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• Angie Bonanno
• Bethan Lodge
• Sandra Melgar
• Kirtee Ramo
• Zoe Shinefield
• Allison Velasquez
• Riley Zheng 

Angie Bonanno

Advisor: Arlo Weil

Using Structural and Paleomagnetic Data to Explore Hypotheses of Mechanisms for Laramide Deformation

The Laramide belt is located in the Cordilleras of western North America and is constrained geographically from central Montana to southern New Mexico. The Laramide belt is characterized by thick-skinned, contractional deformation that is dated to the Late Cretaceous to Paleogene. Compared to other mountain ranges, the Laramide has some unusual traits: a variety of orientations to the systems individual mountain ranges, localized and isolated basins, and a location far inboard from its associated active margin. Additionally, the tectonic evolution of Laramide deformation likely involved flat-slab subduction caused by the positive buoyancy of a hypothesized oceanic plateau. I will be working with Dr. Arlo Weil and fellow student Allison Velasquez in order to better understand the deformation history of the Laramide. Our exploration will involve fieldwork in southern Montana and the “four-corners” region, looking at patterns of deformation found in individual Laramide ranges to test existing hypotheses of the tectonic evolution of the belt. We will characterize the orientation and distribution of shortening directions and how these orientations relate to the geometry of the studied Laramide structures. To do this, we will measure mesoscopic structures in the field (such as minor faults, stylolites, fractures, etc.) to estimate paleo-stress directions, as well as collect core samples to measure their anisotropy of magnetic susceptibility (AMS) as a proxy for paleo-stress directions, and paleomagnetism to constrain any vertical axis rotation. Ultimately, we hope to use this data to test hypotheses regarding mechanisms of stress transmission during Laramide deformation.

Bethan Lodge

Advisor: Pedro Marenco

Geochemical investigation of the microbialite-bearing Notch Peak Formation at Lawson Cove, Utah

The Notch Peak Formation is located in west central Utah and consists of the Hellnmaria, Red Tops, and Lava Dam members.  The formation is Late Cambrian in age (~500 million years old).  The rocks in this formation are primarily marine dolomites with intervals of poorly-exposed siliciclastics.  The Notch Peak Formation is well-known for its abundance of microbialites—rock structures built by the activities of microbial mats.  Microbialites used to be much more common before the evolution of animals, but are rare today.  The Cambrian represents a transitional period during which animals were on the rise and microbialites were on the decline. Thus, these rocks represent a record of this important change in the history of Earth’s oceans. We set out to better understand this transition by studying the geochemistry of the microbialite-bearing intervals of the Notch Peak Formation in order to investigate the marine environmental conditions that allowed for the formation of microbialites.

We collected rock samples from the upper part of the Hellnmaria and the lower and middle parts of the Red Tops Member from the Notch Peak Formation at Lawson Cove, Utah. The samples were collected in approximately 1.5 meter intervals over a total range of 56.5 metres, which will allow for the production of a high resolution elemental and carbon isotopic dataset from these rocks.  From these samples we will create a chemostratigraphic column, analysing the inorganic and organic carbon isotopic content of the samples, alongside elemental data (in particular major elements Ca, Mg; minor elements Fe, Mn, Sr; and trace elements U, Th) to interpret changing environmental conditions during this interval.  Better understanding the diagenetic processes which these rocks have undergone and their chemical composition will allow for correlations to be identified between the results and will allow us to make inferences about the environment in which the rocks were deposited.

Sandra Melgar

Advisor: Katherine Marenco

Fossil Communities Associated with Microbialites in the late Cambrian Notch Peak Formation, Utah

My project will focus on microbialites that are preserved in rocks of the Notch Peak Formation, which formed in a shallow-water marine environment during the late Cambrian (~500 million years ago). During this time photosynthetic microbes lived on the seafloor forming sticky mats. As sediment accumulated on top of the mats it prevented sunlight from reaching them, and the mats grew over the sediment. This process of upward growth formed thin layers of sediment that became cemented together by crystals that precipitated under the conditions of the growing mats. Over time these layers accumulated into dome and branching structures, known as microbialites, that are preserved as rocks. Living nearby and in association with the microbial mats were multicellular organisms. When these organisms died their shells accumulated along with the sediment on and around the microbial mats. In my research I will test the hypothesis that some organisms interacted directly with the mats and others lived independently of the mats on the surrounding seafloor. In order to do this, I will compare the fossils that are preserved within the microbialites to those preserved in the surrounding sediment. I collected samples from four distinct microbialite units in the Notch Peak Formation in western Utah in June 2021. I will use a variety of lab techniques to compare the microbialite and non-microbialite portions of my samples. For example, I will prepare thin sections and acetate peels to look at microscopic fossils and sedimentary features. I will also use polished slabs and rock cores drilled vertically into the samples to look at larger scale features. Studying the characteristics of the fossils and sediment grains will allow me to interpret the relationship between environmental conditions and animal diversity/microbial mat growth among the four microbialite units. My data will help uncover small and large scale changes over time in both the community of multicellular organisms and the microbialites that developed during the deposition of the Notch Peak Formation.

