Oh, the shark has pretty teeth, dear...

In the last post, I talked about the triple-layer enameloid that is one of the defining characteristics of a modern shark.  That enameloid has an outer single crystallite enameloid/shiny-layered enameloid (SCE/SLE) that resists the spread of cracks in the teeth; a middle parallel-bundled enameloid (PBE) that resists compressional (straight down) force; and an inner tangled-bundled enameloid (TBE) that resists rotational (twisting) forces.  These are tremendous properties for a shark that bites big chunks out of something else and needs to chew them up.  A Cretaceous predator, Squalicorax curvatus from the Western Interior Seaway of Kansas (about 90 million years ago), has teeth that everyone would recognize as shark's teeth.  Squalicorax has a labiolingually compressed (flat) shape, with a strong triangular cusp and a shoulder with serrated edges (like a steak knife).  These teeth are perfect for running up on something even bigger than the shark, slicing out a chunk of prey and chewing it up.

Squalicorax curvatus teeth coated with ammonium chloride to show detail

Squalicorax curvatus would be very recognizable to the casual observer as a shark.  It just LOOKS like a shark.  Mouth behind and below snout, large dorsal fin, fusiform body, mouth full of nasty teeth and big (up to about 10 feet long).  A few extremely well preserved specimens have been found, including a nearly complete skeleton (very rare for cartilage - even calcified cartilage) recently sold by PaleoSearch, Inc. in Hays, KS from the Smoky Hill Chalk of Kansas (about 85 million years ago).

Reconstruction of Squalicorax curvatus  by Dmitry Bogdanov

Exceptional Squalicorax skeleton - absolute once-in-a-lifetime find

Squalicorax skull detail

Squalicorax curvatus SLE and PBE - surface etch.  Size bars: (1,2,6)
1 micron, (3) 100 microns, (4) 50 microns, (5) 5 microns.

There is no argument in the literature that this particular shark is a selachimorph neoselachian (read SHARK).  The external anatomy of Squalicorax curvatus teeth was examined first using teeth that had not been exposed to 10% hydrochloric acid (HCl) (panel 1), treated with HCl for 30 seconds (panel 2) or 3 minutes (panel 3-6).  There is not much relief on the surface of the untreated teeth, but you can easily see randomly oriented enameloid crystallites on the surface of a tooth treated for 30 seconds with 10% HCl.  Longer treatments remove all of this SCE/SLE from the surface and expose the parallel bundled enameloid of the Squalicorax tooth.  Panel three shows the parallel bundles at the level of the serrations in the tooth.  As the parallel bundles approach the serration, they turn direction, so that they point towards the edge of the serration, instead of towards the apex of the tooth.  As you zoom in on the parallel bundles, it is possible to see that there are two populations of bundles; one that runs parallel to the long axis of the tooth, and one that runs perpendicular to the long axis.

Cross section of Squalicorax teeth.  Size bars: (1) 500 microns,
(2,3,6) 50 microns, (4) 20 microns, (5) 5 microns

It is possible to see all three enameloid layers simultaneously in sectioned teeth.  In panel 1, the lighter area is the enameloid and the darker area inside is the dentine of the tooth.  The tooth is embedded in plastic.  In the upper right and lower left of the picture, you can see the serrations (cutting edges) of the teeth.  In panel 2, we are looking at the interface between the enameloid upper right and the dentine (left).  The arrows show where the dentine and enameloid meet.  The TBE (T) is seen next to the dentine (left) in panel 3, and the PBE (P) is to the right.  Panels 4-5 show the interface between the TBE and dentine.  As the dentine is approached, the enameloid becomes more like an SCE/SLE.  The dentine has a structure that looks a lot like bone, with channels for odontoblasts that are surrounded by concentric rings of dentinal material.  Shark teeth have not changed a whole lot in appearance in the past 90 million years.  There are small changes, but those mostly reflect stress introduced onto the tooth what the shark eats.

Almost to the pay-off for the paper.....

Fossil Safari: Cleveland-Lloyd Quarry

Two buildings cover the bonebed

Beds rich in fossils are very rare.  In a very few places, conditions preserve the fossils in such detail that things such as pigmentation, three dimensional structure and cellular structure can be seen.  These areas are called Lagerstätten or Konservat-Lagerstätten.  And they always seem to be way out in the middle of nowhere.  Is that really necessary?  As you can tell by the picture to the left, the Cleveland-Lloyd Dinosaur Quarry in Utah is no exception.  It contains the densest concentration of Jurassic dinosaur fossils found anywhere in the world.

