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132-459: The Chinle Formation is an Upper Triassic continental geological formation of fluvial , lacustrine , and palustrine to eolian deposits spread across the U.S. states of Nevada , Utah , northern Arizona , western New Mexico , and western Colorado . In New Mexico, it is often raised to the status of a geological group, the Chinle Group . Some authors have controversially considered

264-454: A Grama Bouteloua /Galleta Hilaria (plant) Steppe ( 53 ) potential vegetation type with a Desert Grassland ( 12 ) vegetation form and a Juniper / Pinyon pine (23) vegetation type with a Great Basin montane forest /Southwest Forest (4) vegetation form. A 2005 survey found that 447 species of flora, of which 57 species are invasive , occur in the park. Although the park is known for its fossils and eroded badlands, its main environment

396-631: A conodont, Misikella posthernsteini . As of 2010 , the base of the Norian has not yet been established, but will likely be based on conodonts. The late Triassic is also divided into land-vertebrate faunachrons . These are, from oldest to youngest, the Berdyankian , Otischalkian , Adamanian , Revueltian and Apachean . Following the Permian–Triassic extinction event , surviving organisms diversified. On land, archosauriforms , most notably

528-680: A discontinuous patchwork up to the San Rafael Swell . The stratigraphic nomenclature used in southern Utah is also utilized in Monument Valley , where the coarse-grained lower members of the Chinle form a caprock for many famous buttes which characterize the valley. In this region, the stratigraphically lowest unit in the Chinle is usually the Shinarump Conglomerate (or Shinarump Member), which thins northward but

660-559: A dry windy climate with temperatures that vary from summer highs of about 100 °F (38 °C) to winter lows well below freezing. More than 400 species of plants, dominated by grasses such as bunchgrass , blue grama, and sacaton , are found in the park. Fauna include larger animals such as pronghorns , coyotes , and bobcats ; many smaller animals, such as deer mice , snakes, lizards, and seven kinds of amphibians ; and more than 200 species of birds, some of which are permanent residents and many of which are migratory . About one third of

792-427: A gift shop, a gas station, a post office open from 11 a.m. to 1 p.m. Monday through Friday, a postal drop box, and public restrooms. The Rainbow Forest Museum complex 2 miles (3.2 km) north of the park's south entrance offers services including information and "Timeless Impressions" showings once every half-hour. It has a bookstore, fossil exhibits, an interactive Triassic Virtual Tour, limited food service,

924-496: A gift shop, and public restrooms. The Painted Desert Inn, 2 miles (3.2 km) north of the Painted Desert Visitor Center, offers visitor information. It has a bookstore, museum exhibits (including the building itself), and public restrooms. No campgrounds or overnight lodging are available in the park, although nearby communities such as Holbrook offer motels and other accommodations. Overnight parking

1056-548: A high concentration of reworked zircons must be accounted for when inferring an accurate age of deposition. The true duration of the Sonsela Member is likely from around 218 Ma to 213 Ma (2020), though older estimates place its base at 220-219 Ma (2011, 2013). A prominent biological turnover is found at the Adamanian-Revueltian boundary in the middle of the Sonsela Member, around 214 Ma. It may correspond to

1188-473: A large lake basin covered much of northeastern Arizona. The older (lower) layers of the formation consist of fluvial and lacustrine (lake-related) deposits of silt, sand, and clay. The younger (upper) Bidahochi contains ash and lava from volcanoes that erupted nearby and as far away as southwestern Nevada. Although much of the Bidahochi has since eroded, a small part of it outcrops in the northern part of

1320-882: A local extinction, or simply represents a time period which is truncated by slow deposition or a geological hiatus. The thin Sonsela Sandstone bed, the namesake of its corresponding member, has been dated to 216.6 Ma (2019) at its type locality at Sonsela Buttes in Arizona. The first Chinle U-Pb age data to be published referred to the Black Forest Bed, a sandstone layer near the top of the Petrified Forest Member in PEFO. U-Pb estimates for this layer include ~213 Ma (2003 maximum), ~211 Ma (2009), and ~210 Ma (2011, 2020). A presumably older exposure of

1452-620: A patina known as desert varnish . Most of the petroglyphs in Petrified Forest National Park are thought to be between 650 and 2,000 years old. From the 16th through the 18th centuries, explorers looking for routes between Spanish colonies along the Rio Grande to the southeast and other Spanish colonies on the Pacific coast to the west passed near or through the area, which they called El Desierto Pintado ,

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1584-495: A segment of Triassic sediments which are so diverse and extensive that it is sometimes raised to its own formation, subdivided further, or redefined more narrowly. In its widest definition, the Petrified Forest Member (or Formation) is split into three sections: the muddy Lower Petrified Forest and Upper Petrified Forest, and the sandy Sonsela Sandstone bed, which separates them. The Lower "Petrified Forest Member"

1716-481: A small fraction of the logs and most of the park's petrified animal bones have cells and other spaces that are mineral-filled but still retain much of their original organic structure. With these permineralized fossils, it is possible to study the cellular make-up of the original organisms with the aid of a microscope. Other organic matter—typically leaves, seeds, pine-cones, pollen grains, spores , small stems, and fish, insect, and animal remains—have been preserved in

1848-531: A small masonry structure built from petrified wood that is open to the public) signaling a greater degree of residential permanence. During the Late Pueblo II and Early Pueblo III periods 1050–1225 local population size grew rapidly. Similar to much of the Ancestral Pueblo world, population density increased rapidly at this time and nearly 1,000 sites dating to this period have been identified in

1980-596: A talk or walk along the Giant Logs Trail behind the museum, and a Puerco Pueblo guided walk. The park hosts special events related to Earth Science Week and National American Indian Heritage Month . On Saturdays from Memorial Day weekend through Labor Day at the Painted Desert Inn, artisans from the region give cultural demonstrations related to ancient peoples, intertribal relationships, and European-descent cultures. For students and teachers,

2112-546: A type of large scale volcanic activity that releases a huge volume of lava in addition to sulfur dioxide and carbon dioxide. The sudden increase in carbon dioxide levels is believed to have enhanced the greenhouse effect , which acidified the oceans and raised average air temperature. As a result of the change in biological conditions in the oceans, 22% of marine families became extinct. In addition, 53% of marine genera and about 76–86% of all species became extinct, which vacated ecological niches; thus, enabling dinosaurs to become

2244-476: A year. The epoch had a fluctuating, warm climate in which it was occasionally marked by instances of powerful heat. Different basins in certain areas of Europe provided evidence of the emergence of the "Middle Carnian Pluvial Event." For example, the Western Tethys and German Basin was defined by the theory of a middle Carnian wet climate phase. This event stands as the most distinctive climate change within

