Exploring the Tecopa region … and finally the trilobites!

March 14th, 2013

SaltSpring031413ZZYZX, 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.

TafoniMelissa031413One 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.

ShoshoneMuseum031413We 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.

Archidiskodon_tamenensis031413The 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.

OliviaBrownResting Springs031413The 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.

JonahDragFold031413In 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).

TrilobiteCollecting031413At 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.

TrilobiteWhole031413The 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.

ChinaRanchSign031811aFollowing 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.

TecopaPlaya031413While 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.

WadeExit031413Last 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.

Enjoying the geology of the Mojave National Preserve

March 13th, 2013

StudentsLavaCave031313ZZYZX, CALIFORNIA–Today the Wooster Geologists explored the Mojave National Preserve. It is a beautiful, spacious, diverse place well maintained and protected by the National Park Service. Our first stop of the morning is shown above. We explored a lava tube in the cinder cones portion of the preserve. We descended into the dark tunnel by the steps above, and then studied the walls and ceiling with our flashlights, as Melissa Torma is doing below.
MelissaCave031313Lava tubes are formed when a lava flow cools on the top and sides, and then the remaining lava flows out, leaving behind the empty shell. In this particular lava tube we could see various level markings the lava left on the walls as it drained away. We also saw spatter and “lavacicles” hanging from the ceiling much like icicles or stalactites in a cave. My favorite part is where we can see from below a granitic boulder that was caught up in the flowing lava.
CambrianLimestoneOutcrop031313South of the lava tube along Kelbaker Road is a small outcrop of Cambrian limestone. We examined these rocks for a short time (above) to sort out their lithologies and the paleoenvironment in which the sediment accumulated. The clues included extensive and diverse horizontal burrow systems (shown below) and numerous oncoids with shelly nuclei.
BurrowsLimestone031313The students determined that the burrows were filled with dolomite from later diagenesis of the sediment, and that the oncoids showed the system was deposited well within the photic zone. We think this rock is a biomicrite formed around the storm wavebase on a shallow carbonate platform.

KelsoDunes031313One of our favorite places is Kelso Dunes. These massive piles of sand are stabilized at their bases but still moving about at their crests. We’ve studied them so many times in the Desert Geology and Sedimentology & Stratigraphy courses that we needed to say little about them. The students raced to the top, noting the diverse sand composition (so much more than just quartz) and eolian structures on the way.

TafoniAnanda031313Ananda Menon is here showing us one of the magnificent tuff beds at the Hole in the Wall locality in the easternmost portion of the Mojave National Preserve. The holes in the wall (is that how the place was named?) are examples of tafoni, a rock weathering pattern. We hiked the Rings Loop Trail examining the tuff units and their diverse clasts, including pumice and charcoal. We also saw good examples of Indian petroglyphs of unknown age.

QtzMonzoniteCimaDome031313While crossing Cima Dome on the way back to Zzyzx, the group visited an outcrop of quartz monzonite which forms at least part of the intrusive body under the uplift. As with most of our outcrops, it was a story of both petrology and structural deformation.

AlienFreshJerky031313Finally, at the end of the day I could not resist taking the Wooster Geologists to the unique store in Baker called “Alien Fresh Jerky“. Half the group loved it, the other seemed offended by the epic cheesiness. At least Melissa Torma and Jonah Novek enjoyed meeting members of the Galactic Peace Patrol parked in front.

Folded rocks, volcanoes, and a little of the Old West

March 12th, 2013

CalicoMemberFolds031213ZZYZX, 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.
ShelleyCalico031213As 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!
StudentsCalico031213After 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!)
AmboyCrater031213In 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.

InsideAmboy031213
Verbena031213The 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!)

