Research Project Year
Laura Branch
Research Project Title

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.

Righetti High School
Grade Level
High School
Teaching Position:
Geology Chemistry in the Earth System AP Environmental Science
Francis Macdonald
Earth Science
Eliel Antilla

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