2376-541: Is a national park of the United States in Navajo and Apache counties in northeastern Arizona . Named for its large deposits of petrified wood , the park covers about 346 square miles (900 square kilometers), encompassing semi-desert shrub steppe as well as highly eroded and colorful badlands . The park's headquarters is about 26 miles (42 km) east of Holbrook along Interstate 40 (I-40), which parallels

2508-547: Is a reliable component of outcrops throughout the region. In several areas, a thin layer of mottled paleosols , the Temple Mountain Member , may be superimposed onto the Shinarump and underlying Moenkopi Formation. The Monitor Butte Member overlies the Shinarump and Temple Mountain members in southeast Utah and Monument Valley. This unit comprises drab and generally fine-grained sediments, equivalent to

2640-496: Is allowed in the wilderness areas; water for horses is available at the service station near the Painted Desert Visitor Center. Riders and hikers are asked to travel along dry washes as much as possible to reduce the impact on fragile desert soils. Rangers offer a variety of programs about the park. Regularly scheduled events include a Painted Desert Inn tour, a Triassic program at the Rainbow Forest Museum sunroom,

2772-917: Is entirely Late Triassic in age. Tetrapod biostratigraphy for the Chinle was first developed based on phytosaurs and aetosaurs , which in 1998 were combined into global biozones in Spencer G. Lucas 's Land Vertebrate Faunachrons system. Simplified stratigraphy based on Litwin. Note that age inferences devised by Lucas do not necessarily align with other chronological methods used in the Chinle Formation. Other works on Chinle biostratigraphy, such as Martz & Parker (2017), are better integrated with magnetostratigraphy and radiometric dating, and are considered more accurate. Machaeroprosopus ( Smilosuchus , Leptosuchus , etc.) ( Paleorhinus / Parasuchus ) Since 2011, widespread radiometric dating has helped to refine precise age data for part of

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2904-644: Is followed by the youngest and sandiest subunit of the Chinle, the Rock Point Member . The Rock Point is distinct enough that it was previously considered a unit of the Wingate Sandstone , a latest Triassic - early Jurassic aeolian formation which overlies the Chinle in many areas. Unambiguous exposures of the Chinle Formation extend into central New Mexico, beyond the eastern edge of the Colorado Plateau. Most of these are found in

3036-531: Is generally known as the Blue Mesa Member . In Petrified Forest National Park (PEFO) and its vicinities, the Sonsela Sandstone is thick enough that it can be resolved into several distinct sandstone-rich layers. It is renamed as the Sonsela Member in this situation. The Sonsela Sandstone is a collection of braided-stream channel facies. The Upper "Petrified Forest Member" is sometimes called

3168-452: Is not allowed except in the case of backpackers with wilderness hiking permits. Sightseeing is available by private automobile, motorcycle, commercial tour, bicycle, and hiking. The park road, parking lots, and turn-outs are big enough to accommodate large recreational vehicles. Off-road vehicle travel, including by mountain bike , is not allowed. With a few exceptions such as unpaved Old Highway 66, bicycles must stay on paved roads such as

3300-652: Is now deposited at the University of California Museum of Paleontology . In 1919, a phytosaur skull was discovered near Blue Mesa in the Petrified Forest by Ynez Mexia and sent to the Museum of Paleontology in Berkeley. In 1921, Annie Alexander , founder of the museum, visited Blue Mesa to collect more of the phytosaur and other specimens; this led to further excavations by paleontologist Charles Camp . Camp

3432-645: Is often synonymized with the Shinarump Conglomerate, though it may be derived from a different erosional source. It is often preceded by a very thin layer of silty mottled strata. This mottled strata is sometimes termed the Zuni Mountains Formation, though the application of this term beyond the Zuni Mountains is questionable. In the Chama Basin at least, the mottled strata is derived from the eroded and pedogenically modified surface of

3564-633: Is practically identical to the Blue Mesa Member, and likely represents the same depositional environment along the ancient river system responsible for the Chinle Formation. It is also distinct from the Monitor Butte Member, which has more evaporite deposits and fewer red sandy layers. The drab mudstone of the Monitor Butte and Cameron members are succeeded in a few areas by a thin section of massive conglomeratic sandstone,

3696-571: Is semi-desert shrub steppe. Protected from development and overgrazing for many years, the park has some of the best grassland in northeastern Arizona. In the northern part of the park, the volcanic soils of the Bidahochi Formation support abundant plant life along the Painted Desert rim. In contrast to the relatively bare badlands below, the rim is covered with shrubs, small trees, grasses, and herbs. The dominant plants in

3828-450: Is still a problem. Despite a guard force of seven National Park Service rangers , fences, warning signs, and the threat of a $ 325  fine , an estimated 12 short tons (11,000  kg ) of the fossil wood is stolen from the Petrified Forest every year. Jessee Walter Fewkes , the first archeologist to visit Puerco Ruin, predicted in the late 19th century that it would yield many artifacts. Conservationist John Muir conducted

3960-416: Is the golden eagle , with a wingspan of up to 7 feet (2 m). The park is open every day except Christmas on a schedule that varies slightly with the seasons. In 2010, it and its Painted Desert Visitor Center and Rainbow Forest Museum were open from 7 a.m. to 7 p.m. from May 9 through September 6 but opened as early as 8 a.m. and closed as late as 5 p.m. during other parts of

4092-566: Is the informally-named “ siltstone member ”. This unit is best exposed at Ghost Ranch, where it has produced the famous Whitaker Quarry, also known as the Coelophysis quarry due to a high concentration of fossils belonging to the theropod dinosaur Coelophysis bauri . The "siltstone member" may be equivalent to the Rock Point Member, and some authors refer to it as such. The Chinle continues northwards into southern Utah and

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4224-400: Is the largest and most often seen. Plateau striped whiptails , a species consisting entirely of females, prefer grasslands and developed areas. Side-blotched lizards live in rocky areas of the park but are seldom seen. Gopher snakes , which sometimes imitate rattlesnakes when disturbed, are among the most common snakes in the park. The Prairie rattlesnake , the only venomous snake found in

4356-585: The Moss Back Member . This member represents sandy river channel deposits and is likely equivalent to part of the Sonsela Member. Elsewhere, the Monitor Butte grades into the Petrified Forest Member, which in Utah includes the thin but geographically extensive Correo Sandstone Bed. The Petrified Forest Member is followed by the Owl Rock Member. A unit of drab interbedded coarse and fine sediments,

