Wooster Geologists | A World to Explore

Plunging into Lake Manix

March 15, 2011 11:11 pm

ZZYZX, CALIFORNIA–East of Barstow and west of Afton Canyon was a very large pluvial lake during the Pleistocene. This Lake Manix was hundreds of feet deep, and its catastrophic drainage through Afton Canyon about 185,000 years ago must have been a great spectacle. This afternoon we explored one of the southern shores of this ancient lake, and then climbed down through its eroding bottom sediments.

Shoreline of Pleistocene Lake Manix. The dark rocks to the left apparently are remnants of an alluvial fan delta which extended into the lake shallows. The light-colored sediments below and to the right are from the lake itself. The white band in the foreground appears to be a type of coastal tufa formed by the agitated lake waters mixed with waters coming from the fan.

Lake Manix bottom sediments consisting mostly of fine silts and clays.

The plateau above the lake sediments includes windswept desert pavements and beautiful ventifacts (wind-carved stones) like this one.

Posted in Uncategorized | Tagged Mojave Desert, Pleistocene | Leave a comment

A morning with the Barstow Formation

Mark Wilson

March 15, 2011 10:48 pm

Greg Wiles explores the top of a wadi in Owl Canyon. The debris here consists of blocks of Barstow Formation eroded during recent floods.

ZZYZX, CALIFORNIA–It is hard to believe that the Mojave region once had vast lakes, erupting volcanoes and a diverse mammalian fauna including camels and horses. The most important record of this time is the Barstow Formation (Miocene — about 15 million years ago). This unit contains river and lake sediments along with volcanic ash, all of which produce a diversity of colors leading to the name “Rainbow Basin” for the best exposures outside Barstow, California.

The Wooster geologists spent the morning with the Barstow Formation in Owl Canyon and Rainbow Basin. The highlights included a group analysis of dozens of rock specimens, a desert tortoise crossing the road, and meeting old friends Buzz and Phyllis Sawyer from Barstow.

The Wooster geologists in Rainbow Basin with the Barstow Syncline in the background. Image by Buzz Sawyer.

Posted in Uncategorized | Tagged Miocene, Mojave Desert | 6 Comments

Death Valley Day

Mark Wilson

March 14, 2011 11:01 pm

ZZYZX, CALIFORNIA–Our Wooster geological crew awoke to a spectacular sunrise over the Soda Lake playa this morning. We drove north from Zzyzx through Baker and Shoshone into Death Valley by way of Jubilee Pass. The weather could not be better with daytime temperatures in the low 80s and brilliant blue skies. Shelley Judge gave us an overview of the tectonics that formed Death Valley, Meagen Pollock helped us sort out the poikilitic textures in basalts along Artists Drive, Greg Wiles discussed the declining levels of Lake Manly, and I helped out with interpretations of sedimentary structures in Miocene deposits exposed along Golden Canyon. Students kept their end of the bargain with challenging questions. A most excellent day.

Part of Death Valley's charm is in its extremes. This is Telescope Peak on the western side of the valley. It is 11,049 feet above sea level. Note the snow cover.

And here are salt deposits below Telescope Peak at 275 feet below sea level, baking in the relentless sunlight.

The Wooster students on the 2011 Mojave Desert field trip.

Posted in Uncategorized | Tagged Death Valley, Mojave Desert | 2 Comments

Wooster Geologists return to the Mojave Desert

Mark Wilson

March 13, 2011 10:59 pm

ZZYZX, CALIFORNIA–All four geology faculty members, our administrative coordinator Patrice Reeder, Jesse Wiles and eight students have safely arrived at the Desert Studies Center in the delightful Zzyzx. We spent a few hours exploring the Jurassic sandstones exposed in the Red Rocks Conservation Area outside Las Vegas (with marvelous dune cross-bedding) and then slogged through horrible Los Angeles-bound traffic from Las Vegas to Baker, California. (All too typical for a Sunday night here.)

Unfortunately bandwidth is highly restricted, so our posts will be infrequent until we return to Wooster.

Lichen and bits of desert varnish on the cross-bedded sandstone at the Red Rocks National Conservation Area.

