Geology of the Canyonlands area

The geology of the Canyonlands is very varied. In Canyonlands National Park in Utah rock formations 12 are open-minded, whose age ranges from the Pennsylvanian ( Upper Carboniferous ) to the Cretaceous period. The oldest and perhaps most interesting formation consists of evaporites, which are due to eindampfendes seawater. Foray end and back retreating warm shallow seas, leaving the remainder of the Paleozoic various fossil -rich limestones, sandstones and shales.

The detritus of the nearby mountains of the Uncompahgre Mountains then mingled in the Permian deposits of the coastal dunes and sand bars. At the end of the Paleozoic and the beginning of the Mesozoic, the sea withdrew forever from the region of Canyonlands back. A very flat landscape was dominated in the Triassic of alluvial plains and marshes. Further inland there was dry climate. Vast deserts covered large parts of North America. Only a short time there was a return of more humid climatic conditions, documented in competing with dune deposits river sediments.

In the late Cretaceous, the gradual uplift process of the Rocky Mountains began. For the Canyonlands this had serious consequences, the erosion rates were, for example, greatly increased. The Pleistocene glaciations latter experienced a further acceleration. Only since the recent past, the erosion is again much slower.

Stratigraphy

Hermosa Group

In the early Pennsylvanian Canyonlands were covered by a vast sea. In the east it came to the uplift of a mountain range, the Uncompahgre Mountains. The immediate consequence was a crustal depression on its west side - it was the Paradox Basin, a typical foreland basin. In this very rapidly subsiding basin, several thousand meters were at evaporites ( anhydrite and gypsum first, then later halite and sylvite ) excreted from the seawater during the Middle Pennsylvaniums due to the arid climate. The salt layers interlock frequently with siliciclastic entries which were washed out in a storm periods from the Bergmassif. Fresh sea water occasionally filled the basin again, but could the supersaturated salts pool water never completely displace ( it layered system only the denser pool water and remained confined to the surface ). The precipitated Evaporitlagen solidified later for Paradox Formation, part of the Hermosa Group. During the later Pennsylvanian the areas under the compression of the applied load increasing salt layers began to deform plastically and force upon higher ground. The main phase of salt tectonics is likely to have lasted until the end of the Jura. Satellite-based measurements, however, show that even up to the present day, the salt and gypsum layers are not yet come to rest and continue to deform overlying sedimentary layers.

The Paradox Formation is locally up to 1520 meters thick. In the National Park it is in the lower section of the Cataract Canyon as gypsum rock with black shale interlayers. Diapirartiges upgrade the Paradox Formation may also explains the emergence of Upheaval Dome, even if the formation should not be open-minded there. The prevailing theory is, however, still the impact of a meteorite.

Towards the end of Pennsylvaniums returned a warm shallow sea withdrew to the region of Canyonlands. On the mighty salt beds now lime sludge, sand and clay were sold. These sediments were added to the Fossilkalken, sandstones and shales of the gray-colored Honaker Trail Formation. Outcrops of the Honaker Trail Formation are located in the valley of the deep canyon in the national park, the best are of course on the Colorado River itself

It began then an erosion and there was a hiatus in the geologic record.

Cutler Formation

In the Early Permian was a Meerestransgression of the West, whose sediments now form the Elephant Canyon Members of the Cutler formation. The Elephant Canyon Members interlocks to the east with the continental sediments of the Halgaito Shale Members. Both members can be seen in Cataract Canyon and Elephant Canyon.

The Uncompahgre Mountains were exposed at the time of serious erosion. Large alluvial fans backfilled the transition zone between the mountain range and the Paradox Basin. Therefore, the resulting red beds of the undifferentiated Cutler Formation consist mainly of iron-rich Arkosesandsteinen. Marine sand bars and coastal sand dunes interlock with the red beds, they were later to white colored, steep wall forming Cedar Mesa Sandstone Members. These two competing rock units are now open in the National Park in a 6.4 to 8 km wide band that extends from the " Needles " on the " Maze " up to " elaterite Basin ".

