Day 1, Stop 1
Inverted Channels
Location: N of I-70W on Rt. 24 (exit 149). Turn right (N) on Rt. 24 exit. Park when road turns to dirt.
GPS Location:38o 55.545' N 110o 22.711' W
Ages: Late Jurassic (155-148 Ma)
Rock Units: Morrison Formation: Salt Wash Member of the Jurassic Morrison Formation; Cretaceous Burro Canyon Formation (possible).
Features Present: Exhumed channels of the Salt Wash Member (Fig. 1) exhibiting trough cross bedding (Fig. 2) and fining upward sequences (Fig. 3). Large clasts are mostly chert.
Depositional Environment:Fluvial system flowing to the east (Turner and Peterson, 2004).
Interpretation: Resistant channel sandstones were surrounded by soft shales (floodplain deposits). As the area was uplifted and erosion occurred, the soft shales eroded more easily exposing the more resistant, cemented channel sandstones These are excellent examples of channel sandstones that analogous to features imaged on Mars (Williams et al., 2007).
Other:Exhumed channels on top of high cliffs are probably Cretaceous Burro Canyon Formation channels (Fig. 4).
Figure 1:Exhumed Salt Wash channels outlined in dotted lines.
Figure 2: Trough cross bedding in Salt Wash Member (outlined with dotted lines). This view is along strike of flow (~70°).
Figure 3:Fining upward in trough cross bed sequence. Tick marks on top of card = 1 cm. Grain size becomes smaller (along arrow) due to reduction of energy in river flow through channel.
Figure 4: Exhumed Burro Canyon Formation (?) channels (top of cliffs adjacent to road). This formation is coarser grained than the Salt Wash Member.