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Petrified Forest

National Park


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Petrified Forest National Park, Arizona

Petrified Forest is primarily a geological park. The stunning vistas and barren “badlands” of the park are a result of the interaction between geology and climate. The paleontological resources, which the park was initially created to protect, are exposes from the substrate by rain- and wind-induced erosion in the park. Consistent with the rest of the Puerco River Basin (Webb et al., 1987), the bedrock in the park is composed of gently northeast dipping Mesozoic sedimentary rocks. The interbedded shales and siltstones of the Chinle formation provide the components necessary for both the erosion-resistant sandstone caps of the cuestas and mesas and the highly erodable underlying shale and siltstones. Triassic volcanism resulted in the deposition of the ash in the park that weathered to form the montmorillonite clay (also referred to as bentonite) found in the park today. The source zone for this material is believed to be the Mogollon Highlands to the south of the park (National Park Service, 1991). Volcanic ash may have been transported by the wind from volcanic fields as far to the West as Nevada (Harris, 1977). The deposited ash served as the source for the leached silica believed to be responsible for the petrifaction of the logs which are the park's main attraction. The Triassic sediments were subsequently buried and then re-exposed during the past 35 million years of uplift and erosion (National Park Service, 1991). The oldest exposed formation is the park is the Moenkopi, deposited in the middle Triassic. The Moenkopi is overlain by the Chinle, the formation in which the fossils and petrified wood are located. The Chinle Formation is composed of the Shinarump, the Lower and Upper Petrified Forest, and the Owl Rock Members. The Shinarump is a basal conglomerate, made up of Paleozoic clastic and igneous cobbles. The Petrified Forest Member is composed primarily of alluvial shales and siltstones (Harris, 1977). The colors of the Painted Desert are created by iron and manganese oxides contained in the Chinle Formation. The Pliocene Bidahochi Formation may be found on some mesa tops in the Painted Desert (National Park Service, 1991).

Uranium is found in sandstone deposits in both the Chinle and Moenkopi formations. In typical sandstone type uranium deposits, the uranium is emplaced by groundwater solutions with their origins in igneous rock or volcanic ash. Because a reducing environment is necessary for the precipitation of uranium-bearing minerals, it often occurs in the presence of organic material or iron sulfides (Christensen, 1979) such as the buried trees, ferns and fauna of the Petrified Forest Member.


The park soils are derived from the bedrock and are composed primarily of silts, clays, and sands derived from the Chinle formation. The soils are calcareous and moderately alkaline, pH 7.9 - 8.4. The most fertile soils within Petrified Forest National Park are generally found in the rolling grasslands, which are often located between mesas and badlands, as well as on a few of the mesa tops. These soils are composed of alluvial and wind-blown sands, making the soils quite permeable. The park's badland soils are composed of material derived from shales and have low permeabilities and high salt content (National Park Service, 1991). Clayey soils are particularly inhospitable to vegetation because the capillary pressure, or tension with which soil water is bound to soil particles, is very high in soils with small average particle sizes. The capillary pressure must be overcome by the osmotic pressures in plant roots in order for plant roots to take up water. Water held at tension too high to be overcome by plants is effectively unavailable, and the amount of water available to plants in clayey soils is quite low. In an arid environment, the presence of clayey soils significantly limits the potential for the development of organic soils and vegetation. The Federal Highway Administration site analysis of the Jim Camp Wash established that the sediments in the wash vary from a fine sandy loam to a silty clay loam. The deposits were deep and composed primarily of silts and sands deposited during flash flood events (Slettin, 2000). Soil survey data for those parts of the park located in Apache County are available in hard copy at the park and digitally. The digital data may be downloaded from the Ft. Worth Natural Resources Conservation Service web site (http://www.ncgc.nrcs.usda.gov/). Less detailed, 1:1,000,000 scale GIS data are available from the state of Arizona (http://www.land.state.az.us/). These data must be ordered, but can be obtained free of charge by government agencies.