Lindsey Bowman apparently saves Becky Alcorn with a dramatic backdrop of cross-bedding.

Posted in Uncategorized | Tagged deliberate practice, Jurassic, Mojave Desert, sandstone | 1 Comment

Wooster Geologist safe in Japan

Mark Wilson

March 13, 2011 3:20 am

Tsunami bearing down on a Japanese village (March 11, 2011). From the Associated Press.

HORONOBE-CHO, HOKKAIDO, JAPAN–I am relieved to report that my friend and fellow Wooster Geology classmate Kaz Aoki and his family survived last week’s devastating earthquake and tsunami. Kaz, his wife Sachiko, their four daughters and their new son-in-law all are unscathed, considering themselves “very lucky”. Their previous hometown, Kamaishi-shi was severely damaged. They say a tsunami warning 30 minutes before the event saved many lives.

Kaz is working in crisis mode right now. He is a Principal Senior Scientist in the Japan Atomic Energy Agency (JAEA) at the Geological Isolation Research and Development Directorate. We can only imagine the stress in the face of repeated failures in several nuclear power plants.

The Wooster Geology Department, all four faculty members, our Administrative Coordinator Patrice Reeder, and a group of students are leaving this morning for our field trip in the Mojave Desert. This blog will be filled with fun posts and colorful images, as it should be. We will not forget, though, the current travails of the Japanese people and our particular friends the Aoki family.

Posted in Uncategorized | Tagged earthquake, Japan, tsunami | Leave a comment

Wooster’s Fossil of the Week: A sweet local scallop (Lower Carboniferous of Wooster)

Mark Wilson

March 13, 2011 1:56 am

The delicious scallop has a long, long history. Wooster’s variety, known as Aviculopecten subcardiformis, is about 345 million years old. The beauty above was found in the Logan Formation, a conglomeratic sandstone that underlies much of the city, including the college. This particular fossil is preserved as an external mold, meaning the shell is dissolved away and only an impression remains in the surrounding sediment. Note that this preservation is still so good that we can count all the ribs and even growth lines.

Scallops are characterized by a nearly-symmetrical shell. They have extensions along the hingeline (at the top of the image) that are commonly called “ears” and technically termed auricles. They have one large muscle (adductor) used to close the shell. It is relatively large and the part of the clam we find so tasty.

Pecten jacobaeus from the Mediterranean Sea. (Photo courtesy of Andreas Tille of en.wikipedia.)

Many modern scallops use that large adductor muscle to clap the valves together when they are threatened, enabling them to swim short distances. As an early warning system to detect predators (including us, I suppose), they have rows of tiny eyes in the soft tissue around the edge of the shell (see below).

The eyes of this living scallop are the small bluish spheres along the edge of the mantle.

We can’t tell if our ancient scallop was able to see its enemies and swim away. It does, though, take us back to a time when a warm shallow sea covered our little patch of Ohio.

Posted in Uncategorized | Tagged Carboniferous, Fossil of the Week, fossils, Ohio | 1 Comment

Experiential Learning in the Desert

mpollock

March 11, 2011 12:00 am

As Dr. Wilson so gleefully pointed out today, the last several blog posts have been about fossils. I think it’s about time for a change of subject, don’t you?

Spring break officially begins tomorrow, and this is what Wooster looks like tonight:

A view of the snow covered street from my living room. I had to take the picture tonight because Dr. Wilson would have undoubtedly beat me to it in the morning.

The Wooster Geologists are ready to leave all of the snow behind! In a few short days, we’ll be headed to the warm and sunny Mojave Desert. The Desert Studies Center will serve as our base camp while we explore Death Valley, the Mojave National Preserve, and Barstow, CA (Dr. Wilson’s hometown). We invite you to follow us on our week-long adventure. Be on the lookout for posts that feature blue skies, stunning vistas, and geologists learning about the desert through direct experience. (It’s good to be a geologist.)

Posted in Uncategorized | Tagged deliberate practice, Mojave Desert | 1 Comment

Wooster’s Fossil of the Week: A tiny sclerobiont community (Middle Jurassic of Poland)

Mark Wilson

March 6, 2011 1:15 am

T=thecideide brachiopod; B=cyclostome bryozoans; S=sabellid worm tubes; g=gonozooids on one of the cyclostome bryozoans.