4488-587: The Archaic Period , nomadic groups established seasonal camps in the Petrified Forest from which they hunted game such as rabbits, pronghorn antelope, and deer and harvested seeds from Indian ricegrass and other wild plants. By at least 1000  BCE and through the Basketmaker II period (400  BCE –500  CE )Ancestral Puebloan farmers began to grow corn. Between 200–500  CE population size grew rapidly. Many families built houses in

4620-587: The BNSF Railway 's Southern Transcon , the Puerco River , and historic U.S. Route 66 , all crossing the park roughly east–west. The site, the northern part of which extends into the Painted Desert , was declared a national monument in 1906 and a national park in 1962. The park received 644,922 recreational visitors in 2018. Averaging about 5,400 feet (1,600 m) in elevation, the park has

4752-479: The BNSF Railway , and the Puerco River bisect the park generally east–west along a similar route. Adamana , a ghost town , is about 1 mile (1.6 km) west of the park along the BNSF tracks. Holbrook , about 26 miles (40 km) west of park headquarters along I-40, is the nearest city. Bisecting the park north–south is Park Road, which runs between I-40 near park headquarters on the north and U.S. Route 180 on

4884-519: The Bureau of Land Management , and private land, much of it used for cattle ranching, adjoin the other borders. The park's elevation above sea level varies from a low of 5,340 feet (1,630 m) along the Puerco River to a high of 6,230 feet (1,900 m) at Pilot Rock; the average elevation is about 5,400 feet (1,650 m). The terrain varies from gentle hills and major petrified wood deposits in

5016-657: The Chama Basin of north-central New Mexico, particularly several famed paleontological sites at Ghost Ranch near Abiquiu . Minor exposures also occur in the Lucero Uplift west of Albuquerque , as well as other areas along the Rio Grande Rift . As in the Colorado Plateau, the lowest major unit in north-central New Mexico is a sandstone-rich member. This layer, the Agua Zarca Sandstone ,

5148-606: The Colorado Plateau have been investigated since the 19th century, the Chinle Formation was only formally named and described by Herbert E. Gregory in 1917. It was named for Chinle Valley in Apache County, Arizona , land which is largely within the Navajo Nation . Gregory did not designate a type locality . He split the Chinle into four subunits, labelled A (youngest) to D (oldest). This did not include

5280-558: The Colorado Plateau , of which the park is part, was pushed upward by tectonic forces and exposed to increased erosion. All of the park's rock layers above the Chinle, except geologically recent ones found in parts of the park, have been removed by wind and water. In addition to petrified logs, fossils found in the park have included Late Triassic ferns, cycads , ginkgoes , and many other plants as well as fauna including giant reptiles called phytosaurs , large amphibians, and early dinosaurs. Paleontologists have been unearthing and studying

5412-748: The Kane Springs beds , develops in the Paradox Basin. The Kane Springs beds are river deposits which are likely equivalent to the Owl Rock Member and the upper part of the Petrified Forest Member. Finally, either the Rock Point Member or Church Rock Member overlie the Owl Rock. Some researchers feel that the Church Rock and Rock Point members may be synonymous. They are complex heterolithic units, representing variously braided-river facies, lacustrine, and overbank deposits. The Chinle Formation

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5544-574: The Mesa Redondo Member at PEFO have been dated to ~225 Ma (2011) or ~228 Ma (2013), though these may be influenced by recycled grains. Later estimates from a major core drilling project support a more recent depositional age of 223-222 Ma (2020). This firmly suggests that practically all of the Chinle Formation was deposited in the Norian stage; According to the consensus "long Norian" hypothesis and radiometric assessments of marine strata,

5676-593: The Mesozoic era, about 225-207 million years ago. During this epoch, the region that is now the park was near the equator on the southwestern edge of the supercontinent Pangaea , and its climate was humid and sub-tropical. What later became northeastern Arizona was a low plain flanked by mountains to the south and southeast and a sea to the west. Streams flowing across the plain from the highlands deposited inorganic sediment and organic matter, including trees as well as other plants and animals that had entered or fallen into

5808-867: The National Register of Historic Places . Eight other sites within the park are also on the National Register, including the Painted Desert Inn and associated cabins, the Agate House Pueblo , the Painted Desert Petroglyphs and Ruins Archeological District, Newspaper Rock Petroglyphs Archeological District , Puerco Ruin and Petroglyphs , the Flattop Site (an archeological site), the Twin Buttes Archeological District , and

5940-717: The Painted Desert area. In western New Mexico (particularly the Zuni Mountains area), the Mesa Redondo Member may be replaced by another sandy unit known as the Zuni Mountains Formation . Sediments from this time interval are followed by a geological unit called the Bluewater Creek Formation . Most Chinle outcrops in the Painted Desert have traditionally been placed within the following Petrified Forest Member ,

6072-625: The Painted Desert gets its name, is up to 800 feet (240 m) thick in the park. It consists of a variety of sedimentary rocks including beds of soft, fine-grained mudstone , siltstone , and claystone —much of which is bentonite —as well as harder sandstone and conglomerate , and limestone . Exposed to wind and water, the Chinle usually erodes differentially into badlands made up of cliffs, gullies, mesas , buttes , and rounded hills. Its bentonite clay, which swells when wet and shrinks while drying, causes surface movement and cracking that discourages plant growth. Lack of plant cover makes

6204-534: The Placerias Quarry near St. Johns . Fossil invertebrates include freshwater snails and clams . The oldest fossil crayfish , Enoploclytia porteri , was also described from the park, although it is not considered a crayfish proper (instead placed in Erymidae ). New animal species that were first identified from localities within the current park boundaries, some of which remain known only from

6336-582: The U.S. Congress to create a petrified forest national park. Although this first attempt failed, in 1906 the Antiquities Act signed by President Theodore Roosevelt was used to create the Petrified Forest National Monument as the second national monument . Between 1934 and 1942, the federal Civilian Conservation Corps built road, trails, and structures in the monument, and the government acquired additional land in

6468-538: The dinosaurs became an important faunal component in the Late Triassic. Likewise, bony fishes diversified in aquatic environments, most notably the Neopterygii , to which nearly all extant species of fish belong. Among the neopterygians, stem-group teleosts and the now extinct Pycnodontiformes became more abundant in the Late Triassic. The Carnian is the first age of the Late Triassic, covering

6600-522: The 10-mile-per-hour (16 km/h) average wind causes frequent sandstorms and dust devils , some of which reach altitudes of several thousand feet. Rain is heaviest from July through September, when 42 percent of the park's annual average precipitation falls. August is the wettest month. At an elevation of more than 5,000 feet (1,500 m), Petrified Forest National Park has a chance of light snow from October through March, although snow cover rarely persists. The annual average relative humidity of