It is also noteworthy in the

Bones situated where they were found in 3D-space

abundance of carnivorous dinosaurs.  About 2/3 of the dinosaur fossils found are of theropods, mostly the apex predator Allosaurus fragilis.  Sauropods, the big long-necked dinosaurs like Brachiosaurus, Camarasaurus, and Barosaurus, are found to a lesser extent.  Ornithischians like Stegosaurus are also represented in the bone bed.  To date, over 12,000 bones have been collected and accessed into museum collections.  The Utah Museum of Natural History, University of Utah, Brigham Young University and Princeton University are major excavators of this bonebed, which is now a National Natural Landmark administered by the Bureau of Land Management.

Students excavating on site

Two buildings now cover the part of the bonebed with the densest concentration of dinosaur bone.  This protects the site from sunlight, weather, bone poachers and vandals.  It also makes excavation conditions right tolerable in the summertime.  Excavations are still taking place and bones are uncovered, removed for study and then some are returned for display in the place and orientation in which they were discovered.  When we were there, two college students were working on excavations and acting as interpreters of the bone barn.  Walkways allow the visitors to look over the bonebed without actually touching the surface.

When you study fossils from a

Walkway and bonebed

particular location long enough, you start to be able to identify where they are from by their coloration.  The Cleveland-Lloyd Dinosaur Quarry fossils are recognizable by their beautiful black color.  This is due to the unique blends of minerals found at the location during the time that the bone bed was formed.  This fossil bed is in the Upper Jurassic Morrison Formation (156-147 million years old).  Specifically, this bed is in the Brushy Basin Member, which is mostly mudstone made from volcanic ash.  Braided rivers flowed from the west into a basin, forming Lake T'oo'dichi' (Gesundheit).  This lake would have been salty and alkaline, much like modern Great Salt Lake.

Allosaurus fragilis maxillary, vertebrae and chevrons

Exactly why this fossil bed is here and why it contains the mix of organisms that it does.  It is very rare for a fossil assemblage to contain more carnivores than it does herbivores.  One idea is that as seasonal droughts set in, ground water would turn the volcanic ash into mud, trapping dinosaurs that came in for a drink.  Packs of young carnivores may have found the temptation to scavenge an easy meal great, especially as the smell of rotting meat increased.  The predators would then become mired in the mud and eventually die of starvation.  A competing hypothesis is that this low spot would be one of the last surviving watering holes and that the carnivores came here to hunt herbivores.  After the supply of herbivore meat was exhausted, the carnivores turned on each other and those left eventually died around here as the result of drought conditions.

Why do we have to be out in the sticks/BFE?

Mostly theropod bones

To have a really good fossil location you first have to have access to exposed rocks of the proper age. The more extreme the climate, the more that physical forces such as cycles of freeze/thawing and erosion can break down sediment and expose fossils. The fossil hunter also has to be at the location at the time that the fossil is exposed and collect the fossil. The ideal area is not impacted greatly by human activities than can destroy the fossils. Fossil sites are often exposed by construction, but paleontologists are usually given a very short time frame to come and remove fossils before the construction project resumes. I have seen more than one Pennsylvanian-era fossil forest fall to the bulldozer in Kansas City.

Long time working

It is likely that dinosaur bones were found by farmers as they drove livestock through the area.  The first organized excavation of record was conducted by F.F. Hintze and the Geology Department of the University of Utah in 1927.  A crew from Princeton University worked the quarry for the 1939-1941 field seasons under W.F. Stokes.  The quarry was idle until 1960 and a variety of institutions have conducted field work there since, including the Utah Museum of Natural History, the University of Utah and Brigham Young University.

Allosaurus fragilis arm

The Cleveland-Lloyd Dinosaur Quarry was named a National Natural Landmark in 1965.  The Bureau of Land Management established its very first visitor center on the site in 1968.  A new visitor center has since been constructed and opened in 2007.  This new visitor center is run entirely on electricity gathered using rooftop solar panels.  The visitor center houses exhibits detailing the history and geology of the site.  An excellent mounted Allosaurus skeleton is exhibited here.  If you like dinosaurs and are looking for something a little bit different, this is a nice drive and worth the effort.

