Tuesday, October 21, 2014



Wanda Williams
A Gem of a Different Color
           
            On a beautiful October morning our small group eagerly piled into the SUV at Snow College. The time of year couldn’t have been more perfect; the weather was amazing. Our clan consisted of Snow students impassioned in the field of geology, and paleontology. We had our esteemed leader, Geologist and instructor Renee Faatz, to guide us. Sailing over the dirt roads, like a ship with the wind in her sheets, we first headed out to Topaz Mountain. The mountain is not much to look at with its gloomy, grey slopes and patchy scrub. But it seems that the most wonderful things come out of drab, dreary rock – and Topaz Mountain is certainly no exception. Besides bearing its namesake, Topaz Mountain’s rhyolite is also host to quartz, garnet, pseudobrookite, bixbyite, and the elusive red beryl. These are just a few of the treasures tucked away within the unassuming gray walls. The topaz, however, was the main reason for our being there.
            The Thomas Range topaz formed from trapped volcanic gasses. Six to Seven million years ago, volcanic vents emerged along faults in the area. The thick, gaseous lava flow contained numerous bubbles called vugs. Inside the vugs, fluorine-bearing vapor sublimated from the lava. In the last stages of solidification, the trapped vapor cooled and formed beautiful topaz crystals.
The topaz at Topaz Mountain can be found in a small variety of colors. The colors range from a nice rich sherry, to light pink, to clear. The reason for this color palette has something to do with good ol’ wholesome sunshine. When the crystals are exposed to sunlight they tend to fade over time. I thought this was rather curious, so I decided to find out why. I rummaged through my field books, remembering that I own a copy about Topaz Mountain; the author and expert on this location, John Holfert, offers this explanation:

            Unfortunately, the color of the Thomas Range topaz is not stable when crystals are left exposed to direct sunlight for extended periods of time. . . .The sherry color of the unexposed crystals is a direct result of exposure to naturally occurring ground radiation for millions of years, probably from trace amounts of uranium in the rhyolite. Radiation causes electrons to be displaced to a higher energy state giving the crystal a temporary color center. Exposure to direct sunlight excites the electrons causing them to return to their normal state, thereby eliminating the color center, resulting in a color shift from sherry to colorless. (4)

Holfert goes on to express that the rich sherry color can be restored if the crystal is exposed to, “strong radiation for a short period of time” (4). This makes sense because I also found out that this is precisely how most blue topaz are created. According to the Department of Geological Sciences at the University of Texas, “Most natural topaz is colorless or very pale blue; the dark blue color, so commonly seen today is produced by irradiation, usually followed by heating” (Topaz).
            Holfert assures his readers that the color change takes about a week to ten days to take place. He also states, “Artificial light, including florescent and halogen light, does not appear to have any negative effect on the color stability of the topaz” (5). I found this to be a relief because I was trying to keep my topaz in eternal darkness to preserve their coloring. Now I can display them without any worries, as long as they stay out of direct sunlight.
            After a very satisfying expedition to Topaz Mountain we were back in the SUV, being blown by the wind to our next grand adventure. Most of us found some very pretty topaz crystals. We all had a really great time.

Notice how the topaz in the foreground is a light pinkish color, while the topaz in the back is a deeper sherry hue.

In contrast, this topaz from Topaz Mountain is colorless. (Mike)






Works Cited

Holfert, John. A Field Guide to Topaz and Associated Minerals of the Thomas Range, Utah (Topaz Mountain) Volume 1. UT: HM Publishing, Dec. 1996. Print.
Mike. CSMS Geology Post. Colorado Springs Mineralogical Society. 5 June 2013, Web. 18 October 2014.
Topaz. Deptartment of Geological Sciences, University of Tx. 1998, Web. 18 October 2014.

Monday, May 5, 2014

Weathering Rinds by Jonathan Major

While on a field trip working in the Grand Staircase Escalante National Monument (GSENM) , a few members in our group came upon several cobbles of chert and quartzite cobbles with an unusual surface that I can best describe as a rind.   Each cobble of chert and quartzite had a black rind 1- 2 cm thick around it.  The cobbles are part of units such as the Canaan Peak.  The same cobbles are found Dakota Formation near Capitol Reef National Park.  The units were deposited in streams during the Cretaceous period of time.   The cobbles have since been reworked and deposited in the GSENM in alluvial terraces.

These rinds, sometimes referred to as patina apparently form from weathering on the outside of the cobbles that were deposited in braided streams deposits.  Analysis of similar rinds show iron, manganese and other elements like silica leaching out of the rock over time.  Some suggest  that the microflora aid in this process. 


Try as we might, we can't find any papers that are specific to the rinds on these Cretaceous conglomerates.  We would like to know more - the composition of the rinds, why they are so common in the Cretaceous (Sevier Orogenic) conglomerates.    Looks like a great future research project.



