Wooster Geologists

gwiles April 15th, 2011

The crew in their XtraTufs. From L-R: Stephanie, Deb, Dan, and Greg.

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Stephanie Jarvis, a senior geology and biology double major from Shelbyville, KY.  Here is a link to Stephanie’s final PowerPoint presentation on this project as a movie file (which can be paused at any point). You can see earlier blog posts from her field work by clicking the Alaska tag to the right.

For my IS field work I traveled to Glacier Bay National Park & Preserve, Alaska with my geology advisor, Greg Wiles.  Our field crew also consisted of Deb Prinkey (’01), Dan Lawson (CRREL), and Justin Smith, captain of the RV Capelin.  My focus was on sampling mountain hemlock (Tsuga mertensiana (Bong.) Carrière) at treeline sites to study climate response and forest health using tree ring analysis.  While in Glacier Bay, we also sampled interstadial wood (from forests run over from the glaciers that were now being exposed on the shore) and did some maintenance work on Dan’s climate stations throughout the park.  Back in the lab, Wooster junior Sarah Appleton kept me company and helped me out with some of the tree-ring processing, as did Nick Wiesenberg.

The view from treeline.

An interstadial wood stump, in place. The glacier ran over this tree and buried it in sediment, which is now being washed away.

Site map

I ended up processing cores from only one of the three sites I sampled this summer (the others can be fodder for future projects!).  In addition, I used data from several other sites sampled in previous years.  My data consisted of 3 mountain hemlock sites forming an elevational transect along Beartrack Mountain in Glacier Bay (one described by Alex Trutko ’08), 3 mountain hemlock sites at varying elevations from the mountains around Juneau, AK, and 2 Alaskan yellow-cedar sites (Chamaecyparis nootkatensis (D. Don) Spach) from Glacier Bay used by Colin Mennett (’10).   My purpose was to look into the assumption of stationarity in growth response to climate of trees over time and changing climatic conditions.  According to the Alaska Climate Research Center, this part of AK as warmed 1.8°C over the past 50 years.

Tree-ring base climate reconstructions are important in our understanding of climatic variations and are a main temperature proxy in IPCC’s 2007 report on climate change.  Climate reconstruction is based on the premise that trees at a site are responding to the same environmental variables today that they always have (thus, they are stationary in their response), allowing for the reconstruction of climatic variables using today’s relationship between annual growth and climate.

Greg coring a tree at treeline.

Crossdating using patterns of variations in ring width.

Temperature reconstructions using different proxies, including tree-rings, from the Intergovernmental Panel on Climate Change’s 2007 report.

Recent observations, such as divergence (the uncoupling of long-term trends in temperature and annual growth) and worldwide warming-induced tree mortality, suggest that this assumption of stationarity may not be valid in some cases.  Using mean monthly temperature and precipitation data from Sitka, AK that begin in the 1830s, I compared correlations of annual growth in mountain hemlock to climate at different elevations over time.  My results indicate that mountain hemlocks at low elevations are experiencing a negative change in response to warm temperatures with time, whereas those at high elevations are experiencing a release in growth with warming.  Low-elevation correlation patterns are similar to those of lower-elevation Alaskan yellow-cedar, which is currently in decline due to early loss of protective snowpack with warming.  An increasing positive trend in correlation to April precipitation and mountain hemlock growth indicates that spring snowpack may be playing an increased role in mountain hemlock growth as temperatures warm.  The high elevation mountain hemlock trends suggest the possibility of tree-line advance, though I was not able to determine if regeneration past the current treeline is occurring.  Tree at mid-elevation sites seem to be the least affected by non-stationarity, remaining relatively constant in their growth response throughout the studied time period.  This indicates that reconstructions using mid-elevation sites are likely to be more accurate, as the climatic variable they are sensitive to is not as likely to have changed over time.

Cedar chronologies (green lines) compared to temperature (brown line). Bar graph represents correlation coefficients between annual ring width and temperature, with colors corresponding to labels on the chronologies (orange is lowest elevation PI, blue is higher elevation ER). Asterisks represent significant correlations. Note that the relationship has changed from being positive at ER during the Little Ice Age to negative by the second half of the 20th century.

