| Principal Investigator: | Macdonald, Francis A (1) |
| Licence Number: | 16564 |
| Organization: | University of California at Santa Barbara |
| Licensed Year(s): |
2019
|
| Issued: | Jun 17, 2019 |
| Project Team: | Becky Flowers, Paul Hoffman |
Objective(s): To constrain the timing, magnitude, and spatial heterogeneity of erosion that lead to development of the Great Unconformity.
Project Description: This proposal aims to constrain the timing, magnitude, and spatial heterogeneity of erosion that lead to development of the Great Unconformity (GU) to test hypotheses for oxygenation and the Cambrian explosion. The GU is one of the most geologically significant and largest temporal gaps in the rock record, marking the boundary between Precambrian and Phanerozoic time. It has been proposed that erosion below the GU delivered bio-limiting phosphorous to the ocean, which spurred organic carbon burial, oxygenation of the ocean-atmosphere system, and the rise of animals. Determining when the GU developed, whether during Rodinia mantle upwelling, early Rodinia breakup, the Cryogenian Snowball Earth glaciations, or Late Ediacaran rifting, and deciphering the size of the last erosion event preceding GU formation, whether km’s or 100s of m, are critical for identifying viable mechanisms for evolutionary change during this pivotal interval of Earth history. However, because the temporal gap across the GU is so substantial, the timing and magnitude of erosion under the GU are largely unconstrained. Recent advances in allow access to the thermal histories required to unravel the history of this iconic feature. This proposal outlines a strategy to acquire zircon and titanite data for samples along two regional transects characterized by minimal post-GU burial overprinting from the Slave Craton. Study sites will be targeted to fully exploit Neoproterozoic and Cambrian geologic constraints, which will be vital for narrowing the range of viable thermal histories to enable discrimination between GU formation models. The results will dramatically improve constraints on the Neoproterozoic cooling history of North America, which will be used to test competing models for GU development and significance. The research team will collect samples formed before 700 Ma and separate zircon, titanite, and apatite from these samples. The team will then date these samples with U/Pb, and then analyze these samples for tatanite to reconstruct their thermal history. In season 2 the research team will visit Lutsel K'e and present the research to the community. The fieldwork for this study will be conducted from August 1, 2019 to August 12, 2019.
