Geology of the Verde Valley (Continued)
Bell Rock showing slope erosion
The
Hermit Formation floodplain was covered by wind blown sand dunes coming
from the northwest. Following this the Pedregosa Sea washed in
from the southeast, reworking the dunes into a flat bedded sandstone
layer called the Schnebly Hill Formation. The red colors are due to
iron oxide staining of the sandstone over time. The multiple thin
white layers record the times when the Pedregosa Sea eased in and out
of this area, depositing limestone conglomerate.
Sand dunes showing
iron oxide coloration
The land continued to drop or subside, and the Pedregosa
Sea covered the Schnebley Hill sands, depositing the Fort Apache member. This
thin, gray limestone conglomerate is present about 2/3 of the way up the red
rocks. When the Pedregosa Sea made its final retreat, the Fort Apache member
was covered with blowing sand creating cross-bedded sand dunes. This gradually
became the Coconino Sandstone formation, the cream colored formation above
the red Schnebly Hill Formation.
Courthouse Butte with Schnebley
Hill Formation at base, Fort Apache member grey lines and Coconino
sandstone above it, with typical eroded slopes.
The sea returned, advancing from the west, depositing the Toroweap Formation. Sedona was near the shoreline, and the Grand Canyon was lower than Sedona. Sycamore Canyon, west of Oak Creek Canyon, was a shallow marine mud flat. Just 5 miles east in the area of Oak Creek Canyon, a shallow shoreline environment existed. This little area was a unique environment that eventually was known as Sedona Red Rock Country.
