RESESS 2009

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The 2009 RESESS protégés celebrate another summer of hard work:
Kneeling (L to R):Stephen Hernandez, Fernando Martinez Torres, Katherine Fornash, John Braswell, Ezer Patlan

Four RESESS protégés applied themselves for ten weeks to a broad array of geoscience research topics in 2009. Read their abstracts below. Ezer Patlan also participated in the poster presentation at the end of the summer.

Download the 2009 publication of Earth, Wind, Sea, and Sky containing the full RESESS and SOARS protégé abracts.

RESESS operates in partnership with the well-established SOARS (Significant Opportunities in Atmospheric Research and Science) internship program at UCAR (University Corporation for Atmospheric Research). In 2008, protégés participated in a SOARS-sponsored leadership orientation, team-building exercises, seminars, and writing workshops. These students form a core learning community from which they draw upon for peer support and shared experiences. RESESS aims to strengthen the presence of underrepresented groups within the solid earth sciences and increase the completion of master's and PhD degrees by these groups in the field.

John J. Braswell

Understanding past conditions of early Earth using trace metals in sulfide minerals

It is widely believed that drastic changes in Earth’s biosphere led to the great oxidation event (GOE),a sudden increase in atmospheric oxygen approximately 2.5-2.4 Ga. Nickel is an essential nutrient for methanogens, and there was a decrease in nickel Production during this time due to Earth's cooling. The emergence of cyanobacteria and the declining population of methanogens resulted. Cyanobacteria are photosynthetic bacteria that supplied an appreciable amount of oxygen to the atmosphere by first oxygenating the ocean surface. This created an iron oxide which settled to the bottom of the ocean floor as sediments in layered deposits called banded-iron formations (BIF). Once iron was nearly depleted, the release of oxygen from the oceans filled the atmosphere. BIF store geochemistry signatures from early Earth that contain sulfide minerals with various amounts of trace metals in each sulfide mineral. By studying the abundance of trace metals (Ni, Zn, Cu, Co, Mo) before and after GOE, we can better understand the catalytic processes that were influential. Through use of an electron microprobe, new lines of evidence can be obtained to support the theory of the rise of atmospheric oxygen. Analysis of Ni/Fe ratio coincides with the nickel famine theory. During the GOE, there was a decrease in Co/Fe ratios. The other trace metals noted above are under further investigation.

Katherine Faye Fornash

Geochemical evidence for flat-slab subduction in Cenozoic western North America

Voluminous intermediate to silicic composition magmatism occurred in the Cenozoic throughout much of western North America and is generally attributed to melting in the upper mantle triggered by shallowing and resteepening of oceanic lithosphere subducting along the western continental margin during this time. If so, then not only should there be systematic variations in the position of the magmatic activity through time, but these magmas should also should carry geochemical signatures characteristic of arc magmatism, including enrichments in the abundances of large-ion lithophiles (LIL) relative to high-field-strength elements. With this issue in mind, a re-examination of space-time-composition patterns of Cenozoic magmatism in the western United States and northern Mexico is presented here, using igneous rock data compiled in the on-line western North American Volcanic and Intrusive Rock Database (NAVDAT).

An investigation of 5,625 volcanic rocks from the Rocky Mountain region in the western United States revealed latitudinal variations in the age of the mid-Tertiary magmatic pulse, and longitudinal variations in chemical composition, with alkalic character increasing to the east, and the highest Sr/Nb concentrations found in the central Rocky Mountain region. Isotopically, there was little to no variation in initial 87Sr/86Sr ratios, while there were marked differences in initial ENd values, with values increasing to both the east and west of the central Rockies. Space-time patterns from 6,788 volcanic and plutonic rock samples from northern Mexico indicate that while there is evidence for periods of magmatic migration from 120 Mya to the present, these migrations are confined to the northernmost latitudes (36° N–28° N).

Taken together, these observations suggest that (1) variations in the mantle source region and the intensity of metasomatism existed during the mid-Tertiary in the western United States, and (2) flat-slab subduction did not extend into the southernmost latitudes (28° N–16° N) of northern Mexico.

2009 RESESS protégé Stephen Hernandez

Stephen Hernandez

Shear Wave Splitting Analysis from Newly-Installed Seismic Stations in Antarctica

The tectonic fabric of the upper mantle is inferred using SKS and SKKS splitting analysis of data from 15 newly-installed broadband seismic stations in West and East Antarctica. Data collected between December 2007 and December 2008 from 5 stations from the Polar Earth Observing Network (POLENET experiment) and 10 stations from the Gamburtsev Antarctic Mountains Seismic Experiment (GAMSEIS experiment) are used to perform an SKS and SKKS anisotropy analysis of the regions. In West Antarctica, POLENET stations straddle the West Antarctic Rift System (WARS) while in East Antarctica GAMSEIS stations are centered on and around the Gamburtsev Subglacial Mountains (GSM). POLENET stations show splitting times ranging from .85s to 1.25s and fast axes in cursory agreement with the inferred direction of WARS extension. For the larger focus of our study, GAMSEIS stations show a wider range of delay times (.65s to 1.55s) and fast splitting directions that may indicate the existence of 2 distinct tectonic regimes.

Fernando A. Martinez Torres

A Study of Gully Erosion Dynamics and Processes at Bijou Creek, Colorado, using Laser Scanning and Aerial Photography

The process of gully erosion is not completely understood by geologists due to insufficient data. We use various techniques including 3-D laser scanning (terrestrial and airborne), real-time kinematic-GPS and aerial photography to acquire new data from a study site at Bijou Creek, Colorado, to help improve our understanding of this process. Analysis of the data shows that the average rate of erosion in the head cut of this specific gully is 0.5 meters per year with the rate of movement every year to be generally very constant. We also analyzed the rate of erosion of other gullies in Bijou Creek and found that their rates of erosion vary depending on the location of the landscape. The aerial photographs confirm the rate of erosion for the general head cut of the gully, but with TLS, we can analyze the locations of the gully being eroded the quickest and how much each area has been eroded. By comparing TLS scans from 2008 and 2009, we observed that the main erosion is in the head cut of the gully; everything else in the scan area was seen to move at a slower rate (or showed no movement over the this period).

Full color point cloud image printed in the 2009 Earth, Wind, Sea, and Sky. The colors show the difference in meters from 2008 to 2009.

Students interested in applying for the 2010 RESESS program should submit an application before February 1, 2010. The application form will be available soon.

Photo credits: Carlye Calvin of UCAR Communications.