Getting There

From I-70, turn north onto UT-10.  Turn right (east) onto UT-155 and go into Cleveland, UT.  If you feel like you have to take a relief break, Cleveland is your last chance at comfortable facilities for about an hour.  In Cleveland, turn right (south) onto S. Center Street/CR-204 (1.5 mi).  Turn left (east) onto S. Flat Bus Loop (0.3 mi), then slightly right onto CR-208 (1.4 mi), then continue onto CR-206 (2.1 mi).  Turn left (north) onto Vicor Reef Rd (4.0 mi).  Turn right onto Dinosaur Quarry Rd/CR-216 (5.1 mi) and then turn slightly left onto the road to the Cleveland-Lloyd Quarry Visitors Center (1 mi).  You are there.  Good luck getting back; hope you left some breadcrumbs.

Waypoint: Latitude 39.324019 N; Longitude 110.687683 W

Making a Mark: Art for Art's Sake

Golden Eagle in San Rafael Swell

On more than one vacation, we have found ourselves on a little gray line with no number out in the middle of nowhere to see one sight or another.  Most of these are dirt or gravel roads.  Sometimes you find what you are looking for, sometimes not.  Sometimes you even end up with a busted tire.

Cottonwood Wash and Buckhorn Wash roads run through the middle of fantastic red sandstone formations of the Jurassic Navajo Sandstone Formation, the Triassic Wingate Sandstone and Permian Coconino Sandstone in an area called the San Rafael Swell.  This area is rich in archaeological evidence of Fremont, Paiute and Ute cultures.  The Fremont people lived in the area about 2000 years ago, at about the same time as the neighboring Pueblo peoples and may have been an offshoot of the "Anasazi" cultural group.  Evidence suggests that the Fremont were a foraging and corn/maize farming culture, with smallish villages with pithouses.  Climate change seems to have displaced the culture about 950 A.D.   They certainly moved westward and some may have found their way to Nebraska/Kansas as the ancestors of the Dismal River culture.

The Barrier Canyon culture left art throughout modern Emery County, Utah. One of the most impressive is the Buckhorn Wash pictograph panel.  You can see the scope of the panel in the picture to the left using Nadienne and short Christian for scale.  The pictographs were made on a freshly exposed sandstone canvas.  Red pigment composed of ground hematite (iron (III) oxide) was likely mixed with animal fat, egg, or water, and brushed onto the surface of the rock with brushes made from animal fir or plants.  The pigment soaked into the porous rock and has stayed visible for about two thousand years.  Weather and modern vandals are the primary threats to the continued existence of this art panel.

Some of the figures are obviously human.  Many of the figures have holes pecked in their chest.  What they originally represented is unknown and why holes have been deliberately picked in their chest is also a mystery.  It may be that the figures held some power for the Fremont peoples and the holes released the power of the art, maybe by a rival or later culture.  Were the figures ritually killed?  All questions with no answers.

An attempt to cover some of the figures with yellow paint was made long ago.  Again one asks "Why?"  Did the aesthetics of the culture change?  Did a later culture try to alter or cover them up?

Look a little closer

We would like to know what it all means, but we'll just have to keep guessing and enjoying.

Uplifted sandstone - see the ripple marks?

Figures with vandalism apparent

Extreme close-up

Bird-Men or Angels?

Chiselers

The area also contains petroglyphs, which are pictures chiseled out of the rock.  The sandstone is polished and the iron oxidizes (rusts) over time, leaving a reddish varnish on the rock.  By pecking away at this layer, one can create images in the stone.  These designs may be of animals, people or symbols.  Meanings are largely unknown, but guesses are handy.

The lower part of the image above could be interpreted as a sheep, but what about the square subdivided into four squares?  Is it a representation of the four winds?  These drawings may have been painted at some point in the past.  Are they the embodiment of power that the artist was calling upon?  Ritual?  Creativity?

A human riding a deer? Turtles? People?

Long Long Ago....

Vacation with the Hoffmans is hard work

Getting There

Take Buckhorn Wash/Draw Road (Rd 332) north from Exit 131 of I-70 in Utah for 22.7 miles.

