Paleoclimatology and Paleoceanography
Brad Sageman's stratigraphic research includes studies of the sedimentary expression of orbital forcing of climate. Most of this work has focused on the rhythmic shale-carbonate facies of the Cretaceous Western Interior basin in the United States. Two recent Ph.D. theses were focused on this subject: Steve Meyers, now faculty at University of WI-Madison, worked on the Cenomanian-Turonian strata of the Greenhorn Formation and was responsible for developing several new spectral techniques, including evolutive harmonic analysis and average spectral misfit. Rob Locklair, now a geologist at Chevron, worked on the Conicacian-Santonian strata of the Niobrara Formation and his project fostered collaboration with industry colleagues on the shale gas potential of the Niobrara. Both studies sought to develop high resolution time scales for fine-grained, organic-carbon rich facies in order to improve the power of geochemical proxy data by making possible calculation of mass accumulation rates. Sageman is currently collaborating with Meyers and his UW colleague Brad Singer, an Ar-Ar geochronologist, on a project to integrate new radioisotope dates with floating astronomical time scales in order to refine and improve the Cretaceous time scale.
Matthew Hurtgen's research integrates elemental abundances, stable isotopes, and sedimentological data to investigate the biogeochemical cycling of sulfur, carbon, iron, and oxygen in sediments as old as 2.7 billion years and as recent as today. Most notably, Dr. Hurtgen's research centers on the biogeochemical cycling of sulfur in the late Neoproterozoic - a period encompassing global glaciations that may have endured for tens of millions of years (snowball Earth hypothesis), a significant increase in oxygen concentrations in the coupled ocean-atmosphere system, and the evolution of multi-cellular (metazoan) life. Ongoing efforts focus on the dynamics and internal cycling of sulfur within the marine system at both local and global scales and use both the sulfur and oxygen isotope composition of sulfate-bearing minerals and phases in ancient carbonates. These studies span nearly all of Earth history and include (but are not limited to) the late Archean, Neoproterozoic, Cambrian, Ordovician, Triassic, Cretaceous, and Plio-Pleistocene.
Yarrow Axford’s research focuses on the climate history of the Quaternary, up to and including present day. Quaternary sediments -- lake sediments, peats, soils, and many other geological deposits laid down within the past two million years -- provide diverse and detailed archives of dramatic environmental changes, including global-scale swings from glacial to interglacial climates and widespread human impacts on the environment. A paleolimnologist, Axford focuses much of her attention on using lake sediments to reconstruct Holocene climate changes in Arctic and alpine regions, from Alaska to the Peruvian Andes. The paleolimnologist’s toolkit is broad, and may include paleoecological methods, geochemical analyses including major and trace elements and stable isotopes, magnetostratigraphy, tephrostratigraphy, and a range of geochronological methods including radiocarbon and other radio-isotope dating techniques. Holocene climate changes can be reconstructed in remarkable detail thanks to widespread, well-preserved geological archives of this most recent phase of Earth’s history, combined with the wide range of proxies and dating methods that are applicable to this time period. Holocene climate changes thus function as relatively well-characterized natural experiments, addressing fundamental questions about the causes and consequences of climate change, and the role of humans in the Earth system.
Neal Blair’s organic geochemical and isotopic studies of marine and lacustrine sediments have revealed the impacts of climate, tectonics, and humans in watersheds and the adjacent marine portion of the continental margin during the Holocene and Anthropocene. The interplay between land use, climate, tectonics, ecosystems and the biogeochemical cycling of C and N is the central focus of the lab’s efforts. How do the forcing functions influence the cycling, and how can we use the biogeochemical cycle signatures to reflect on the forcing functions through time and space? Field areas include the east and west coasts of the U.S., the Midwest, the Amazon delta, and the Pacific Rim.
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