyanbito from Zuni northward to Toadlena, New Mexico. The Wingate and other formations of the Glen Canyon Group thin and wedge out southward and eastward in northeast Arizona. The J-2 unconformity truncates the Wingate Sandstone and the underlying J-0 unconformity, 5 km north of Toadlena.
Suggested Citation
Robertson, J., O'Sullivan, R.B., 2001, The Middle Jurassic Entrada Sandstone near Gallup, New Mexico: Mountain Geologist, v. 38, no. 2, p. 53-69.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | The Middle Jurassic Entrada Sandstone near Gallup, New Mexico |
| Series title | Mountain Geologist |
| Volume | 38 |
| Issue | 2 |
| Year Published | 2001 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Mountain Geologist |
| First page | 53 |
| Last page | 69 |