������̳

• Abby Letts
• Chloe Li
• Helen Whitty
• Matthew Willig
• Yezi Yang

Abby Letts
Dr. Don Barber
Geology Department

The effect of volcanic eruptions on carbon burial rates in salt marshes

Saltmarshes sequester large quantities of carbon due to the anaerobic conditions in coastal wetland soils. Deep saltmarsh peat layers can also provide proxy records of past environmental conditions at the coast. This summer research project investigates how and why carbon accumulation/burial rates have varied over the last two thousand years in the saltmarshes of eastern North America. I am analyzing the carbon concentration and stable carbon isotopic composition in salt marsh organic matter from cores in North Carolina, Delaware, and Massachusetts. Preliminary studies of cores from the study area suggest correspondence between volcanic eruptions and a subsequent drop in organic carbon content. My analyses target these intervals of known climate variations. The analyses will test hypotheses regarding the climate mechanisms by which large explosive volcanic eruptions induce the observed marsh responses; e.g., reduced organic matter preservation due to increased decomposition and/or reduced belowground plant growth.

Differential decomposition of belowground biomass fragments will be analyzed at sites with varying salinities, elevations and and plant communities (e.g., Juncus, Spartina alterniflora or S. patens). Marsh vegetation comprises multiple organic fractions with different carbon isotope ratios. Measurements of these ratios will help determine whether changes in organic material production or preservation are associated with the drop in organic carbon content. The organic carbon content and carbon isotopic composition of the marsh peat will be compared across different time intervals and also among different coastal regions. Along with the carbon analyses described above, the studied marsh cores will be analyses for C/N ratio, bulk density and loss-on-ignition. Lastly selected samples will be submitted for radiocarbon dating in order to strengthen the core chronology.  Overall, the project aims to elucidate how effective saltmarshes are carbon sinks, and why carbon burial rates vary in response to short-lived climate perturbations.

Chloe Li
Mentor: Selby Cull-Hearth
Department: Geology

Research on Mapping on Mars and Iceland,  Total Synthesis of Ferrihydrite, and Database Construction

This summer, I am working with Professor Selby Cull-Hearth on four laboratory research project investigating mapping minerals on Mars, mapping alteration of Basalts on Iceland, total synthesizing Ferrihydrite, and creating a database of current minerals found.

The distribution in space and time of liquid water on Mars is relevant to astrobiology and astroclimatology. To date, most orbital observations that attest to past fluvial and lacustrine activity on Mars have been dedicated to surficial landforms. This summer we focus on the Valles Marineris. By using the CRISM database and analysis of optical spectrum, we will locate precise latitude and longitude of relevant papers, and then map the minerals and CRISM ID on google earth.

Ferrihydrite is a widespread hydrous ferric oxyhydroxide mineral at the Earth’s surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydrothermal hot springs and scales, soils, and areas affected by mining. This summer we aim to find a feasible method to synthesize Ferrihydrite in lab by chemical reactions of iron chloride and iron nitrate, and analyze its optical spectrum.

The alteration of basalts includes metamorphism and weathering of basalts. Basalts are important within metamorphic belts, as they can provide vital information on the conditions of metamorphism within the belt. Also compared to other rocks found on Earth’s surface, basalts weather relatively fast, so the calcium released by basalts will bind up carbon dioxide from the atmosphere. Basalts often are associated with the release of large quantities of carbon dioxide into the atmosphere from volcanic gasses. So in this summer, we will access the database of the alteration of basalts on Iceland and map them in system to provide information to analyze and predict the volcanism on Iceland.

The last work is to create a database of all the minerals collected both within the U.S. and outside the U.S. The database will include the type of minerals, place found, collecting method, and other relative data of the minerals.

