Petrified-Forest-Nationalpark

The Petrified Forest National Park is a national park in the United States in northeastern Arizona. The park is part of the southern Colorado Plateau and the Painted Desert, a desert approximately 1800 m above the sea. He preserved geologically remarkable sedimentary rocks of the Upper Triassic with a variety of fossils. In the area are extensive sites of silicified wood, hence the name " Petrified Forest ".

On December 8, 1906, part of the sites was made a national monument under protection in 1932 was a part of the Painted Desert to the reserve included since an area approximately 378 km ². The Congress of the United States classified the area in 1962 to the National Park. 1970 slightly more than half of that area were placed under the protection of an extended Wilderness Areas. Since 2004, a program for expansion of the parking area of 885 km ². Adjacent surfaces of other federal agencies are to be transferred to the National Park, private property be purchased when funds are available. In September 2011, approximately 105 km ² have been added to a purchased ranch to the park.

• 4.1 settlement
• 4.2 Commercial Use

Overview

In the northern part of the park, which lies above the Interstate 40 between Holbrook and Navajo, is the " Painted Desert ". This is a dry wasteland, where erosion has created a colorful landscape.

Most petrified wood can be seen in the southern part of the National Park, here you will also find ancient rock carvings, known as petroglyphs. The best known are attached to the " Newspaper Rock ". In the vicinity are the ruins of a pueblo of the 11th century, the Puerco Pueblo.

Attractions

• Painted Desert - from the northern entrance to the park, the road at the edge of the " Painted Desert " along. Some viewpoints offer a beautiful view over the highlands.
• The tepees - because of its conical shape of teepees of the Plains Indians reminiscent rock formations. To them by the various strata of the Blue Mesa Members are very easily recognizable.
• Blue Mesa - about a 5 kilometer road winds through the hilly landscape, in addition there is a small trail. The visible here clay of the Blue Mesa Members from white to blue-gray color gave this part of the land its name.
• Crystal Forest - here there is a small trail, about half a kilometer long. Along the circular path are strains with a thickness of sometimes almost a meter. The special feature of the strains are clear quartz and amethyst crystals that have formed in cavities.

Geology

The dry desert area on the edge of the Colorado Plateau particularly impressed by the many colors that shows this landscape. Particularly striking to show it in the " painted desert " and the " tepees ". As if drawn with a ruler appear the overlying rock layers:

• Their base is made partly of iron oxide reddish colored rock,
• The white layer above consists of sandstone,
• It is followed by a bright red colored layer of sedimentary rock interspersed with iron ( silt ),
• The bell finally consists of dark clay, which got its color by the addition of organic carbon.

Within the park can be easily observed the progression of erosion. While the top layer of clay is almost worn to the " tepees ", only this is in the upper section of the " Blue Mesa " yet visible.

General Overview

The pending in the territory of the national park rock strata belong to the Upper Triassic Chinle Formation, which consists essentially of fluvial and lacustrine deposits from here. They are generally shallow and very weak one to the south. In the park next layer elements are open ( from young to old):

• Owl Rock Members
• Upper - Petrified Forest Member
• Sonsela - Sandstone Members
• Blue Mesa Members

On the northern edge of the park, the Chinle Formation is unconformably by the volcanogenic Bidahochi - formation from the Upper Miocene and Lower Pliocene superimposed. In late Pleistocene and Holocene follow dunes and alluvial deposits.

Stratigraphic description

The approximately 225-220 million years old Blue Mesa Member consists mainly of brightly colored ( gray, blue, purple and green ) mudstones with a few sandstone benches such as the Newspaper Rock Sandstone. It is best exposed in the vicinity of the " tepees ".

The approximately 216 million years old Sonsela - Sandstone Members, often only Sonsela Members, can be three parts:

• Flattops -One Bed, a thick, resistant, oblique stratified sandstone unit.
• Jim Camp Wash Beds, blue, gray and purple shales, alternating with numerous gray and white sandstone layers.
• Rainbow Forest Bed, White obliquely stratified sandstones and conglomerates of rounded pebbles and cobbles. In this situation, there are silicified tree trunks. It forms the final topcoat on Blue Mesa, Agate Mesa and north of Rainbow Forest.

The Upper - Petrified Forest Members, often only Petrified Forest Members, leads red-colored mudstones and brown sandstone. It is well exposed in the flattops and contains numerous fossilized tree trunks. In the Painted Desert, it is formed as a white and pink unit containing refurbished sediments of volcanic origin. When on, Black Forest Bed has been radiometrically dated to 213 ± 1.7 million years ago.