Mountain hemlock chronologies (green lines) compared to temperature (brown line). The top graph is of the Glacier Bay sites, the bottom is of the Juneau sites. Red represents the low elevation sites, green the mid-elevation, and purple the high elevation. Note that the low elevation sites are decreasing in correlation as the cedars have, while the high elevation sites have experienced a release in growth with warming.

 

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Mark Wilson April 11th, 2011

A typical Menuha Formation outcrop south of the Makhtesh Ramon structure.

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Andrew Retzler, a senior geology major from Wooster, Ohio.  Here is a link to Andrew’s final PowerPoint presentation on this project as a movie file (which can be paused at any point). You can see earlier blog posts from his field work by clicking the Israel tag to the right. Andrew also created a Wikipedia page on the Menuha Formation.

It all began with an 11-hour flight from NYC to Tel Aviv, Israel with Dr. Wilson and fellow geology senior Micah Risacher. The airport process required for international travel of this sort was an adventure in itself. Thorough baggage checks, stern looks from security personnel, and a bombardment of questions dealing with our reasons for travelling were all offset by a seemingly endless and free movie selection on the flight! Eventually, we reached our arid destination of Mitzpe Ramon, the city that would serve as our basecamp for the next two weeks.

One of the reasons behind our trip was to scour the Menuha Formation outcrops throughout the Makhtesh Ramon region (shown above). We were hoping to collect and analyze various fossils in order to reconstruct an environment that once flourished during the Cretaceous. This process also involved taking detailed measurements and notes on each outcrop to create stratigraphic columns of each locality. This would become the basis of my thesis. Of course, none of this could have been possible without the help of our all-knowing field guide, Yoav Avni, and our shark specialist, Stuart Chubb, from the Birkbeck College of London.

Although my thesis has a strong focus on the shark and other fish teeth collected from the Menuha Formation, it also incorporates oysters, trace fossils, and several benthic/planktic foraminiferans. At least ten different species were represented in the isolated teeth: Cretalamna appendiculata, Cretoxyrhina mantelli, Squalicorax falcatus?, Squalicorax kaupi, Scapanorhynchus rapax, Scapanorhynchus raphiodon?, Carcharias samhammeri, Carcharias holmdelensis, and two other fish (Hadrodus priscus and Micropycnodon kansasensis?). Many of these fish were thought to occupy outer shallow marine realms, where the continental shelf begins transitioning into the slope. A few of the sharks are also known for being top Cretaceous predators, four or more meters in length, whose diets included plesiosaurs, mosasaurs, and ichthyodectids.

Cretalamna appendiculata tooth, a shark often considered to be an ecological generalist.

Scapanorhynchus rapax tooth. Related to the extant Goblin Shark, S. rapax had the ability to protrude its mouth in order to capture prey.

Cretoxyrhina mantelli tooth. Considered a superpredator of the Cretaceous seas, this shark could reach 5-6 meters in size.

Squalicorax kaupi tooth. The Squalicorax genus is the only group to exhibit serrated dentition, like so, in the Late Cretaceous.

Hadrodus priscus pharyngeal teeth. These teeth would have been found near the back of the throat arranged in a comb-like structure to help crush exoskeletons.

LEFT: The extended left valve of a Pycnodonte vesicularis. RIGHT: Planktic, biserial foraminiferan test (possibly Heterohelix sp.) that has been replaced by silica.

The Menuha Formation consists mainly of white and yellow/brown, glauconitic chalks that were often marly or conglomeratic. This chalk comprised a variety of phosphatic peloids, microteeth, irregular echinoid spines, and benthic/planktic foraminiferans that clearly represent a shallow marine environment.

Irregular echinoid spine recovered from the partially dissolved Menuha chalk.

Microtooth from the Menuha chalk.

Correlating the paleontology with their lithological context, a shallow marine outer continental shelf/middle continental slope environment is suggested as the paleoenvironment of the Menuha Formation. This environment would have also flourished with a variety of small to medium-sized fish, squid, and larger vertebrates (plesiosaurs and mosasaurs) in order to sustain such a shark population. Unlike the deep environment that has often been suggested, my thesis provides strong evidence towards a shallow marine environment during the early formation of the Makhtesh Ramon structure. My work also marks the first identification of the fish teeth within the Menuha Formation, beginning my contributions to the scientific world.