6732-533: The 28-mile (45 km) main park road and stay off trails and unpaved surfaces. The park's seven maintained hiking trails, some paved, vary in length from less than 0.5 miles (0.8 km) to nearly 3 miles (4.8 km). Pets are allowed on these trails if kept on a leash, but bicycles are not. These named trails are Painted Desert Rim, Puerco Pueblo, Blue Mesa, Crystal Forest, Giant Logs, Long Logs, and Agate House. There are also nine recently developed day-hike routes on unpaved and largely unmarked routes called "Off

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6864-473: The 35th Parallel Route (also known as the Beale Camel Trail). The Painted Desert Inn was upgraded to a National Historic Landmark in 1987. The visitor center, which is near the north entrance to the park, offers visitor information and shows a 20-minute orientation movie, "Timeless Impressions", once every half-hour. It has a bookstore, exhibits, a restaurant open from 8 a.m. to 3 p.m.,

6996-698: The Adamana train station, book a hotel room, and take a tour of what was then called the Chalcedony Forest. Over the years, the line changed hands, becoming the Atchison, Topeka and Santa Fe Railway , and then the BNSF. More than 60 BNSF trains, mostly carrying freight, pass through the park every day. U.S. Route 66, a former transcontinental auto highway developed in 1926 from part of the National Old Trails Road , ran parallel to

7128-500: The Beaten Path" hikes. Hikers and backpackers may also visit the park's wilderness areas. Free permits are required for overnight stays; they are issued from the Painted Desert Visitor Center, Painted Desert Inn, and Rainbow Forest Museum. Most backpackers enter the wilderness at the north end of the park, where parking and an access trail are available at Painted Desert Inn. Group camping is limited to eight people. Horseback riding

7260-525: The Blue Mesa Member and Bluewater Creek Formation found further south. The facies of this interval have been interpreted as overbank (distal floodplain ) and lacustrine deposits. At Zion National Park, the Monitor Butte Member is replaced by a thick time-equivalent unit, the Cameron Member , which is also found in the Navajo Nation near its namesake of Cameron, Arizona . The Cameron Member

7392-493: The Carnian-Norian boundary is tentatively set to ~227 Ma. At PEFO, U-Pb estimates from the Blue Mesa Member include 223 Ma (2011), 222 Ma (2020), and 221-218 Ma (2020). Dated outcrops of drab mudstone near St. Johns, Arizona fit this general time period as well. The fossiliferous Placerias quarry, previously regarded as belonging to an older subunit, is likely part of the Blue Mesa Member based on an age date of 219.4 Ma (2014). At Six Mile Canyon near Fort Wingate, New Mexico ,

7524-447: The Chinle Formation, particularly in areas with a more complete stratigraphic record such as Petrified Forest National Park (PEFO). Volcanism further southwest along the Cordilleran magmatic arc supplies zircon crystals to the Chinle system, allowing for U-Pb dating of layers which host zircon grains. Eroded sediments from the Ancestral Rocky Mountains , Ouachita Mountains and Mogollon Highlands also supply older reworked zircon to

7656-523: The Chinle and Bidahochi. Older dunes range in age from 500,000 years at higher elevations in the northern part of the park to about 10,000 years in sandy drainage areas such as Lithodendron Wash. Stabilized by grasses and other vegetation, young dunes of about 1,000 years old are found throughout the park. During the Late Triassic, downed trees accumulating in river channels in what became the park were buried periodically by sediment containing volcanic ash . Groundwater dissolved silica (silicon dioxide) from

7788-422: The Chinle especially susceptible to weathering. About 60 million years ago, tectonic movements of the Earth's crust began to uplift the Colorado Plateau , of which the Painted Desert is part. Eventually parts of the plateau rose to 10,000 feet (3,000 m) above sea level. This warping of the Earth's surface led to the gradual and continuing destruction of the plateau by erosion. An unconformity (break in

7920-438: The Chinle reaches a maximum thickness of a little over 520 meters (1,710 ft). Typically, the Chinle rests unconformably on the Moenkopi Formation . The Chinle Formation was probably mostly deposited in the Norian stage, according to a plethora of chronological techniques. It is a thick and fossiliferous formation with numerous named members (subunits) throughout its area of deposition. While colorful Triassic sediments of

8052-419: The Chinle to be synonymous to the Dockum Group of eastern Colorado and New Mexico, western Texas , the Oklahoma panhandle, and southwestern Kansas . The Chinle Formation is part of the Colorado Plateau , Basin and Range , and the southern section of the Interior Plains . A probable separate depositional basin within the Chinle is found in northwestern Colorado and northeastern Utah. The southern portion of

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8184-428: The Chinle. "red siltstone member" "sandstone and conglomerate member" (UT) "ocher siltstone member" (UT) Kane Springs beds (in part) Kane Springs beds (in part) Bluewater Creek Formation (NM) Cameron Member Gartra Member ? Shinarump Conglomerate Zuni Mountains Formation (NM) "mottled strata" Temple Mountain Member Some of the most extensive deposits of the Chinle Formation are found in

8316-626: The Four Corners Region was established by the late 1950s. In 1956, Economic geologist Raymond C. Robeck identified and named the Temple Mountain member as the basal-most unit in the area of the San Rafael Swell of Utah. In 1957, John H. Stewart revised the Shinarump Conglomerate and renamed it the Shinarump member of the Chinle formation. Study of the formation expanded northwards into northern Utah and Colorado, facilitated through papers by Forrest G. Poole and Stewart (1964) and Steve W. Sikich (1965), who named informal local members equivalent to those of Arizona and New Mexico. The complete areal extent of

8448-457: The Four Corners area, though it thins greatly to the northwest. A narrow band of undifferentiated purplish sediments from the lower part of the formation extend into vicinity of St. George . The formation thickens eastward into Zion National Park and Grand Staircase–Escalante National Monument . The Chinle is a prominent component of badlands and outcrops in the various national parks, monuments, and recreation areas of southeast Utah, extending in

8580-487: The Hopi Mesas in Northern Arizona and at the Pueblo of Zuni in northern New Mexico, where the descendants of the ancient Petrified Forest farmers still live today. Some researchers have argued that a persistently dry climate led to out-migration, and the last residents left Puerco Pueblo in about 1380 CE. At Puerco Pueblo and many other sites within the park, petroglyphs —images, symbols, or designs—have been scratched, pecked, carved, or incised on rock surfaces, often on