The about 205 million years old, Owl Rock Member consists of pink to orange -colored shales alternating with thin hard Kalklagen. It also contains gypsum lenses ( selenite ) that formed in the evaporation of former lakes. The Owl Rock Member is present at the Chinde Mesa on the northern edge of the park.

The approximately 16-4 million years old Bidahochi formation follows a roughly 184 million years -long hiatus unconformably on the Owl Rock Member of the Chinle formation. In its lower part it leads fine-grained fluvial and lacustrine sediments ( silts, clays and sands) - at the time of northeastern Arizona by an extensive network of ephemeral lakes was covered. In follow volcanics: phreatomagmatic ash and lava flows. The origin of this volcanic entries is usually local in nature, but can sometimes down to the southwestern Nevada ( Southwest Nevada Volcanic Field) are pursued. The subsequent erosion has since removed a large part of Bidahochi lineup again, remained some cinder cones and maars. In the area of ​​erosion- resistant lava flows (eg, Pilot Rock and Hopi Buttes ) were, however, preserved the underlying sediments. The northwest subsequent Hopi Buttes Volcanic Field has one of the largest collections of maars world.

Float over the volcanic rocks in the late Pleistocene aeolian and alluvial deposits. The oldest dune fields are about 500,000 years old, they are in the higher parts of the national park and show northeast-southwest orientation. In recent rivers such as the sand -rich Lithodendron Wash occurs a younger generation dunes, which is only about 10,000 years old. Recent up to a maximum of 1,000 -year-old dunes can be actually seen everywhere; they are usually stabilized by grass cover. In these Quaternary sediments even the remains of an original trunk animal were discovered.

The erosion progresses even now continues to advance, so deepen the Little Colorado River and its tributary, the Puerco River, resistant their canyons relatively soft Chinle formation and the associated " Washes » remove these sediments then including overlapping Bidahochi lineup more and more from.

Genesis

Before about 215 million years ago, during the time period of the late Triassic, here was a mixed bag of many rivers alluvium. Araucaria, tree ferns and conifers were the vegetation. Crocodile -like reptiles, giant amphibians, smaller dinosaurs lived in this country. Testimony be many finds of fossils in the Chinle formation.

Fallen trees were buried under mud and silt from floods. Burial of further deposits slowed down the natural decay of the wood due to lack of oxygen. Under the increasingly thick sedimentary cover leaked silica -rich groundwater into the tree trunks. Quartz and chalcedony were deposited in the cavities of tribes, gradually replaced the cell tissue and so were the wooden structures of the tribes in stone.

The layers plummeted further and were flooded again. More and more layers of material by water herangetragenem encamped from it. Much later onset of tectonic movements in the earth's crust (see Lara mixer orogeny ) lifted out the land surface, the occurring stresses within the rock layers could break the stems. The now increasingly onset of erosion by wind and water contributed to and from after the softer layers of the sediments and thus laid the petrified tree trunks, which consist of hard quartz substance free.

History

Colonization

Petroglyphs, finds of sherds as well as remains of settlements in favor of a settlement by humans about 2,000 years ago. Precise knowledge about there are not sure, however, that there have been several settlement phases. These range from early nomadic tribes to the Pueblo culture around 1100 bis 1400th For the period after 1400 there is no more evidence of human habitation.

Middle of the 19th century, the land surveyor of U.S. troops arrived in the area. Based on their reports they brought stories about a " painted desert " and turned into stone trees back east. They were followed by the first settlers and ranchers.

Commercial use

The bright colors and patterns of various mineral deposits, particularly come into their own after grinding and polishing, make petrified wood is an ideal material for the decorative arts. Some time was the petrified wood, primarily, literally mined for the gift shop. When they saw that these deposits were limited, were the first voices to get some of the particularly rich deposits. The current park now protects them and thus preserved for future generations an insight into the history of the people and in the geological evolution of the Earth.

Jewelry ( eg, tags ), animal figures and various decorative objects, but also unprocessed or only polished pieces are commercially available. Outside the park there are more sites and only from this source of material for it. No matter how small piece may be taken from the park itself. Violations of these precautions are punished with draconian penalties. When you leave the park you have to expect with car controls. Also, the walk off the beaten path is strictly prohibited.