Dynamic Development and Reactivation of a Newly

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Dynamic Development and Reactivation of a Newly
Discovered Frictional-Plastic Deformation System
Joseph L. Allen, Department of Physical Sciences,
Concord University, Athens, WV
Understanding the origin and early geologic
evolution of faults is important to petroleum
exploration and reservoir development because
they serve as zones of weakness in the crust that
are preferentially reactivated and rejuvenated
through time. The reactivation of old zones of
weakness can subsequently serve as a path for the
migration of fluids. Reactivation can also
influence the distribution, thickness, and 3-D
shape of overlying sedimentary strata that form
petroleum traps.
The goal of this research is to define controls
on the location, geometry, and dynamics of fault
rupture in the middle part of the Earths crust
(approximately 10-12 km deep), and investigate
how these geologic structures localized shallow
fault reactivation that affected sedimentary
strata 1.4 billion years later. We have mapped
the geometry of fault-related rupture in the
middle crust (see photo above left of
frictionally melted fault rock from the study
area). These fault rocks are the fossil record of
ancient earthquakes in the middle crust. The
fault zone core preserves overprinting brittle
and plastic fabrics within a mid-crustal thrust
fault (see figure below left). Early fabric
development and cyclic brittleplastic faulting
controlled brittle reactivation in the shallow
crust (lt10 km deep) 1.4 billion years later (see
photo below right showing northeast-oriented fold
in younger sedimentary strata).