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Thesis Defense: Daniel Woodworth, Ph.D. Candidate, April 22 @ 2 p.m.

April 15 @ 8:00 am - 5:00 pm CDT

Thesis Defense: Daniel Woodworth, Ph.D. Candidate, April 22 @ 2 p.m.

Student: Daniel Woodworth
Department: Earth, Environmental and Planetary Sciences
Defense Date: April 22, 2022
Time: 2:00 p.m.

Location: KWGL 123

Thesis Title:

High-Resolution Pacific Apparent Polar Wander Since the Paleocene: Evidence for Two Episodes of True Polar Wander and Two True Polar Stillstands

Abstract:

Paleomagnetic poles from the continents have long provided evidence for apparent polar wander (APW), the motion over geologic time of the spin axis relative to a continent or tectonic plate. In contrast, the APW paths of oceanic plates are much less developed, mainly because oceanic plates lack subaerially exposed surface, making conventional paleomagnetic approaches difficult or impossible.

Herein two alternative approaches, skewness analysis of marine magnetic anomalies and paleo-spin axis estimation from the distribution of paleo-equatorial sediment bands, are developed and applied. With these approaches we determined a high-resolution APW path for the Pacific Plate from 56 Ma to 12 Ma. Combined with existing Pacific poles for 72 Ma to 58 Ma, our Pacific APW allows study of finer detail than is possible using conventional methods. We identify two tracks in the Pacific APW path, suggesting northward plate motion relative to the spin axis 72 Ma to 56 Ma and 46 Ma to 12 Ma.  Surprisingly, there is no net apparent polar wander between 12 Ma and the present and during the gap between these tracks southward motion from 56 Ma to 46 Ma is indicated. When reconstructed into the reference frame of the Pacific hotspots, which has been used to approximate an absolute reference frame, the two Pacific APW tracks correspond to two stillstands in the motion of the paleo-spin axis at locations significantly different both from one another and the present spin axis. These locations are separated by spin axis motion from 56 to 46 Ma and 12 Ma to the present. We interpret these stillstands in paleo-spin axis motion relative to the Pacific hotspots as true polar stillstands and the intervals separating them, corresponding to anomalous Pacific APW, as episodes of true polar wander of 7° and 3°, respectively.

Details

Date:
April 15
Time:
8:00 am - 5:00 pm CDT

Venue

Keith-Wiess Geological Laboratories
Rice University, 6100 Main Street, MS 126
Houston, TX 77005 United States
+ Google Map
Phone:
713-348-4880
View Venue Website

Details

Date:
April 15
Time:
8:00 am - 5:00 pm CDT

Venue

Keith-Wiess Geological Laboratories
Rice University, 6100 Main Street, MS 126
Houston, TX 77005 United States
+ Google Map
Phone:
713-348-4880
View Venue Website

For outside visitors, the best way to get to our department is to come in on Rice Blvd and turn left into entrance 20 (intersection of Rice and Kent St.). At the stop sign, you will see a visitor parking lot on your right.  From there, walk east to the department.  The google map below shows exactly where our building is.