April 20 @ 4:00 pm - 5:00 pm CDT
Current Research in Earth Science Seminar
Who: Nick Swanson-Hysell, Assistant Professor, Department of Earth and Planetary Science, UC-Berkeley
What: “Rapid rates of Proterozoic paleogeographic change”
Progressions of paleomagnetic poles are known as apparent polar wander paths (APWPs) and enable the development of ancient paleogeographic reconstructions. In Precambrian time, reliable paleomagnetic poles on a given craton are often widely spread in time restricting the possibility of generating well-resolved APWPs. The development of the North American Midcontinent Rift between ca. 1110 and 1080 Ma has provided an opportunity to develop extensive paleomagnetic data sets spanning this time period resulting in an APWP for Laurentia that goes from a high latitude apex known as the Logan Loop into a swath known as the Keweenawan Track. A long-standing challenge of these data was the appearance of asymmetry between relatively steep reversed polarity data from older rift rocks and relatively shallow normal polarity data from younger rift rocks that was used as support for an interpretation that there were large non-dipolar components to the geomagnetic field at the time. Data sets we have developed support the interpretation that this directional change was progressive and therefore a result of very rapid motion of Laurentia rather than stepwise change across non-dipolar reversals. Constraining these data with new high-precision U-Pb dates and applying novel inversion techniques constrains this motion to have been ~26 cm/year—significantly faster than the fastest plate rates in more recent time.
When: 4:00 pm, Thursday, April 20, 2017
Where: Room 100, KWGL