A plan view geometric model for simple, parallel, differential displacement
s is presented. As an analogue for models of arcuate mountain belt formatio
n we use the model to predict strain patterns produced by parallel displace
ment in front of a rigid versus deformable indenter. A rigid indenter is si
mulated by an irregular quadrilateral displaced a constant amount along its
hinterland boundary. A deformable indenter is simulated by an irregular qu
adrilateral displaced along a hinterland boundary that is allowed to rotate
. Some simple test cases show that the deformable indenter model leads to a
pattern of strain very similar to that encountered in arcuate mountain bel
ts. Short axes orientations are most deviated from the transport direction
along the lateral edges of the model with minimum displacement and shorteni
ng and vary across the central domain, mirroring strain features with varia
ble orientations from mountain belts such as fold trends and minor deformat
ion features such as horizontal stylolite peaks. The rigid indenter model a
lso generates short axes deviated from the transport direction but showing
far less variation. Displacement-strain relationships from the Jura mountai
ns (Switzerland and France) are quantified based upon a simplified version
of the finite displacement field for the Jura fold-thrust belt of Philippe,
Y. (1995) ["Rampes laterales et zones de transfer dans le chaines plissees
". (Unpublished PhD thesis, Universite de Savoie)]. We find that the model
short axis orientation pattern is very similar over at least the eastern an
d central Jura to the stylolite patterns from the region whilst the long ax
es closely match the fold axes trends. The model suggests that the Jura mou
ntains could have formed as a result of a progressive deformation with unif
orm transport in a general northwest direction. (C) 2000 Elsevier Science L
td. All rights reserved.