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Vanadium, Uranium, Tantalum, Niobium, and Jet Petrified Wood.

Last Updated: 17th May 2018

By Dave Crosby

In 1988 I visited Upheaval Dome (~24 miles west of Moab Utah) Which is estimated to be between 5 and 10 km in diameter and between 170 and 70 million years old.
aerial view of Upheaval Dome

Upheaval Dome, Wayne Co., Utah, USA
Upheaval Dome Cross section

Upheaval Dome, Wayne Co., Utah, USA
Upheaval Dome Rock Formations

Upheaval Dome, Wayne Co., Utah, USA

and met Fran Barnes, who introduced me to Robert's Rift which is at least 30 miles long, and several thousand feet deep.
All agree it was opened up by the impact strike.
Robert's Rift and Upheaval Dome

Moab Area, Grand Co., Utah, USA

Sure I could narrow down the time of impact, I began a search of the area. It happened AFTER the Navajo Sandstone was laid down.
Waves in the Dewy Bridge member of the Curtis Formation, and cracks in the above Entrada Sandstone verified it happened after them.
Dewey Bridge Drawing

Grand Co., Utah, USA
Below the Entrada Slick Rock is the Dewey Bridge Member which consist of red, interbedded, muddy sandstone and siltstone. It is the stratigraphic equivalent to the Carmel Formation and was deposited in a tidal flat environment on the margin of a seaway that occurred to the west.
The Dewey Bridge member is more susceptible to erosion so it occurs at the base of overhangs
and arches. Bedding in the Dewey Bridge is contorted and wavy, which is unusual
considering the units above and below it are undeformed. There are two possible
explanations for this feature. The sediments may have been deformed prior to lithification
and deposition of the overlying Slick Rock Sandstone, possibly due to slumping.

An alternate explanation is that deformation occurred long after deposition and lithification of this unit.
Structurally the Dewey Bridge is a relatively ductile unit confined between two
resistant brittle units. During deformation the Dewey Bridge Member behaved plastically and was folded, whereas the units above and below behaved brittlely and were fractured.

Below the Dewey Bridge Member is the Navajo Sandstone.

Above the Entrada Sandstone is the Dakota Sandstone - Sumerville Sandstone - Morrison Formation.

All is normal in the bottom layer of the Morrison, the Tidwell Member, but
"all hell broke loose" as the Salt Wash Member began ~ 150 million years ago.

What happened at the moment of Impact?
I spent a lot of time experimenting at the Purdue Impact site. I suspect a comet impact with a LOT of water, but if it was an asteroid this seems pretty close:

Impact Earth

The Earth

Data from the Purdue Impact site:

Heavy Body Asteroid Upheaval Impact

0.2 Mi diameter
The projectile begins to breakup at an altitude of 23300 meters = 76300 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 29.6 km/s = 18.4 miles/s
The impact energy is 6.1 x 10^19 Joules = 1.46 x 10^4 MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 1.01 km by 0.504 km

Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 6.89 km ( = 4.28 miles )
Transient Crater Depth: 2.44 km ( = 1.51 miles )
Final Crater Diameter: 8.9 km ( = 5.53 miles )
Final Crater Depth: 571 meters ( = 1870 feet )
The crater formed is a complex crater.

The volume of the target melted or vaporized is 0.271 km^3 ( = 0.0651 miles^3 )
Roughly half the melt remains in the crater, where its average thickness is 7.29 meters ( = 23.9 feet ).

10 Miles away
The ejecta will arrive approximately 57.4 seconds after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments.
Average Ejecta Thickness: 4.81 meters ( = 15.8 feet )
Mean Fragment Diameter: 7.08 meters ( = 23.2 feet )

Time for maximum radiation: 266 milliseconds after impact
Visible fireball radius: 7.85 km ( = 4.88 miles )
The fireball appears 111 times larger than the sun
Thermal Exposure: 1.12 x 10^8 Joules/m^2
Duration of Irradiation: 1.71 minutes
Radiant flux (relative to the sun): 1090

Effects of Thermal Radiation:
Clothing ignites. Much of the body suffers third degree burns.
Newspaper ignites. Plywood flames. Deciduous trees ignite. Grass ignites.