Surface Water

Petrified Forest National Park straddles the boundaries of three USGS hydrologic catalog units (Figure 4). Most of the park is located within the Lower Puerco Watershed (USGS HUC 15020007), part of the larger Puerco River Watershed. The Puerco River, now named for its sediment-laden flow, was once called Tó Nízhóní or “beautiful water” by the Navajo (Wirt, 1994). The Upper Little Colorado River Watershed (USGS HUC 15020002) drains the southwest corner of the park. The northern boundary of the Upper Little Colorado River HUC cuts southeast across the park in the area of the Flattops. Leroux Wash (USGS HUC 15020009) drains the extreme northwest corner of the park. The hydrologic boundary of this hydrologic unit is located within the park in the hills southeast of Digger Wash.

Streams within Petrified Forest National Park are ephemeral in nature and only flow in response to rain and snow melt in the spring, and flash-flooding during the summer monsoon rain season. The major surface water features include the Puerco River as well as Lithodendron, Dry, and Jim Camp washes. All drainages within Petrified Forest National Park ultimately flow into the Little Colorado River, a tributary of the Colorado River.

There are no USGS stream gages currently operating in the area of the park. Historic flow data can be gathered from two inactive gages that were located in and around the park (National Park Service, 1999). The two historical gages located in the park were USGS09396500 along the Puerco (1940-1949) and USGS09396400 along a tributary of Dead Wash (1963-1975) (National Park Service, 1999). The stream data may be retrieved at https://waterdata.usgs.gov/nwis-w/AZ/. More recent stream flow information must be inferred from a USGS stream gage located on the Puerco near Chambers, approximately 25 miles upstream from the eastern boundary of the park. The gage, USGS 09396100, near Chambers, records only flows exceeding 500 ft3/s. Historical and real-time stream flow data demonstrating the episodic nature of flows in the Puerco are available at the Arizona USGS water resources web site.

Surface water within Petrified Forest National Park is also available seasonally in small pools (tinajas), springs / seeps, and abandoned stock impoundments, which are referred to locally as “tanks”. Since the amount of surface water within the park is limited, the availability and quality of water at the small pools and seeps take on additional significance, yet they are the most poorly characterized and understood water resources in Petrified Forest National Park. These waters serve as hatching areas for insects, amphibians and watering areas for larger animals. At Capitol Reef National Park, the tinajas have proved to be critical water supplies to several species of toads, frogs, bats and ungulates (Spence and Henderson, 1993).

Stratigraphy and morphology typically control the location of points at which groundwater “daylights” (i.e., reaches the ground surface from below ground) forming springs or seeps. On the mesas of Petrified Forest National Park, rainwater infiltrates permeable surface materials, often aeolian sands and soils and then the fracture systems in the eroding sandstone. When percolating rainwater encounters an unfractured rock layer of a much lower permeability, it travels horizontally, down-dip along the contact. If at some point the contact is exposed, for example along the vertical wall of mesa, the water daylights (Spence and Henderson, 1993). Within the park, the areal extent of beds supplying water to seeps and springs are limited and are therefore unlikely to produce large volumes of water (Aughenbaugh, 1970).

There are believed to be only three springs in the park. The 1957 Water Resources Report documents a flow from a spring on Blue Mesa that was sizable enough to be collected (Palmer, 1957). Active springs in both the Zuni Well and Agate Bridge areas were reported by Jones (1986). The presence of a spring along the mesa face at Agate Bridge was verified by park staff (C. Dorn, Petrified Forest National Park, personal communication, 2000).

Tinajas are rock depressions which are typically filled by rain or overland flow. They may be small and ephemeral or somewhat larger and perennial. While spring fed rock depressions are not technically “tinajas” the term is often is often applied to any water-filled rock depression within the park. Kokopelli or Celebration Man Tinaja, visited during November of 2000 following the second consecutive summer of regional drought conditions, provides a good example where water running off the top of the mesa contributes to the water in the pool, with some of the water remaining in the pool, even during extreme droughts. As petroglyphic evidence suggests that water may have been present in the pool in the distant past as well (C. Dorn, Petrified Forest National Park, personal communication, 2000), it is likely that the pool is at least partly supplied by groundwater.

The primary source of information regarding the location of the flowing and non-flowing waters within the park is the park-based field staff (rangers, interpreters, resource managers, maintenance employees, etc.). Park Resources Management staff have only recently begun to map the locations of tinajas, seeps and other hydrologic features. In order to understand the ecological significance of hydrologic features in the park, their density and geographic distribution must be understood.