8712-563: The Late Triassic Epoch did not prove to be as destructive as the preceding Permian Period, which took place approximately 50 million years earlier and destroyed about 70% of land species, 57% of insect families as well as 95% of marine life , it resulted in great decreases in population sizes of many living organism populations. The environment of the Late Triassic had negative effects on the conodonts and ammonoid groups. These groups once served as vital index fossils , which made it possible to identify feasible life span to multiple strata of

8844-422: The Late Triassic, including Plateosaurus , Coelophysis , Herrerasaurus , and Eoraptor . The Triassic–Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth. The Triassic was named in 1834 by Friedrich von Alberti , after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany :

8976-448: The Late Triassic. Conclusions summarized that the correlation of these sediments led to the modified version of the new map of Central Eastern Pangea, as well as that the sediment's relation to the "Carnian Pluvial Event" is greater than expected. The extinction event that began during the Late Triassic resulted in the disappearance of about 76% of all terrestrial and marine life species, as well as almost 20% of taxonomic families. Although

9108-399: The Moenkopi Formation. The coarse lower unit grades into the fine-grained Salitral Formation , which is equivalent to the Blue Mesa Member and Bluewater Creek Formation. In south-central New Mexico, it may instead grade into the San Pedro Arroyo Formation , a similar heterolithic unit. Coarse sandstone returns along a sharp contact with the following Poleo Formation , an equivalent of

9240-421: The Painted Desert Member, or simply referred to as the Petrified Forest Member in a more restricted definition of the term. The Petrified Forest is predominately overbank deposits with thin lenses of channel-deposit facies and lacustrine deposits. The Petrified Forest Member grades into the Owl Rock Member , a marginal lacustrine to lacustrine facies possibly representing a large lake system. The Owl Rock Member

9372-491: The Painted Desert section. The monument became a national park in 1962. Six years after the signing of the Wilderness Act in 1964 by President Lyndon B. Johnson , wilderness areas (where human activity is limited), were designated in the park. In 2004, President George W. Bush signed a bill authorizing the eventual expansion of the park from 93,353 acres (about 146 mi or 378 km ) to 218,533 acres (about 341 mi or 884 km ). Theft of petrified wood

9504-459: The Painted Desert. However, the park's oldest Spanish inscriptions, left by descendants of the region's early Spanish colonists, date only to the late 19th century. After the Southwest became part of the U.S. , explorers continued to look for good east–west routes along the 35th parallel . In 1853, a crew led by U.S. Army Lieutenant Amiel Whipple surveyed along a sandy wash in

9636-477: The Petrified Forest Member, the Hayden Quarry at Ghost Ranch, is dated to 212 Ma (2011). A similar age was found for the middle part of the member in PEFO. The end of the Petrified Forest Member was probably close to 208 Ma, meaning that overlying strata is presumably latest Norian-Rhaetian in age. Geologic Province: Parklands: Other: Late Triassic Many of the first dinosaurs evolved during

9768-541: The Petrified Forest and for the first time began to stay there year-round. During the Basketmaker III period, 500–700  CE , families occupied shallow subterranean pit structures, at first on mesas or other vantage points and later at the base of bluffs and in lowlands, where the soil was better. Settlement patterns shifted and population size grew during the Pueblo I era between 700 and 900 CE and for

9900-523: The Petrified Forest in the early 1940s identified most of the large sites with stone ruins, and subsequent surveys since 1978 have identified a total of more than 600 artifact sites, many of them small. The earliest paleontological exploration of the region that is now the park was made in 1899 by paleobotanist Lester Ward , material of which is now deposited in the Smithsonian Institution . Muir also collected some fossil material, which

10032-494: The Petrified Forest migrated to join rapidly growing communities on the Hopi Mesas to the northwest and the Pueblo of Zuni to the east–these locations are still home to thousands of descendant community members today. More than 1000 archeological sites, including petroglyphs , have been discovered in the park. These ancestral places remain important to descendant communities. In the 16th century, Spanish explorers visited

10164-512: The Sonsela Member. The Poleo Formation grades into the thick colorful sediments of the Petrified Forest Member. Authors which raise this member to a formation subdivide it into the lower Mesa Montosa Member and the upper Painted Desert Member. The Petrified Forest Member is fossiliferous in the Chama Basin, with major sites including the Hayden, Canjilon, and Snyder quarries of Ghost Ranch. The stratigraphically highest unit in north-central New Mexico

10296-538: The Triassic Period. Sediments that include red beds, which are sandstones and shales of color, may suggest seasonal precipitation. Rocks also included dinosaur tracks, mudcracks, and fossils of crustaceans and fish, which provide climate evidence, since animals and plants can only live during periods of which they can survive through. The Late Triassic is described as semiarid. Semiarid is characterized by light rainfall, having up to 10–20 inches of precipitation

10428-454: The Triassic Period. Propositions for its cause include: Theories and concepts are supported universally, due to extensive areal proof of Carnian siliciclastic sediments. The physical positions as well as comparisons of that location to surrounding sediments and layers stood as basis for recording data. Multiple resourced and recurring patterns in results of evaluations allowed for the satisfactory clarification of facts and common conceptions on

10560-559: The Triassic strata. These groups were severely affected during the epoch, and conodonts became extinct soon after (in the earliest Jurassic). Despite the large populations that withered away with the coming of the Late Triassic, many families, such as the pterosaurs , crocodiles , mammals and fish were very minimally affected. However, such families as the bivalves, gastropods , marine reptiles and brachiopods were greatly affected and many species became extinct during this time. Most of

10692-577: The Triassic. The end of the Triassic also brought about the decline of corals and reef builders during what is called a "reef gap". The changes in sea levels brought this decline upon corals, particularly the calcisponges and scleractinian corals. However, some corals would make a resurgence during the Jurassic Period. 17 brachiopod species were also wiped out by the end of the Triassic. Furthermore, conulariids became extinct. Petrified Forest National Park Petrified Forest National Park

10824-552: The University of Chicago (Michael Parrish), the Field Museum of Natural History (John Bolt), and Yale University (Paul Olsen). Since then, more than 300 fossil sites have been documented in the park. Research in paleontology and archeology continues at the park in the 21st century. According to the A. W. Kuchler U.S. Potential natural vegetation Types, Petrified Forest National Park encompasses two classifications;

10956-444: The area is below 50 percent and at times less than 15 percent. More than 1200 archeological sites have been found inside the boundaries of Petrified Forest National Park. Evidence suggests that the earliest inhabitants of the park arrived over 12,000 years ago. Clovis and Folsom-type spear points made from petrified wood are among the earliest artifacts of Paleoindians found in the park. Between 8,000 and 1,000  BCE ,