Wooster Geologists in ancient lakes

March 11th, 2013

Manix031113ZZYZX, CALIFORNIA–Today Team Mojave studied the remains of ancient lake systems in the dry, dry desert. Early in the morning we drove west from Zzyzx to the Harvard Road exit off Interstate 15 and took a series of sandy roads to Bulwada Ridge on the shoreline of ancient Lake Manix. This Pleistocene, pluvial lake occupied a huge basin east of Barstow, California. Above we see laminated muds deposited in the lake itself. In the foreground are bouldery shoreline sediments. In the background you can see a scarp cut by the modern Mojave River (all underground at this point). Lake Manix was fed by the ancient Mojave River and supported a diverse fauna of fish and invertebrates.

MeagenBeachRidge031113Just to the north of the shoreline are long, twisting gravel bodies. Meagen Pollock is pondering one which has been truncated by modern erosion and now is topped by a beautiful desert pavement. (She found a beautifully polished artifact on one of these surfaces, by the way. It is a scraper with one bifacially-worked edge.) These gravel deposits are ancient beach ridges made by storm waves on Lake Manix.

OwlCanyonGroup031113After our visit to Lake Manix, we traveled to much older lake and river deposits in the Barstow Formation (Upper Miocene) exposed in Owl Canyon near Barstow. Our tradition here is that the students first explore the exposures and then bring back rocks to the picnic area for group analysis and discussion. The students above are clearly happy with all that they learned. (The two distinguished people in the background, by the way, are my parents Gary and Corinne Wilson who came to enjoy the geological fellowship.)

OwlCanyonTeaching585

A view from the other side of the table. Photo by Gary Wilson.

DesiccationCracks031113Kyle Burden found this beautiful example of two-stage desiccation cracks, preserved here as molds in the overlying sandstone.

RainbowBasin031113Another Wooster tradition is the group photograph in front of the outstanding syncline in the Barstow Formation exposed in nearby Rainbow Basin.

AftonSide031113Our final stop was in Afton Canyon about 50 miles east of Barstow. This narrow passageway is where Lake Manix drained into Soda and Silver Lakes, apparently more than once in a catastrophic manner. We crossed the mighty Mojave Rover on foot and then walked up this side canyon to check out the flood deposits and the lake deposits high on the skyline. These mark the highest level Lake Manix reached before it overtopped its dam and drained very quickly.

Another stimulating day which ended with a chicken dinner at the Desert Studies Center. Tomorrow we will return to the Barstow region but this time concentrating on structural issues and volcanic and plutonic rocks.

 

Death Valley Days

March 10th, 2013

BadwaterGroup031013DEATH 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.

Zabriskie031013We 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.

ZabriskieOtherSide031013I 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.

ZabriskieStudents031013

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

DanteView031013

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.

DanteViewFan031013Looking 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.

Wooster Geologists return to the Mojave Desert

March 9th, 2013

DSC030913

ZZYZX, CALIFORNIA–It is officially now a Wooster Geology tradition: every other year we take a Spring Break field trip with students, faculty and staff. So far all of our trips have been to the Mojave Desert, for reasons that will be apparent in the following posts. This expedition is the highlight of our Desert Geology course this spring.  This year we have the largest group yet: eleven students, three faculty (Meagen Pollock, Shelley Judge and me — Greg Wiles could not join us because of his leave activities) and two staff (Administrative Coordinator Patrice Reeder and Geological Technician Nick Wiesenberg). We are delighted to also have with us Yoav Avni, a desert geomorphologist with the Geological Survey of Israel (and my good colleague and friend). Four vans of enthusiastic geologists!

We left Wooster very early this morning (5:30 a.m.) to catch a non-stop flight to Las Vegas from Cleveland. After picking up our vehicles at the Las Vegas airport, we drove to the Desert Studies Center (DSC) in delightfully named Zzyzx, California. We’ve stayed here many times before. The station is shown above from the mountain just to its west. Astute observers who visited this little paradise before may notice on the far right side a new solar array to supply electricity to the facility. It is all off the grid and self-contained. It feels in some ways like being on a ship at sea. On the far side of the station you can see the expanse of Soda Lake and some of the mountain ranges in the Mojave National Preserve.