A number of studies have been conducted on the tinajas of nearby Capitol Reef National Park in Utah. The studies may be of interest in that they have examined the change in the volume of tinajas in the water pocket fold during the course of a summer (Baron et al., 1998) and examine the effects of flooding and drying on biological diversity and community recovery. The Capitol Reef system, is however, very different from that at Petrified Forest in several important ways. The Waterpocket Fold system contains many tinajas and large rains may actually cause overflow from one tinaja to another. There are fewer tanks and tinajas at Petrified Forest and they are located remotely from one another. It is also likely that the Petrified Forest tinajas are located in more diverse geological settings than those at Capitol Reef, which are nearly all located in the Navajo Sandstone (Spence and Henderson, 1993).


Petrified Forest National Park overlies two aquifers from which significant amounts of water can be withdrawn. The Puerco River Alluvial Aquifer is a narrow ribbon of alluvium associated with the Puerco River. The Coconino Regional Aquifer or C Aquifer includes the sequence of sedimentary rocks from the top of the Kaibab Formation through the upper part of the Supai Formation (Hart et al.,2002) It is named for the primary water-bearing rock unit of the aquifer, the Coconino Sandstone.

The Puerco River Alluvial Aquifer underlies the river and is recharged during periods of flow. The aquifer is composed of interbedded gravel, sand, silt and clay although the spatial variation in the composition and hydrologic properties of the aquifer are not well understood (Webb et al., 1987). The wells drilled into the Puerco alluvium have been relatively shallow. Puerco Well No. 1 was drilled in 1957 to a depth of 48 feet, with the depth to water being 10 feet. For modeling purposes, Van Metre and Gray (1992) estimated that the porosity of the Puerco River Alluvial Aquifer materials, which they defined as “predominantly medium-fine sand” to be about 30%. Although the stratigraphy of the alluvial aquifer is unknown, several wells have been drilled up to 200 ft deep without encountering bedrock (Webb et al., 1987).

The Coconino Regional Aquifer or C Aquifer is much deeper. The C Aquifer underlies much of northeastern Arizona and northwestern New Mexico including Hubbel Trading Post National Monument and the Flagstaff Parks (Hart et al., 2002). There are two wells in the park that are completed in the C Aquifer. The Rainbow Forest Well is 980 feet deep and the Agate Bridge Well is 780 feet deep. The C Aquifer is confined in the area of the park and the groundwater gradient is to the northwest. Water from the Agate Bridge and Rainbow Forest wells is not used in the park because of its high dissolved solids concentrations.

The long-term impacts of ground water withdrawals from the C Aquifer by the Cholla Generating Station in Joseph City and the Coronado Generating Station in St. Johns are a concern of the National Park Service (B. Hansen, NPS Water Resources Division, personal communication, September, 2000).

There are three operational wells in the park, only one of which produce water suitable for domestic use. The Puerco No. 2 Well is the former source of park drinking water. It is completed in the Puerco River Alluvial Aquifer in Section 9, T18N.,R24E. Two additional wells completed in the C Aquifer are maintained, but unused. They are located at Agate Bridge and Rainbow Forest. All other wells in the park have been capped.

In 1959, Puerco Well No. 2 was constructed to replace a well drilled in 1934 which was abandoned when silt clogged the well and reduced production. Puerco Well No. 2 is connected to a concrete reservoir located at an elevation of 5916 ft. msl on Hill 5924 (BM) T19N R24E section 4 elevation 5322.5 ft msl). Puerco Well No. 2 is currently maintained and "exercised", but is not used as a water supply (C. Thomas, Petrified Forest National Park, personal communication, 2000). The well house is located on the north bank of the river, in clear sight of the bridge. Numerous water quality samples from the well show a consistent concentration of total dissolved solids around 950 mg/l. Although water from the Puerco No.2 Well meets primary drinking water standards, it is marginal being high in sodium and sulfate. Poor water quality and concerns about relying on a potentially contaminated water source caused the park to connect to the regional water supply system operated by the Navajo Tribal Utility Authority.