11088-422: The area, and by the mid-19th century a U.S. team had surveyed an east–west route through the area where the park is now located and noted the petrified wood. Later, roads and a railway followed similar routes and gave rise to tourism and, before the park was protected, to large-scale removal of fossils. Theft of petrified wood remains a problem in the 21st century. Petrified Forest National Park straddles

11220-403: The ash and carried it into the logs, where it formed quartz crystals that gradually replaced the organic matter. Traces of iron oxide and other substances combined with the silica to create varied colors in the petrified wood. In Petrified Forest National Park, most of the logs in the park retained their original external form during petrification but lost their internal structure. However,

11352-568: The base of the Blue Mesa Member (or its local equivalent) is defined by a distinct sandstone bed, which has been dated to 221-219 Ma (2009) or 218 Ma (2011). The underlying Bluewater Creek Formation has also been dated to 221-219 Ma (2014), suggesting that it overlaps in time with the Arizonan Blue Mesa Member and possibly part of the Sonsela Member. Radiometric dates are well-recorded for the Sonsela Member , though

11484-849: The basin. Chinle radiometric dating is complicated by lithological quirks of zircon deposition. Taken at face value, U-Pb dates from coarse-grained layers are often several million years older than expected based on magnetostratigraphy, while mud-dominated layers are generally more accurate despite a lower sample size. This is likely because sandy rivers receive a higher proportion of recycled zircon grains from distant eroded rocks, while muddy plains are supplied with fresh zircon-rich ash from contemporary volcanic eruptions. While zircons from sandstone-rich layers are less useful for inferring direct depositional ages, they can be very useful for inferring sediment sources: each igneous or metamorphic sediment source has its own set of old (usually Precambrian) zircon ages, which can be traced in Triassic sediments. Outcrops of

11616-424: The border between Apache County and Navajo County in northeastern Arizona. The park is about 30 miles (50 km) long from north to south, and its width varies from a maximum of about 12 miles (20 km) in the north to a minimum of about 1 mile (1.6 km) along a narrow corridor between the north and south, where the park widens again to about 4 to 5 miles (6 to 8 km). I-40 , former U.S. Route 66 ,

11748-465: The dominant presence in the Jurassic Period. While the majority of the scientists agree that volcanic activity was the main cause of the extinction, other theories suggest the extinction was triggered by the impact of an asteroid, climate change, or rising sea levels . The impacts that the Late Triassic had on surrounding environments and organisms were wildfire destruction of habitats and prevention of photosynthesis. Climatic cooling also occurred due to

11880-544: The end of the period, continental drift occurred which separated Pangea. At this time, polar ice was not present because of the large differences between the equator and the poles. A single, large landmass similar to Pangea would be expected to have extreme seasons; however, evidence offers contradictions. Evidence suggests that there is arid climate as well as proof of strong precipitation. The planet's atmosphere and temperature components were mainly warm and dry, with other seasonal changes in certain ranges. The Middle Triassic

12012-588: The evidence suggests the increase of volcanic activity was the main cause of the extinction. As a result of the rifting of the super continent Pangea , there was an increase in widespread volcanic activity which released large amounts of carbon dioxide. At the end of the Triassic Period, massive eruptions occurred along the rift zone , known as the Central Atlantic Magmatic Province , for about 500,000 years. These intense eruptions were classified as flood basalt eruptions, which are

12144-793: The fastest land animals in North America, are capable of 60-mile-per-hour (97 km/h) sprints. They are the second fastest land animal on Earth. The blood vessels in the huge, thin-walled ears of the jackrabbits act as heat exchangers. These hares are known for their bursts of speed, long leaps, and zigzag routes, all of which protect them from being eaten by golden eagles and other predators. The prairie dogs live in large colonies or "towns", near which many other species find food and shelter. Coyotes dine largely on rodents but also eat fruits, reptiles, insects, small mammals, birds, and carrion . Bobcats and bullsnakes hunt smaller animals, such as deer mice and white-tailed antelope squirrels in

12276-541: The first dinosaurs came at about the same time as the Carnian pluvial episode , at 234 to 232 Ma. This was a humid interval in the generally arid Triassic. It was marked by high extinction rates in marine organisms, but may have opened niches for the radiation of the dinosaurs. The Norian is the second age of the Late Triassic, covering the time interval from about 227 to 208.5 million years ago. During this age, herbiverous sauropodomorphs diversified and began to displace

12408-543: The first excavations of the ruin in 1905–06. Although he did not publish his findings, he urged the federal government to preserve Petrified Forest. Professional archeological work in the park began in the early 20th century when Walter Hough conducted excavations at Puerco Ruin and other sites. In the 1930s, the Civil Works Administration funded research in the park by archeologists H.P. Mera and C.B. Cosgrove. A National Park Service resurvey of

12540-542: The first time large groups of families aggregated together and formed large villages. During this period, each household built large well-insulated subterranean residential pit structures to keep warm during the cold winter months and several adjacent above ground rooms made from stone and jacal similar to adobe—used for food storage and daily activities during the warmer months. During the early Pueblo II period (900–1050  CE ) Ancestral Pueblo farmers began constructing above-ground masonry architecture (for example Agate House,

12672-435: The large herbivorous therapsids , perhaps because they were better able to adapt to the increasingly arid climate. However crurotarsans continued to occupy more ecological niches than dinosaurs. In the oceans, neopterygian fish proliferated at the expense of ceratitid ammonites. The Manicouagan impact event occurred 214 million years ago. However, no extinction event is associated with this impact. The Rhaetian Age

12804-509: The late 19th century, settlers and private stagecoach companies followed similar east–west routes. Homesteaders who stayed in the area developed cattle ranches on the grasslands, and cattle grazed in the Petrified Forest until the mid-20th century. Also close to the 35th parallel was the Atlantic and Pacific Railroad . Its opening in the early 1880s led to the founding of towns like Holbrook and Adamana. Visitors could stop at

12936-516: The lower Buntsandstein (colourful sandstone ) , the middle Muschelkalk (shell-bearing limestone) and the upper Keuper (coloured clay). The Late Triassic Series corresponds approximately to the middle and upper Keuper. On the geologic time scale , the Late Triassic is usually divided into the Carnian, Norian, and Rhaetian ages, and the corresponding rocks are referred to as the Carnian, Norian, and Rhaetian stages. Triassic chronostratigraphy

13068-569: The name Dolores Formation as a parochial synonym for the Chinle Group. Overviews of the Chinle were created by Dubiel and others (1992) and Hintze and Axen (1995). The Chinle Formation is fossiliferous, with a diverse array of extinct reptile, fish, and plant fossils, including early dinosaurs and the famous petrified wood of Petrified Forest National Park in Arizona . The formation members and their thicknesses are highly variable across