This delightful little community is the subject of a current research project that developed from Independent Study fieldwork in 2006. Elyse Zavar (’07) and I traveled to southern Poland to work on Jurassic fossils associated with a carbonate hardground at the Callovian-Oxfordian boundary near the village of Zalas (the link goes to Elyse’s photographs). With our Polish colleagues we found complex stratigraphy and an even more complex set of fossils. Now Elyse (a graduate student in the great state of Texas) and I have joined with Michał Zatoń of the University of Silesia in Sosnowiec, Poland, and submitted a manuscript describing and interpreting the sclerobionts (hard substrate dwellers) on the large limid bivalve Ctenostreon proboscideum. Michał is the lead author because of his long experience with these fossils and the complicated stratigraphy.

The hardground complex in the Zalas Quarry, southern Poland. It is Callovian below the blade of the well-traveled hammer and Oxfordian above (both stages of the Jurassic).

I have a soft spot for thecideide brachiopods, so they’re the stars of this show for me. I’ve come across them on Jurassic hard substrates many times, so they are old friends. They are filter-feeders like their larger brachiopod cousins, but they cemented one valve to a shell or rock for stability. The bryozoans in this community are also fun, especially when they have gonozooids as imaged above. A gonozooid is a specialized zooecium for brooding eggs and larvae. They are sometimes the only diagnostic features on sheet-like cyclostome bryozoans. There are plenty of serpulid and sabellid worm tubes as well, along with occasional oysters, calcareous sponges, and borings.

A sabellid worm tube and other encrusters.

We are comparing this Polish Jurassic community to others of the same time interval around the world. Curiously and probably not by chance, a similar sclerobiont assemblage is found in the Middle Jurassic of southern Israel — the subject of another Wooster study.

An encrusting oyster.

Posted in Uncategorized | Tagged Fossil of the Week, fossils, Jurassic, Poland | 2 Comments

Wooster’s Fossil of the Week: The ‘osses ‘ed clam (Upper Jurassic of southwestern England)

Mark Wilson

February 27, 2011 1:16 am

Katherine Nicholson Marenco (’03) and I did delightful fieldwork on the Isle of Portland in Dorset, England, during the summer of 2002. We collected fossils from the famous Portland Limestone (Upper Jurassic) in a series of working quarries. Katherine completed her Independent Study thesis on the topic (“Paleoecology of a cryptic shell-encrusting community: observations from ‘upside-down’ encrusters in internal molds (Upper Jurassic of southern England)”) and the next fall gave her first GSA talk about her findings. Now Katherine is a paleontologist at Bryn Mawr College.

One of the common fossils in the Portland Limestone is the trigonid bivalve Laevitrigonia gibbosa (J. Sowerby, 1819) pictured above. It is usually preserved as an internal mold, meaning that the aragonitic shell dissolved away, leaving the sediment fill. The Dorset quarrymen thought these fossils resembled horses’ heads (in their dialect this comes out as “‘osses ‘eds”) and the name stuck among collectors. If you hold the internal mold upside down, there is a vague resemblance.

Trigonid bivalve in an outcrop of the Portland Limestone. It is "butterflied" meaning that the valves were still attached to each other by the ligament.

Our scientific fascination with this fossil went beyond its preservation and paleobiology (it was a mobile infaunal suspension feeder). After the clam died and the soft parts rotted away, a variety of organisms settled on the inside of its shell. These sclerobionts are preserved upside-down on the internal mold.

Close-ups of the outside of the L. gibbosa internal mold showing "upside-down encrusters": an encrusting oyster Liostrea expansa (o), a colony of the cyclostome bryozoan Hyporosopora portlandica (b), and a serpulid worm (s).

Katherine was able to sort out the identity of these encrusters (not an easy task from the bottom!), their succession and their growth and development. Entire communities lived in these half-closed shells lying on a shallow seafloor 150 million years ago. An ordinary ‘osses ‘ed yields extraordinary paleontological detail.