Remarkable Geology: Utah’s Gravel & Long Canyons


CEDAR MESA SANDSTONE:

The Cedar Mesa Sandstone is the type of rock that will be most abundant throughout Gravel and Long Canyons.  This formation was created by eolian deposits after the levels of the sea surrounding the Ancestral Rockies dropped.  Large amounts of cross bedding were created due to fluctuating wind directions and other varying conditions.  The Cedar Mesa Sandstone is “a white to pale reddish brown cross-bedded unit” (Geology: Permian Period).  The sandstone formations could also quite possibly resemble sand dunes in the solid state.  Cross-bedded lines should indicate wind direction and portray the variability thereof.

ORGAN ROCK SHALE:

As the eolian deposits of sandstone tapered off, deposits from the erosion of the Uncompahgre Uplift created overlying deposits.  Silt was deposited via streams, and flood plains that carried the sediment from the Uncompahgre mountain range of the ancestral Rockies.  This layer of silt is most commonly seen in varying shades of purple and red that overlies the white to light brown layers of Cedar Mesa Sandstone.  Very similar shale formations are found in the Grand Canyon.


WHITE RIM SANDSTONE:

The White Rim Sandstone was created in a similar fashion to the Cedar Mesa Sandstone.  Easterly eolian forces from the sea pushed the sand inland and “deposited this complex cross-bedded unit” (Geology: Permian Period).  This formation is also of a white to light red and brown color.  Overlying the Organ Rock Shale, the White Rim Sandstone frequently acts as a cap that protects the underlying shale, which is more easily eroded due to its soft nature.  Underlying shale often erodes away and causes collapses of Sandstone.  This process of erosion has caused some of the down-cutting that created the canyons.  This layer of sandstone was the last formation created in the Permian Period.


HOW THE CANYON WAS CREATED:

An increased level of elevation due to regional uplifts caused an amounted level of precipitation.  Greater amounts of moisture and the low quantities of plant life cause quick erosion of the sandstone and silt.  The amounted levels of precipitation formed streams that flowed in random turns and bends known as entrenched meanders.  Entrenched meanders form due to low angle plains, which cause the random flow of water.  Steeper grade plains create straighter streams.  The entrenched meanders, over time, cut away meandering sections of the plains.  This process of erosion produces canyons and is a quite common factor that created the canyon lands.


THE COLORADO PLATEAU:

The Colorado Plateau is an oval section of land that covers the four-corners area.  The plateau covers roughly 300,000 square miles and is home to the most pristine canyon lands and epic desert locations such as Moab, Utah.  The plateau contains such a wide variety of environmental beauty that there are dozens of national parks and monuments.

Over 500 Million Years old, the plateau was gradually uplifted and accumulated over the course of the last half billion years.


THE TRIASSIC PERIOD (245-208 MYA):

Following the Permian Period, the Triassic continued to deposit overlying layers of sediment.  The first deposit of the Triassic Period was called the Moenkopi Formation and was a mixture of silt and sandstones.  These layers of sediment were deposited on account of the sea that surrounded the four-corners region and that of the Ancestral Rockies.  The Moenkopi Formation is brown in color and has characteristic ripple marks and mud cracks that are still visible today.

The Chinle Formation was deposited after an erosional period.  The Chinle Formation is composed of mud, silt, and small grain sand and has “a mottled apperarance of purple, white, yellow, and brown” (Geology: Triassic period)..  It was accumulated when rain fell and formed streams that carried these materials to lower elevations.

Both the Moenkopi and Chinle Formations overly Permian rock, which make up the majority of the Gravel and Long Canyons.  These two formations however, can be seen from time to time in canyon lands and would overly the White Rim Sandstone.