Other historic wells include the Zuni well which appears on the topographic map marking the location of an old oil prospecting well, which was drilled to a depth of 3000ft (Aughenbaugh, 1970). This well was later plugged and completed as a water well (Palmer, 1957). Other references to the Zuni water wells refer to a series of four production wells and six test wells that were located in Lithodendron Wash in section 5 T19N, R24E and section 32 T20N, R24E in the Painted Desert Section of the park (Palmer, 1957). They were believed to draw water from a lens in the Chinle formation, rather than from a regional aquifer (Palmer, 1957). Like the water produced in deep park wells, the Zuni wells water was highly mineralized (1680 mg/L TDS) (Aughenbaugh, 1970). The Zuni water wells were capped in 1968.

A well was drilled in the Rainbow Forest area in 1932-1933. It is completed in the Coconino Aquifer and never produced potable water. Saline waters are believed to be entering the well bore from the overlying Moenkopi formation (Palmer, 1957). In 1970, the location of the Rainbow Forest Well was unknown and it is believed to be capped and buried.

The current Rainbow Forest Well was drilled to a depth of 980 ft. in 1984 and is located in T17N R23E section 35. An analysis of pumped water in 1984 yielded a TDS concentration of 9,910 mg/L. The well is not pumped and there are no plans to use the well for anything other than monitoring water levels.

A private well completed in the Puerco alluvial aquifer is located inside the park, west of Newspaper Rock. It was accidentally drilled on park property and a special use permit was issued for its use for cattle watering (Permit No. 14-10-0333-1573) (Aughenbaugh, 1970). The well water was sampled as part of the alluvial aquifer analysis conducted by Webb and others in 1987. The well, (A-18-24)16bbb01, is referred to as both the Petrified Forest Windmill Well and the Pausel Well.

Monthly water level measurements at the Puerco Well No. 2 and Agate Bridge wells are made by the Resource Management staff. Water samples are collected from the Puerco Well No. 2 for chemical analysis quarterly. The water samples are shipped to the University of Virginia where pH, conductivity, alkalinity, and Ca2+, Na+, and Mg2+ concentrations are measured. Analysis of a sample from Agate Bridge Well yielded a TDS concentration of 19,800 mg/L shortly after the well was drilled in 1984.


While all streams in Petrified Forest National Park are ephemeral, riparian zones along these stream corridors support a riparian vegetation ranging from “none” to zones dominated by tamarisk, to well developed cottonwood/willow communities. The condition of the riparian communities along the larger streams, such as the Puerco River is thought to be poor, with large areas dominated by tamarisk and little cottonwood production. However, there is no current information on why different streams support different riparian communities .

A research proposal has recently been funded which will allow for researchers from Colorado State University to begin to characterize the riparian community potential of the streams within Petrified Forest National Park, based upon their physical environment. Information form this study will be used to identify areas where tamarisk control and riparian restoration efforts could result in each site returning to its natural, potential biological community. It is anticipated that this project will lead to the development of a Riparian Area Resource Management Plan, including a Tamarisk Integrated Pest Management Plan and Environmental Assessment (Dr. David Cooper, Colorado State University, PMIS project proposal #85644, 2002).

Radionuclide Contamination of Park Waters

Measured concentrations of radionuclides in the Puerco River are influenced by its source including both the natural erosion of uranium-bearing rock as well as past mining-related activities. Radionuclides can be transported into and through the system dissolved in the water, bound to filterable particles, or bound to colloids. The phase and composition of the radionuclides entering the Puerco River is a function of their origin.

Natural eroding radionuclide-bearing rocks are more likely to contribute sediment-bound radionuclides, than would settling pond waste. The highly variable areal distribution of precipitation in Arizona determines which tributaries contribute flow to the main Puerco River during a storm event. Sediments are known to be key transporters of radionuclides and other contaminants through the Puerco River Basin.

Heavy sediment loads are common for Puerco flows exceeding 3000 cfs (Webb et al., 1987). Such flows are highly episodic but are not rare, especially in the summer. Suspended particle-bound radionuclides may be transported some distance downstream from their origin and deposited in the riverbed. Deposited particles may be resuspended during subsequent storm events and transported further downstream (Webb et al., 1987), or they may be buried by subsequent erosion events until exposed by erosion at some later time. Particle-bound radionuclides may ultimately be transported out of the system in the sediment load of the stream. There is also inter-tributary variation in the amount of exposed radionuclide-bearing strata subject to erosion, meaning that the volume of radioactive material entering the Puerco varies from storm to storm depending on the contributing streams. The amount of uranium-bearing rock subject to erosion also varies temporally in each tributary (Gray and Webb, 1991).

