Well, the trip to Lee’s Ferry went well. The area is gorgeous. I definitely recommend Lee’s Ferry as a vacation spot for anyone that truly enjoys the outdoors and everything that comes with it. As for my project, my partner and I collected samples from the various layers of the Chinle Formation. Samples were taken from four different locations along a trail where the formation was well exposed. Our next step is to analyze the samples to see if there are any chemical or physical variation that lends to the change in colors and/or textures of the layers of the Chinle. I took a number of pictures while out in the field that show these changes. I will post those pictures later today for anyone that cares to take a look at them.
Jordan and I are planning on taking samples of the Bentonitic Clay layers from multiple locations in and around Lee’s Ferry, Arizona. Upon returning to Norman, we hope to perform a number of tests on our samples, including: SEM scanning, observing specific interactions with water, chemical composition, etc. We then plan to compare our findings with studies that have been published about the same layers that occur in surrounding areas. Riggs et al., 2003 discussed the Petrified Forest Member within Arizone, but used locations from the northern, central, and southern parts of the state. Stewart et al., 1984 used samples taken from the southern portion of Arizona and northern Mexico in an attempt to ascertain a source for the volcanic material that ultimately formed the bentonitic clay layers.
According to Stewart et al., 1986, about 75% of the lower Chinle formation contains volcanic deposits. The volume of these volcanic deposits was estimated to be as much as 70,000 cubic kilometers. Fragments of lava, tuff, and specific minerals, such as biotite, sanidine, and bentonite, have all been identified within the Chinle. The source of these deposits was originally believed to lie south of where the present-day deposits are found, but in the 1986 ariticle, Stewart et al., determined that the ages of the deposits near the supposed “source” were significantly younger than the volcanic detritus found within the Chinle Formation.
This is a really cool picture of the banding that, hopefully, we will get to see, within the Chinle formation in Arizona. This picture was taken in the Vermillion Cliffs National Monument in Arizona.
Riggs et al(2003) used zircon crystals found within the finer grained ash deposits of the Chinle Formation to determine a reasonable age of the generation of the ash. Using multiple methods with individual and multiple grains, they determined the age of deposition of the ash layers within the Chinle Formation to be 209 +_5 Ma (Riggs et al., 2003).
In a more recent paper, Ramezani et al determined the age of the ash deposits within the Petrified Forest Member of the Chinle Formation to be 207.79 ± 0.15 Ma. They also used zircon crystals found within the ash layer to acquire these age estimates (Ramezani et al., 2011).
Upon doing more research about the Chinle Formation, and with the gentle nudge or our professor, my research partner and I found localized volcanic ash deposits that we have decided to focus our research around. The ash deposits are specifically found within the Petrified Forest Member of the Chinle (I have also found a few papers saying that they have found the same type deposits within the Sonsela Member as well). The ash deposits contain relatively high amounts of the mineral bentonite.
For Spring Break this year my Intro to Field Geology class will be camping near Lee’s Ferry in North-Central Arizona. Lee’s Ferry is the only location for a great distance where people have direct access to the Colorado River. It is a major launching-off point for rafting along the Grand Canyon. The location is named for John Doyle Lee, who operated a ferry for crossing the river in the late 1800’s (Wikipedia).
On a personal note, I don’t know how I feel about this trip. My interests are more in the igneous side of geology, and I don’t know how much of that we will be seeing out there. Despite this, I’m sure it will be a good learning experience.