Highlighted Research & Publications

We have acquired a 5-spectrometer Cameca SX-100 electron microprobe from Sandia
National laboratory through the laboratory equipment donation program managed by the U.S. D.O.E. A recent NSF grant will provide for the most modern operating and automation
system, and a Si-drifted solid-state detector for rapid energy-dispersive x-ray analysis. The
SX-100 will replace our existing SX-50 instrument in October of 2014.

National Science Foundation, Earth Sciences Division, Instrumentation and Facilities Program,
Acquisition and Implementation of a Cameca SX-100 Electron Microprobe,
University of Oklahoma, EAR-1401940,
$143,244 (David London and George Morgan), 2014-2015.

U.S. Department of Energy, Office of Science and Technology, Laboratory
Equipment Donation Program,
Item 8975793213S7130, a Cameca SX-100 electron microprobe with five wavelength-dispersive x-ray spectrometers,
$600,001, 2013.

The laboratory and details of usage are provided on this site:
http://ors.ou.edu/Microprobe/OUEMPLhome.asp.

Bulk chemical analyses of dust and rocks on Mars, as well as minerals observed in SNC meteorites, and orbital spectra suggest that Mars hosts geographically widespread salt deposits. These salts likely formed through the evaporation and/or freezing of near-surface high salinity brines at various times in Mars history. Indeed, brines are frequently invoked as important geochemical and geomorphic agents on both ancient and modern Mars.  Yet, chemical weathering in high salinity fluids remains poorly understood since most mineral dissolution studies are conducted in dilute solutions analogous to modern terrestrial surface waters. While mineral dissolution rates in dilute waters commonly decrease with reaction time, our recent work investigating jarosite dissolution rates in NaCl and CaCl₂ brines suggests that jarosite dissolution accelerates with time due to Cl^- attack at the mineral surface coupled to precipitation of poorly soluble sulfate minerals.  This project aims to compare silicate, carbonate, phosphate and sulfate mineral dissolution rates and mechanisms in dilute solutions and eutectic NaCl, CaCl₂, NaClO₃, and NaClO₄, and NaSO₄ brines. This study will contribute significantly to our understanding of mineral alteration processes in high salinity brines which may have been active on the surface of Mars throughout its geologic history. In addition,  results  can  also  be applied to  Earth environments, to  better  understand  mineral  paragenesis  in evaporite systems,  as  well  as high salinity basins. 

Funded through NASA for $280,000; PI: M. Elwood Madden, Co-Is: A. S. Madden and B. N. Pritchett

Project duration: 2012-2015

For more information:
http://faculty-staff.ou.edu/E/Megan.E.Elwood.Madden-1/

The Permian Period (~300-250 million years ago) is a time of great change, including an end to the long-term mountain building that formed the supercontinent Pangaea, the end of a major continental glaciation, and the prelude to the largest mass extinction in Earth history.  Continental sedimentary rocks, including red-bed siliciclastics  and evaporites, were deposited during the Permian throughout the midcontinental United States and record major climate change. This research will integrate sedimentologic and geochemical data from outcrops and cores to interpret depositional environments and paleoclimate from these mid-upper Permian redbeds and evaporites.  The goal of this research is to determine whether: 1) the mid-continent was dominated by extensive lakes, including freshwater and saline perennial as well as saline and acid-saline ephemeral types; (2) regional climatic changes are faithfully recorded in these strata; and (3) “redbeds” record a causative link between iron-rich eolian dust and extremely acid saline lakes. Understanding these abrupt climatic and environmental changes in the past improves our ability to test and refine climate models.

Funded through NSF to PI: Michael J. Soreghan, co-PI Gerilyn S. Soreghan, collaborating with Dr. Kathy Benison (West Virginia University)

Project duration: 2011-2014

For more information:

http://www.ou.edu/content/mcee/geology/people/faculty/michael_j_soreghan.htm

http://www.ou.edu/content/mcee/geology/people/faculty/gerilyn_s_soreghan.html

Glacial systems contribute significantly to physical weathering fluxes, creating large volumes of unsorted sediment dominated by small grain sizes relative to other physical erosion mechanisms, potentially even in cold-based glaciers. In contrast, chemical weathering in glacial systems has long been presumed minimal owing to the requisite low-temperature conditions (and hence lower chemical reaction rates). However, recent studies show that glacial systems contribute significantly to global chemical weathering, largely by production of fresh mineral surfaces, and solute data confirm significant chemical weathering fluxes in glacial streams. In addition, observed differences in solute chemistry between glacial and nonglacial watersheds suggest that the mechanical comminution of glacial sediments produces a different chemical weathering signature in glacial streams relative to chemical weathering fluxes produced in nonglacial systems. In this project, we are  testing the hypothesis  that measures of chemical and physical weathering in proximal alluvial sediments will show systematic and measurable variations between glacial and nonglacial systems even among hot-arid and cold (humid and arid) conditions owing to differences in initial sediment surface area, temperature, and aqueous conditions. We are currently conducting field work followed  by sediment and  water analyses  to  compare proximal alluvial sediments of modern hot-humid and hot-arid nonglacial systems with cold-humid and cold-arid glacial systems. The ultimate goals are to better understand weathering as a function of climate, especially between glacial and nonglacial systems by constructing a matrix of chemical and textural attributes to differentiate sediments formed in contrasting climates. Ultimately, chemical and textural attributes will be used to help differentiate paleoclimatic conditions –especially glacial versus nonglacial-- where facies evidence alone may be ambiguous. These metrics will inform sedimentologically based studies of paleoclimate, and shed light on silicate weathering, and thus biogeochemical cycling, in end-member climates.

Sponsored by NSF; PIs: G. Soreghan and M. Elwood Madden

Project Duration: 2013-2016

For more information:

http://www.ou.edu/content/mcee/geology/people/faculty/gerilyn_s_soreghan.html

http://www.ou.edu/content/mcee/geology/people/faculty/megan_e_elwood_madden.html

Lake Tanganyika, Africa is the second largest lake on Earth, but is under threat from land-use and climate change. The goal of this project is to study one habitat of the lake—the shell beds—that comprise patchy but extensive regions of the shallow substrate of Tanganyika.  These shell beds consist of modern “coquinas” that persist for >1000 yrs, forming long-term habitats for a community of endemic species; the origin of these shell beds, however, are not well understood. Comparison of sedimentologic, taphonomic, geophysical and chronologic data collected along the Tanzanian shoreline across four field sites over the next couple summers will allow us to determine whether the accumulation of the shells record lake-wide or regional changes and whether the distribution of modern organisms using the shell beds as a habitat vary as a result of land-use or climatic changes.  These results will impact researchers interested in the biodiversity, conservation and evolutionary history of Lake Tanganyika and other modern and ancient tropical lakes. Our collaboration with several environmental non-governmental organizations will provide their scientists with data to inform their management of these critical ecosystems. The shell beds also may prove an important analog for ancient coquinas found within buried lacustrine rift basins.

Funded through NSF to Lead-PI: Dr. Michael Soreghan  co-PIs: Dr. Andrew Cohen (University of Arizona); Dr. Jon Todd (British Natural History Museum)

Project duration: 2014-2017

For more information:

http://faculty-staff.ou.edu/S/Michael.J.Soreghan-1/AfricanResearch.html