13200-502: The northern part of the Petrified Forest. So impressed was Whipple by the petrified wood along the banks of the arroyo that he named it Lithodendron Creek (Stone Tree Creek). Geologist Jules Marcou , a member of the Whipple expedition, observed that the petrified trees were from the Triassic. A slightly later route along the parallel was a wagon road, built between 1857 and 1860, that involved experimental use of camels as transport. In

13332-480: The ocean, as well as some organisms known for reef -building, and the pelagic conodonts . In addition to these species that became extinct, the straight-shelled nautiloids , placodonts , bivalves , and many types of reptile did not survive through this age. During the beginning of the Triassic Period, the Earth consisted of a giant landmass known as Pangea, which covered about a quarter of Earth's surface. Towards

13464-527: The park as compression fossils , flattened by the weight of the sediments above until only a thin film remains in the rock. Much of the park's petrified wood is from Araucarioxylon arizonicum , an extinct conifer tree, while some found in the northern part of the park is from Woodworthia arizonica and Schilderia adamanica trees. At least nine species of fossil trees from the park have been identified; all are extinct. The park has many other kinds of fossils besides trees. The Chinle, considered to be one of

13596-524: The park at a wide variety of locations—at the mouths of washes , near seeps , and on moisture-holding sand dunes. Between 1250 and 1450 CE Ancestral Pueblo families gathered into large apartment building-like masonry structures (also known as pueblos) with several hundred people living together in close quarters These large villages were often located near important water sources. Ancestral Pueblo people constructed more than two of these large pueblos, one called Stone Axe, about 0.5 miles (0.8 km) east of

13728-560: The park include more than 100 grass species, many native to the region. Growing among the grasses are flowering species such as evening primrose , mariposa lily , and blue flax , and shrubs such as sagebrush , saltbush , and rabbitbrush . Among the wide variety of grasses are native perennial bunchgrass , blue grama , sacaton , sideoats grama , bearded sprangletop , and bush muhly . Invasive species that crowd out slower-spreading natives include annual lovegrass and brome (cheat grass). Trees and shrubs grow in riparian zones along

13860-494: The park is designated wilderness —50,260 acres (79 sq mi; 203 km ). The Petrified Forest is known for its fossils, especially fallen trees that lived in the Late Triassic Epoch , about 225 million years ago. The sediments containing the fossil logs are part of the widespread and colorful Chinle Formation , from which the Painted Desert gets its name. Beginning about 60 million years ago,

13992-535: The park's fossils since the early 20th century. The park's earliest human inhabitants arrived 13,000 years ago. These Clovis-era people are the ancestors of Native Americans. By about 2,500 years ago Ancestral Pueblo farmers were growing corn and living in subterranean pit houses in what would become the park. By one-thousand years ago Ancestral Pueblo farmers lived in above-ground, masonry dwellings called pueblos and gathered in large communal buildings called great kivas. By AD 1450 Ancestral Pueblo farmers in

14124-552: The park's riparian zones. Western pipistrelle bats feast on insects, and pallid bats eat beetles, centipedes , cicadas , praying mantises , scorpions , and other arthropods . On the Painted Desert rim, small animals find food and shelter among the denser foliage, and mule deer sometimes frequent the area. More than 16 kinds of lizards and snakes live in various habitats in the park and consume large quantities of insects, spiders, scorpions, other reptiles, and small mammals. The collared lizard , which occurs in every habitat,

14256-479: The park's washes. Willows and cottonwoods are the larger plants, joined by rushes and sedges. Here the invasive Eurasian tamarisk , also known as saltcedar, threatens native plants by crowding, using most of the available water, and increasing soil salinity by exuding salt through its leaves. Some of the larger animals roaming the grasslands include pronghorns , black-tailed jackrabbits (hares), Gunnison's prairie dogs , coyotes , bobcats and foxes. Pronghorns,

14388-516: The park, 6 other species probably do, and 18 species live in the park year-round. Thirty-five species live in the park only during the summer and 11 species only during the winter. The greatest diversity of birds occurs during fall and winter migrations. Raptors , songbirds, and ground birds are found in the park's grassland, while the Puerco River's riparian corridor is a good place for year-round residents as well as migrants such as warblers , vireos , avocets , and killdeer . Developed areas around

14520-440: The park, and the other at Puerco Pueblo, which overlooks the Puerco River near the middle of the park. There they built roughly 200 rooms around an open plaza. Some rooms had no windows or doors and could be entered by climbing a ladder and descending through a hole in the roof. At its peak, perhaps 200 people lived in this pueblo. Over time, however, Ancestral Pueblo families undertook migrations and joined rapidly growing towns on

14652-617: The park, are listed below. According to the Köppen climate classification system, Petrified Forest National Park has a cold semi-arid climate ( BSk ). According to the United States Department of Agriculture , the plant hardiness zone at the Painted Desert Visitor Center 5,764 feet (1,757 m) is 7a with an average annual extreme minimum temperature of 3.1 °F (−16.1 °C). Winter winds can reach 60 miles per hour (97 km/h). Summer breezes are lighter, but

14784-493: The park, prefers grasslands and shrub areas. Seven kinds of amphibians , which drink no water but absorb it through their permeable skins, have been identified in Petrified Forest National Park. Tiger salamanders , found in grassland and near major drainages, are the only salamander species known in Arizona. Woodhouse's toads , which are seldom seen, are the largest toads in the park. They like grasslands, riparian corridors, and developed areas. Red-spotted toads , most active in

14916-590: The park—on Pilot Rock in the park's wilderness section and along the rim of the Painted Desert between Pintado and Tawa points. Exposed by erosion of the Bidahochi are volcanic landforms called maars (flat-bottomed, roughly circular volcanic craters of explosive origin). A maar vent can be seen from the Pintado Point lookout. During the Quaternary Period (2.6 million years ago up to today), deposits of windblown sand and alluvium covered much of

15048-488: The railroad tracks until it was decommissioned in 1985. The park has preserved within its boundaries a small grassy section of the road. Interstate 40 , which crosses the park, replaced the older highway. Increasing tourist and commercial interest in petrified wood during the late 19th century began to alarm residents of the region. In 1895, the Arizona Territorial Legislature asked

15180-516: The rainy season, July through September, are found in rocky areas near streams and in canyons. The Great Plains toad , the most common toad in the park, prefers grasslands. Resident spadefoot toads include the New Mexico, plains, and Couch's varieties. A survey conducted in 2006 identified 216 species of birds known to have occurred in Petrified Forest National Park since the park became a protected area in 1906. Of those, 33 species breed within