The major seismic shaking will arrive approximately 3.22 seconds after impact.
Richter Scale Magnitude: 7.4
Mercalli Scale Intensity at a distance of 16.1 km:
General panic. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluviated areas sand and mud ejected, earthquake fountains, sand craters.
Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly.

The air blast will arrive approximately 48.8 seconds after impact.
Peak Overpressure: 1780000 Pa = 17.8 bars = 253 psi
Max wind velocity: 1040 m/s = 2330 mph
Sound Intensity: 125 dB (Dangerously Loud)

Damage Description:
Multistory wall-bearing buildings will collapse.
Wood frame buildings will almost completely collapse.
Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.
Highway truss bridges will collapse.
Highway girder bridges will collapse.
Glass windows will shatter.
Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.
Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

From here on there is a lot of repeat information, so I have deleted a lot of it.
20 Miles away:
The ejecta will arrive approximately 1.36 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments.
Average Ejecta Thickness: 60.1 cm ( = 23.7 inches )
Mean Fragment Diameter: 1.13 meters ( = 3.7 feet )

The major seismic shaking will arrive approximately 6.44 seconds after impact.
Richter Scale Magnitude: 7.4
Mercalli Scale Intensity at a distance of 32.2 km:

The air blast will arrive approximately 1.63 minutes after impact.
Peak Overpressure: 386000 Pa = 3.86 bars = 54.8 psi
Max wind velocity: 438 m/s = 981 mph
Sound Intensity: 112 dB (May cause ear pain)

40 miles away:
The ejecta will arrive approximately 1.92 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments.
Average Ejecta Thickness: 7.52 cm ( = 2.96 inches )
Mean Fragment Diameter: 18 cm ( = 7.07 inches )

The major seismic shaking will arrive approximately 12.9 seconds after impact.
Richter Scale Magnitude: 7.4
Mercalli Scale Intensity at a distance of 64.4 km:

The air blast will arrive approximately 3.25 minutes after impact.
Peak Overpressure: 90700 Pa = 0.907 bars = 12.9 psi
Max wind velocity: 160 m/s = 359 mph
Sound Intensity: 99 dB (May cause ear pain)

80 Miles away:
The ejecta will arrive approximately 2.73 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments.
Average Ejecta Thickness: 9.4 mm ( = 3.7 tenths of an inch )
Mean Fragment Diameter: 2.86 cm ( = 1.13 inches )

The major seismic shaking will arrive approximately 25.8 seconds after impact.
Richter Scale Magnitude: 7.4
Mercalli Scale Intensity at a distance of 128.8 km:

The air blast will arrive approximately 6.51 minutes after impact.
Peak Overpressure: 24500 Pa = 0.245 bars = 3.48 psi
Max wind velocity: 52.6 m/s = 118 mph
Sound Intensity: 88 dB (Loud as heavy traffic)

Damage Description:
About 30 percent of trees blown down; remainder have some branches and leaves blown off.


What was it made of?

Delete the normal elements of the area and what is left over came from the impacting body which was vaporized along with a simalar part of the target area. That heavy vapor cloud penetrated everything in those swirling winds, cooled down, and became part of the area. What do we find?

Here is another look at Google Earth:

Most of the mines were in the Salt Wash Member of the Morrison. An interesting exception was the Happy Jack Mine in the shinarump. At first they were mining carnotite, but soon recognized roscoelite, then added vanadium, tantalum and niobium. I'm sure more will be found.



Deposits of vanadium-bearing sandstone are widely distributed in western Colorado and eastern Utah and have been the principal domestic source of vanadium, uranium, and radium. Except during a few years when operations were relatively small, deposits at one or more places in this region have been intensively mined since 1909. Production has increased considerably each year since 1937.
Most of the deposits are in the Morrison formation, but there are two important deposits in the Entrada sandstone and several small deposits in the Shinarump conglomerate. Recent X-ray studies indicate that the principal vanadium mineral, heretofore considered to be roscoelite, belongs to the hydrous mica group of clay minerals. This mineral, along with other vanadium minerals of minor importance, impregnates sandstone. Shale pebbles and clay films on bedding planes in ore-bearing sandstone are rich in absorbed vanadium, and fossil plants in and adjacent to ore bodies are richly mineralized with vanadium and uranium in places.

Vanadium ore of milling grade contains from about 1 to 5 percent V2O5, and most of it contains less than 1 percent U3O8. Ore containing as much as l.5 percent U3O8 is usually sold as uranium ore.