References
Baker, J. C., Edmonds, W. J., Ogg, C. M. (2001) Research Gate. Retrieved from http://www.researchgate.net/publication/232149104_Quartzite-Cobble_Weathering_in_Alluvial-Fan_Soils_of_the_Virginia_Blue_Ridge

Rajamani, V., Tripathi, J. K. (1999). Current Science. Retrieved from http://www.currentscience.ac.in/Downloads/article_id_076_09_1255_1258_0.pdf

Viveen, W., et al., Reconstructing the interacting effects of base level, climate, and tectonic uplift in the lower MiƱo River terrace record: A gradient modelling evaluation, Geomorphology (2013), http://dx.doi.org/10.1016/j.geomorph.2012.12.026

Wagner, G. A., (1998). Google Books. Retrieved from http://books.google.com/books?id=ADuZDCa08kwC&pg=PA37&lpg=PA37&dq=iron+rinds+on+chert+in+alluvial+terraces&source=bl&ots=txI_5azP_I&sig=PtZAyR89-EaP4nBfxXuCLq8ehVc&hl=en&sa=X&ei=6iVRU_6PJqbq2gXF0IGQAw&ved=0CEYQ6AEwBQ#v=onepage&q=iron%20rinds%20on%20chert%20in%20alluvial%20terraces&f=false

Sunday, May 4, 2014

Diablo the Ceratopsian and more by Jason Scott Dillingham



Many animals and reptiles that exist today can seem relatable to the creatures in the past.  Imagine the beautiful Serengeti, the dry sun beating on your face.  Suddenly you feel the ground pounding and across the way you notice a muscular grey animal with large plates covering its body charging on all fours through the wilderness, armed with a horn atop its nose.  
Now, notice the sun getting warmer and more humid; the plant life: taller, greener, everywhere.  The ground shakes even more as a “snorting, stampeding, five-ton animal the size of a car, with a giant bony frill on its head, and you've got a fairly accurate picture of a ceratopsian dinosaur such as Triceratops” - a larger friend of the rhinoceros - charges by (Carroll, 1988). 
Ceratopsians (Greek for “horned faces”) date back to the late Jurassic period in Asia.  These species preceded Triceratops (up to the Late Cretaceous) and lacked the frills and horns that Triceratops had. Over time, predators such as the Tyrannosaurus Rex  came along and the Ceratopsians slowly evolved to defend themselves (Strauss, 2014). 
On our Geology field trip to the Grand Staircase, we first had to transport - before we even got to any digging sites - a skull of a Ceratopsidea (a frilled Ceratopsian) named Diablo to a museum where he could be displayed for people to view.  It was exciting to relate how large the animal could have been by the size of its skull, and encouraged me, personally, to get into the field and begin finding new things.

Throughout the trip, we broke up into two/three groups, one with Scott Richardson, the other with Alan Titus.  I was fortunate to participate in the group with Scott that went to a site where a discovery had already been made, but not completed.  “[Scott] discovered what is thought to be a previously unknown species of dinosaur similar to a triceratops, the latest in an extraordinary series of dinosaur finds in the area over the past 15 years (Hollenhorst, 2014).”  The discovery is still unclear, but the excitement endures on.

Sources


Carroll, R.L. 1988. Vertebrate Paleontology and Evolution. W.H. Freeman and Company, New York.  Found on: http://www.ucmp.berkeley.edu/diapsids/ornithischia/ceratopsia.html


Strauss, Bob.  Ceratopsians - The Horned, Frilled Dinosaurs.  http://dinosaurs.about.com/od/typesofdinosaurs/a/ceratopsians.htm . 2014

Photo courtesy of James Montgomery

Thursday, April 24, 2014

Ripples


James Montgomery

             On the last day of our exploration into the Grand Staircase Escalante National Monument we ventured into a Hackberry Canyon, exploring millions of years of rock formations. While walking in and around the small creek that ran through the middle of canyon we noticed ripples in the water. Upon closer inspection we could see the soft sand ripples at the bottom of the stream migrating slowly forward with the current. Ripples begin to form through when the water disrupts the grains of the sand on the bottom of the body of water.  The steeper, down current side of the ripple is always at the angle of repose.
            Deeper in the canyon, we noticed a large boulder with lithified ripples dating back to the Jurassic Period.  These embossed ripples had been preserved over millions of years.
What a great example of uniformitariansim.  We could see modern ripples forming in a stream bed next to ripples formed in the Jurassic almost 200 million years ago.




               

Monday, April 21, 2014

The Kaibab Monocline



            During our Geology Field Studies trip to the Grand Staircase - Escalante National Monument the class camped within a structure called the Kaibab Monocline.   To the right is a cross section of the Kaibab Monocline as it looks near the North Rim of the Grand Canyon.   A monocline is a one-sided fold.  This particular one stretches north-south for about 240 km and dips steeply to the east  - up to 60o-70o.  This monocline was formed by subsurface movement on a fault during the Laramde Orogeny between 50 and 80 million years ago.  (Tindall, 2000).