Waypoint: Latitude 39.123533 N; Longitude 110.693870 W

Further Reading

Emery County Sights

White Sands National Monument

Continental rifts produce some interesting geography. We have visited the Rio Grande Rift several times and found something new to see each time. Just north of El Paso, Texas and Las Cruces, New Mexico is a field of dunes composed of the whitest and finest sand you'll likely see. White Sands National Monument preserves much of one of the more unique geological features in North America.  Gypsum transported from the surrounding mountains collect in the bowl that is the Tularosa basin and forms dunes of varying heights.  The sand moves so quickly that roads have to be regularly plowed to keep the road clear for automobiles.

From sea to shining sand

The Four Corners area of the US during the Permian period

For most of its history, North America has mostly been covered by shallow epicontinental seas.  The mountains that make up so much of the landscape of the American West have been pushed up fairly recently.  The story of White Sands begins in the Permian period (299-251 million years ago).  During times of sea level rise, southern New Mexico and Arizona were inundated by ocean.  As sea levels fell, and the sea shallowed out or became cut off into inland salt lakes the water would evaporate, concentrating the mineral contained therein.  These crystalline materials are called evaporites. Calcium sulfate precipitates into a mineral called gypsum.  Several episodes of sea level rise and fall eventually formed the Yeso formation, some 1500 feet of gypsum rock that can be seen in the surrounding mountains.

Uplifting experience

Plants helping to anchor sand dunes in place.  San Andres Mountains
form the backdrop

The manufacture of the Rocky Mountains was very complex, and this feature is related to part of that story.  As Pangaea broke up during the Jurassic, oceanic crust of the Farallon plate began to subduct (sink under) the western edge of the North American plate which was located at about Utah at the time.  As the Farallon plate sank under North America at an angle of about 50 degrees, it pulled ocean plateaus and islands to the western edge of North American, fusing them with the continent, forming the land in Nevada and California.  This new land pushed the subduction zone further to the west.  Collision of oceanic crust with North America produced the Sevier orogeny, pushing up mountains from Canada to Mexico, including in Idaho, Utah, Wyoming and Nevada.  In this episode, pressure from the eastward moving ocean plate plus heating caused the crust to shorten and the sedimentary layers to fold and break along weak planes.

Franklin Mountains show deformation from Laramide orogeny but
are mostly built by rifting processes.  See how the rock layers tilt?

About 70-80 million years ago, the Farallon plate began to move more horizontally.  This caused the crust to fold into a series of ridges and basins, and the crust broke along deep fault lines produced during the breakup of Rodinia.  Blocks of crust with basement rock cores were tilted upwards during this orogeny (the Laramide orogeny), which extended deeper into the interior of North America than had the Sevier event.  The Black Hills mark the eastern boundary of this mountain building episode.  This episode ended as the Farallon plate cooled, became denser and started sinking again about 35-55 million years ago.

Drift in the rift

32-34 million year old pyroclastic flows and lava
Organ Mountains on east side of Rio Grande Rift

An upwelling of magma generated a period of tremendous volcanism throughout the southwest US starting about 35 million years ago and ending about 20 million years ago.  The magma produced a thinning of the crust and it extended up to 50% in the late Oliogocene.  The Rio Grande rift started forming about 30 million years ago.  As the crust extends, it cracks along pre-existing faults and the block on one side of the fault drops in comparison that on the other side.  The rift trends northwards and extends from Chihuahua State, Mexico into Colorado.  The thinning crust resulted in further subsidence; most basin-building took place in the last 10 million years.

Rio Grande/Rio Bravo south of White Sands

The first period of extension, during the Oligocene, lasted from 30-19 million years ago or so.  The second period of extension began during the Miocene, about 17 million years ago and continues to this day.  The area of rifting is at least 180 miles wide, and stretches about 1.5 mm per year from east-west in Colorado to 2.5 mm per year in northern Mexico.  The basins that make up the visible portion of the rift average 30 miles across.  The rift valley is partly filled up with sediment that has accumulated to a depth of nearly 5 miles.  The Rio Grande River occupies the rift valley.

