Rock Springs Uplift and Adjacent Areas (cont.)
Green River Basin (cont.)
1.2 White Mountain
White Mountain appears as a mountain only when seen from Rock Springs and the Bitter Creek-Killpecker Creek valleys. Actually it consists of the flat eastern edge of the Green River basin overlooking the western boundary of the Rock Springs uplift. It is the continuation of the Palisades of figure 1.5 (preceding page) first to the east-northeast, then along a south-north line from Rock Springs to the Killpecker Sand Dunes. In the latter section, erosion along the blind reverse fault that borders the Rock Springs uplift to the west has exhumed more layers than can be seen in the Palisades and other valleys of the area. The steep cliffs of the Palisades are absent here and the slope in the Laney layer at the top is about the same than in the Wilkins Peak layer, which ends in subhorizontal terraces, the lowest of which exposing the Tipton Shale member of the Green formation. The valley lies on the Wasatch formation, and beneath it on the Fort Union formation. White Mountain is dominated by the Pilot Butte mesa, a Quaternary lamproite volcano (see Leucite Hills, next page).
Figure 1-7. Geologic map of White Mountain near Rock Springs, Wyoming.
White Mountain (Tertiary rocks) overlooks Rock Springs and the western part of the Rock Springs uplift (Cretaceous rocks). Pilot Butte is a Quaternary volcano (consisting of lamproite, a potassium-rich lava). The dashed line follows the trace of the blind reverse fault separating the Green River basin and the Rock Springs uplift.
Tgl: Laney member (marlstone, shale, sandstone ) of the Green River formation (lower Eocene)
Tgw: Wilkins Peak member (sandstone, shale and marlstone) of the Green River formation (lower Eocene)
Tgt: Tipton Shale member (shale, marlstone) of the Green River formation (lower Eocene)
Twn: Niland Tongue (mudstone) of the Wasatch formation (lower Eocene)
Twm: Main body of Wasatch formation (sandstone, claystone, siltstone; lower Eocene)
Tfu: Fort Union formation (Paleocene sandstone and shale)
Map and abbreviations from the 30x60 min. Rock Springs geologic map.
Figure 1-8. White Mountain seen from Rock Springs, Wyoming.
View to the northwest. See explanations of symbols in figure 1-7.
Figure 1-9. Top of White Mountain, Wyoming.
Top of White Mountain above Rock Springs, Wyoming. Notice its flatness, characteristic of the Green River basin. The brown top layer is the Sand Butte Bed sandstone of the Green River formation Laney member (Tgl). The gray layer below is the Wilkins Peak member of the same formation (Tgw). See descriptions of rocks in figure 1-7.
Figure 1-10. Top of White Mountain, Wyoming: Tgl-Tgw contact.
Contact between the Sand Butte Bed sandstone (Tgl) and the Wilkins Peak layer (Tgw). See description of rocks in figures 1.7 and 1.9.
Figure 1-11. Close-up of the Sand Butte Bed sandstone (Tgl, Laney member of the Green River formation).
Figure 1-12. Close-up of the Wilkins Peak member (Tgw) of the Green River formation.
White Mountain, Wyoming: Wilkins Peak layer and terrace in the Tipton Shale layer.
View to the northeast from White Mountain towards Rock Springs (left background). Foreground: Wilkins Peak unit (Tgw). In the left center, terraces in the Tipton Shale (Tgt). Further in the center of the photograph, the Killpecker Creek valley on rocks of the Wasatch Formation (Twn-Twm) and the Fort Union formation (Tfu). Cretaceous rocks of the Rock Springs uplift in the background, east of the city. See description of layers in figure 1.7.
Figure 1-14. Top of the Tipton Shale member (Tgt) of the Green River formation.
Figure 1-15. Close-up of the lower (main) member of the Wasatch formation (Twm).
The Wasatch formation is exposed in the major part of the Killpecker Creek valley, at the bottom of White Mountain.