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Absolute Age Dating Carbon Burial in the Monterey Formation using U-Pb Zircon Geochronology
The Miocene aged Monterey Formation found along the coast of California is known as a major source of oil in California. It is also a storehouse of carbon and an important link to past climate change. For this project, samples were collected along the cliffs of Arroyo Burro Beach in Santa Barbara, California, with the focus on the ash layers found within different depths of the Monterey Formation. These ash layers, which were deposited by nearby volcanic eruptions, hold zircons which were picked after cleaning clay from the sample by using a simplified bentonite separation process and panning which leaves behind the denser minerals, including the zircons. After mounting the picked zircons, laser ablation along with a mass spectrometer is used to find the geochronology of U-Pb ratios. Uranium decay to its daughter element lead decays at a predictable rate. Therefore, looking at the ratios of uranium to lead gives these samples an absolute age date which is used with other data such as total organic carbon, sedimentation rate and organic carbon accumulation rate to support the idea of the Miocene Climatic Optimum (MCO) and the Middle Miocene Climate Transition (MMCT), a warming and cooling trend (transgressive/regressive sequence) within the Mid-Miocene Epoch.
Global Climate Shifts Over Time—Using Evidence & Reasoning to Make a Scientific Claim
This is a two week long, five-lesson unit designed for a physical geology course but can be adapted to a NGSS aligned Chemistry in the Earth System course. In this unit, students are encouraged to make scientific claims using evidence and reasoning from different types of data, specifically using real world climate data in a “5E” format. The central phenomenon has students learning about the different types of data climate scientists use to study climate shifts over time, and a “hands-on” portion of this work has students taking data from teacher-made ice cores and subsequently provide reasoning behind any scientific claims and data interpretations. Each subsequent laboratory experience has students collecting data in order to use ERC: Evidence and reasoning to make a scientific claim.