"Fault Dates to Orogenic Rates" : Dr. Ben van der Pluijm Speaks this Week
EES welcomes our Distinguished Speaker Dr. Ben van der Pluijm, University of Michigan.
"From Fault Dates to Orogenic Rates"
Patterns of timing of fault activity in fold-thrust belts is becoming sufficiently dense to constrain rates of regional deformation and crustal evolution. Newly-formed, illitic clays are common in foreland fold-thrust belts, and the ages of fault-zone mineralization allows first-order constrains on the timing and progression of regional deformation. We briefly discuss our method of authigenic clay dating using sample encapsulation and multiple Ar ages for each sample, followed by application to select foreland fold-thrust belt settings. Regional fault dating in the Canadian Rockies shows that multiple cycles (“pulses”) of orogenic wedge formation occurred, each lasting 4-8 m.y., separated by longer periods of tectonic quiescence, instead of continuous forward progression of faulting (“stick-slip orogeny”). In contrast, fault ages in the eastern Pyrenees foreland show modest shortening over a relatively long time window of ~20 m.y. (30-50Ma), giving a strain rate of an order of magnitude less. Strain rates in foreland wedges of orogens reflect tectonic setting and deformation style, with finite displacements in accordance with modern fault seismicity.
Join us for more on Friday, January 25, 2019 at 12:30 PM in Room 204, Natural Science Building on the East Lansing campus.