NickKyle030913This year we arrived a bit earlier than usual, so we got a chance to explore the neighborhood around the DSC. Here you can see Nick Wiesenberg and Kyle Burden checking out some nearby outcrops of deformed carbonates (probably the upper part of the Bird Springs Formation, which is Permian in age). This was a chance to break in our boots and stretch our legs before settling into our quarters. The weather is overcast right now, but will dramatically improve tomorrow for the rest of the week.

The weather promises to be excellent for the week we are in the Mojave. All is well as the adventure begins!

 

Wooster’s Fossil of the Week: a cameloid footprint (Miocene of California)

August 19th, 2012

This fossil is from near my hometown of Barstow, California. It was collected many years ago loose in talus from the Barstow Formation (Barstovian, Miocene). I note this carefully because today collecting such specimens from the Fossil Beds of the Rainbow Basin Natural Area is illegal, as it should be. This is one of the most fossiliferous Miocene deposits in the world, and it has been heavily vandalized over the years.
The Barstow Formation (in a wonderful syncline) at Rainbow Basin, Mojave Desert, California.

This two-toed footprint is Lamaichnum alfi Sarjeant and Reynolds, 1999. It is preserved as a convex hyporelief, which is essentially a filling of the actual footprint. It was made by a camel-like animal (there are many choices) that walked through stiff volcanic mud along a stream during the Miocene. The impression of this foot was quickly filled with later sediment, probably from an overbank flood.

When I was a kid we found dozens of these footprints in long trackways throughout the Barstow Formation at the Fossil Beds. Those fossils are all gone now, most lost to collectors with rock saws and sledge hammers. Fortunately many have been lovingly preserved in the Raymond M. Alf Museum in Claremont, California. You will note that the ichnospecies of our fossil was named for the charismatic Raymond Alf, a legend in the study of vertebrate trace fossils and a spectacular teacher.

Reference:

Sarjeant, W.A.S. and Reynolds, R.E. 1999. Camelid and horse footprints
from the Miocene of California and Nevada. San Bernardino Museum
Association Quarterly 46: 3-20.

Wandering in the wilderness one last time

March 11th, 2010

ZZYZX, CALIFORNIA–This was our last full day in the Mojave Desert, at least for this trip. Technically it was our coldest start yet (40°F), but the bright sun and lack of wind made it seem like our warmest. The day was mostly unstructured because we were going to try to find a geological site none of us had seen here: the lava tubes in the cinder cones area of the Mojave National Preserve. It was a good thing we left our schedule open because we missed not one turn, not two turns, but three crucial turns before we finally entered the tubes. I’ll take full responsibility, although in my defense I must point out that the Preserve is very coy with their signage and directions!

While exploring the desert during our lost phase today, Rob McConnell found this excellent volcanic bomb on one of the cinder cones. Note the streamlines formed as the molten lava cooled as it was thrown into the air. We can even tell which end hit the ground as it landed (the left).

Rob Lydell at the entrance to the lava tube complex in the cinder cones region of the Mojave National Preserve.

Michael Snader, Andrew Retzler and Stephanie Jarvis (looking very straight up!) inside one of the lava tubes with light behind them shining through a hole in the roof.

This light shaft is outlined by eolian dust it is passing through.

After another delicious lunch packed for us by the Desert Studies Center staff (a shout-out to the world-class cook, our friend Eric), we drove north to Resting Springs Pass to study a famous exposure of a welded tuff.  Our last stop was a descent through the 500,000 year-old beds of ancient Lake Tecopa to China Date Ranch where we looked around the oasis and had the famous (and expensive .. and over-rated) “date shakes”. (Think flurry with little date bits thrown in.) The students and other faculty enjoyed them, though, and they were in their eccentric way a fitting end to our Mojave adventure.

Wooster geologists on the welded tuff at Resting Springs Pass.

Adam Samale, Megan Innis, and Rob McConnell sampling the hottest part of the welded tuff series at Resting Springs Pass. (Oh those youthful days of casually perching on cliffsides!)

