Sawtooth National Forest, Cassia Mountains, southern Idaho
field work in the Cassia Mountains, southern Idaho; L to R: Moses Jatta,
Madeline Marshall, Lauren Bergeron, and Kim Lau |
Marine Redox and Nutrient Cycling in the Permian Phosphoria Rock Complex: southern Idaho
Phosphorus is the ultimate limiting nutrient. On geologic time scales, phosphorus controls marine primary productivity and the deposition of organic carbon on the sea floor. The cycling and deposition of phosphorus is controlled by a delicate balance of diagenetic processes, ocean oxygenation, and depositional conditions. The aim of this research is to better understand the marine redox conditions that allow for the accumulation of massive phosphorite deposits in ancient shallow epeiric seaways, with the Permian Phosphoria Basin as a case study. We use a variety of geochemical and sedimentary proxies to interpret paleoceanographic conditions such as water column and sediment porewater redox conditions, nutrient cycling, and basin restriction. Collaborators: Kimberly Lau, Joshua Garber, & Georgia Soares, Pennsylvania State University Madeline Marshall, Albion College Jeremy Owens, Florida State University |
field work in the Prague Basin, Czech Republic; L to R: Nevin Kozik, Seth Young, Chelsie Bowman
photo credit: Jiri Fryda |
Extinction, Carbon Cycling, and Intensified Global Marine Anoxia in the late Silurian: Tennessee, Nevada, Estonia, Czech Republic
The late Silurian Lau/Kozlowskii extinction event (~425 million years ago) was the 10th most severe extinction in geologic history and is associated with the Lau carbon isotope excursion, the largest perturbation of the global carbon cycle in the last ~540 m.y. The aim of this research is to document changes in local and global marine redox conditions in the late Silurian and their relation to the extinction event and carbon cycle perturbation. We use a suite of geochemical proxies in carbonate and shale strata to elucidate spatiotemporal changes in water column and sediment porewater redox conditions, carbon and pyrite burial (C, S, Tl isotopes, major and trace element concentrations). We are also using carbonate microfacies analyses to understand trends in biodiversity through the extinction and documenting the extensive presence of unusual microbial and abiotic carbonate facies in the late Silurian. Collaborators: Seth Young, Jeremy Owens, Lindsi Allman, Florida State University Anders Lindskog & Mats Eriksson, Lund University Dimitri Kaljo, Olle Hints, Tõnu Martma, Tallinn University of Technology Theodore Them II, Charleston College Jiri Fryda, Czech University of Life Sciences |
field work at Red Rock Canyon in the Mojave Desert
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You are What You Eat - Fossil Tooth Enamel and the Evolution of Grasslands: southern California
Grasslands are a relatively recent evolutionary development in the world of terrestrial flora. The timing of the evolution of grasslands is regionally variable through the Oligocene and Miocene epochs of the Cenozoic. Grasses use a unique photosynthetic pathway in order to create biomass under low atmospheric CO2 conditions, which allows them to be differentiated from plants using other pathways using carbon isotopes. When herbivores consume plants the carbon from the plant biomass (and its isotopic signature with a known biological fractionation) is incorporated into tooth enamel. We used the carbon isotopes of fossilized herbivore tooth enamel to investigate the timing of the evolution of grasslands in the Mojave tectonic block of southern California. Collaborators: Yang Wang, Florida State University Xiaoming Wang & Gary Takeuchi, Los Angeles County Museum |