std page banner

Rock Springs Uplift and Adjacent Areas (cont.)

4 Rock Springs Uplift (cont.)

4.2 Rock Springs Uplift Lower Units:
Baxter Shale, Blair Formation

The Cretaceous Baxter shale, the oldest rock exposed at the surface of the Rock Springs uplift, outcrops in the Baxter basin, in the center of the uplift; divided by the Bitter Creek into a northern and a southern part, the basin is flat, except where it has been subjected to fluvial erosion. The Baxter shale, also Cretaceous, but younger, consists of soft sandy shale and somewhat harder shaly sandstone. It is a very thick unit (ca. 1300 m), the upper part of which has been removed by erosion. The Blair formation is made of shale interbedded with thin layers of sandstone, which renders it more resistant to erosion. It forms gentle hills above the Baxter shale. The much harder Rock Springs formation (mostly sandstone) makes the steep cliffs above the Blair formation.

Baxter basin: Baxter Shale and Blair formation; Rock Springs uplift, Wyoming

Figure 4-6. Baxter shale in Baxter basin.

View to the east. Baxter basin is pretty flat, where it has not been dissected by fluvial erosion. Kba-Baxter shale, Kbl-Blair formation.

Baxter basin; gully in Quaternary alluvia; Baxter shale; Rock Springs formation

Figure 4-7. South Baxter basin

Gully in the valley of a small subsidiary of Bitter Creek. View to the northwest. Baxter shale forms the flat surface of the basin. Low hills in the background are carved in Blair formation. Cliffs in the background belong to the Rock Springs formation; the Killpecker Creek valley and Rock Springs are behind them. Qal-Quaternary alluvial deposits, Kba-Baxter shale, Kbl-Blair formation, Krs-Rock Springs formation.

Gullied Baxter shale in South Baxter basin, Wyoming

Figure 4-8. Gullied Baxter Shale

Eroded Baxter shale on the southern flank of Bitter Creek.

North Baxter basin in Rock Springs uplift, Wyoming

Figure 4-9. North Baxter basin, Wyoming

View to the northeast. North Baxter basin (Kba-Baxter shale) is in the center. In the foreground, cliffs cut in the Rock Springs formation (Krs) above gentler slopes in the Blair formation (Kbl). The eastern flank of Baxter basin is in the background (Kbl and at the top, Krs).

South Baxter Basin, Wyoming. Contact between the Blair and Rock Springs formations

Figure 4-10. Contact between the Blair and Rock Springs formations in the South Baxter basin, Wyoming

View to the south in the western half of the Rock Springs uplift, southwest of Rock Springs. A roadcut nicely exposes the contact between the Rock Springs formation (Krs), which disappears completely at left, and the Blair formation (Kbl). Although it is not evident in the photo, the strata slightly dip to the west (to the right), which explains the end of the Rock Springs formation, because of erosion. The center of the uplift (South Baxter basin) is towards the left (east).

Next: Rock Springs uplift middle units

1 Green River Basin
1.1 Overview

1.2 White Mountain

2 Leucite Hills

3 Killpecker Sand Dunes

4 Rock Springs uplift - 4.1 Overview

4.2 Rock Springs uplift lower units (this page)

4.3 Rock Springs uplift middle units:
4.3.1 Rock Springs formation

4.3 Rock Springs uplift middle units (cont.):
4.3.2 Ericson sandstone
4.3.3 Almond formation

4.4 Rock Springs uplift upper units

References (opens in new tab)