David Decker ($3000)
Department of Earth and Planetary Sciences
University of New Mexico
Effects of Landscape Evolution on the Growth of Sub-aqueous Speleothems - Rise of the Guadalupe Mountains
Abstract - The timing of the rise of the Guadalupe Mountains is in dispute. One model suggests they didn't reach their present height until recently, during the Rio Grande rifting. A second model suggests that the Laramide orogeny was the culprit for the major uplift. I suspect there were three instances of mountain building, and a combination of the three led to the present 2 km+ height of the Guadalupe Mountains.
A new technique that will better constrain the orogenic episodes will be tested in the Guadalupe Mountains to evaluate its effectiveness in determining the timing and magnitude of the uplift events. By correlating the growth of speleothems (specifically scalenohedral dog tooth spar) both temporally and spatially with the injection of basalt dikes in the region, we can develop a proxy for the timing and uplift of the mountains. Using radiogenic isotopes (U, Th & Pb) to determine the age of the cave formations, and stable isotope analysis of fluid inclusions to gain information on temperature of formation and formation waters as well as chemical signatures of the intrusive igneous rocks in the region, we can develop a method for correlating the growth of the sub-aqueous speleothems with the igneous intrusions and from there determine the processes that may have been occurring at the surface during the growth of the spar as well as the timing of these processes.
This method may be expanded by use of vein filling and nail head spar, and will be a valuable process for determining landscape evolution in other areas of the country, specifically the Colorado Plateau, the Ozark Mountains and the Black Hills.
John DeDecker ($1500)
University of North Carolina, Chapel Hill
Correlating Lava Tube Morphology with the Petrologic Characteristics of the Host Rock
Abstract- There is an inverse relation between length and viscosity in the Hagen-Poiseuille equation used to model tube confined flow. Lava viscosity is related to the compositional and textural properties of the lava. Lava viscosities can be estimated from subsolidus basalts using the compositional and petrographic properties of the rock and methods developed by Marsh , McBirney and Murase , Ishibashi and Sato , Giordano et al. .
According to the Hagen-Poiseuille equation there should be a correlation between lava tube morphology (length in particular) and the petrographic and petrologic characteristics of the lava that solidified at the time of tube formation. This study seeks to determine whether such a correlation exists by estimating the viscosity of the lava using compositional and textural data acquired from samples collected from lava tubes, and by constructing 3D maps to constrain the length, radius, and slope of sampled lava tubes. It is expected that longer lava tubes will be correlated with rock compositions and petrographic textures indicative of lower viscosity lavas, and shorter lava tubes will be correlated with compositions and textures indicative of higher viscosity lavas.
Christopher Myers ($2800)
Department of Earth and Environmental Sciences
Paleoseismology of the Shillong Plateau, India: Constraints from U/Th dating of tectonically broken cave deposits
Abstract - Recent uplift of the Shillong Plateau in northeast India has produced numerous mega earthquakes such as the estimated 8.7 magnitude Great Assam Earthquake of 1897. Previous paleoseismic research of Shillong Plateau has relied upon radiocarbon techniques to date organic material found in liquefaction features created by large seismic events. A lack of observable surface ruptures on the plateau, 50,000yr-dating limit, and large age uncertainties (~150yrs) limits the accuracy as well as the temporal (~2,000 years) and spatial span of this paleoseismic approach. Broken cave deposits (speleothems) can experience various forms of breakdown during seismic events such as sub-horizontal fracturing and collapse of stalagmites as well as fracturing of thin soda straw stalactites. U-series dating of carbonates such as speleothems allows breakage events to be dated more accurately over longer time scales (500,000yrs) than previously possible with radiocarbon techniques. An initial U-series analysis has produced errors of +/- 65 years for a 15,000-year-old aragonite stalagmite from the plateau suggesting thatspeleothems from this region can be dated with high precision. Using broken speleothems aspaleoseismic archives allows for a more precise way to date paleoseismic events and estimate reoccurrence intervals more accurately. I propose to constrain speleothem breakage events caused by mega earthquakes on the Shillong plateau using U-series dating techniques. If successful my proposed research would greatly increase the current record of seismic events in northeast India, and provide invaluable risk assessment information for the people of northeast India and Bangladesh.
Daniel Nedvidek ($1500)
Department of Geography and Geology, Hoffman Environmental Research Institute
Western Kentucky University
Evaluating the Impact of Injection Wells and the Effectiveness of Regulatory Sampling Protocols for Stormwater on Groundwater Quality in Karst Regions
Abstract -The City of Bowling Green (CoBG) is situated on a karst landscape, typified by a lack of surface streams, numerous sinkholes and thin soils. The lack of surface streams in the Bowling Green area, combined with thin soils, makes the cave systems in the area natural candidates for stormwater runoff control through the use of injection wells, which direct water into underground streams and aquifer systems. Understanding the impacts of Class V injection wells on groundwater is necessary, as these unfiltered, uncased wells are allowable under EPA regulation as long as they do not impair underground sources of drinking water (USDW), including those sources currently under use and those that could be used in the future (US EPA 40CRF 144.3). Although the CoBG primarily obtains its drinking water from the Barren River, which has significant karst spring inputs, the entire watershed is impacted by urban and agricultural land use impacts both upstream and down. Under the Safe Drinking Water Act and the Federal Underground Injection Control Program, preventing the contamination of the CoBG's groundwater is important for regulatory compliance, and also for downstream users and the overall health of the ecosystem. While results from previous studies suggest that the harmful stormwater runoff and the use of injection wells to control that runoff are mitigated by dilution provided by the Lost River, we expect to show that expanding population and changing land use make stormwater runoff a much more credible threat to groundwater quality than it has been in the past.
Nicole Ridlen ($1000)
Department of Geosciences
Mississippi State University
Speleothem Strontium Concentrations as a Function of Aragonite/Calcite Inversion
Abstract -The presence of strontium (Sr) in carbonate rocks has documented and has been recognized as a contributor to the trace element content of speleothems used for paleoclimate reconstruction. The Sr in speleothems can originate from multiple sources although the majority of Sr analysis in speleothems has been assumed to be infiltrated from a surface. The aragonite crystal structure allows for a greater amount of Sr to exist in the bedrock. It is hypothesized that younger carbonates, such as those in the Caribbean, can contain more Sr than older carbonates that have already inverted to calcite prior to cave formation. Island carbonates, such as the carbonate units deposited as aragonite on Curacao, are terraced where the oldest unit is on top and inland, and the youngest on the bottom and seaward. Samples from Bahamian caves of similar age should provide a comparison with a climatic variant.
Three questions are to be asked during this research. One: Does the primary aragonite content of the young carbonate host rock register as the Sr content of Caribbean speleothems and have a direct relationship with the age of the host rock at the time of precipitation? Two: Do older speleothem layers contain less Sr than younger speleothem layers in the same climatic setting from young carbonate host rock with the same initial primary aragonite content? Finally, three: is there a variation in the primary aragonite content and hence Sr content, of speleothems in young carbonates of the same age but from different climates?