Archive for March, 2010

Dr. Whitey Hagadorn presents “The First Animals on Land” for the 29th Annual Osgood Memorial Lecture at Wooster

March 24th, 2010

WOOSTER, OHIO–This evening Dr. Whitey Hagadorn, an assistant professor of geology at Amherst College, gave the 29th Annual Richard G. Osgood Memorial Lecture to a large crowd of students, faculty and community members in Wishart Hall at The College of Wooster.  His topic was “The First Animals on Land”, which was an account of research he and his students did with remarkable Cambrian trace fossils (tracks, trails and burrows) in sandstones in Wisconsin.

Sedimentary structures In Upper Cambrian sandstones, Wisconsin, USA. On the left are ripples with raindrop imprints; on the right is an intertidal channel. Photographs courtesy of Whitey Hagadorn.

Dr. Hagadorn showed in his presentation how he and his team first recognized ancient shoreline deposits by tracing sedimentary structures such as ripples, channels and raindrop imprints on extensive sandstone bedding planes in quarries.  They could then follow trace fossils of mollusks, worms and arthropods out of the water onto what were sandy beaches in the Cambrian.  Some of those organisms seem to have been carrying shells with them as protection from desiccation in the dry air.  Dr. Hagadorn answered many questions after his lecture from the audience and from a good crowd at the following reception.  We were impressed not only with the beautiful trace fossils and what they tell us about early land life, but also how such significant work could be done with simple tools and clever analyses.

Trace fossils in Upper Cambrian sandstones, Wisconsin, USA. Photographs courtesy of Whitey Hagadorn. More details are available on his website linked in this post.

Dr. Hagadorn will be leaving Amherst College this summer to become the Curator of Earth Sciences at the Denver Museum of Nature and Science.  We wish him well.

The Richard G. Osgood, Jr., Memorial Lectureship in Geology was endowed in 1981 by his three sons in memory of their father, a paleontologist with an international reputation who taught at Wooster from 1967 until 1981. Funds from this endowment are used to bring a well-known scientist interested in paleontology and/or stratigraphy to the campus each year to lecture and meet with students.

The Mojave Desert Field Trip and Wikipedia

March 23rd, 2010

Tertiary debris flow at Resting Spring Pass near Shoshone, California. This is an image from the field trip now posted on Wikipedia.

WOOSTER, OHIO–One of the primary joys of being a geologist is the opportunity to see so many interesting sights in the field.  We can share a bit of the pleasure and advance public knowledge by posting some of our photographs on the free online encyclopedia Wikipedia.  Here are some linked Wikipedia articles which have been improved with public domain images from this month’s Mojave Desert field trip:

Amboy Crater
Aztec Sandstone
Barstow Formation (a new page)
Lake Manly
Calico Ghost Town
Conglomerate
Curtis Howe Springer
Debris Flow
Desert Pavement
Desert Studies Center
Dune
Kelso Dunes
Lake Manix
Lake Tuendae
Mojave River
Pluvial Lake
Red Rock Canyon National Conservation Area
Syncline
Tuff
Volcanic Bomb

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.

Calico rocks

March 9th, 2010

ZZYZX, CALIFORNIA–The day started very cold with a stiff, persistent wind and low dark clouds moving quickly across the mountain north of Soda Lake. We are comfortable in our rooms and the dining hall, but tend to notice the cold in the shower building which is, shall we say, a tad breezy. Fortunately our first stop would be mostly in buildings and underground mines.

Calico is a reconstructed mining town east of Barstow.  It was founded in March 1881 and was soon the richest silver mining district in California. It began to decline with silver prices in 1907 and dwindled to a few shacks until Walter Knott renovated the buildings in 1951 and turned the site into a tourist attraction. Now it is a county park with numerous private businesses operated inside. We visited it today to see the old silver mines and mining techniques and to look at the mineralized Pickhandle and Barstow Formations which host the ores.

Calico Ghost Town from the scenic viewpoint to the north.

Megan Innis showing us excellent desiccation cracks (from drying mud) preserved in the Barstow Formation (Middle to Late Miocene) at Calico.

Rob Lydell, Adam Samale, Rob McConnell and Andrew Retzler relaxing outside a Calico business. Andrew is drinking, of course, a sarsaparilla.

Sure it is a bit windy out here, but look at these folds!