During the period of uranium mining dewatering effluent and other treated uranium process waters were treated in settling ponds and contained limited amounts of radionuclides in the suspended phase. Van Metre and Gray confirmed the influence of radionuclide origin on composition in their 1992 study of dewatering effluent impacts on the Puerco River. In a stretch of the Puerco River upstream from the Gallup municipal Wastewater Treatment facility, they observed dissolved gross alpha, gross beta, uranium and radium activities declined after the cessation of mining activities. No statistical change, however, was observed for suspended phase radiation or in dissolved molybdenum or selenium (Van Metre and Gray, 1992). Studies in other systems have shown selenium, molybdenum and uranium comprise a larger fraction of the total concentration of released radionuclides in mining process waters than would be found in runoff (Van Metre and Gray, 1992).

Dissolved and colloidal-phase radionuclides may be removed from the system with the river water assuming that flow volumes are large enough that the river is flowing downstream from the park. Dissolved-phase radionuclides may be removed from solution by several particle-related processes. Radionuclides may bind to the surface of clays and other sediment grains. Under some circumstances, radionuclides may precipitate or co-precipitate, substituting for similarly shaped elements in the formation of minerals. The colloids to which radionuclides are bound may aggregate and form particles large enough to settle or be filtered, in which case they behave as suspended sediment-bound radionuclides. Dissolved or colloidal phase radionuclides are more likely to infiltrate the alluvial aquifer than suspended phase radionuclides.

Radionuclides, both dissolved and sediment-bound phase, may be taken up by biologic material, both plants and animals (US Geological Survey, 1987). A New Mexico Environmental Improvement Division study found that stock grazing in an area near the spill in the early 1980s showed elevated levels of uranium in their tissues (Millard et al., 1983, 1984). Webb et al. (1987) and others (US Geological Survey, 1987) found no significant uptake of radionuclides by perennial grasses and the biota are not believed to be responsible for any significant reduction in the amount of radionuclides in the system.

A threat can also be posed by blowing river sediment-bound radionuclides that might be inhaled or ingested by humans working in the streambed area. The USGS has, in fact, recommended the use of dust masks by those working in the area of the riverbed under no-flow conditions (Wirt, 1994). Ketterer's more recent work, however, indicated that radiation levels in the Puerco River surface sediment within the park have returned to levels considered "background" (2-3 ppb) and that sediments in the Puerco pose no greater threat than those of any of the other washes in the park (M. Ketterer, Northern Arizona University, personal communication, 2001).The water in the Puerco No. 2 well, has to date, been unaffected by anthropogenic releases of radionuclides upstream of the park. However, the USGS has recommended continuing intermittent sampling of the well water to establish that no significant water quality changes have taken place.

Erosional Impacts

Erosion, both wind and water driven, is a threat to the park’s paleontological and cultural resources. Fossil remains and petrified wood are themselves subject to the destructive effects of erosion once exposed. Unexposed resources, both archeological and paleontological, are often better protected from chemical and physical erosion as well as from theft.

While erosion poses a risk to the park’s paleontological and cultural resources, it is also the process responsible for the fantastic badland landforms of the Painted Desert and the Teepees. Badlands are formed where rapid soil erosion rates and/or unsuitable soil types prohibit the establishment of vegetation that might stabilize the soils and help to inhibit erosion (Mears, 1963). There is little organic material in the park's badland soils, and rains are both rare and intense, further limiting the ability of the vegetation to establish itself and stabilize slopes. The abundance of volcanically-derived bentonite, an expanding clay that undergoes dramatic volumetric changes, in park soils makes slopes less stable than they might be otherwise.

The park’s mesas, too, are erosional landforms. More erosion-resistant sandstone caprocks protect the underlying shales and siltstone. When the capstone is completely removed, teepees or pinnacles form from the remaining material (Harris, 1977). During a runoff event, the water flowing over the eroding siltstone surfaces runs through and further incises "shoestring" rills. Further discussion of badland landforms and references to other materials on the topic is found in Mears (1963).