Kirtee Ramo

Advisor: Selby Hearth

Addressing the discontinuities in the geologic time of the Jezero Crater

In February 2021, NASA landed the much-awaited Perseverance rover at Jezero Crater on Mars. It is thought that the crater was an ancient lake and, therefore, it has the potential to give information about possible life on the planet. In order to learn about the geologic history of the Jezero Crater, I’ll be working with Dr. Selby Hearth this summer to go through the available literature about the crater and find discontinuities in the geologic timeline.  Then, we will design and execute a research project to address this gap. To analyze the surface of the crater, we are planning to use publicly released data from the Mars Reconnaissance Orbiter and the Perseverance Mars Rover. Additionally, I am planning for this project to lead into my senior capstone for my major in geology.

Zoe Shinefield

Advisor: Don Barber

The Impact of Land-Use Patterns on Carbon Sequestration in North Carolina Salt Marshes

          Salt marsh ecosystems help mitigate emission-driven climate change by absorbing large amounts of carbon dioxide from the atmosphere and sequestering it in coastal sediments. Rates of carbon uptake can be altered by land-use patterns in and around ecosystems. Carteret County, North Carolina contains a range of estuarine, intertidal and upland environments, including carbon-sequestering wetlands, active agricultural land, and agricultural land that has been recently restored to wetlands. This project uses sediment core analyses to examine how sedimentation rates and plant community compositions over the past 150 have been impacted by adjacent upland land-use patterns in coastal North Carolina. Sediment core analyses of carbon density and isotopic composition of sediments are indicators of carbon storage and plant community composition, respectively. When compared with recorded changes in land-use over time, sediment core analyses can be used to reconstruct a history of carbon sequestration. Preliminary studies suggest that less belowground carbon storage occurs in marshes that are exposed to agricultural runoff than in undisturbed marshes. I hypothesize that there is a significant difference in carbon storage between marshes that are adjacent to upland agricultural areas and those that are not.

          Understanding the past and present conditions of these wetland sites has important implications for both coastal management and the broader field of climate change research. The data compiled in this research will contribute to broader efforts within the scientific community to compile and share coastal wetland data. Human land-use patterns combined with altered precipitation and accelerated sea-level rise due to climate change are likely to alter carbon sequestration rates in coastal wetlands. Understanding these relationships will inform adaptation and management efforts to maximize carbon sequestration while maintaining these important ecosystems.

Allison Velasquez

Advisor: Arlo Weil

Exploring Laramide Deformation in the Four Corners Region

          The Rocky Mountains of western North America is a large-scale tectonic system that has been deformed into various ranges that extend from arctic Canada to Mexico. In the western region of this system is the Laramide belt, which is restricted to the area from central Montana to New Mexico. The Laramide belt is unusual compared to other known mountain systems in that its main ranges have odd orientations and its location is far inland relative to the ancient plate boundary. These atypical characteristics have inspired many questions regarding how and why these mountains formed. There have been several hypotheses over the past century that have been proposed to explain the phenomenon of the Laramide Orogeny. Presently, the most accepted model is that the main tectonic driver for the Laramide was flat-slab subduction. However, identifying a mechanism of the Laramide does not provide an answers as to why individual Laramide mountain ranges have the orientation they do, and why the Laramide does not appear similar to other known and studied mountain ranges.

          In an effort to answer these questions, I will be working along side Dr. Weil to gather and collect field data from the four corners region and parts of southern Montana. The goal is to search and identify patterns of deformation, specifically the orientations of shortening directions, found in Laramide ranges to test hypotheses of the region’s tectonic evolution. We will collect core samples to measure the anisotropy of magnetic susceptibility and measure mesoscopic-scale structures like minor faults, stylolites, fractures etc., in order to estimate paleo-shortening directions. Ultimately, these data will allow us to further study Laramide deformation as well as help us to better understand the mechanisms behind their present structures.

Riley Zheng

Advisor: Pedro Marenco

Microbialites are rocks produced through the activities of ancient microbial communities, whose buildups are sometimes large enough to be classified as reefs. They are distinguished by their round shapes and the specific lamination patterns. Microbialites are rare today, but were much more common in the oceans for the ~3 billion years before the advent of abundant animal life. It is possible that some combination of animal grazing activity and changing environmental conditions led to the pronounced decrease in microbialite abundance through time. Studying the geochemistry of microbialites can help us understand the environmental conditions that favor their formation.

My project is mainly based on two sets of microbialite samples found from different formations separated by about 250 million years. One set of samples is from the Lower Triassic Virgin Limestone Formation of Nevada (~250 Ma). These rock samples have clear laminations alternating between dark grey and light brown. My previous stable isotopic results show a relatively large difference in the carbon isotopic composition of dark versus light laminations in which the brown layer is about 1.6 ‰ lighter than the grey layer on average. X-Ray Diffractometer and petrographic analyses reveals that the light brown laminations contain more quartz and exhibit increased porosity than the darker laminations.  These mineralogical and geochemical differences likely represent fluctuating environmental conditions that affected microbial mat growth.

The other set of samples was collected this summer from the Notch Peak Formation in Utah. They are Late Cambrian (~500 Ma) microbialite samples which likely represent different environmental conditions than those of the Early Triassic Period. The Notch Peak microbialites exhibit similar laminated cross sections of the microbial mats with alternating colors. We have collected both float and in-situ microbialite samples from different stratigraphic horizons across the formation for detailed geochemical analysis. For my summer science research project, I will measure carbon isotopic and elemental data from these Late Cambrian microbialites to compare with those from the Lower Triassic. Comparison of the data collected from both sets of microbialites will help reveal commonalities in the environmental conditions required for the formation of microbialites.