Everything about The Kayenta Formation totally explained
The
Kayenta Formation is a geologic
layer in the
Glen Canyon Group that's spread across the
Colorado Plateau province of the
United States, including northern
Arizona, northwest
Colorado,
Nevada, and
Utah. This rock formation is particularly prominent in southeastern Utah, where it's seen in the main attractions of a number of national parks and monuments. These include
Zion National Park,
Capitol Reef National Park, the
San Rafael Swell, and
Canyonlands National Park. The Kayenta Formation frequently appears as a thinner dark broken layer below
Navajo Sandstone and above
Wingate Sandstone (all three formations are in the same group). Together, these three formations can result in immense vertical cliffs of 2000 feet or more. Kayenta layers are typically red to brown in color, forming broken ledges.
Southwest Utah
The red and mauve Kayenta
siltstones and
sandstones that form the slopes at base of the
Navajo Sandstone cliffs record the record of low to moderate energy streams. Poole (1997) has shown that the streams still flowed toward the east depositing from 150 to 210 m (500 to about 700 feet) of
sediment here. The
sedimentary structures showing the channel and
flood plain deposits of
streams are well exposed on switchbacks below the tunnel in Pine Creek Canyon.
In the southeastern part of Zion National Park a stratum of
cross bedded sandstone is found roughly halfway between the top and bottom of the Kayenta Formation. It is a "tongue" of sandstone that merges with the Navajo formation east of
Kanab, and it shows that
desert conditions occurred briefly in this area during Kayenta time. This tongue is the ledge that shades the lower portion of the Emerald Pool Trail, and it's properly called Navajo, not Kayenta.
Fossil mud-cracks attest to occasional seasonal
climate, and thin
limestones and fossilized trails of
aquatic snails or
worms mark the existence of
ponds and
lakes. The most interesting fossils, however, are the
dinosaur tracks that are relatively common in Kayenta mudstone.
These vary in size, but all seem to be the tracks of three-toed
reptiles that walked upright, leaving their tracks in the muds on the flood plains. Unfortunately, so far no bone materials have been found in the County that would enable more specific identification.
Apparently during Kayenta time Zion was situated in a climatic belt like that of
Senegal with rainy summers and dry winters at the southern edge of a great desert. The influence of the
desert was about to predominate, however, as
North America drifted northward into the arid desert belt.
Southeast Utah
In most sections that include all three
geologic formations of the
Glen Canyon group the Kayenta is easily recognized. Even at a distance it appears as a dark-red, maroon, or lavender band of thin-bedded material between two thick, massive, cross bedded
strata of buff, tan, or light-red color. Its position is also generally marked by a topographic break. Its weak beds form a bench or platform developed by stripping the Navajo sandstone back from the face of the Wingate cliffs. The Kayenta is made up of beds of sandstone,
shale, and limestone, all, uneven at their tops, and discontinuous within short distances. They suggest deposits made by shifting
streams of fluctuating volume. The sandstone beds, from less than 1 inch to more than 10 feet thick, are composed of relatively coarse, well-rounded
quartz grains cemented by
lime and
iron. The thicker beds are indefinitely cross bedded. The shales are essentially
fine-grained, very thin sandstones that include lime
concretions and balls of consolidated
mud. The limestone appears as solid gray-blue beds, a few inches to a few feet thick, and as lenses of limestone
conglomerate. Most of the limestone lenses are less than 25 feet long, but two were traced for nearly 500 feet and one for 1,650 feet.
Viewed as a whole the Kayenta, is readily distinguished from the geologic formations above and below it. It is unlike them in composition, color, manner of bedding, and sedimentary history. Obviously the conditions of sedimentation changed in passing from the Wingate Sandstone formation to the Kayenta and from the Kayenta to the Navajo sandstone, but the nature and regional significance of the changes have not been determined. In some measured sections the transition from Wingate to Kayenta is gradual; the material in the basal Kayenta, beds seems to have been derived from the Wingate immediately below and redeposited with only the discordance characteristic of fluviatile sediments. But in many sections the contact between the two formations is unconformable; the basal Kayenta consists of conglomerate and lenticular sandstone that fills depressions eroded in the underlying beds. In
Moqui Canyon near Red Cone Spring nearly 10 feet of Kayenta limestone conglomerate rests in a long meandering
valley cut in Wingate. Likewise, the contact between the Kayenta and the Navajo in places seems to be gradational, but generally a thin jumbled mass of sandstone and shales, chunks of shale and limestone, mud balls, and concretions of lime and iron, lies at the base of the fine-grained, cross bedded Navajo. Mud cracks, a few
ripple marks, and incipient drainage channels were observed in the topmost bed of the Kayenta on
Red Rock Plateau; and in west Glen Canyon, wide sand-filled cracks appear at the horizon. These features indicate that, in places at least, the Wingate and Kayenta were exposed to
erosion before their overlying geologic formations were deposited, are it may be that the range in thickness of the Kayenta thus in part (is) accounted for.
Grand Canyon
The Kayenta Formation is approximately 400 feet thick and consists of a fine-grained sandstone interbedded with layers of siltstone. The alternation of these units generally produces a series of ledges and slopes between the cliffs of the Navajo and
Moenave formation
s. Dinosaur tracks are fairly common in the siltstone, and
fresh water mussels and
snails occur but are rare. The Kayenta Formation is colored pale red and adds to the splendor of the
Vermilion Cliffs. It accumulated as deposits of rivers.
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