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Mark Wilson April 11th, 2011

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Micah Risacher, a senior geology major from Columbus, Ohio.  Here is a link to Micah’s final PowerPoint presentation on this project as a movie file (which can be paused at any point). You can see earlier blog posts from Micah’s field work by clicking the Israel tag to the right.

In the summer of 2011 Wooster geologists Mark Wilson, Andrew Retzler, and I went to the Negev Desert in southern Israel.  We were met by a colleague from England, Stewart Chubb as well as our guide and host Yoav Avni of the Geological Survey of Israel.  The small town of Mitzpe Ramon on the edge of the Makhtesh Ramon (Figure 1) would serve as our home for the next two weeks as we explored the Ramon structure.

Figure 1. A look into the Makhtesh Ramon structure.

My research includes the Zichor Formation which can be found throughout the Makhtesh Ramon structure.  However I focused on three separate locations known as the northern, southern, and western locations.  Each location had different features exposed, the southern location (Figure 2) exposed the Zichor very well, yet it was quite hard to get at it.

Figure 2. Southern section with the Zichor section labeled.

The purpose of my I.S. was to determine the paleoenvironment of this particular formation (Zichor) using the paleontology, sedimentology, and stratigraphy seen in the field/lab.  I found many well preserved echinoids (not destroyed by churning waters), Thalassinoides trace fossils, high mud content and shell fragments in the lithology, as well as several minor regression/transgression cycles.  All of these point to a primarily shallow marine environment that would slightly deepen once or twice before shallowing again.

The echinoids (Figure 3) found were so well preserved that they could be identified down to the species level and greatly helped to correlate this assemblage with others like it around the world during that time.  This process both helps to verify my results as well as put my sites in perspective with similar ones around the world.  Hopefully, this study will go a ways into settling the current dispute as to whether or not this region was a shallow or deep sea environment during the Late Cretaceous.

Figure 3. The most prevalent echinoids Hemiaster batnensis and Rachiosoma delamarri respectively; scale bars=1cm.

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Mark Wilson April 8th, 2011

This is my research team at a road-cut locality in Mississippi. (Photo courtesy of George Phillips.)

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Megan Innis, a senior geology major from Whitmore Lake, Michigan. Here is a link to Megan’s final PowerPoint presentation as a movie file (which can be paused at any point). You can see earlier blog posts from Megan’s field work by clicking the Alabama and Mississippi tags to the right.

During the summer of 2010, I traveled to Alabama and Mississippi with my research team including Dr. Mark Wilson, Dr. Paul Taylor, and Caroline Sogot.  Our trip was about ten days and included fieldwork and research. The purpose of our research was to collect fossils from below and above the Cretaceous-Paleogene (K/Pg) boundary to try and understand the Cretaceous mass extinction from a microfaunal level.

I chose to focus my thesis on oysters and the sclerobionts associated with these calcareous hard substrates.  Although my study was focused on oysters, I also collected a wide variety of other specimens including nautiloids, ammonites, belemnites, corals, sharks teeth, and bryozoans.

The oyster species present in each system.

When I got back to school in August, I identified all of my oyster species (three total) and began to identify and collect data for the sclerobionts. The oysters from the Cretaceous included Exogyra costata and Pycnodonte convexa and the oysters from the Paleogene included Exogyra costata, Pycnodonte convexa, and Pycnodonte pulaskiensis.

Sample specimens that I collected in Alabama and Mississippi. The oysters in yellow boxes and circles are the oyster species that were used in my study.

I identified nine sclerobionts including Entobia borings; Gastrochaenolites borings; Oichnus borings; Talpina borings; serpulids; encrusting oysters; encrusting foraminiferans; Stomatopora bryozoans; and “Berenicia” bryozoans.  My research showed:

1) Bioerosion of oyster hard substrates was common in the Late Cretaceous and Paleogene and sclerobionts were abundant before and after the extinction.

2) Entobia sponge borings appear to increase in abundance across the K/Pg boundary and become more common in the Paleogene.

3) Gastrochaenolites borings, made by bivalves, and serpulids were more prevalent in the Late Cretaceous, suggesting boring bivalves and serpulids were significantly reduced after the extinction.

4) Encrusting oysters and foraminiferans were more common in the Late Cretaceous, but also relatively abundant on Pycnodonte pulaskiensis in the Paleogene.

