Paper No. 6
Presentation Time: 8:00 AM-6:00 PM
EVIDENCE OF MICROBIAL WEATHERING OF PYRITE IN MISSISSIPPI SANDSTONE
AINA, Eyitayo
1,
DEGNY, Assonman1, KIRKLAND, Brenda L.
1, LYNCH, F. Leo
1, MCBRYDE, Will
2, MILLER, Tracy S.
3, SCHMITZ, Darrel W.
1, SHERMAN-MORRIS, Kathy
1, WEEKS, Brittany L.
1 and WRIGHT, Kendra
1, (1)Department of Geosciences, Mississippi State University, P.O. Box 5448, Mississippi State, MS 39762, (2)Department of Geosciences, Mississippi State University, Mississippi State, MS 39762, (3)Department of Physics and Astronomy, Mississippi State University, PO Box 5167, Mississippi State, MS 39762, add159@msstate.edu
Pyritic and hematitic burrows were collected from four sites along an outcrop of the Eutaw Formation on Highway 45 North, Columbus, Mississippi, in an effort to search for microbial origins of Fe-rich hardgrounds. X-ray diffraction (XRD), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) were used to search for organic textures within the samples and determine mineralogy. Grain sizes of the burrows and surrounding soils ranged from 3.5φ – 1.0φ; however, no direct relationship could be determined between the grain size, porosity, and preferential flow patterns.
SEM analysis of the pyritic samples revealed an abundance of bacterial forms, organic textures, and minimal evidence of dissolution. It also confirmed the sandstone consists of quartz grains and diagenetic Fe-rich cement. XRD analysis indicated the presence of quartz, pyrite, and muscovite. EDS analysis confirmed the XRD results; detecting Fe, S, Si, and Al.
Observation of hematite samples by confocal microscopy suggested associated organic matter and minerals; however, SEM observation revealed no distinct evidence of organic matter. SEM analysis also revealed extensive dissolution of the cement, prevalence of organic debris, and suggested dissolution of the quartz grains within the hematite sample. XRD analysis detected only quartz.
An abundance of cocci, bacilli, and other organic matter in the pyritic sample, and lack of organic evidence in the hematitic sample suggest sulfide-oxidizing bacteria may play a role in weathering of these burrows.