Carrizozo lava field, LandSat 7 NASA photo

Evidence of the volcanism associated with rifting abounds in the region.  Hot springs, extinct cinder cones, mountains built from lava.  Lava field badlands (malpais) are present.  Just north of the White Sands is a gash of black lava, the Carrizozo lava field.  This flow of lava erupted from a shield volcano about 5,200 years ago.  The high basalt content provides the black color, and the thin consistency of the lava allowed it to flow freely down the rift valley.  There are also cinder cones in the field.  It is likely that humans were present to witness this eruption.

Part of another lava field near Grants, New Mexico forms a part of El Mapais National Monument.  Ben still gets a ribbing from our visit there when he was 5ish.  Another day.

Ice, ice, baby

Lake Otero, NPS

During the last Ice Age, glaciers did not reach this far south.  However, the climate was cool and wet.  Large amounts of rainfall would fall, percolate through the porous rocks, dissolving the gypsum in the Yeso Formation.   Spring running out of the mountains plus runoff gathered into the bowl of the Tularosa basin, forming a large lake, called Lake Otero.  Calcium sulfate would continue to increase in concentration in the low-lying lake, precipitating into crystals from time to time.  This crystallization accelerated as the climate warmed, became drier and the lake shrank.  Today, the remnants of the lake are Lake Lucero at the south end of the dune field, Alkali Flats and a playa on the east side of the dunes.

Surrounding mountains provided much of the gypsum

Gypsum.  You can blame the playa

Playa near Visitor Center.  Lake Lucero is part of White Sands Missile Range
and can only be reached in a monthly ranger-led tour.
Check website for schedule

The crytalline gypsum that erodes out of the shallow basin lake (playa) and alkali flats is called selenite.  This mineral forms thin sheets that break apart readily.  As the cycles of wind and heating and cooling break down the selenite crystals, the become a very fine white sand.  The sand drifts and gathers into dunes.  Very strong winds can lift the sand and blow it over the Sacramento mountain range, as in the NASA satellite view below.  This also gives you a good idea of the prevailing wind pattern in this part of the country.  The dunes are formed by winds blowing from southwest to northeast.

Selenite crystals at Lake Lucero - NPS photo

White Sands NM at left center, trailing gypsum dust plume to northeast
NASA photograph from Aqua satellite

Making dune

Barchan dunes towards the west side of the park

To make a dune, you need a very strong wind, sand grains small enough to be carried by the wind, and friction / resistance of some kind to get the sand to stick together somewhat.  The sand will start to pile up forming a shallow angled ramp that the wind carries sand up.  When sand reaches the top, gravity may take over and the sand grains fall down in the stagnant air behind the dune.  This side of the dune is called the slip-face.  The sand on this face tends to be looser and the slope is steeper, making it more difficult to walk up than the windward side.

A "blowout" happening just right of center
Sacramento Mountains form the background

When there is a high wind velocity and a limited amount of sand, dunes will form as barchan dunes, which are horseshoe shaped with the arms pointed downwind.  This form of dune is plentiful along the Loop Drive.  Sometimes barchan dunes unite into a line called a transverse dune.  Dunes that suffer a "blowout" often have plants covering the dune, so the denuded area travels quickly and the arms more slowly resulting in a horseshoe that points with its arms upwind and the arc downwind.  These parabolic dunes are common on the outer edges of the park, except in the west.

Rio Grande Cottonwood (Populus deltoides)
growing on top of a dune

The dunes at White Sands are relatively easy to walk upon because of the soluble nature of gypsum.  Rains will solubilize some of the gypsum, which will recrystallize and cement neighboring gypsum granules together.  This layer will also protect a groundwater from evaporating.  Plants that are trapped by an advancing dune may increase stem length to keep leaves above the level of the sand.  These plants can then tap into the protected groundwater for their own survival.  Plants such as the cottonwood that can extend roots down to groundwater are called phreatophytes

Another plant that seems adept at stem elongation is the soaptree yucca plant.  Young flowering plants may be about 3 feet tall, but by stem elongation, they may reach 18 feet.  The yucca is well adapted to a variety of climates, but they are only pollinated by one moth, the yucca moth (Tegeticula yuccasella).  At that, it is only the female yucca moth that visits the flowers of this plant, since the males complete their life cycle after mating (they die).  The egg-laying habits of this moth push pollen down into the pollen tube of the yucca flower.  Yucca moths lay their eggs in the flowers, and the young will develop in the yucca fruit, drilling through the outer skin to escape.  This yucca has a sap that contains a natural soap, which accounts for the name.

