Cryptobioturbation and the Work
of Sedimentologically Friendly Organisms
Pemberton, S. George1, James
A. MacEachern2, Murray K. Gingras1, Thomas Saunders3
(1) University of Alberta, Edmonton, AB (2) Simon Fraser University, Burnaby,
BC (3) University of Alberta, Edmonton
Biogenic chaos, from an ichnological point of view, can be defined as total bioturbation of sediment by organisms, such that the
original sedimentary fabric and associated sedimentary structures are
destroyed. Nevertheless, not all forms of thorough bioturbation
are purely destructive. As improbable as it first sounds, sediment can be
pervasively (potentially 100%) bioturbated, and yet
have suffered little distortion of original bedding. Owing to its diminutive
and obscure nature, cryptobioturbation has not
received widespread attention. As the name implies, cryptobioturbation
is characteristically small in scale and exceedingly subtle in expression. What
sets it apart from other forms of bioturbation,
however, is the tendency to preserve, rather than to destroy, the sediment's
primary physical structure. The fabric that results from crytobioturbation
can have significant influence on resulting permeability and porosity trends.
The effect of the cryptic bioturbation does not
result in enhanced permeabilities, but rather,
promotes a reduction in internal heterogeneities, leading to a more uniform
permeability distribution. Similar cryptically bioturbated
facies are very widespread in the rock record and
have been encountered in the Berriasian Toro
Sandstone in the Iagifu field,
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California