15312-645: The richest Late Triassic fossil-plant deposits in the world, contains more than 200 fossil plant taxa . Plant groups represented in the park include lycophytes , ferns , cycads , conifers, ginkgoes , as well as unclassified forms. The park has also produced one of the most diverse assemblages of fossil vertebrates from the Late Triassic. Among the groups represented are early theropod dinosaurs, crocodile-line archosaurs, temnospondyl amphibians, lissamphibians, non-archosauromorph diapsids, and other dinosauromorphs and archosauromorphs. Dicynodonts are extremely rare despite being abundantly represented at

15444-517: The rock record) of about 200 million years occurs within the park, where erosion has removed all the rock layers above the Chinle except geologically recent ones. The Bidahochi Formation , laid down only 4 to 8 million years ago, rests directly atop the Chinle, and rocks laid down in the Jurassic , Cretaceous , and much of the Tertiary are absent. During the period of the Bidahochi deposition ,

15576-482: The soot in the atmosphere. Studies also show that 103 families of marine invertebrates became extinct at the end of the Triassic, but another 175 families lived on into the Jurassic. Marine and extant species were hit fairly hard by extinctions during this epoch. Almost 20% of 300 extant families became extinct; bivalves, cephalopods, and brachiopods suffered greatly. 92% of bivalves were wiped out episodically throughout

15708-560: The south to eroded badlands in the north. Most of the park's intermittent streams—including Lithodendron Wash, Dead Wash, Ninemile Wash, and Dry Wash—empty into the Puerco River. In the southern part of the park, Cottonwood Wash and Jim Camp Wash flow into the Little Colorado River . Petrified Forest National Park is known for its fossils , especially of fallen trees that lived in the Late Triassic Epoch of

15840-464: The south. Historic Highway 180, an earlier alignment of the modern route, crosses the southern edge of the park. Like Route 66, it has deteriorated and is closed. Many unpaved maintenance roads, closed to the public, intersect Park Road at various points. The fee area of the park owned by NPS covers about 230 square miles (600 km ). The Navajo Nation borders the park on the north and northeast. State-owned land, federal land controlled by

15972-552: The southern Colorado Plateau, including Arizona and the western portion of New Mexico. In this region, the oldest and stratigraphically lowest portion of the Chinle is the Shinarump Conglomerate . The Shinarump includes braided-river system channel-deposit facies . The Shinarump interfingers with a finer-grained subunit, the Mesa Redondo Member , one of the oldest widespread units in the badlands of

16104-400: The time interval from 237 to 227 million years ago. The earliest true dinosaurs likely appeared during the Carnian and rapidly diversified. They emerged in a world dominated by crurotarsan archosaurs (ancestors of crocodiles ), predatory phytosaurs , herbivorous armored aetosaurs , and giant carnivorous rauisuchians , which the dinosaurs gradually began to displace. The emergence of

16236-444: The underlying Shinarump Conglomerate (named by G. K. Gilbert and Edwin E. Howell in 1875), which he considered a separate formation. United States Geological Survey geologists and paleontologists continued to map out the Chinle Formation through the 20th century, revising the unnamed subunits of Gregory. A basic stratigraphy of the formation was developed for north-central New Mexico by Wood and Northrop (1946), and stratigraphy in

16368-407: The unit was mapped by R.F. Wilson and Stewart in 1967. Stewart and his colleagues created an expansive overview and revision of the formation in 1972, summarizing previous knowledge on Chinle stratigraphy. V.C. Kelley assigned more members and revised the unit in 1972. Spencer G. Lucas and S.N. Hayden did the same thing in 1989. The Rock Point Member was assigned by R.F. Dubiel in 1989. The Chinle

16500-417: The visitor center and museum attract western tanagers , hermit warblers , house finches , and others. Occasional shorebirds and eastern birds also visit the park. Birds commonly seen in the park include the common raven and the western meadowlark , known for its charming song. Anna's hummingbird , which can hover and fly backwards as well as forwards, is among the smallest birds in the park. The largest

16632-467: The water. Although most organic matter decays rapidly or is eaten by other organisms, some is buried so quickly that it remains intact and may become fossilized. Within the park, the sediments containing the fossil logs for which the park is named are part of the Chinle Formation . The colorful Chinle, which appears on the surface in many parts of the southwestern United States and from which

16764-585: The year. The Painted Desert Inn (a historic museum and bookstore) is open from 9 a.m. to 5 p.m. year-round except Christmas. Park clocks are always set to Mountain Standard Time , as Arizona does not observe Daylight Saving Time . The Painted Desert Visitor Center, designed by modernist architect Richard Neutra , is part of the Painted Desert Community Complex Historic District listed on

16896-425: Was known to have consistent intervals of high levels of humidity. The circulation and movement of these humidity patterns, geographically, are not known however. The major Carnian Pluvial Event stands as one focus point of many studies. Different hypotheses of the events occurrence include eruptions, monsoonal effects, and changes caused by plate tectonics. Continental deposits also support certain ideas relative to

17028-512: Was originally based on ammonite fossils, beginning with the work of Edmund von Mojsisovics in the 1860s. The base of the Late Triassic (which is also the base of the Carnian) is set at the first appearance of an ammonite, Daxatina canadensis . In the 1990s, conodonts became increasingly important in the Triassic timescale, and the base of the Rhaetian is now set at the first appearance of

17160-490: Was raised to group rank by Lucas in 1993, thus also raising many of the members to formation status. He also included the formations of the Dockum Group of eastern New Mexico and west Texas within the "Chinle Group". This modified nomenclature is controversial; many still retain the Chinle as a formation and separate out the Dockum Group . The Dockum was named in 1890, before the Chinle. Lucas also advocated abandoning

17292-488: Was the final age of the Late Triassic, following the Norian Age, and it included the last major disruption of life until the end-Cretaceous mass extinction . This age of the Triassic is known for its extinction of marine reptiles , such as nothosaurs and shastasaurs with the ichthyosaurs , similar to today's dolphin . This age was concluded with the disappearance of many species that removed types of plankton from

17424-614: Was the most prolific collector in the early 20th century, but collections were also made by Maurice Mehl (University of Missouri), Edwin Colbert (American Museum of Natural History), and park naturalists like Myrl Walker. In the latter half of the 20th century, the park was inventoried by staff at the Museum of Northern Arizona (Richard Cifelli, Will Downs), with renewed collection made by researchers from Berkeley (Robert Long, Kevin Padian),

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