College of Mines and Earth Sciences
61 What Can Magnetic Biomarkers Tell Us About the Eocene-Oligocene Transition in the North Atlantic?
Margaret Call and Peter C. Lippert
Faculty Mentor: Peter Lippert (Geology and Geophysics, University of Utah)
One of most significant episodes of climatic change in the past 66 million years was the Eocene-Oligocene Transition (EOT), a global cooling that began approximately 33.3 million years ago and happened gradually over half a million years. The glaciation of Antarctica began during the EOT. While the climate records and proxies for EOT have been investigated in detail in the Southern and Pacific oceans and the impacts on marine ecosystems there are better understood, there remain major geographic and ecological areas of impact that lack information. These gaps include the impacts of this change on thermohaline circulation in the North Atlantic, which serves a major control for global temperature regulation. My project aims to improve this knowledge gap by measuring high-resolution records of environmental change across the EOT by studying fossil remains of magnetotactic bacteria (MTB). MTB are a rich archive of environmental change because they are sensitive to oxygen and nutrients, which allows us to use their fossil record as a pathway to understand the impact of global cooling on deep sea communities. By using core samples retrieved from Site U1411, collected offshore of Newfoundland during International Ocean Discovery Program (IODP) Expedition 342, we will document the concentration and preservation quality of these fossils across the Eocene-Oligocene Boundary in high resolution. We will accomplish this by performing two types of measurements on these sediment samples: First Order Reversal Curves (FORCs) and analytical electron microscopy. FORCs and their corresponding FORC diagrams can be used to assess the relative contributions of different magnetic particles within a bulk sample and across a sample set. This allows us to isolate the signal from the magnetofossils efficiently from other magnetic material to the bulk sample. We use these data to select a few samples of interest to prepare examine magnetic extracts using the Scanning Transmission Electron Microscope at the University of Utah EM Surface Analysis Lab. These observations will provide physical images and chemical composition (via electron diffraction and energy dispersive X-ray spectroscopy) of the fossils we are studying and allow us to understand their level of preservation over the duration of the EOT and confirm our previous findings. By understanding the fossil remains of some of the smallest organisms in the ecosystem and how they are preserved over time, we can learn more about the deep-sea oxygen, nutrient availability, and redox conditions on the sea floor during the transition from a greenhouse to icehouse world.
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