Danny Bowman

Advisor: Karl Wirth
Senior Honors Thesis: 2008

Seismicity and Evidence for Undersea Hydrothermal Activity on Deception Island, South Shetland Islands, Antarctica

Danny Bowman This thesis presents results from 43 days of continuous seismic data recorded at Deception Island, an active shield volcano in the South Shetland Islands, Antarctica. A total of seven volcano-tectonic and three hybrid events were detected, and comparisons with seismicity recorded by previous studies indicate that this result represents unusually low seismic activity. The depth of a well-constrained volcano-tectonic hypocenter located within the Deception Island caldera is consistent with tomographic evidence of a magma chamber lying less that two kilometers beneath the volcano. This survey also found over four thousand small events occurring exclusively within the flooded caldera. They last less than four seconds, have particle motions consistent with S wave energy, and generally occur less than three kilometers away from the recording station. These events are not described by previous literature on volcanic seismology and may be unique to this environment. They are most likely caused by hydrothermal activity.

Robin Canavan

Advisor: Ray Rogers
Senior Honors Thesis: 2008

Authigenic Cements and Rare Earth Elements Signatures in Microfossil Bonebeds from the Upper Cretaceous Judith River Formation, Northcentral Montana

Robin CanavanThe Upper Cretaceous Judith River Formation of northcentral Montana preserves numerous microfossil bonebeds. Bone is resilient and captures geochemical indicators of its depositional environment in the form of authigenic mineral void fills and rare earth elements (REEs) taken into the bone matrix during fossilization. Authigenic minerals and REEs reflect specific pH and redox conditions. The goal of this endeavor was to understand the result of chemical reactions controlled by the interplay between bone substrate, pore-fluid and enclosing sediment, in order to make a well substantiated interpretation of the diagenetic history of fossil material. I analyzed bones from high-energy channel-hosted bonebeds and low energy floodplain-hosted bonebeds in the tidally influenced fluvial facies of the Judith River Formation. An understanding of the sedimentology and stratigraphy of the deposits was combined with information gained about authigenic minerals and REE enrichment. Authigenic cements were analyzed using a petrographic microscope and a scanning electron microscope. REE concentrations were obtained using laser ablation-inductively coupled plasma-mass spectrometry.

Authegenic minerals were not abundant in the fossil material. The most common minerals were hematite, barite, and pyrite. These minerals were not unique to different sites but present to some extent in all bonebed samples. In addition, variability within a single bone made authigenic cements poor indicators of specific depositional environments. REEs were determined more reliable indicators of specific paleoenvironments. Both channel-hosted bonebeds exhibited HREE enrichment, which is consistent with the expected chemistry of their depositional environment. The floodplain-hosted bonebed also retained a HREE signature, which is not the predicted signature for floodplain-hosted bone. This HREE enrichment is possible due to the tidal conditions that impacted the Judith River coastal plain. Variability in REE enrichment patterns within a channel-hosted bonebed is interpreted to signify more temporal and spatial averaging. Due to their ability to track paleoenvironment, REE enrichment signatures supported physical evidence that fossil material within the channels was reworked from bone that originally accumulated in the floodplain. This study utilized multiple datasets to better understand the dynamic history of fossilization and deposition of microfossil bonebed.

Sophia Kast

Advisor: Ray Rogers
Senior Honors Thesis: 2008

Reconstructing Late Cretaceous Climate in the Mahajanga Basin of Northwestern Madagascar

Sophia Kast The Upper Cretaceous Maevarano Formation, situated in the central part of the Mahajanga Basin in the northwestern Madagascar, has yielded some of the most well-preserved vertebrate fossils known from Gondwana. These fossils provide important insights into Late Cretaceous faunas in general, and they also yield information that pertains to the timing and sequence of the breakup of Gondwana. In this thesis, I invesitage the sedimentology of the unit in an effort to provide a more exacting paleoenvironmental framework for the ancient Malagasy fauna. I focus in particular on the Masorobe Member, which comprises the lower 80 meters of the Maevarno Formation. The Masorobe Member consists of fluvial and floodplain deposits that are heavily modified from a pedogenic perspective. I examined the clay and framework mineralogies, geochemical climofunctions, and particle-size distributions of sample collected from the Masorobe Member to elucidate aspects of paleoclimate. Precipitation levels affect the clay assemblages that form in paleosols. I used x-ray diffraction to identify the clays and found the dominant clay species to be saponite, montmorillonite, and sepiolite. These clays are most commonly developed in the sub-humid to semiarid climates. Sepiolite in particular is an arid indicator. The composition of framework grains in sandstones is also affected by climate because labile minerals (such as feldspars) weather more quickly than more resistant minerals (such as quartz). My analyses of framework mineralogy are also consistent with the premise that the Late Cretaceous Mahajanga Basin was semiarid. The geochemistry of selected soils in the study interval also supports this interpretation, with rainfall estimates ranging between 430 and 110 mm/year. Finally, my work has confirmed the presence of fine-grained debris flow deposits in the Masorobe Member of the Maeverano Formation, and their presence is suggestive of a highly seasonal environment prone to flooding

Alexandros Konstantinou

Advisor: Karl Wirth
Senior Honors Thesis: 2008

Origin of Lake Superior Region Super-Mature Quartz Arenites: Evidence from U-Pb Detrital Zircon Ages of Early Paleozoic Sandstones

