Paleosols
(photo credit: Sherry Stafford, Ph.D., 2006, University of Pittsburgh)
Palesols are a selective record of soil
atmosphere in the past. The
photomicrograph above is of a Precambrian paleosol from the Steep Rock Lake
Quarry (Canada; photo credit Sherry Stafford), formed during time when the
EarthÕs atmosphere may or may not have contained significant oxygen. The mineralogy (mostly quartz and
biotite in a matrix of white mica, chlorite, sericite, kaolinite and carbonate;
with opaques of iron oxides and pyrite, and trace amounts of minerals like
sphene/titanite) records geochemical alteration during pedogenesis. Redox-sensitive element suites in part
constrain the redox state of the soil during its formation.
Prior work includes dating with radiogenic isotopes,
determination of the chemical alteration index, and determination of trace
elements such as REE and redox-sensitive elements. Future work includes further investigation into the redox
element suite, determination of soil pH using pH sensitive element
distribution, and geochemical modeling of the Precambrian atmosphere as a means
of investigating constraints on pedogenesis. Other
parallel projects include investigation of similar element suites in Permian
and Pennsylvanian paleosols in Kansas and Pennsylvania.
Abstracts
Stafford, Sherry L., Rosemary C. Capo, Brian W.
Stewart, and G. L. Macpherson,
2005, Geochemical and Textural Investigation of an Archean Paleosol, South
Roberts Pit, Steep Rock Area, Ontario, Canada: AGU Fall Meeting, San Francisco, EOS.
Stafford, Sherry L.,
Brian W. Stewart, Rosemary C. Capo, and G. L. Macpherson, 2005, Geochemical and
textural investigation of an Archean Paleosol, South Roberts Pit, Steep Rock
Area, Ontario, Canada: GSA Abstracts with Programs Vol.
Stafford, Sherry
L., Rosemary C. Capo, Brian W. Stewart, G. L. Macpherson, and Hiroshi Ohmoto,
2005, Preservation of REE signatures in an Archean weathering profile, lessons
from Steep Rock, Ontario, Canada:
PSARC Annual Meeting, May , 2005.
Macpherson, G.
L., Sherry L. Stafford, Rosemary C. Capo, Brian W. Stewart, and Hiroshi Ohmoto, 2000, Geochemistry of an
Archean Paleosol, Steep Rock, Ontario, Canada: whole rock and LAM-ICPMS analysis: Geological Society of America, Abstracts with Programs,
32(7): pg. A-485
Stafford, Sherry
L., Rosemary C. Capo, Brian W. Stewart, G. L. Macpherson, and Hiroshi Ohmoto,
1999, Micromorphology and geochemistry of an apparent Archean weathering
profile, Ontario, Canada: American
Geophysical Union, Fall Meeting, EOS, Transactions of the Amer. Geophys. Union,
v. 80, p.
Link to Dr. Rosemary Capo, University of Pittsburgh, for more information.