and Vendeville, B. C., 2002, Experimental insights on the geometry
and kinematics of fold-and-thrust belts above a weak, viscous evaporite
décollement: Journal of Structural Geology, v. 24, p. 1729-1739.
and Vendeville, B. C., 2001, Diapirism in convergent settings triggered
by hinterland pinch-out of viscous décollement: a hypothesis
from modeling, in Koyi, H. A., and Mancktelow, N. S., eds., Tectonic
modeling: a volume in honor of Hans Ramberg: Boulder, Colorado,
Geological Society of America Memoir 193, p. 123-130.
Modeling of Contractional Systems Detaching on Evaporites
Experimental Insights on the Geometry and Kinematics of Fold-and-Thrust
Belts Above Weak, Viscous Evaporitic Décollement
and associated published paper, discusses the differences in mechanical
properties and kinematics between fold-and-thrust belts detaching
on evaporitic décollements and those detaching on stronger
detachments. Physical experiments are described that model shortening
of a thick brittle cover overlying a weak, viscous décollement
to gain a better understanding of these differences. We tested the
influence of (1) the décollement layer thickness and (2)
the presence of a deformable backstop on the hinterland side and
of a décollement pinch-out on the foreland side. Because
of the very low shear strength of the viscous décollement,
folds and thrusts did not propagate according to a piggy-back sequence
but by centripetal, back-and-forth propagation. Additional shortening
was accommodated by growth of all existing structures. Fold symmetry
and thrust vergence varied between experiments. Models confined
between two rigid, vertical endwalls always deformed by symmetric
folding and thrusting. In models having a deformable backstop and
a foreland décollement pinch-out, forethrusting initially
dominated, folds were asymmetric, and fault blocks rotated. In models
having a thick décollement layer, folds kept growing asymmetrically.
Diapirism also depended on the initial décollement geometry.
Diapirs formed only in models having a deformable backstop and were
restricted to the hanging wall of a fault-related fold. Finally,
the implications of such kinematics on the thermal history are discussed
as well as the likelihood of hydrocarbon maturation and preservation.
Diapirism in Convergent Settings Triggered by Hinterland Pinch-Out
of Viscous Décollement: A Hypothesis From Modeling