During the 1980s, an earth flow led to the closure of a trail and threatened Newspaper Rock, an important petroglyph resource (Haiges, 1995). In the Newspaper Rock case, precipitation infiltrated the highly permeable windblown deposits located on top of the mesas, percolating through a fracture system to sandstone-shale contact where the water flowed laterally until reaching the mesa wall. The flow from the spring and increased precipitation were significant enough to undermine the side of the mesa.

In the mid 1950s, Park Paleontologist Edwin Colbert placed a series of stakes in the Blue Forest (later renamed Blue Mesa) area in order to measure erosion (Colbert, 1956). The stakes were arranged at a series of locations along a slope and an analysis of data a decade later (Colbert, 1966) indicated that erosion occurred up to a maximum of ¼ inch per year and that the rate of erosion was generally related to the degree of the slope. There were, however, some sites at which the effect of local topographical features outweighed the effect of the site slope (Colbert, 1966).

Park staffing levels and the size of the park are such that many areas of the park cannot be regularly patrolled to discover all the effects of erosion. The park policy on uncovered archeological resources (e.g. charcoal, ash, fire rocks, building materials, etc.), excluding human remains, is to allow them to erode naturally, although in the case of standing structures some form of stabilization may be considered (B. Parker, Petrified Forest National Park, personal communication, 2002). Human remains uncovered by erosion are treated in accordance with the legal mandates required by the Native American Graves Protection and Repatriation Act (PL 101-661) (B. Parker, Petrified Forest National Park, personal communication, 2002).

Paleontological resources, including fossil bones of prehistoric animals, remnants of plants, and preserved tracks or trails of prehistoric animals, differ greatly in their susceptibility to erosion and are preserved differently. Fossil wood consists almost entirely of silica and therefore is more resistant to erosion than even the surrounding rock. Therefore, it is allowed to erode naturally and is only protected against theft. Fossil leaves occur in specific geological layers. Although these layers are subject to erosion, it is slow enough not to be a potential threat. Fossil tracks and burrows (trace fossils) always occur in resistant sandstones and are not readily destroyed by erosion. If this type of fossil is threatened it will be collected and curated into the museum collection to ensure its preservation. However, many trackways including those of dinosaurs can be exposed for very long periods of time with no adverse impact (B. Parker, Petrified Forest National Park, personal communication, 2002).

The fossilized bones of dinosaurs and other prehistoric animals are extremely fragile and very susceptible to erosion. Upon exposure to the elements, these resources will be quickly and completely destroyed. It is the current practice of the park to monitor sites where bones occur and to excavate any threatened significant fossil resources, and place them in the museum collections for preservation (B. Parker, Petrified Forest National Park, personal communication, 2002).

In cooperation with the Cooperative Ecosystem Studies Unit at the University of Arizona (CESU / UA), an erosion prediction model was developed by members of the University of Arizona Advanced Resources Technology Program (ART), a division of School of Renewable Natural Resources (http://www.srnr.arizona.edu/ART/publications/pfa_pap/index.html). The objective of this research was to integrate the park’s geo-spatial resources protection data with predicted erosion rates to maximize the effectiveness of park resource protection efforts. The study group from the ART predicted the regions in the park subject to the greatest amount of erosion using the universal soil loss equation. Input values were obtained using GIS-calculated slope information and precipitation and soil records. Areas with both high predicted-erosion rates and high resource site density were identified for more intense patrols. The model, however, has not proved to be as effective in predicting the exposure of previously covered resources as was initially hoped.

Ferrellgas Petroleum Storage at Adamana

Ferrellgas, Inc. operates a liquefied petroleum gas (LPG) storage terminal in the old railroad town of Adamana. Adamana is located approximately 0.8 miles west of the park boundary at the Rio Puerco. The facility stores LPG in underground caverns in the Supai Formation. Ferrellgas has obtained an ADEQ Aquifer Protection Permit for the operation of four surface brine impoundments, twelve injection wells and sub-surface storage caverns. The lined brine impoundments, (two of which are clearly visible in the USGS aerial photograph of the Ferrellgas facility (1996)) are located a quarter of a mile north of the main well field facility. The first impoundments were installed prior to 1980. According to the Aquifer Protection Permit (No. P-102338) construction on the third impoundment was completed in 1995 and the fourth impoundment was to have been constructed in 1998. The brine is used to displace the LPG from the caverns in the Supai Formation where it is stored. (The Supai contains evaporite beds in which the storage caverns are located. Brine is used, instead of water, to displace the LPG to prevent further dissolution of the confining materials.) As the petroleum is typically drawn down during the winter and stored during the warmer months, the largest volumes of brine will be present in the impoundments in the early fall. Less brine will be stored at the surface during the winter and spring. The combined storage capacity of the brine impoundments is approximately 80 million gallons. It would appear, based on the draft aquifer protection permit, that the maximum elevation of the brine in pond three will be approximately 5426 ft. MSL.

