...and another abstract

Today was the abstract deadline for CGU, a smaller (but friendly and low-key) meeting. I put an abstract in on behalf of an undergrad working with me:

Mantle Fabric and Lithospheric Thickness Beneath the Superior Province

S.-K. Miong and A.W. Frederiksen
Department of Geological Sciences, University of Manitoba

The Superior Province, the largest Archean craton in the Canadian Shield, represents an ideal laboratory for understanding the nature and development of cratonic lithosphere. Ontario spans a major portion of the Superior, and, under the auspices of the POLARIS and FEDNOR projects, is in the process of being instrumented with broadband seismometers on a large scale. We present the result of SKS splitting analyses for FEDNOR and CNSN stations spanning the breadth of Ontario, covering the Eastern and Western Superior Province. The Western Superior exhibits very large SKS splits (averaging 1.4 seconds) with a consistent ENE fast direction (averaging 69 degrees azimuth). In the Eastern Superior, the fast directions are much more variable (ranging from east to northeast), with smaller split times averaging 0.8 second. In the Western Superior, the split times align closely with both the current direction of absolute plate motion and the orientation of structural belts in the crust; we therefore interpret the strong splits in this region to represent a combination of lithospheric and asthenospheric fabric sharing a common alignment. In the east, the fast directions show appreciable scatter around the direction of plate motion, though there is general agreement; given the weaker split times in this area, we take the variability to reflect a weaker and more inconsistent lithospheric fabric, since the asthenospheric fabric should vary little across the Superior. Results from other studies, including tomography, heat flow, and elastic plate thickness studies, suggest the possibility that the cratonic lithosphere may have been significantly reworked or thinned beneath the eastern portion of the Superior Province.

This one's a little more definite because, well, the work's mostly already done.