Alexandros KonstantinouThe origin of Early Paleozoic super-mature quartz Arenites of the Lake Superior region has puzzled geologists for over a century. Results from previous studies gave evidence about the origin of the same formations using their mineralogy and sedimentology. U-Pb isotopic dating of detrital zircon Was used to provide evidence about the origin of the Lake Superior Super-Mature Quartz Arenites. The 207Pb/206Pb ages of detrital zircons from these arenites, determined by laser ablation inductively-coupled plasma mass spectrometry, range from 3200 to 950 Ma. Several zircon age populations are identified: Archean (3000-2600 Ma), Middle Proterozoic (1500-1350 Ma), and Middle Proterozoic (1300-900 Ma). Most of these age groups correlate well with the ages of near and distant provinces such as the Superior province and the Minnesota River Valley (3600-2600 Ma), the 1500-1350 MA Anorogenic granite suite, and the Greenville orogen suite (1300-900 Ma).

The presence of similar zircon age population in all the samples suggest recycling of the sediments in the Early Paleozoic. Variations in the proportion of the zircon age groups occur both temporally and spatially between the samples. Temporal variations in the zircon age groups are probably related to the time between major unconformities and sequence boundaries such as the Sauk – Tippecanoe sequence boundary (Oneta – St. Peter). Spatial variations in age groups may be attributed to differences in sediment transport from different local river inputs, or due to difference in sedimentation patterns between deeper currents and long-shore currents. Systematic sampling of a specific horizon of a formation from different geographic location and high – resolution sampling at one geographic locality, might offer greater resolution of zircon age population patterns and test the question raised in this study.

Scott Persons

Advisor: Ray Rogers
Senior Honors Thesis: 2008

A Field Laboratory Study of the Ediacaran Fossils of Hewitt’s Cove: Evidence of Tectonic Deformation and Consideration of Paleobiology

Scott PersonsEdiacaran fossils have baffled scientists since their original discovery in 1868. As the oldest unambiguously organisms with tissues, Ediacaran organisms (or simply Ediacarans) represent a key stage in the evolution of life, and understanding their fossil record is essential to understanding the status of life prior to the great radiation of forms seen in the Cambrian. However, the bizarre shapes and structures of many Ediacarans have made placing them in phylogenetic context with modern taxa and determining their ecological roles difficult. Although few remarkable sites – such as the famous Mistaken Point and the ediacaran Hills localities – have yielded an abundance of extremely well preserved specimens, the overall Ediacaran record is poor, and the vast majority of specimens give few clues to the nature of the whole organisms. This has made Ediacarans difficult to interpret and identify. Here, the Ediacaran fossils of a 575 Ma argillite bed of the Cambridge Formation, exposed at Hewitt’s Cove, Massachusetts, are described, and the fossils are considered in relation to current theories of Ediacaran paleobiology. All documented fossils belong to a single genus, Aspidella. The fossils were found to be elliptical in shape and to all have a similar orientation with respect to each other and to bedding. Their consistent shape and shared orientation are interpreted as likely results of tectonic stretching. This interpretation is consistent with all previously described Aspidella specimens. Size distribution among the Aspidella fossils gives no indication that more than one species is present. Examination of the size distribution also showed large members of the population to be up to 15 times the size of small members, casting doubt on the theory that Aspidella reproduced through equal (one-splits-into-two) divisions. The argillite rocks are composed of thinly laminated sediments, and thin section examination of the Aspidella fossils shows no evidence of disturbance around the fossils and, thus, no evidence that Aspidella moved through the sediment while alive (i.e. bioturbation).

Tom Tobin

Advisor: Kelly MacGregor
Senior Honors Thesis: 2008

Water Discharge and Glacier Hydrology at West Washmawapta Glacier in British Columbia, Canada

Tom TobinCirque glaciers are small bodies of ice that do significant geomorphic work at high elevations in alpine landscape. Unlike alpine or valley glaciers their fluid dynamics and hydrology are not well understood. As part of a larger project investigating West Washmawapta Glacier (WWG) in British Columbia, this study explores englacial, subglacial, and proglacial hydrology.

Several methods of measuring water discharge were tested for their usefulness in the alpine setting of the field area during summer 2007. Salt tracer dilution proved the safest as most reliable technique, and two variations on this method were examined. For the proglacial system around WWG, dry salt injection proved the most practical and precise. Measurements of water discharge were used to construct ratings curves for two locations in the proglacial system. Water discharge from WWG joins with meltwater runoff from Washmawapta Icefeild, and stream gauges were established upstream and downstream of water input from WWG to isolate the signal from WWG from the water from Washmawapta Icefeild.

Rating curves allowed for the calculation of discharge continuously throughout the field season at both stream gauges. From this data, the discharge from WWG could be determined. Analysis of this signal showed four distinct periods based on the diurnal cycle. Calculations of surface melt flux, stream flux, and examination of the relationship between discharge and temperature demonstrated that these period were a consequence of development of either englacial or suglacial water transport systems. Incorporation of this data with other field observations revealed that there were likely two independent glacial hydrologic systems, one of which showed increased ability to transport melt to the proglacial system over the field season.