The vanadium-bearing hydrous mica is in part uniformly disseminated through the sandstone and in part concentrated along bedding planes and in thin zones that cut across bedding.

As the zones that cut across bedding are curved or wavy, they are called rolls by the miners.

The ore bodies are spotty and form irregularly tabular masses that lie essentially parallel to the sandstone beds, but they do not follow the beds in detail. They range in content from a few tons of ore to many thousand tons. The trend of many elongate bodies is indicated by the orientation of the rolls within the ore, and this trend also suggests the probable alinement of any adjacent ore bodies; mapping of ore bodies and rolls is therefore an aid to prospecting and development.

No satisfactory explanation can yet be offered for the origin of these deposits.

The ore bodies do not appear to have been localized by such geologic structures as fractures or folds, but within limited areas they are restricted to certain stratigraphic zones.

- - -
Fossil tree trunks and branches are common in the ore-bearing sandstone. Some are 1 ft or more in diameter and as much as 100 ft long. These logs were rafted into place by streams that deposited the enclosing sands, and when they came to rest in the stream beds, many of them were oriented parallel to the general direction of stream movement, as evidenced by lensing and foreset-bedding of the sandstone. Ore rolls are peculiar concretionary structures in the ore. They are conspicuously elongate in one direction, ranging from 10 to 100 ft or more in length. Locally the long axes of the rolls have a common trend, which is parallel to the dominant orientation of the fossil logs. Ore bodies are also elongate in this same general direction (Fischer, 1942, p. 390).

The common orientation of ore rolls and fossil logs is about normal to the local trend of the Uravan mineral belt (pi. 2). The alinement of ore deposits in a cluster, and the trend of favorable ground enclosing the cluster, likewise are generally normal to the local trend of the mineral belt (see pp. 6-10 and figs. 2,3,4,5). It must be assumed that some geologic conditions having widespread influence controlled the orientation of the fossil logs and the ore rolls in the area of the mineral belt.


The ore, averaging about 0.25 percent U3O8 and 2 percent V2O5, impregnates sandstone. The ore bodies are irregular tabular layers, with an average thickness of 2 to 4 ft. They lie generally parallel to the sandstone bedding. They range in size from a few feet wide, containing only a few tons of ore, to several hundred feet wide, which may contain many thousand tons. In most areas the deposits are confined largely to sandstone in a single stratigraphic zone. Within this zone the deposits have a spotty distribution but tend to be clustered in relatively small, poorly defined patches. The deposits are thought to have formed from ground-water solutions migrating through ore-bearing beds, probably soon after the accumulation of the sands. Precipitation likely resulted from slight changes in the chemical composition of the solutions, perhaps in the environment of decaying organic material.

An interesting and revealing insight is presented by The Happy Jack Mine in the Shinarump layer of the Chinle:

Oh yes, Jet.

Jet Petrified Wood - Locations

Henry Mts, Garfield Co., Utah, USA

150 Ma - JET - Petrified (Coalified) Wood. “Jet is a product of high pressure decomposition of wood from millions of years ago, commonly the wood of trees of the Araucariaceae family. Jet is found in two forms, hard and soft. Hard jet is the result of the carbon compression and salt water; soft jet is the result of the carbon compression and fresh water.”

During the 15th and 16th century it became fashionable to give Mourning Jewelry of black and white stones to relatives of the deceased
Mourning jewelry made of Jet (182 million year old early Jurassic, from Whitby, North Yorkshire, England) reached its height of popularity in England after the death of Prince Albert in December 1861. Queen Victoria went into deep mourning, which was imitated by her subjects when faced with their own bereavements.
Jet jewelry made a comeback with all the flu deaths and the first World War in 1918, and was adopted by the Flappers of the 1920's.

In 1916-18 Tiffany & Co of NYC heard of Jet being discovered near Hanksville Utah and purchased most of the entire production until supply finally overran demand in 1926.
In Utah it is found in two Cretaceous Rock Formations, The Dakota Sandstone and the Straight Cliffs.

The accepted explanation is that the uranium eroded out of nearby granite.

QUESTION: IF the uranium was coming out of decomposing granite, WHY did the vast majority of it begin AND end within an 80 mile radius from Upheaval Dome in the Salt Wash Member? WHY didn't it continue to accumulate in the overlaying Brushy Basin and other upper layers?