Andrew Retzler is standing on the down-dropped block on the left side of a fault at Resting Springs Pass, and Stephanie Jarvis is on the upthrown side. What kind of fault is it?

Travis Brown at the front of the store at China Date Ranch near Tecopa, California.

Proof that the date shakes at China Date Ranch were popular. From the top left, clockwise: Andrew Retzler, Micah Risacher, Greg Wiles, Rob McConnell.

Unless my colleagues surprise me this evening, this will be our last post from the Mojave. We will have many more entries for this field trip, though, as we sort through student images and observations back on campus. We will also add more technical notes about the sites we saw, and maybe even throw in a video or two. It has been an extraordinary trip which will live in our departmental memory for a very long time.

Geological diversity: Tuffs, Sands, Limestones and Lava Flows

March 10th, 2010

ZZYZX, CALIFORNIA–One of the most attractive aspects of geology is how many materials and processes are included in the study of the Earth. Today’s field experiences show this diversity. One of the best reasons to teach in a liberal arts geology program is that we are continually in touch with topics outside of our original disciplinary training. This trip has been so much fun in part because all four of our faculty are involved at each of our stops, and we always learn from each other by having no fear about asking any questions. We seem to be successfully modeling this attitude with our students because they certainly have no hesitation in asking questions either.

Our teaching approach in the field has been to introduce students to the general framework of information about a particular site, and then let them explore the area, each bringing back questions, observations and specimens for a summary session with all the faculty. This has worked very well with this class because they are advanced and very enthusiastic students. Their curiosity has been an inspiration.

This morning was sunny, windy and cold (starting in the forties and not getting past 53°F). It hardly mattered though because we had so many interesting outcrops to study.  Our first stop was Hole-In-The-Wall in the southeastern quadrant of Mojave National Preserve. Here are magnificent tuffs from an explosive volcano eruption about 18.5 million years ago. Dr. Pollock will have more to say about the geological details.

An exposed tuff at Hole-In-The-Wall showing "tafoni", which are small cave-like erosion features.

The loop trail around the major tuff exposure involved a steep climb through a slot canyon with the help of embedded rings. It was indeed physically challenging. Dr. Shelley Judge is shown climbing out with skill; Megan Innis points out the warning.

Our second stop was to climb the Kelso Dunes in the southwestern portion of the Preserve. The pile of sand here reaches 160 meters. It is trapped against the Granite Mountains in an endless swirl of winds. The students climbed the highest and most popular dune in the complex while the faculty chose to ascend a slightly lower but untrampled dune. Oddly enough, when we stood on these dunes in the middle afternoon, for the first time the wind stopped!

The graceful top of one dune at Kelso showing the shallower stoss side, steep lee side, and a small sand avalanche.

Dr. Greg Wiles made a trace fossil in the Kelso Dunes to confound future paleontologists.

Our last two stops were relatively brief.  One was at an outcrop of the Chambless Limestone, a Cambrian unit showing oncolites and dolomite-filled burrow systems.  The other was at the tip of a lava flow from the cinder cones near the center of the Preserve.  We returned to the station in the early evening with sand-filled shoes and sun-reddened faces. Another wonderful day in the Mojave.

Micah Risacher looming dramatically over our Cambrian limestone exposure.

Dr. Pollock wanted us to find her a lava tube. We did, albeit a small one, and she seemed happy enough with it.

A most impressive volcano

March 9th, 2010

ZZYZX, CALIFORNIA–Our second and last stop of the day was Amboy Crater, which is about halfway between Barstow and Needles, California, near Route 66. Meagen Pollock, our ace petrologist, prepared us well for this visit, so we’ll wait for her to post the geological details and her expert observations. I want to prepare the ground with some photos of our hike up this remarkably recent cinder cone.

Wooster geologists walking across the lava field to Amboy Crater.

A very happy Meagen Pollock with a volcanic bomb tossed from Amboy Crater.

Wooster geologists on the rim of Amboy Crater trying very hard not to be blown down either the steep slope into the crater or the steeper slope down the outside.

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