Wooster Geologists

ZZYZX, CALIFORNIA–This was our last full day of geological adventures in the Mojave Desert for 2013. The weather was even warmer than yesterday, with the temperature in Baker at 4:00 p.m. a delightful 94°F. We began in the usual way from our temporary home at the Desert Studies Center, heading north of Baker again to Shoshone and the Tecopa area. Our first stop was at Salt Creek Spring in the Salt Spring Hills, one of the rare riparian environments in this part of the desert. This place is also notable as the first place gold was found in southern California. This discovery in 1849 began the boom in mining throughout the Mojave Desert.

One of the interesting geological features we noted was the occurrence of the familiar tafoni, but this time in a deeply eroded outcrop of quartz monzonite (shown above with Melissa Torma). Our companion Yoav Avni believes this may represent a Pleistocene pluvial phase of erosion that has been exhumed in the modern landscape. Tafoni features in granite would seem to require more water than is present today in this system, thus placing these features during a wet interval makes sense.

We next returned to the little settlement of Shoshone, this time visiting the town museum (above). It is well worth touring for its local artifacts, some wildlife displays, and the bones and teeth of the Shoshone Mammoth found in the Tecopa lake sediments.

The mammoth (Archidiskodon tamenensis on the sign) has been very well preserved by the lake clays and silts, especially the diagnostic teeth and jaws. It is an impressive find and an important addition to our knowledge of the ancient Lake Tecopa ecosystem.

The Resting Springs Welded Tuff exposed east of Shoshone is one of the most famous roadcuts in the Mojave Desert. Above we see Olivia Brown exploring the glassy black middle of the unit. The colors and hardnesses of the rocks here show degrees of welding from the intense heat developed in this pyroclastic flow. It is technically a devitrified pumice tuff, welded tuff, and vesicular vitrophyre dated by K-Ar methods as 9.5 million years old. The fiamme are fantastic.

In the same outcrop of the Resting Springs Tuff are some impressive faults. Jonah Novek is showing above how he knows this is a normal fault because the drag fold shows downward movement of the hanging wall (the side he is standing on).

At lunchtime we arrived at Emigrant Pass east of Tecopa to collect trilobites from the Cambrian Carrara Formation exposed on the north side of the highway (which happened to be the Old Spanish Trail). After a bit of exploring, our ace field geologist Shelley Judge found the most fossiliferous outcrops. We found hundreds of the fascinating critters, leaving most for future field trips. I like the view above, by the way, because it shows Telescope Peak on the far distant skyline.

The best trilobite of the day (and there were many good specimens) was collected by Olivia Brown. It is a rare whole specimen, apparently of the genus Olenellus. You can see all the thoracic segments and spines, as well as the pygidium. The way the cephalon is separated from the thorax may indicate that it is a preserved exuvium (molt). Very nice.

Following a geological tradition transferred from Sonoma State University geologists to us via my friend Matthew James, we visited China Ranch south of Tecopa and had date milkshakes. Delicious and refreshingly cool on what turned out to be a very hot day. We also had a good geology lesson with the fanglomerates and ancient lakebeds exposed around the date groves.

While driving out of Tecopa, we stopped to walk out onto the Lake Tecopa playa, which was covered by a thin crust of salts. From the left are Meagen Pollock, Melissa Torma, Shelley Judge and Olivia Brown. We observed the modern playa sediments juxtaposed with the ancient lake strata exposed as low mounds.

Last of all was a stop to briefly recognize the Harry Wade exit route out of Death Valley at an historical marker on the highway back to Baker. We came full circle at this point, since we started with Death Valley and now ended looking back into that source of such hardship in 1849.

Our final scientific event of the day was an excellent tour of the night sky by the Laboratory Technician of the Vassar College Environmental Sciences and Geography Department, Rick Jones. The sky is very dark and inviting in this lonely part of the desert.