Colorful Colored ( red to brown ), oxidized mudstones were then deposited over the Cedar Mesa Sandstone Members. They now form the Organ Rock Shale Member, a relatively susceptible to weathering rock unit that comes to light in the so -called " Land of Standing Rocks ."

Coastal sand dunes and marine sand bars returned again and left obliquely stratified, steep wall-forming White Rim Sandstone Members. It is 365 feet below the top of the " Iceland in the Sky " a striking platform, which earned the latter 's name. It is also open along the " White Rim Trail " and the " elaterite Basin " (as fossilized former sandbar ). The elaterite Basin takes its name from an outcropping here, dark brown, oily- tar-like substance, the Elaterit (elastic bitumen ).

The Permian sea retreated, long -lasting erosion began and there was again a hiatus.

Moenkopi Formation and Chinle Formation

In the Triassic siliciclastic red beds were deposited on the planarized surface Paleozoic. The sediments were from rivers that drained a broad, gently sloping plain to the west towards the open sea. In Marsh to Schlick took off, who would later form the shales of the Moenkopi Formation. Examples of this formation with ripple marks and desiccation cracks can be observed in the northern and western part of the park.

The sea retreated again and it came to a further erosion phase. On this erosion surface then the brightly colored shales of the slope forming Chinle Formation deposed. At the foot of the slope of the Chinle formation of petrified wood is found in the Petrified Forrest Members often.

Glen Canyon Group

The Glen Canyon Group comprises the following formations ( from young to old):

• Navajo Sandstone
• Kayenta Formation
• Wingate Sandstone

These rock units are best digested in the western and northern part of the park.

The Triassic climate was gradually dry, it emerged sand dunes, buried the dry valleys and associated floodplains among themselves. These dunes solidified the steep wall forming and over a hundred meters thick, rotgefârbten Wingate Sandstone. The sandstone wall runs in the terrain often hundreds of kilometers without major interruption and is therefore often presents an obstacle to traffic

Briefly, the climate was more humid again, so that now the river runs through the dunes paved their way. They left red-brown to lavender -colored sandstones, siltstones and shales alternated with - it resulted in the slope -forming Kayenta formation.

The recent formation of the Glen Canyon Group was formed again under arid environmental conditions. At the time, a very dry, sahara desert similar had formed in western North America, which covered approximately 388000 square kilometers. Oblique layered sand dunes reached enormous heights, especially in nearby Zion National Park and Kolob Canyon in (see geology of the Zion National Park ). It was the slightly orange colored Navajo Sandstone, the huge cliffs, rock towers and sometimes rocky gates ( such as the Millard Canyon Arch ) may form.

This was followed by re- ablation to form a layer gap.

San Rafael Group

In the ablation area of ​​the Glen Canyon Group emerged Watten, later Carmel formation. Then the massive Entrada Sandstone was deposited over the erodible sediments of the Carmel Formation, also a steep face images. Prolonged erosion activity away then again a large part of the San Rafael Group and any Cretaceous sediments.

Tectonic uplift

Before around 70 million years ago began the Lara mixer orogeny, which lasted until well into the Tertiary. Result of this process was the gradual emergence of the Rocky Mountains. The area of Canyonlands has been raised in this case by about a thousand feet without the original layers association was thereby disturbed stronger. The layers continue to remain in its original horizontal position. The slow lifting caused a pronounced fracturing of the rock formation, which in turn took great influence on erosion patterns.

When the salt beds of the Paradox Formation were obtained from ground water, readily soluble salts went into solution, only the plaster remained. In the field of " trench " It came even to the extent that higher layer lying limbs nachstürzten in the thus formed salt cavities empty.

During the Pleistocene glaciations, the erosion rate had increased tremendously, so that the canyons were now dispelled quickly. Broadening and deepening of the canyons had been particularly accelerated very strongly in the Green River and the Colorado River, as these rivers led glacial melt water from the Rocky Mountains. This landscaping processes sat down in the Canyonlands to the Holocene ( and now time) gone, but now run much slower due to the increased aridity.