Dating the Great Unconformity in the Grand Canyon

The Precambrian-Cambrian, crystalline basement-sedimentary contact, or the Great Unconformity,
represents a prominent erosion surface observable across North America and globally. Geologists have
debated whether the erosion processes that created the Great Unconformity are related to the Rodinia
supercontinent cycle or Snowball Earth.

The timing of these weathering processes has broad implications for resolving the Great Unconformity’s association with key changes in oceanic and atmospheric chemistry and subsequent development of the Cambrian explosion. The current debate as to the formation of the GU therefore centers on the timing of basement erosion, whether erosion was globally synchronous, and the composite or singular nature of the GU erosion surface. We apply the zircon (U-Th)/He (ZHe) thermochronometer to model thermal histories of basement rocks of eastern Grand Canyon. These models use radioactive decay of uranium within zircon (a very strong and durable mineral) to determine when the erosional event that formed the Great Unconformity occurred and whether or not that timing lines up with the formation and break-up of Rodinia or with the development of Snowball Earth.

All are welcome! Science majors are strongly encouraged to attend!

Snacks will be provided.