5) Encrusting bryozoans were more common in the Late Cretaceous and absent in the Paleogene, suggesting bryozoans were severely affected by the extinction.

6) Talpina borings were only found on Pycnodonte pulaskiensis in the Paleogene, but no significant data was collected elsewhere.

To my knowledge, this is the first study of bioerosion on oysters across the K/Pg boundary.

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Mark Wilson February 18th, 2010

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Rob McConnell, a senior geology major from Darby, Montana.  Here is a link to his final PowerPoint presentation on this project.

In the summer of 2009, Wooster paleontologists Dr. Mark Wilson, Palmer Shonk, and I traveled to Estonia with fellow Ohio State University paleontologist Dr. Bill Ausich. Olev Vinn of the University of Tartu greeted us at the Tallinn Airport. We then proceeded by car to the island of Saaremaa in western Estonia. The city of Kuressaare would serve as our home for the next week as we conducted our research on the island.

My research describes two members of the Jaani Formation (Silurian, Wenlock): the older Mustjala Member and the younger Ninase Member. Samples of these two members were collected from three sites along the northern Saaremaa coast:  Liiva Cliff, Suuriku Cliff, and Panga Cliff (Figure 1).

Figure 1. Jaani Formation at Panga Cliff, Saaremaa, Estonia.

The purpose of my research is to describe and recreate the paleoenvironment of the Jaani Formation. I am doing this by analyzing thin-section slides, stromatoporoid sponges (Figure 2), and various other fossils such as corals and brachiopods. It appears thus far that the lower Mustjala Member is far more fossiliferous and contains larger stromatoporoids, many of which are still in life position. This indicates a tranquil shallow marine environment. Smaller and flatter sponges are found in the upper Mustjala Member, close to the Mustjala/Ninase boundary. This is likely because of a shallowing of the water through time (a regression).

Figure 2. Stromatoporoids from the Mustjala Member, Jaani Formation (Silurian, Wenlock) on Saaremaa, Estonia.

The Ninase Member has different characteristics than the Mustjala. In general, it is better cemented and contains fewer fossils. It also contains more brachiopods and fewer sponges. It may have been deposited in a higher energy environment. Continued analysis of both members is required to gain a better understanding of this approximately 420 million year old environment.

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Mark Wilson February 15th, 2010

Editor’s note: Senior Independent Study (I.S.) is a year-long program at The College of Wooster in which each student completes a research project and thesis with a faculty mentor.  We particularly enjoy I.S. in the Geology Department because there are so many cool things to do for both the faculty advisor and the student.  We are now posting abstracts of each study as they become available.  The following was written by Palmer Shonk, a senior geology major from Dublin, New Hampshire.  Here is a link to his final PowerPoint presentation on this project.

I traveled to Estonia in July of 2009 with my advisor, Dr. Mark Wilson, Dr. Bill Ausich of The Ohio State University, and fellow Wooster geology major Robert McConnell. Upon arrival, we were greeted by Dr. Olev Vinn, his wife Ingrid, and their baby daughter. Olev is a geology professor at Tartu University in Estonia. The seven of us then headed for the island of Saaremaa, where I carried out my research. We stayed in the town of Kuressaare, on the southern shore of the island. My field site, the Äigu Beds, is about a 20 minute drive southwest of Kuressaare, on the western shore of the Sõrve Peninsula.

The Äigu Beds (Figure 1) are part of the Kaugatuma formation, named after the nearby town of Kaugatuma. My goal is to use the fossils and lithology at the beds to reconstruct an environment 418 million years old. My group assisted me in collecting fossils from three distinct layers. The first layer, about 8 cm thick, is an argillaceous limestone and contains many fossils still in life position, particularly crinoid holdfasts (Figure 2). This layer represents a calm, shallow-marine environment with soft, submarine dunes. The second layer, about 17 cm thick, shows evidence of a high energy event such as a storm. Fossils in the second layer have been crushed and are cemented together. The third layer, about 30 cm thick, is comprised again of the argillaceous limestone of layer one, but also shows evidence of a small scale high-energy event due to its “mashed” fossil specimens.

Figure 1. Part of the Äigu Beds on Saaremaa Island, Estonia; Late Silurian in age; note green pen for scale.

Figure 2. Crinoid holdfast from the first layer at the Äigu Beds; note tip of pen for scale.

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