Wooster Geologists

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Richard Torres was advised by Mark Wilson (me!). The following is his thesis abstract —

In this study, I investigated changes in diatom population composition in relation to water chemistry in North American Upper Midwest lakes over the past three decades. I collected diatom samples from several lakes (Ohio, Minnesota, Wisconsin, North and South Dakota) using sediment cores and sediment traps. I observed an increase in the average diversity of diatoms over the three decades, but no significant similarity between the diversities of the lakes. I calculated the dissimilarity of the populations through Bray-Curtis Dissimilarity, finding it to be moderate to high between the lakes through time, with an average dissimilarity of 70 percent, which indicates a high difference between the population makeups between the lakes, past and present.

To analyze how diatom assemblages shifted regarding changes in water chemistry and other environmental factors, I used both bivariate correlation on diversity and general linear models with repeated measures on diatom population composition. From this analysis, I found that pH has a stronger effect and specific conductivity has a weaker effect on diatom diversity when compared to three decades ago. On individual genera, pH and water clarity did not have a significant effect on diatom assemblages, while total dissolved solids did. Moreover, individual genera were less influenced by specific conductivity than they were three decades ago. When analyzing modern diatom assemblages in relation to water chemistry, I found that pH, oxidation-reduction potential, specific conductivity, salinity, total dissolved solids, and water density all had significant effects.

There were potential difficulties and sources of error in this study. For instance, I used a smaller number of diatoms than recommended in other studies, and there were difficulties in identifying certain genera. Survivor bias was also possible, where the diatoms studied might not be representative of the lakes’ populations as some might have been destroyed between life and being mounted on the slide, by predation, silica dissolution, and fragmentation during centrifuging, among other hazards. This study holds implications for lacustrine resource management and climate reconstruction, as there is little to no research regarding changes to diatom ecology in the American Midwest in the past 20 years, furthermore, no research has been done looking at the effects of water density on diatoms. Further research is needed to better understand diatom’s complex interactions with their environment.

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Lucie Fiala was advised by Mark Wilson (me!) and was on Team Utah 2022. The following is her thesis abstract —

This Independent Study investigates the paleoecology and stratigraphy of the lower Carmel Formation in southwestern Utah. The Co-op Creek Member and the here proposed Gunlock Member of the Carmel Formation are mostly limestone units formed during the Bajocian (Middle Jurassic). During the Middle Jurassic, much of western North America was covered by an epicontinental seaway called the Sundance Sea, which stretched from southern British Colombia to Utah. In this study there are four principle locations (Eagle Mountain Ranch, Manganese Wash, Dammeron Valley, and Jackson Peak) of study. The proposed Gunlock Member was formed in a low energy, intertidal environment. It is characterized by stromatolite and thrombolite layers, trace fossils, and bivalves. The overlying Co-op Creek Member was formed after a transgression in a high energy, subtidal environment and is characterized by its ooid-rich limestones, shales, and abundant fossils.

The boundary between the Co-op Creek and proposed Gunlock divides these members into the underlying stromatolitic member and the overlying ooid-rich member, and indicates a significant transgression. The Bajocian saw a few notable global transgressions that roughly coincide with that of the Sundance Sea; while there are several theories as to the cause of these rises in sea level, tectonic and glacial activity are the most likely.

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Addie Tagg was advised by Mark Wilson (me!). The following is her thesis abstract —

The nuclear densitometer, or nuclear gauge, is a tool that is used to take the most accurate measurements of density and moisture content in soils, aggregates, and other materials. These measurements are used for many aspects of construction. The gauge takes density measurements based on the radioactive source Cesium-137. Key concepts for understanding how the gauge operates include photoelectric absorption, Compton scattering, and pair production. It is impossible to measure the reaction of a beam through a material, but it is possible to calculate the percentage of a source that is absorbed. The source that is not absorbed is reflected. The denser that a soil is, fewer waves are detected. After the device is calibrated and the number of reflected particles is counted, this number can then be translated into wet density. Alternative methods of recording density include the dynamic cone penetrometer and sand replacement. Overall, the nuclear densitometer is the easiest and least destructive method of density testing. The gauge does not directly measure water content, but instead measures hydrogen. This fact led me to an experiment to inquire if a common household weed killer would affect the gauge’s ability to take accurate measurements. The experiment included three trials using two layers of crushed limestone, each with a different substance applied (dry stone, water, or weed killer), compacted with a hand tamper and measured for compaction with the nuclear gauge. Overall, the weed killer did not affect the gauge’s ability to take an accurate measurement.

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Ryan Sullivan was advised by Mark Wilson (me!). The following is his thesis abstract —

In this study I created a hydrological and geological profile across a series of private groundwater wells in Shreve, Ohio. I started by making a cross section of this area through well log data. I discovered that this consists of alternating layers of shale and sandstone, as well as varying depths of glacial deposits. These changes in sediment and bedrock allow for a distinct groundwater flow, as well as different extraction rates. By analyzing the topography of the greater Shreve area, I also identified the drainage basin for this aquifer and potential sources of surface water and groundwater interactions. To assess water quality, I sampled two private wells located above this aquifer, testing for major trace elements. I found that the water utilized by these residents of Shreve is mostly free of contamination; however, there is eight to nine times the accepted maximum concentration limit of thallium. Long-term exposure to excess thallium can result in adverse health effects, so I present possible mitigation strategies, as well as a new potential well site that could be utilized to maximize groundwater extraction while minimizing contamination levels.

Editor’s Note: Independent Study (IS) at The College of Wooster is a three-course series required of every student before graduation. Earth Sciences students typically begin in the second semester of their junior years with project identification, literature review, and a thesis essentially setting out the hypotheses and parameters of the work. Most students do fieldwork or lab work to collect data, and then spend their senior years finishing extensive Senior I.S. theses. Shipei (Vicky) Wang was advised by Mark Wilson (me!) and was on Team Utah 2022. The following is her thesis abstract —

My research is about the invertebrate trace fossils in the Middle Jurassic (Bajocian) Carmel Formation of southwestern Utah. In this study, I focus on three types of trace fossils, Gyrochorte Heer, Lockeia James, and Lingulichnus Hakes, 1976. In De Gibert and Ekdale’s (1999) research, the trace fossils they found in the Carmel of central Utah represent an environmentally-stressed benthic community in a marginal marine, restricted setting, with salinities above normal marine and with depletion of oxygen in pore waters. Our study site is in southwest Utah, which was more marginalized and restricted than that of De Gibert and Ekdale (1999) in the Bajocian. My hypothesis is that our trace fossils will have a similar restricted trend with what De Gibert and Ekdale (1999) found in central Utah but show more characteristics related to marginalized and restricted marine settings (such as lower diversity and smaller sizes). In my study, the width of Gyrochorte fossils do not have a significant difference from what De Gibert and Ekdale (1999) found in central Utah. Besides that, the trace fossils we found in the Bajocian of southwest Utah have less diversity. My results did not show characteristics related to more marginalized and restricted marine settings.

Lingulichnus in bedding plane view. (See this blog post for details.)