Helen Whitty
Department: Geology
Advisor: Arlo Weil

Structural and Paleomagnetic Analyses of Structural Deformation in the South-Central Andean System

Along the western coast of South America, the Nazca Plate, composed of dense oceanic crust, is actively subducting beneath the South American Plate, which has caused the Andean orogeny. Deformation styles vary along the length of the orogen, which makes this region ideal for studying intraplate contractional deformation at a convergent ocean-continent boundary. Variations in crustal architecture may be influenced by a number of factors, including subduction geometry, shortening rates, stress/strain directions, and vertical axis rotation.

This research project seeks to better understand the factors that control variation in structural deformation along the Andean orogenic system, specifically in the south-central Andean system, which is made up of thick-skin, thin-skin, and hybrid components. Through structural and paleomagnetic studies of rocks from this region, we will test the relationships between subduction geometry, stress/strain directions, and vertical axis rotation.

Scientific knowledge gained through this research will contribute to a broader understanding of the previous and ongoing kinematic evolution of this particular orogenic system as well as that of convergent ocean-continent boundaries in general.

Matthew Willig
Advisor: Selby Cull-Hearth
Geology

This research aims to map morphologies and textures of hydrated deposits in the Valles Marineris, a Martian canyon system spanning roughly the length of the continental United States. We will be analyzing data from the High-Resolution Image Science Experiment (HiRISE) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). CRISM was launched in 2005, designed to search for minerals indicative of the presence of water. Several other remote sensing instruments similar to CRISM orbit Mars as well. Many other research groups have already analyzed spectral data from these instruments and tentatively determined the composition of surface features across the planet. This research will be using a type of remote sensing software called ENVI to synthesize these analyses such that stratigraphic columns of regions within the Valles Marineris canyon system can be generated, a large step forward in the efforts to establish a geologic history of the planet.

A major complication of research dealing with this imaging spectroscopy is presence of “masking minerals” such as ferrihydrite. These minerals, even in small abundances, effectively prevent CRISM from recording the spectral signatures of surrounding mineral deposits. As a result, inferring past environments from a deposit containing masking mineral becomes far more complicated. To address this problem, a second component of this mapping project is synthesizing minerals that are known to mask other spectral signatures and mixing them with other hydrated Martian minerals to determine how strongly these certain minerals mask others. This research hopes to establish definite masking relationships between minerals that can subsequently be used to correct interpretations from spectral data gathered. This process will occur in the geochemistry lab and is intended to facilitate more accurate predictions of relative amounts of minerals in Martian deposits, and subsequently be able to more accurately infer ancient and current presences of water on the planet.

Martian mineralogists largely seek to infer past climates and surface conditions of the planet and more specifically, where water was present and how much was there. Such insights enable predictions regarding whether life has ever and could ever exist on Mars. These questions are particularly important as interest in Mars’ ability to sustain human life grows. 

Yezi Yang
Advisor: Katherine Marenco
Geology Department

Ordovician Receptaculitids from Western Utah: Investigating the Morphology and Paleobiology of an Enigmatic Fossil Group

Receptaculitids are enigmatic organisms that lived from the Early Ordovician through Permian Periods (488-250 million years ago), and are considered important components of Early Paleozoic shallow-water reefs along with sponges and microbial communities. Their body shapes vary widely but in general they share a distinctive helicospiral skeletal structure. Researchers have recognized similarities between receptaculitids and both sponges and algae, but currently there is no consensus on how this fossil group should be classified.

The goal of my research is to investigate the morphology and paleobiology of receptaculitids collected from the Early Ordovician Fillmore Formation of western Utah. Most of the receptaculitid specimens that I will be working with are incomplete and conical or cylindrical in shape, but one fossil is complete and goblet-shaped. I will make thin sections both parallel and perpendicular to the body axis of several of the receptaculitid specimens and polish the surfaces of other specimens in order to reconstruct the three-dimensional skeletal morphology and microstructure of these organisms. Based on my data and the existing literature, I will interpret the physiology and phylogenetic placement of these Fillmore Formation receptaculitids and explore their role within Early Ordovician reef habitats.