Dr. Steve Dworkin

• Aqueous Geochemistry

• Isotopic Geochemsistry

• Sedimentary Petrology

Ph.D., University of Texas - Austin, 1991
M. S., Michigan State University, 1983
B. A., Albion College, 1981

I study the low temperature aqueous and isotope geochemistry of sedimentary rocks and waters. My main focus is on paleoclimate reconstructions of terrestrial environments using the chemistry of paleosol calcite and organic matter. Our research group is currently studying environmental conditions during the Triassic using paleosols preserved in the Chinle Formation at the Petrified Forest National Park, Arizona. We also are continuing our work on paleosols that span the K/T boundary from west Texas.

Considering a possible field vehicle (Model T) found at the Petrified Forest National Park (very close to old route 66).

By measuring the isotopic composition of dispersed organic matter in bulk paleosols, it is possible to reconstruct the carbon isotopic composition of the late Cretaceous and early Tertiary atmosphere. This is being carried out using paleosols from Big Bend National Park in west Texas (Dworkin, 2009).

Well developed paleosols formed on overbank muds that are interbedded with coarse grained channel deposits (Big Bend National Park, Texas). Organic carbon contents of the paleosols vary between 0.05 to 0.3 weight percent.

Reconstruction of the carbon istotopic composition of atmospheric CO2 through the K/T boundary based on the carbon isotopic composition of bulk soil organic matter.

Scott Douglas is a Masters student studying the sedimentology and depositional setting of the Jurassic Norphlet Sandstone in the offshore of the Gulf of Mexico. Scott is in the midst of collecting and synthesizing his data.

Jana Edwards recently graduated with a Masters degree. She studied the organic geochemistry of the Barnett Shale. Her project was funded by the EnCana Oil Company.

Jana is seen here crushing up her black shales in a mortar and pestle.

Stephen Clark recently graduated with a Masters degree. He studied the abundance and character of organic matter in Cretaceous rocks of central Texas.

Stephen Clark (third from left) poses with the rest of the Baylor Field camp just prior to hiking down into the Grand Canyon.

Jenny Seitz recently completed a senior thesis entitled "Temporal Trends in Mineral Assemblages and Abundances from Paleosols that Span the Cretaceous-Tertiary Boundary, Big Bend, Texas". Jenny became proficient at running the X-ray diffractometer and she quantified the abundance of minerals in paleosols.

Jenny Seitz loading a sample into the XRD.

Lisa Turpin recently completed a senior thesis entitled "Grain Size Distribution and Organic Matter Content of Triassic Paleosols in the Chinle Formation, Petrified Forest National Park, Arizona. Lisa is an avid hiker who really enjoyed the long hikes out to her field area.

Lisa preparing her paleosols for quantification of organic carbon.

Gabriela Keeton recently completed a senior thesis entitled "Grain Size Distribution and Organic Matter Content from Paleosols that Span the Cretaceous-Tertiary Boundary, Big Bend, Texas". Gabby spent long hours using the elemental analyzer and the laser diffraction grain size analyzer.

Gabby loading paleosols samples into the elemental analyzer.

Gabby using the laser diffraction grain size analyzer.

Amy Fitzpatrick recently completed a Senior Thesis entitled "Provenance and Diagenesis of Chinle Formation Sandstones, Petrified Forest National Park, Arizona".

Amy determined the framework composition of Chinle Sandstones by point counting thin sections.

Dworkin, S.I., Nordt, L., and Atchley, S., 2009, A 7 MA record of 13CO2 derived from organic matter in late Cretaceous and early Tertiary paleosols, GSA abstracts w/programs, v. 41

Seitz, J., Dworkin, S.I., Nordt, L., and Atchley, S., 2008, Temporal trends in mineral assemblages and abundance from paleosols that span the Cretaceous-Tertiary Boundary, Big Bend, Texas, GSA abstracts w/ programs, v. 38.

Keeton, G., Dworkin, S.I., Atchley, S., and Nordt, L., 2008, Grain size distribution and organic matter content from paleosols that span the Cretaceous-Tertiary boundary, Big Bend, Texas, GSA abstracts w/ programs, v. 38.

Cleveland, D.M., Nordt, L.C., Dworkin, S.I., and Atchley, S.C., 2008, Pedogenic carbonate isotopes as evidence for extreme climatic events preceding the Triassic-Jurassic boundary: Implications for the biotic crisis?: Geological Society of America Bulletin, v. 120, p. 1408-1415.

Feng Z. D., Wang L.X., Ji Y.H., Guo L.L., and Dworkin S.I., 2007, Climatic dependency of soil organic carbon isotopic composition along the S-N transect from 34N to 52N in central-east Asia, Paleogeography, Paleoclimatology, Paleoecology, v. 257, p. 335-343

Scott JT, Doyle RD, Back JA, Dworkin SI, 2007, The role of N2 fixation in alleviating N limitation in wetland metaphyton: Enzymatic, isotopic, and elemental evidence, Biogeochemistry, v. 84, p. 207-218