> Hi All,
>
> I am thinking about the issue of transient ductile deformation in
>orogenic belts, and was wondering if some of you might have recent
>information on the duration of deformation events during orogenesis.
>
> If one considers, for argument, a plate convergence rate of 10 cm/year,
>and assumes, again just for argument, that the strain is taken up
>homogeneously over a plate-boundary-perpendicular length of 100 km, that
>results in a (conventional) strain rate of 3.17x10-14 if I did my
>back-of-the-envelope math correctly. That means that a stretch of 0.5
>(moderate-strain crenulation cleavage for example) would take about
>500,000 years to accumulate.
>
> Of course, this is silly because strain does not accumulate
>homogeneously, strain is taken up over much longer line lengths in most
>orogens, etc...
>
> Does anyone out there know of good constraints on the time it takes to
>form a crenulation cleavage or other moderate-strain foliation in a mica
>schist? I have not been keeping up with the Ar/Ar work on foliated rocks.
>
> Cheers - Scott
>
>
> *************************************************************************
> Scott E. Johnson
> Department of Earth Sciences
> 5790 Bryand Global Sciences Center
> University of Maine
> Orono, ME 04469-5790
> USA
> email: [log in to unmask]
> phone: (207) 581-2142
> Fax: (207) 581 2202
> http://www.geology.um.maine.edu/user/scott_johnson/HM.html
> *************************************************************************
>
Dear Scott,
perhaps you may be interested in a paper on the duration of deformation
events, that focussed on the criteria for recognition and correct
separation of superposed coaxial deformations in in transpressional
settings. See:
Tavarnelli E. & Holdsworth R.E. (1999) - "How long do structures take to
form in transpression zones? A cautionary tale from California". Geology,
27 (12), 1063-1066.
I hope this information may be of use.
Cheers
Enrico
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-----o00-(_)-00o-----
Enrico Tavarnelli
Dipartimento di Scienze della Terra,
Universita' di Siena,
Via Laterina n. 8,
53100, Siena - Italy,
phone: ++39-(0)577-233 984
fax: ++39-(0)577-233 938
e-mail: [log in to unmask]
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