| dc.description.abstract | One or possibly two overlapping periods of deformation are responsible
for the structures observed in the rocks in the Seine River
area. This deformation has resulted in the formation of tight to isoclinal,
non-plane approximately cylindrical major F1 folds with steeply
dipping E-W striking axial surfaces. A late stage deformation has
resulted in the formation of a crenulation clsavage, kink bands and
minor faulting. There is also I imited evidence of a possible pre-F 1
folding event.
Two major I ithological groups are present in the study area:
shallow water metasedimentary rocks bf the Seine Group and metavolcanic
rocks. The Seine Group metasedimentary rocks are younger than the
metavolcanic rocks in the western part of the area but may be older
than similar metavolcanic rocks in the eastern part of the area. Two
ages of metavolcanic rocks therefore appear to be present: older metavolcanic
rocks in the west which under! ie the Seine Group, and younger
metavolcanic rocks in the east which overlie the Seine Group.
Regional metamorphism to the chlorite to biotite zone greenschist
facies was synkinematic with the deformation of the rocks but may have
outlasted the folding in plates.
Strain analysis from the metasedimentary rocks reveals that the
conglomeratic units are more intensely strained than arenite units,
although alI the strain elI lpsoids are of the flattened (K < 1) type. Average shortening in Z ranges from 52% for arenite units to 75% for
conglomerate units. A new empirical approach suggested by the writer and
Dr. Borradai le for assessing competence contrasts between strain markers
and matrix is outlined. This method uses the effects of competent markers
on cleavage traces in the matrix of conglomerates. | en_US |