Differential erosion of the tilted rock layers exposed along the monocline has created a series of east dipping ridges and valleys. Differential erosion occurs because less resistant rock layers like shale will wear away more quickly than more resistant rock layers like sandstone.   Here, the less resistant Tropic Shale and Carmel Formations weathered to form valleys, while the more resistant layers like the Navajo Sandstone and Dakota Sandstone formed ridges.  Stream erosion of the ridges creates the triangular hogbacks seen here.   Locally, this is called the Cockscomb. It was the down-warping on the east side of the monocline that allowed the young layers of the Wahweap and Kaipairowits to be protected from erosion.  Had it not been for the monocline, these layers and all the dinosaur bones they contain might have eroded away long before humans came around to discover them.

References

 Reches, Ze'ev. 1977  "Development of monoclines: Part I. Structure of the Palisades Creek branch of the East

Kaibab monocline, Grand Canyon, Arizona." Development of monoclines: Part I. Structure of the Palisades Creek branch of the East Kaibab monocline, Grand Canyon, Arizona. The Geological Society of America, 25 Web. 16 Apr. 2014.    <http://memoirs.gsapubs.org/content/151/235.abstract>.
Tindall, Sarah E. 2000 "The Cockscomb Segment of the East Kaibab Monocline: Taking the Structural Plunge." Geology of Utah's Parks and Monuments 28 pages 1-15.

Dinosaur Excavation

Before I went on our geological field studies trip, I thought that by some strange coincidence, paleontologists would just be walking along a random plot of dirt and find T. Rex skulls and bones poking out of the ground, kinda like this 60’s paleontologist guy below.

 How wrong I was! I had no idea how much work and effort a paleontologist puts into finding dinosaur fossils. I found the whole excavation process very fascinating, and so that’s what I will teach you about.
Before a paleontologist even begins digging, he has to survey the area he’s working in, and see if anything promising can be found. Fossils are found in sedimentary rock layers, and the layer we did our work in was the Wahweap Formation. A paleontologist surveys and prospects for fossils while hiking along the bases of hills and such. Fragments of fossils erode out of the ground and tumble downhill, so if any fragments are found at the base of a hill, you search up the hill to find more!
After identifying what has been found (if anything) and if it was actually a fossil, the paleontologist has to decide if it would be worth time and resources to pursue an attempt to excavate any fossils from the ground. On public land, permits must be obtained from the appropriate agency, such as the BLM or the Forest Service, before an excavation can begin. Once a permit is acquired, the paleontologist heads out with an excavation team and begins work. It involves a bunch of digging with shovels and picks until the bone layer is found.
When the bone layer is found, the paleontologist will use only small hand tools and brushes to carefully isolate fossils.

Once the top of the fossil is exposed, hardener is put on the fossil, and then the fossil gets jacketed. The jacket involves lots of wet paper towels and strips of burlap soaked in a liberal amount of Plaster. The jacket sits until it is firm and solid. However, this is only the top of the jacket. Now the paleontologist digs under the fossil and layer of dirt and applies more jacketing material. When the bottom is solid enough to hold the jacket in place, the jacket is flipped over and brought out of the dig site to the lab. Pictured below is a large jacket being removed by an excavation team.

This is the process a paleontologist uses to excavate a fossil, and it’s totally not what most people think happens when fossils are found. I was glad I had the opportunity to go and learn about paleontology.


Wahweap Stratigraphy



           For my blog post I have chosen to write about the stratigraphy of the dig sites where we spent the majority of our time. The two main quarries that we worked in over our two days in the Grand Staircase Escalante National Monument were both located in the Wahweap Formation. The Wahweap Formation is approximately 80 million years old. The climate and geological processes that created it were perfect conditions for dinosaurs to live in and be buried.
            The Wahweap is composed of mainly two types of rocks: sandstone and mudstone. The plant and animal fossils found in these layers, such as petrified wood, Hadrosaur and Ceratopsian bones, indicate that there was a climate that could support both plant and animal life when it was being deposited. These sandstones and mudstones were deposited in swampy lowlands, shallow lakes, slow moving rivers and floodplains (http://www.gsenmschool.org/Geology/Unit_02/). Most of the running water flowing through the area, at the time, was runoff from the Sevier Mountains to the west, flowing toward the Cretaceous Interior Seaway to the east.  
As we look at the different sedimentary structures in the Wahweap, we can see more evidence of its environments of deposition such as fine grained sediment sizes and small scale cross beds which indicate slow moving streams and floodplains. The loose mudstone slopes of the Wahweap also indicate that there were lakes and swamps present.
            This lush and humid climate was perfect for dinosaurs. Erosion of the growing Sevier Mountains created a large source of sediment. The mountain building to the west created a trough in front of it called a foreland basin which allowed the large source of sediment to build up quickly creating perfect conditions for the burying and preserving of the plant and dinosaur fossils found there today.