Almost immediately after the "Uravan" Mineral belt occured, the hot dry area was covered by a new body of water - Lake T'oo'dichi' - and the forming - (Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed. Such deposits are described as authigenic.) - of albite that cemented everything together.


None of the authigenic feldspars in this study show detectable characteristics luminescence. Smith and Stenstrom (1965) examined thecathodo-luminescence of feldspars from a variety of igneous rocks. All their feldspars showed either blue or red luminescence. They did not report any non-luminescing feldspars.
This suggests that cathodo-lumines-cence in feldspars may be related to their different geological origin, and as such luminescence might be used as a criterion for distinguishing between authigenic and non-authigenic feldspars.
To verify this suggestion, the cathodo-luminescence properties of detrital feldspar grains and cores, that are present in many of the authi-genic feldspar-bearing carbonate rocks, were compared with those of specimens from pegmatites and low-grade metamorphic rocks.

TheIuminescence properties of some of these specimens are given in Table 2, and these results and those of Smith and Stenstrom (1965) may be summarized as follows:

1) authigenic feldspars in carbonate rocks show no characteristic lum-inescence.
2) albites from low-grade metamorphic rocks shown no characteristicIuminescence.
3) alkali feldspars from pegmatites and igneous rocks show distinctive cathodo-luminescence.

Luminescence has been shown to depend on defect structures and on the concentration and interaction of a variety of trace elements which act as activators, for example manganese (Kdhler, 1940; Medlin, l963a,b;Claffy and Ginther, 1959; and Long and Agrell, 1965). These activators are presumably present in varying amounts in nearly all geological environments.

The absence of luminescence probably does not indicate that the necessary elements were unavailable during crystallization, but more likely that temperatures were too low for a sufficient amount of activators to be taken up by the feldspar structure.

It is generally true that the concentration of impurity ions or atoms increases with temperature.

The present study supports the suggestion of Smith and Stenstrom (1965)that cathodo-luminescence properties of minerals depend on the temperature of formation.

One of the major conclusions of this study is that authigenic feldspars are homogeneous, stoichiometric end members of the alkali feldspar series.
Authigenic albites contain more than 99 mole percent NaAISLO3 -
and authigenic microclines contain more than 99 mole percent KAISiBO8

A QUESTION: What was the impact of all that radioactivity on the surrounding life forms?
Were there a lot of mutations?

My conclusions:
A hundred and fifty million years ago a COMET hit near the Utah/Colorado line on a low angle that opened Robert's Rift (and more!), created Upheaval Dome, and filled the surrounding area with 4 parts vanadium to one part uranium, tantalum, niobium, and who knows what else.

Why a comet? because of all the water that suddenly appears in every studied report.

EDIT 5/17/2018 Happy Jack Mine

Happy Jack Vanadium, Uranium Mine

Geology of the Happy Jack Mine White Canyon Area San Juan County, Utah

The Happy Jack mine is in the White Canyon area, San Juan County, Utah. Production is from high-grade uranium deposits in the Shinarump conglomerate of Triassic age. The Shinarump strata range from 16 to 40 feet in thickness and the lower part of these beds fills an eastward-trending channel that is more than 750 feet wide and 10 feet deep.The Shinarump conglomerate consists of beds of coarse- to fine-grained quartz- lose sandstone, conglomerate, siltstone, and claystone. Carbonized wood is abundant in these beds, and in the field it was classified as mineral charcoal and coal.

Channels within the Shinarump, cross-stratification, current lineation, and slumping and compaction structures have been recognized in the mine. Steeply dipping fractures have dominant trends in four directions, N. 65° W.t N. 60° E., N. 85° E., and due north.

Uranium occurs as bedded deposits, as replacement bodies in accumulations of "trash," and as replacements of larger fragments of wood. An "ore shoot" is formed where the three types of uranium deposits occur together; these ore shoots appear to be elongate masses with sharp boundaries.

Uranium minerals include uraninite, sooty pitchblende(?), and the sulfates betazippeite, johannite, and uranopilite. Associated with the uraninite are the sulfide minerals covellite, bornite, chalcopyrite, and pyrite. Galena and sphalerite have been found in close association with uranium minerals.

