Late Paleozoic studies
I have been studying lower Permian eolian and lacustrine deposits in Oklahoma and surrounding areas in order to interpret Late Paleozoic paleoclimate. The late Paleozoic was a time of global orogenesis and continental glaciers, which waxed and waned on timescales that were similar to those of the Quaternary, making this time slice a critical period to study in terms of understanding present climatic fluctuations.
One avenue of study is outcrop- and core-based studies of the Permian redbeds within the mid-continent region (Oklahoma, Texas, Kansas). These have been very understudied and our recent analysis suggests that the the depositional and paleogeographic interpretations of the redbeds requires a new vision of the Permian landscape. Along with my colleagues and students were are finding evidence of eolian silt (loessite) deposition as well as the presence of saline lakes. This changes not only the paleogeographic setting of the mid-continent, but also forces new interpretations of the transport and depositional processes active for such an enormous volume of sediment accumulating during this time period.
I am also studying the provenance of these redbeds, and particularly the loessites in order to infer paleowind directions. This seems like a rather odd pasttime, but understanding past atmospheric circulation patterns is critical to providing better constraints to global circulation models, which are used extensively to retrodict past climate and predict future climate. By determining individual U-Pb ages for a population of detrital zircons within a loessite sample, done first at the SHRIMP II facility in Ottawa, Canada, in collaboration with Dr. Michael Hamilton, and more recently at the Geochronology Lab at the University of Arizona with Dr. George Gehrels, we have been able to determine the source region for the majority of the zircon grains and thus the direction from which the sediment was transported–by wind, since loess is, by definition, an eolian deposit. We are also looking at changes in whole-rock and trace-element geochemistry of the loessites from different time slices and different locations to further investigate changes in provenance related to changes in wind direction and this chemical data is also helping address the origin of these low-latitude loessites. Finally, we are also looking at changes in detrital zircons and geochemistry to document changes in wind direction and intensity on glacial-interglaical timescales, which is very exciting.
In combining my interests in Late Paleozoic paleoclimate and my experience in lacustrine systems, I am working on a number of Permian redbed strata in both the U.S. midcontinent and in Africa. In the midcontinent of the U.S., these units had previously been interpreted as tidal or sabhka and we’ve reinterpreted them as lacustrine, altering both the paleogeographic picture of the mid-continent during the Permian as well as the historical record of the vertical facies changes. I am also laying groundwork for a new project to analyze lower Permian lacustrine strata in Tanzania and Malawi. These lacustrine strata record the deglaciation at high latitudes of the Late Paleozoic Ice House. Although these rocks have been studied previously, age control is poor. We are attempting to develop a detailed chronology for these strata in order to compare to the records we have obtained in the southwestern U.S. If we are able to make time correlations, we can begin to address questions about climate change in polar vs equatorial belts.
Selected References
Kushner, B., Soreghan, G. S., Soreghan, M. J., 2022, Late Paleozoic cratonal sink: Distally sourced sediment filled the Anadarko Basin (USA) from multiple source regions. Geosphere, v. 18, 1831-1850.
Soreghan G.S., Soreghan M.J., Heavens N.G., 2019, Explosive volcanism as a key driver of the late Paleozoic ice age, Geology, v. 47, p. 600-604.
Soreghan, M. J., Swift, M. M., Soreghan, G. S., 2018, Provenance of Permian eolian and related strata in the North American midcontinent: Tectonic and climatic controls on sediment dispersal in western tropical Pangea. Geological Society of America Special Paper, 540
Soreghan, G. S., Benison, K. c., Foster, T. M., Zambito, J. J., Soreghan, M. J., 2015, The paleoclimatic and geochronologic utility of coring redbeds and evaporites: A case study from the RKB core. International Journal of Earth Sciences, v. 104, p. 1589-1603.
Evans, J. and Soreghan, M.J., 2015, Long-distance sediment transport and episodic re-sedimentation of Pennsylvanian dust (eolian silt) in cave passages of the Mississippian Leadville Limestone, southwestern Colorado, U.S.A. in J. Feinberg and Y. Gao (eds.), Caves and Karst Across Time, Geological Society of America, Special Paper. v. 516, p. 263-284.
Heavens, N.G, Mahowald, N.M., Soreghan, G.S., Soreghan, M.J., Shields, C.A., 2015, A model-based evaluation of tropical climate in Pangaea during the late Paleozoic icehouse, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 425, p. 109-127.
Soreghan, M.J., Heavens, N.G., Soreghan, G.S., Link, P.K., and Hamilton, M.A., 2014, Abrupt and high-magnitude changes in atmospheric circulation recorded in the Permian Maroon Formation, tropical Pangaea: Geological Society of America Bulletin, p. 1-16. DOI: 10.1130/B30840.1
Soreghan, G.S., Benison, K.C., Foster, T.M., Zambito, J.J., and Soreghan, M.J., 2014, The paleoclimatic and geochronologic utility of coring redbeds and evaporites: A case study from the RKB core (Permian, Kansas, USA): International Journal of Earth Sciences, p. 1-17. DOI 10.1007/s00531-014-1070-1
Foster, T.M., Soreghan, G.S., Soreghan, M.J., Benison, K.C., and Elmore, R.D., 2014, Climatic and paleogeographic significance of eolian sediment in the Middle Permian Dog Creek Shale (Midcontinent U.S.): Palaeogeography, Palaeoclimatology, Palaeoecology, v. 402, p. 12-29. DOI: 10.1016/j.palaeo.2014.02.031
Giles, J.A., Soreghan M.J., Benison, K.C., Soreghan, G.S., Hasiotis, S.T., 2013, Lakes, loess, and paleosols in the Permian Wellington Formation of Oklahoma, U.S.A.: Implications for paleoclimate and paleogeography of the midcontinent, Journal of Sedimentary Research, v. 83, p. 825-846.
Soreghan, G.S., and Soreghan, M.J., 2013, Tracing clastic delivery to the Permian Delaware Basin, U.S.A.: Implications for paleogeography and circulation in westernmost equatorial Pangaea, Journal of Sedimentary Research, v. 83, 786-802.
Zambito, J. J., Benison, K.C., Foster, T.M. Soreghan, G.S., Soreghan, M.J., and Kane, M., 2012, Lithostratigraphy of Permian Red Beds and Evaporites in the Rebecca K. Bounds Core, Greeley County, Kansas: Kansas Geological Survey Open-File Report, v. 2012-15, p. 1–45.
Heavens, N. G., Mahowald, N. M., Soreghan, G. S., Soreghan, M. J., and Shields, C. A., 2012, Glacial-interglacial variability in Tropical Pangaean Precipitation during the Late Paleozoic Ice Age: simulations with the Community Climate System Model, Climate of the Past Discussions, v. 8, 1915-1972, doi:10.5194/cpd-8-1915-2012.
