Volumetric matrix strain related to intraformational faulting in argillaceous sediments
B. Dehandschutter
P. Gaviglio
J. P. Sizun
M. Sintubin
S. Vandycke
N. Vandenberghe
L. Wouters
10.6084/m9.figshare.3454277.v1
https://geolsoc.figshare.com/articles/dataset/Volumetric_matrix_strain_related_to_intraformational_faulting_in_argillaceous_sediments/3454277
<p>Soft-sediment deformation involves complex interactions between discrete fracturing and diffuse bulk strain, described in
terms of volume change and shear strain in a critical state mechanics framework. This study reports on a mesoscale normal
fault zone, intraformational in Oligocene argillaceous sediments from the Boom Formation (Belgium), containing several metre-scale
normal fault strands. They form either discrete fault planes or decimetre-wide shear zones with internal fabric. The faults
have been subjected to microtectonic and petrophysical analysis. Small but significant changes occur in the porous network
of the argillaceous matrix approaching a fault or shear zone, indicating compactional strain in both footwall and hanging
wall. Internal compaction associated with faulting is put forward as a ductile–brittle feedback mechanism in the kinematics
of intraformational fracture systems. Small differential stress induced by compaction and minor regional tectonic forces (differential
uplift and tilt) and subsequent gravitational forces (downslope shear stress) induce small shear bands in nearly critically
stressed weak mud. Shear banding is accompanied by layer-parallel shortening and bulk volume loss. This provides an additional
extension of endogenous origin, accommodated by further deformation. This ductile–brittle feedback mechanism eventually leads
to commonly observed intraformational collapse structures called polygonal fault systems.
</p>
2016-06-21 12:01:11
Volumetric matrix strain
fault planes
Boom Formation
volume change
study reports
shear zone
fault zone
shear strain
intraformational collapse structures
tectonic forces
state mechanics framework
intraformational fracture systems
argillaceous matrix
compactional strain
fault strands
polygonal fault systems
downslope shear stress
bulk volume loss
Oligocene argillaceous sediments
petrophysical analysis
bulk strain
Internal compaction
shear bands
Geology