The gangue minerals include limonite and hematite (present in most of the sandstone beds throughout the deposit), jarosite that impregnates much of the sandstone in the outer parts of the mine workings, gypsum that fills many of the fractures, and barite that impregnates the sandstone in at least one part of the mine. Secondary copper minerals, mainly copper sulfates, occur throughout the mine, but are most abundant in the outermost 30 feet of the workings. The bulk of the country rock consists of quartz and feldspar, and clay minerals.

The amount of uranium minerals deposited in a sandstone bed is believed to have been determined by the position of the bed in the channel, the permeability of the sandstone in the bed, and the amount of carbonized wood and plant remains within the bed. Not all of these features can be demonstrated in the Happy Jack mine itself. The beds considered most favorable for uranium deposition contain an abundance of claystone and siltstone both as matrix filling and as fragments.

Suggested exploration guides for uranium ore bodies include interbedded siltstone lenses, claystone and siltstone cement and pebbles, concentrations of "trash," covellite and bornite, chalcopyrite, and carbonized wood.

The Happy Jack mine contains the largest known uranium deposit in the White Canyon area, San Juan County, Utah (fig. 38). A detailed study was started by the U. S. Geological Survey to determine the mode of occurrence of the uranium minerals, and the structural and lithologic features useful as ore guides at the Happy Jack mine and elsewhere in the White Canyon area.

This report gives preliminary results of detailed mapping done during the 1952 field season, summarizes habits of the uranium deposits, and presents guides that may be useful in exploring for additional deposits. A map of the Happy Jack mine is shown in figure 39. The large-scale map (pis. 8, 9) of part of the mine was prepared by Trites and Renzetti from June 15 to July 4. Between August 7 and October 2 Trites and Chew mapped the walls of about 750 feet of drifts in the northeast part of the mine on a scale of 1 inch = 5 feet. The fracture map (pi. 8) was prepared from the information on the wall maps by projecting all fractures to a waist-high datum plane.The work described in this report was done on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission.

The Happy Jack mine is on the southwest rim above White Canyon in the western part of the White Canyon area, San Juan County, Utah.
The mine is about 15 miles by road east of Hite, Utah, and 75 miles west of Blanding, Utah (fig. 38) ; it is reached either from Hite or Blanding by Utah Highway 95, a graded dirt road that connects Blanding with Hanksville, Utah.

In the White Canyon area the Moenkopi formation of early Triassic age is 195 feet thick and consists of interlayered beds of brown silt- stone, fine-grained sandstone, and shale; locally, it has a bed of conglomerate at the base. The Moenkopi strata just beneath the Shinarump conglomerate consist of brown micaceous sandy siltstone that has been bleached to grayish green. This siltstone is laminated, the laminae averaging 3 mm thick.

The contact of the Moenkopi formation with the overlying Shinarump conglomerate is an erosional unconformity produced by the flowing water that deposited the sediments of the Shinarump conglomerate.

In the White Canyon area the Shinarump conglomerate is discontinuous, occurring in lenticular beds that have exposures ranging from a few hundreds of feet to more than 5 miles in length. A section of the Shinarump as much as 40 feet thick may pinch out within a distance of 2,000 feet.

The Shinarump strata at the Happy Jack mine are about 16 feet thick at the outcrop and thicken to 40 feet behind the rim. The out- crop of the Shinarump strata forms a ledge that extends 1/2 mile northwest and 1 1/4 miles southeast of the mine. Beyond these points the Shinarump pinches out.
The lower beds of the Shinarump conglomerate fill a channel more than 750 feet wide and 10 feet deep cut into the upper part of the Moenkopi formation. Diamond drilling by the U. S. Atomic Energy Commission indicates that the channel trends about due west but that the channel apparently bends rather abruptly beyond the south- western limit of the underground workings and continues southwest.

Diamond drilling further indicates that the channel is not well-defined, and that the bottom is marked by numerous scours.

Channels in the Shinarump are common within the mine and range from a few inches to 10 feet in width. This channeling is indicated by the presence of pinched-out beds and of abrupt lithologic changes both laterally and vertically. Three channels have been mapped in the Shinarump rocks (pi. 8).The Shinarump conglomerate is comprised of beds of coarse- to fine-grained quartzose sandstone, conglomerate, siltstone, and clay- stone. Many of the conglomerate beds grade laterally into coarse- grained sandstone; gradation also has been noted between beds of fine-grained sandstone and siltstone.