At the request of the park, the NPS Water Resources Division, reviewed the potential hydrological impacts of the gas storage operations and brine ponds at the Adamana Ferrellgas facility. They found that the general hydrologic gradient of the area was such that only unusual local surface features such as erosive surfaces would allow for flow of brine into the park in the event of an impoundment dike failure. Moreover, the NPS Water Resources Division concluded that storage in the Supai, some 1000 ft. below the surface and isolated from the Puerco alluvial aquifer from which the park’s well draws water, by the impermeable Moenkopi and Chinle formations, also posed no known threat to water quality in the park (Werrill, 1994). The aquifer protection permit (APP No. P-102338) states that the brine ponds are located one mile north of the Puerco River 100 year flood plain of the Puerco River (Arizona Department of Environmental Quality, 1998). In addition, the NPS Geological Resources Division did an evaluation of the Ferrell Gas Facility and found that there were no additional significant hazards to park resources posed by the plant.

Source: Water Resources Division https://www.nature.nps.gov/water/completedwrsr.cfm


U.S. Environmental Protection Agency. 1995. Quality Criteria for Water 1995. Office of Water Regulations and Standards. Washington , DC .

U.S. Public Health Service. 1988. Petrified Forest National Park Drinking Water Treatment. Memorandum to the Western Regional Office, National Park Service dated July 26, 1988 . Petrified Forest National Park files, Petrified Forest , AZ. 2 pp.

Van Metre, P.C. and J. R. Gray. 1992. Effects of uranium mining discharges on water quality in the Puerco River basin, Arizona and New Mexico . Hydrological Sciences Journal 37:5, 463-480.

Webb, R.H., G. R. Rink and B. O. Favor. 1987. Distribution of radionuclide and trace elements in ground water, grasses and surficial sediments associated with the alluvial aquifer along the Puerco River , northeastern Arizona : A reconnaissance sampling program. USGS Open-File Report 87-206.

Webb, R. H., G. R. Rink and D. B. Radtke.1987. Preliminary assessment of water quality in the alluvial aquifer of the Puerco River Basin , northeastern Arizona . USGS Water Resources Investigation Report 87-4126, 70 pp. Tucson , AZ.

Weimer, W.C., R.R. Kinnison and J.H. Reeves. 1981. Survey of radionuclide distributions resulting from the Church Rock, NM uranium mill tailings pond dam failure: Washington , D.C. U.S. Nuclear Regulatory Commission Report NUREG/CR-2449, 59 pp.

Werrell, W. 1994. Memorandum (dated February 11, 1994 ) Re: Assistance in Reviewing Draft Aquifer Permit, Ferrellgas Inc., Adamana LPG Storage Terminal. 2 pp.

Wirt, Laurie, P. C. Van Metre, and B. O. Favor. 1991. Historical Water-Quality Data- Puerco River Basin , Arizona and New Mexico . US Geological Survey Open File Report 91-196. 339 pp.

Wirt, Laurie. 1994. Radioactivity in the Environment - A Case Study of the Puerco and Little Colorado River Basins , Arizona and New Mexico . U.S. Geological Survey Water Resources Investigations Report 94 - 4192. Tucson , AZ. 23 pp.

Stories of Climate and Culture Told in Stone
This high dry tableland was once a vast floodplain crossed by many streams. To the south, tall, stately pine-like trees grew along the headwaters. Crocodile-like reptiles; giant, fish-eating amphibians; and other plants and animals that are known only as fossils today. The tall trees (Araucarioxylon, Woodworthia, and Schilderia) fell and were washed by swollen streams into the floodplain. There they were covered by silt, mud, and volcanic ash, and this blanket of deposits cut off oxygen and slowed the logs' decay. Gradually silica-bearing ground waters seeped through the logs, and bit by bit, encased the original wood tissues with silica deposits. Slowly the process continued, the silica crystallized into quartz, and the logs were preserved as petrified wood.