Soaptree Yucca (Yucca elata)

Radical animals

While the white sand does not get as hot as fast as darker sand, the desert is still a warm and dangerous place in the daylight.  Most animals in the desert become active in the evening, and many of them may be best evidenced by their footprints.

Beep Beep!  Roadrunners leave X shaped tracks in the sand

Lizards drag their tails behind, making a line between left and right footprints

A tweedle beetle bottle puddle bottle muddle --- bug tracks

Pioneers

Gyp nama (Nama carnosum)

When a dune has passed, the soil has a high gypsum and salt content.  Gypsophiles are plants that are specialized to living in this environment.  These plants are rarely taller than shrub size.  Most of these plants are shorter than two feet tall.  After a few generations of growth, they will enrich the soil with their decaying organic material, creating a soil more friendly to less specialized plants.

You can often spot a gypsophile in a list of plants by its name; they are often called Gyp "something".  For instance, Gyp nama is a little plant that looks like a fir tree.  It has small white flowers in the summer after rains.

Yellow Evening Primrose (Calylophus hartwegii)

Another pretty gypsophile is the yellow evening primrose.  These flowers are yellow by day, but after being pollinated by nocturnal moths, the flower wilts and becomes more orange colored.  The plant that I saw was getting a bit ratty, but it did have some nice flowers.

Not all of the plants here are strictly gypsophiles.  The sandy verbena plant is a generalist.  It can be found on gypsum flats, in interdune areas and on the dunes.  They have little pink flowers in April and May, but sometimes flower after rains in the summer into October.  You couldn't prove it by me, but the sign says that they produce a lilac smell, especially after rains.

Sand Verbena (Abronia angustifolia)

Spring Blooms in the Chihuahua Desert

The first time I visited this area, I was in El Paso for work and stayed over to take a drive out to White Sands in late May.  The second time Ben and I went when he was in middle school during winter break.  Not many blooms then.

Ocotillo (ock-uh-TEE-oh) Fonquieria splendens

Barrel cactus (Ferocactus acanthodes)

Cholla (CHOY-uh) Cylindropuntia imbricata

Yucca (Yucca elata)

Getting There

If you are coming to Las Cruces, New Mexico from the west on I-10, you can catch US-70 heading east at Exit 135 (Alamogordo) OR you can catch I-25 going north at Exit-44, then US-70 east (Alamogord - Exit 6).  From El-Paso, you can take I-10 north to I-25 to US-70 east.  Coming from El Paso, I enjoy driving through the Franklin Mountains - from I-10 take exit 22B and head toward Alamogordo on US-54, exit at Exit-29, take the first left onto Woodrow Bean Transmountain Drive (Loop 375).  If you are getting out in the sticks and going up, you've done it right.  Much of the drive through the Franklin Mountains is a state park, lots of turnouts and trailheads.  Very nice views.  This will take you back to I-10.  You need to go north once on I-10 OR take a scenic route.  I enjoyed driving the backroads to Mesilla and Las Cruces.

The national monument is surrounded by the US Army's White Sands Missile Range and Holloman Air Force Base. The US Army is not nearly as sentimental about nature and geography as we are, since they use their part of the region to test out weaponry. This is a bad news/good news thing:  the bombings destroy some features, but protection from traffic also helps preserve some features.  From time to time, missiles are flown over the national monument, making park and road closures necessary. Good thing, because missiles have fallen on the park and destroyed visitor facilities before.  Check the park website to see when closures are scheduled.   That seems to be the watch word for this park:  Check ahead, especially if you are traveling on a tight schedule or want to visit one feature in particular.  There are border patrol stations on US-70, so be prepared to stop and talk to the nice people.  US-70 may also be blocked during missile tests.  Check ahead, be prepared.

Waypoint:  Latitude 32.7803176 N; Longitude 106.1777423 W
Street Address: 19955 US-70, Alamogordo, NM 88310

Trinity Site, where the first atomic weapon was tested is just north of here and is open for visitation the first Saturdays of April and October.  Going to go there one day.

Further Reading

National Park Service White Sands National Monument Site

White Sands National Monument History