March 9th, 2010

Syncline in the Barstow Formation at Calico Ghost Town. Note that the ductile deformation at the base of the fold becomes brittle toward the top as the fold tightened. Shelley Judge is the one with the explaining hand.

A Windy Desert Day for the Wooster Geologists

March 8th, 2010

ZZYZX, CALIFORNIA–The skies were brilliantly clear early this morning when we left the Desert Studies Center for points west. The price for the passage of the front was a stiff wind that kept up all day and even now is whistling in the darkness past our windows. I don’t mind at all.  It reminded me of delightful spring days in the desert when as kids we flew kites so high we could barely see them.

Our first stop was a visit to the extensive sedimentary layers laid down by the Pleistocene Lake Manix in what is now the lower Mojave River Valley.  We drove several miles on Harvard Road and walked across long stretches of desert pavement with ventifacts and occasional wind-polished agates.

Bottom sediments from the pluvial Lake Manix near Harvard Road. For scale, you may notice Megan Innis and Stephanie Jarvis in the central wash.

We then traveled farther west through Barstow to Owl Canyon and Rainbow Basin a few miles northwest of the city. There we met Buzz and Phyllis Sawyer, childhood friends of mine from Barstow and superb natural historians of the desert. We all enjoyed the diverse facies of the Barstow Formation (Middle to Upper Miocene) as well as the plants and animals in this protected area.

Professor Shelley Judge explains the complicated structure of Owl Canyon to her faculty colleagues using traditional geological hand language.

Wind-blown Wooster Geology field trip participants in Rainbow Basin with the famous Barstow Syncline in the background. This photograph was kindly taken by Buzz Sawyer.

Our last stop was Afton Canyon where we completed the Lake Manix story by looking at the outlet through which it catastrophically drained into Soda and Silver Lakes to the east. The sun had set by the time we gathered back at the vans, ending another productive and thought-provoking field day.

Wooster geologists crossing the mighty Mojave River in Afton Canyon. We don't think this is quite the same river Jedidiah Smith encountered.

Death Valley Day

March 7th, 2010

ZZYZX, CALIFORNIA–Today the Wooster Geology Mojave Desert field trip team visited the southern half of Death Valley National Park.  We left Zzyzx (love that name) early in the morning and drove straight north to the Furnace Creek Visitor Center.  After our orientation we headed south to the Natural Bridge trail.  There we hiked up a narrow canyon to look at the faulting associated with a metamorphic core complex.  As a bonus we studied a beautifully-dissected fanglomerate along the way.  We next spent quality time at Badwater, a fault-dissected cinder cone, and Shoreline Butte with its evidence of the receding levels of the ancient Lake Manly.  The weather could not have been better.  The little bit of rain as we drove back to Zzyzx produced one of the most brilliant rainbows I’ve ever seen.

Fanglomerate-walled canyon near Natural Bridge, Death Valley, with metamorphic highlands of the Black Mountains in the background.

The Natural Bridge made of fanglomerate.

Adam Samale, Jesse Wiles and Rob McConnell at Badwater on a recently-flooded portion of the salt flats.

A bright rainbow near Baker, California, at the end of our field day.

Scarlet and Gray in Southern Nevada

March 6th, 2010

LAS VEGAS, NEVADA–After our long flight we drove our three vans a few miles west of Las Vegas to visit the spectacular Red Rocks National Conservation Area.  Greg Wiles and I were astonished to see how much construction had taken place there since we last visited in 2005.  The visitor center is completely new, and the scenic roads have been redone. We also learned that on a warm Saturday afternoon in March, the place is filled to capacity with people.

The main attraction for geologists is the vivid red rock, which we know as the Aztec Sandstone (Jurassic).  It lies below a gray Paleozoic section which makes up the bulk of the Spring Mountains.  (I did my dissertation on some of those rocks back in the day.)  The Paleozoic dolomites and limestones have been thrust over the Jurassic sandstones.

The Aztec Sandstone with overthrust Paleozoic rocks as seen from the visitor center.

The sandstone itself has many geological mysteries embedded into it, not least is the pattern of reds, oranges and whites seen on the outcrop.

Wooster junior Megan Innis photographing the Aztec Sandstone.

Somewhere some geologist must have explained the following contorted beds in the Aztec!

Contorted bedding in the Aztec Sandstone. The units is thoroughly cross-bedded otherwise, revealing its origin as a set of ancient sand dunes.

At the end of this long day we arrived safely at the Desert Studies Center in Zzyzx, California.  More later!

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