ZZYZX, CALIFORNIA–The spectacular set of folds above are exposed in the lower parking lot of Calico Ghost Town near Barstow, California. This is a famous site that has been visited by hundreds of geologists, but there are still many mysteries about the causes of this deformation and even the correlation of these rocks in the region. The section makes up the Calico Member of the Barstow Formation, which is apparently below the exposed units of the Barstow Formation in Owl Canyon and Rainbow Basin we saw yesterday.
As a true structural geologist, Shelley Judge is here explaining the folding of these beds with her hands and, later, a sketch on notepaper. “Explaining” is not quite the right word: she wrangles information and observations out of the students first before developing the deformation hypotheses. It is not just about a bit of compression!
After exploring a wadi west of the town, we then spent the rest of the morning in Calico. The students above (from the left, Kyle Burden, Steph Bosch, Sarah Frederick, Olivia Brown and Alex Hiatt) are enjoying the main street of this reconstructed 1880s mining community. There are lots of attractions here, from sarsaparilla in the saloon to a classic old-timey mystery shack. One gentleman, hearing that we were geologists, kindly explained to us how Calico Mountain is an extinct volcano with “sandy dikes” full of metals and remnants of lava flows on its sides. It was fun to see our students grapple with the question: do we correct this nonsense or just smile and avoid the hassle? (I just let it pass because I was hungry for lunch!)
In the afternoon we drove south and east along Interstate 40 and Route 66 (yes, the Route 66) to Amboy Crater (shown above). The day had warmed considerably — my thermometer said it was now 94°F. Nevertheless, the stalwart geology crew walked to this gorgeous cinder cone and climbed to its rim from the inside (shown below). I enjoyed learning about the subtle features of the lava flows that emanated from the cone, including pressure ridges and hexagonal cooling joints. This flows and the cinder cone look amazingly fresh. The lava flows have been dated at between 6000 and 500 years old.

The warm temperatures at Amboy brought out some reptiles, to our delight. We saw at least three desert iguanas and many flowers, including the Sand Verbena (Albronia villosa) shown above. It felt like summer, although we were still in the middle of March. Tomorrow is expected to be even warmer. (Yes!)

DEATH VALLEY, CALIFORNIA–All geologists love Death Valley. No other place on Earth has such extraordinarily diverse geology combined with a modern infrastructure and a century of scientific study. The Wooster Geologists had a spectacular time in and around the valley today. Here we are above with the traditional group shot at Badwater. The weather could not have been better.

We left the Desert Studies Center at Zzyzx just after breakfast and drove through Baker and Shoshone to the southern end of Death Valley, seeing many wonderful sites. After lunch at the new National Park Service Furnace Creek Visitor Center, we then drove east and up out of the valley to Zabriskie Point. The above view has been published countless times by geologists and nature enthusiasts, but it has not lost its graphic power. We are looking here to the west at deeply eroded lake sediments of the Furnace Creek Formation. Towards the back of the light-colored material you can just make out the black streak of a basaltic intrusion.

I think the other side of Zabriskie Point — the side looking out over Death Valley — is even more impressive. We see again the Furnace Creek Formation lake sediments, this time with alluvial deposits on top (visible on the right). These materials accumulated in an ancient lake and were lifted up and tilted by the tremendous faulting that formed Death Valley. The pinnacle is called Manly Beacon.

We took advantage of the sunlight and high spirits to take a picture of our Desert Geology 2013 students.

We continued east and then south to Dante’s View, where we looked down into Death Valley from the dizzy heights. In this image we see Telescope Peak towering at 11,049 feet of elevation, while much of the valley floor below is lower than sealevel.

Looking straight down from Dante’s View to Badwater (on the far right), we can see a complete alluvial fan from the narrow channel in the mountain slope to the spreading apron of debris over the salt pan on the valley floor. Badwater Road skirts the periphery of the fan.

After Dante’s View, we continued east and returned to Zzyzx via Death Valley Junction, Shoshone and Baker. Again, I can think of nowhere else one can see so much geological diversity in a single day, from the steamy floor of Death Valley to the heights above where we could walk through patches of snow.