Abstract - Processes accommodating the mutual offsetting of
intersecting conjugate faults are investigated by outcrop examination of
three pairs of conjugate normal faults with maximum throws 5mm to 10cm.
In two cases resolved fault throws decrease sharply towards the intersection
zones which, on the scale of observation, are zones of ductile thinning
of intra-fault layers which accommodate the throw reductions. Strain within
the intersection zone of conjugate faults in fluvio-glacial sands is accommodated
by inter-grain slip and layer thinning is complemented by layer-parallel
extension at constant volume. In the second examplt, strain within the
intersection zone of conjugate faults in interlayered chalk and marl is
accommodated by volume reduction, without layer extension. In the third
example, also in fluvio-glacial sands, strain in the intersection zone
is accommodated by small faults (throws <1mm); when throws on all resolvable
faults are aggregated, there is no decrease in throw towards the conjugate
intersection. The presence or absence of a decrease in resolved throw towards
conjugate intersections and of a complementary ductile zone accommodating
the change in throw, is a function not only of the resolution limit of
the observations but also of the scale of the deformation process within
the conjugate zone.
Journal of Structural Geology 20, 363-370, 1998.