That was about 225 million years ago in the Late Triassic. After that time, the area sank, was flooded, and was covered with freshwater sediments. Later the area was lifted far above sea level and this uplift created stresses that cracked the giant logs. Still later, in recent geological time, wind and water wore away the gradually accumulated layers of hardened sediments. Now the petrified logs and fossilized animal and plant remains are exposed on the land surface and the Painted Desert has its present sculpted form.

Today the ever present forces of wind and water continue to remove sediments. Erosion continues to break down the giant logs and reach for the logs and other remaining fossils still buried below the surface. In some places, up to 90 meters (300 feet) of fossil-bearing material remains. The petrified logs, the other fossils of plants and creatures that lived in the area, and the rocks locking them in place all testify to changes in the environment through millions of years.

Petrified Wood. The first historic record of petrified wood in this region came from a U.S. Army officer who found it near today's Canyon de Chelly National Monument, Arizona. Abundant deposits were recorded south of the present Petrified Forest National Park in the 1850's. By 1900, removal of the wood led to calls for preserving areas with large deposits of it. The park exists for this purpose and there is no collecting or giving out of samples permitted.

Petrified wood can be bought from commercial dealers who collect it from areas outside the park. The commercial wood is from the same geological deposits and of the same wood found in the park. Small pieces are sold, rough, tumbled, or polished. Artists and craftspeople work larger pieces into decorative objects. Jewelry, bookends, and clocks are popular sales items. Minerals and impurities deposited while the wood was petrifying add the bright colors and interesting patterns.

Please do not take even the smallest piece of petrified wood from the park. Multiplied by hundreds of thousands of visitors each year, the small pieces taken from the park quickly amount to tons.

dinosaur drawingDinosaurs. Fossils of some of the earliest dinosaurs, strange-giant reptiles, weird-looking plants, and unusual fish have been found at the park since 1981. Nicknamed "Gertie", one dinosaur was discovered here in 1984. Her place in the dinosaur family confounds paleontologists, who are still looking for clues. Gertie's bones eventually will be displayed at the park. Supported by donations, fossil research here continues to reveal life in Triassic forests of 225 million years ago.

Petrified Forest National Park provides visitors views to the beginning of dinosaurs, pre-historic peoples and modern wildlife.The remains of an ancient forest lies scattered across northeastern Arizona. Fossils of tall trees, strange ferns, large reptiles, small sharks and early dinosaurs provide clues to life 225 million years ago. Prehistoric people settled in the area about 6,000 years ago. Petrified wood provided a natural resource that could be used or traded. Evidence of their existence up to A.D. 1400 remains.

Today Petrified Forest National Park is a high desert with low-growing plants, small animals and soaring birds. A place where the ancient past meets the modern world.

park maps subheading

The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

A general photo album for this park can be found on the park's webpage.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Cover of Guide to Geologic Features at Petrified Forest book

Guide to Geologic Features at Petrified Forest National Park.
Bezy, John V. and Arthur S. Trevena, 2000.
Arizona Geological Survey.
ISBN 1-892001-13-6
paperback, 48 pages, full color photographs.

This is an informative guide which includes photographs and explanations of 21 important geologic features found at Petrified Forest National Park. Includes photos, maps and diagrams to clearly illustrate where these features can be found and how they were formed.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

geologic research subheading

Petrified Forest National Park is a globally significant exposure of fossils from the Triassic Period more than 200 million years ago. The paleontological and stratigraphic information exposed on park land is an invaluable source for the study of these ancient organisms and their environment.

Research on fossils is going on at Petrified Forest National Park right now, for more information about the park's research program check out the park's research webpage.

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Wouldn't it be great if you could incorporate lessons from the classroom into a real world, hands-on situation where what you have been teaching will finally "click" with your students? You can! Many national parks now have curriculum-based programs that utilize national parks as outdoor classrooms. The programs are designed to help you meet your required state standards while allowing your students to participate in hands-on activities at the park. Petrified Forest National Park has a curriculum-based program aligned with the Arizona Statewide Science (5-24-04) and Mathematics Standards for Grades 4-8.

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/pefo/index.cfm   I  Email: Webmaster
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