Dear all,
It seems that the query of Dr. M. Joshi has re-opened
an old debate. As mentioned by many people in the
list, the Geol. Soc. Spl. Publ. 'Thrust and Nappe
Tectonics' distinguished between thrust-nappe and
fold- (or fold-thrust) nappe, depending on whether
large scale recumbent folding is involved or not. We
have generally followed this convention. In central
Indian Precambrians, a large allochnous sheet of
crysalline gneisses overlying younger supracrustals
was earlier named 'Deolapar Nappe'implying a possible
recumbent fold-thrust allochthon. We have recently
reinterpreted it as a thrust sheet without regional
recumbent folding, but retained the name 'Deolapar
nappe'. I am now unsure whether the name is correct or
not. Again, as far as I remember, sliding and folding
of strata over a decollement-type horizon, similar to
the folding of tablecloth mentioned here, was called
'Peel thrusts' (I hope the spelling is correct!) in
Jura (possibly by Bucher). I would appreciate opinions
from experts. Best regards to all.
Anupam
A. Chattopadhyay
Dept. of Geology
Delhi university
Delhi, India
@PGI.WAW.PL> wrote: > short comment - here in Poland
(and Slovakia,
> Ukraine and Romania),
> within the Outer (flysch) Carpathians, term "nappe"
> ("plaszczowina" in
> Polish) is being still often used and in fact it has
> exactly such a
> connotations as given below - large amount of
> tectonic transport along
> almost horizontal basal detachement, completely
> detached from its
> substratum. Also, no particular internal geometry is
> being associated
> with nappe, there are some nappes with high degree
> of internal
> deformations and some less deformed. Modes of
> internal deformations
> could also be different.
>
> Piotr Krzywiec
>
> Matsen Broothaers wrote:
>
> > Hi all,
> > In Olivier Merle's book "Emplacement mechanisms of
> nappes and thrust
> > sheets" the term nappe or thrust sheet is
> presented "to describe huge
> > displacements (several tens of kilometres) on a
> surface close to the
> > horizontal".
> > Furthermore, "the word 'nappe' is of French origin
> meaning tablecloth
> > and reflects the three-dimensional form of these
> geological structures
> > which overlay a large surface whilst having a
> relatively moderate
> > thickness".
> > Hence, no particular geometry (recumbent folds) is
> implied; the
> > displacement or allochthony is the important
> factor. For the recumbent
> > folds the term "fold-nappe" is used, as also
> presented in the
> > discussion in a Geological Society Special
> Publication (McClay & Price
> > 1981). They use the term "thrust nappe" to denote
> " an allochthonous
> > tectonic sheet which has moved along a thrust
> fault".
> >
> > Matsen Broothaers
> >
> >
>
---------------------------------------------------------------------
> > Matsen Broothaers
> > Structural Geology & Tectonics Group
> > Katholieke Universiteit Leuven
> > Redingenstraat 16
> > 3000 Leuven
> > Belgium
> > Tel.: +32 (0) 16.32.64.42
> > Fax: +32 (0) 16.32.64.01
> > E-mail: [log in to unmask]
> > <mailto:[log in to unmask]>
> > URL: http://www.kuleuven.ac.be/geology/hsg/SG&T
> > <http://www.kuleuven.ac.be/geology/hsg/SG&T>
>
>
> --
> Dr Piotr KRZYWIEC
> Polish Geological Institute tel:+48-22-8495351
> ext. 498 (office)
> ul. Rakowiecka 4 0605-242791
> (mobile)
> 00-975 Warsaw, Poland fax: +48-22-8495342
> http://www.pgi.waw.pl/ email:
> [log in to unmask]
>
>
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