Syndepositional Fracture
Patterns of the Devonian Reef Complexes,
Frost, Ned1, Leonel Gomez1 (1) The
Syndepositional opening-mode fractures
known as neptunian dikes are a common feature in many
carbonate systems throughout the geologic record. The
Fracture aperture and spacing were
measured along 1D scanlines in the outcrops of Windjana Gorge. In these data sets we analyzed key fracture
attributes such as orientation, fracture strain, fracture intensity, aperture
scaling, and spatial arrangement. We used Normalized Correlation Count (NCC), a
recently developed analytical technique, to distinguish between five possible
types of spatial arrangements: random, harmonically arranged clusters, fractal,
more abundant than random (plateau), or a combination of the previous four
arrangements.
This study shows strong variations in
fracture patterns as function of depositional facies,
platform margin trajectory, and tectonic setting. Facies
in prograding platforms consistently exhibit higher
values of fracture intensity and extension than their counterparts in
retrograding margins. The backreef is typically the least
fractured; however, discrete zones of high fracture intensity often occur near syndepositional faults and zones of curvature created by
compaction over antecedent topography. Fractal, harmonically arranged, and
random spatial arrangements of fractures are observed, with cluster type,
width, and spacing varying with individual facies.
These variations in fracture characteristics primarily arise from differing
mechanical properties of individual facies, and the
fundamentally different fracture controls acting prograding
and retrograding margins.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California