The sandstone beds range from 1 to 100 feet in length and from a few inches to 4 feet in thickness. A large number of these beds have poorly developed internal stratification, the clarity of this stratification depending upon the type of cross bedding and the angle at which the unit has been transected by the mine working. Most of the stratified units are lenticular, although some tabular units are present. Nearly all of the units have erosional lower surfaces as described byMcKee and Weir (1953).

Structural features within the beds include cross-stratification and contortion of the strata. Cross-stratification is very common in the sandstone beds; most of the sets of cross-strata have planar surfaceso f erosion as their lower bounding surfaces. These planar sets have resulted from beveling of the underlying beds and Subsequent deposition. Nearly all of the cross-stratification sets are lenticular, that is, are bounded by converging surfaces, the lower of which are commonly curved, Most Of the Cross-Strata arch downward and may be described as concave upward, The cross-strata in the part of the mine mapped dip from less than 10° to more than 20° ; the general direction of dip is about N, 65° w, The dip of the cross-strata suggests that the flow of streams here was from the southeast. Most of the cross- strata are termed high angle because the average maximum inclination is greater than 20° (McKee and Weir, 1953). Both medium-scale and small-scale cross-stratification are present, but the medium-scale cross-strata, 1 to 10 feet in length, is more abundant.
Horizontal bedding is common only in sandstone beds and con- glomeratic sandstone beds that immediately overlie siltstone beds in the lower part of the Shinarump conglomerate. These conglomeratic sandstone beds contain abundant interstitial clay and silt.

Many beds have been contorted by slumping that has resulted from the collapse of steep channel sides shortly after consolidation. Such slump features are especially common in fine-grained sandstone and siltstone beds where units as much as 1 foot thick have been distorted. A fault with reverse movement near station R. (pi. 9) has a displacement of 2 feet and is believed to have been caused by rupture and movement at the time the sediments were deposited. Current lineation was observed in the siltstone in the-channel crossing the drift near station 0.

The sandstones are poorly sorted and consist predominantly of grains of quartz, from a trace to 5 percent microcline, and a trace of mafic accessory minerals. Mica seems to be absent in most of the sandstones although it is conspicuous in the sandstone of the Shinarump in most of the White Canyon area. The quartz grains range from angular to subangular, the degree of angularity depending largely upon the amount of authigenic quartz surrounding the original grains. The microcline grains are pale yellow to red, and are commonly subangular. The sandstone is cemented by. clay, iron oxides, and jarosite.

Larger granules and pebbles of quartz, quartzite, siltstone, and claystone comprise from 1 to more than 10 percent of many of the sandstone beds. The pebbles of quartz and quartzite are as much as 1 inch in diameter and are commonly well-rounded. The siltstone and claystone pebbles are most abundant in the lower parts of the sandstone beds and are as much as 4 inches across.

Siltstone occurs in beds ranging from 1 to 4 feet thick and from 10 to 100 feet in length; it is also in small stringers from one-eighth to one-half inch thick and from 1 to 6 feet long. The siltstones are gray, greenish-gray, yellow, pink, or combinations of these colors. Most of the siltstones are sandy, and many grade laterally into sandstones. Horizontal contacts, however, are very sharp and vertical gradations through large ranges in grain size have not been found.

The conglomerate occurs in poorly defined units that are lateral gradations of coarse-grained sandstone. The conglomerate consists largely of pebbles of siltstone and claystone with few pebbles of quartz and quartzite.

Carbonized wood is abundant in the Shinarump conglomerate. Two forms of carbonized woody material have been recognized, a soft black mineral charcoal and a vitreous coal. The wood occurs both as logs and as accumulations of smaller fragments which have been called "trash deposits." These trash accumulations tend to be near the bottom of the sandstone beds, and commonly the contact between two cross-stratified beds will be marked by a thin trash deposit from less than 1 inch to 6 inches thick. Carbonized vegetal material is abundant as partings and fragments in many of the siltstone beds. The largest logs mapped are 2 to 3 feet long and 4 to 6 inches in diameter. Many of the logs have been replaced by sulfide minerals, pitchblende, hematite, limonite, and secondary copper minerals. Many smaller pieces of carbonized wood have been replaced by pyrite.

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