 |
 |
>Tim has an important point but, perhaps some or all fold nappes form >by a rolling hinge(s) mechanism not from initially upright folds. >Whichever may be correct, is there a typical width/length ratio? >Mechanism may be important (basement swallowing as in the Alpine >Urserenzone, gravity spreading, gravity sliding). Also, do nappes >always progress from top to bottom forwards towards the foreland. John Dewey > Hi All >Martin's request and the many responses got me involved, not because >of the length of the nappe, which to me is not important >conceptually. > >What is significant for me is the maximum width of upside down rocks >that exists on our planet in a single coherent sheet parallel to the >assumed transport direction. > >Many of us suspect large nappes form through rotation of initially >upright regional folds on sub-horizontal shear zones. > >If this is the case then the maximum width of upside down rocks >would be quite limited. I know of a stretch in SE New Hampshire that >is upside down for perhaps 5 kms in a coherent block parallel to the >transport direction. > >What is the maximum distance that any of you have come across? > >Cheers >Tim > > > >Prof. T.H. Bell >School of Earth and Environmental Sciences >James Cook University >Townsville >Qld 4811 >Australia >Work Phone +61-7-47814766 >Work Fax +61-7-47814020 >Home Phone+61-7-47723017 >Email [log in to unmask] ><http://www.es.jcu.edu.au/dept/Earth/research/samri/index.html>http://www.es.jcu.edu.au/dept/Earth/research/samri/index.html -- ----------------------------------- John F. Dewey FRS, M.R.I.A., Distinguished Emeritus Professor University of California. Sherwood Lodge, 93 Bagley Wood Road, Kennington, Oxford OX1 5NA, England, UK University College, High Street, Oxford OX1 4BH Telephone Nos: 011 44 (0)1865 735525 (home Oxford) 011 44 (0)1865 276792 (University College Oxford)