SMART, KEVIN J.
School
of Geology & Geophysics, University of Oklahoma, Norman, OK, 73019-0628,
[email protected]
Abstract: Thrust-Related Folds and
Mechanical Anisotropy
: Insights from Finite Element Analyses
The intimate association of folds and
faults in deformed sedimentary rocks is well-established and has led to
many geometric and kinematic models of thrust-related folding. Our mechanical
understanding of this geologic process is not as advanced. Since rocks
are strongly anisotropic materials, it is not surprising that this parameter
should be a focus of mechanical models for thrust-related folding. However,
few numerical studies have addressed the role of mechanical anisotropy
on the development of thrust-related folds because of the inherent difficulties.
Numerical simulation of anisotropic behavior necessitates either a complex
constitutive relationship or elaborate initial configurations. Unfortunately,
each procedure yields a model that is very computationally-intensive. Anisotropic
constitutive relationships also require specification of additional material
parameters that are not particularly well-understood for most geologic
materials.
In this study, methods for introducing anisotropy
into finite element models are evaluated. These include both geometric
anisotropy
, such as simple sedimentary layering, as well as true material
anisotropy
via an anisotropic constitutive relationship, such as anisotropic
plasticity or a "jointed material" model. Based on this evaluation of different
methods, several end-member thrust-related fold types are analyzed. Initial
focus is on the progressive development of detachment, fault-arrest, and
fault-bend folds with respect to the role of mechanical
anisotropy
.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas